JP7478530B2 - Developing device and image forming apparatus - Google Patents

Description

This invention relates to a developing device and an image forming apparatus, and in particular to a developing device and an image forming apparatus that includes a developing tank that contains a developer and supplies the toner contained in the developer in the developing tank to a photoconductor drum via a developing roller.

One example of a conventional developing device is disclosed in Patent Document 1. The developing device in Patent Document 1 uses a two-component developer containing toner and carrier, and has a space separated by a developer supply section that supplies developer to a developing roller (developer carrier) and a developer recovery section that recovers developer from the developing roller, and each space is equipped with a developer tank in which agitating and transporting members (transporting screws) that can rotate in opposite directions are arranged.

JP 2014-10179 A

In the technology of Patent Document 1, the side wall of the developer tank located below the developing roller, that is, the side wall of the developer tank that forms the path for pumping the developer from the stirring and transporting member to the developing roller, is formed to rise in a substantially vertical direction up to the upper end position of the stirring and transporting member. As a result, the amount of developer transported (pumped up) from the stirring and transporting member to the developing roller collides with the side wall of the developer tank in large amounts, hindering the movement of the developer and causing the developer to stagnate. In order to prevent this stagnation of the developer, it is possible to lower the height of the side wall that rises in a substantially vertical direction. However, if the height of the side wall that rises in a substantially vertical direction is simply lowered, the developer that is stirred up by the stirring and transporting member will directly reach the regulating pole (S1 pole) of the developing roller, and the density of the developer will not be sufficiently uniform before it passes the regulating pole, which may result in poor image quality such as banding.

Therefore, the primary object of this invention is to provide a novel developing device and image forming device.

Another object of the invention is to provide a developing device and an image forming apparatus that can properly pump developer from the stirring and transporting member to the developing roller.

A first invention includes a developer tank that contains developer, a developing roller provided in the developer tank, an agitating and transporting member provided in the developer tank at a position diagonally below the developing roller, which transports the developer in the developer tank in the axial direction while agitating it and pumps the developer up to the developing roller, and a layer thickness regulating member that regulates the layer thickness of the developer carried on the outer peripheral surface of the developing roller, the developing roller having a regulating pole provided at a position opposite the layer thickness regulating member and a pumping pole provided at a position opposite the agitating and transporting member that draws the developer in the developer tank to the developing roller, the developer tank is provided below the developing roller so as to extend diagonally upward, and has an inclined surface that forms a pumping path for the developer from the agitating and transporting member to the developing roller, This developing device has a lower end of the inclined surface located lower than the upper end of the stirring and transporting member, and a suppression section that rises in an approximately vertical direction is formed in the central part of the inclined surface in the developer pumping direction, the inclined surface has a suppression section, a first inclined section formed on the upstream side of the suppression section in the pumping direction, and a second inclined section formed on the downstream side of the suppression section in the pumping direction, and the inclination angle of the first inclined section with respect to the horizontal direction is greater than the inclination angle of the second inclined section with respect to the horizontal direction, and the inclination angle of the second inclined section with respect to the horizontal direction is smaller than the inclination angle of the first inclined section with respect to the horizontal direction over the entire length in the pumping direction, and the developer pumping suppression ability of the suppression section is greater in the central part than at both ends of the suppression section in the axial direction of the stirring and transporting member .

According to the first invention, the lower end of the inclined surface is positioned lower than the upper end of the second transport member, and a suppression section that rises in a substantially vertical direction is formed in the central portion of the inclined surface in the direction in which the developer is pumped up. This makes it possible to properly guide the developer to the pumping pole of the developing roller while suppressing the accumulation of the developer. In other words, the pumping of the developer is stabilized, and the developer can be properly pumped up from the stirring transport member to the developing roller.

The second invention is dependent on the first invention, and the upper end of the suppression section is located above the upper end of the stirring and conveying member.

A third invention is according to the first or second invention, and a lower end of the inclined surface is located closer to the layer thickness reducing member than the central axis of the developing roller in the width direction of the developing device.

A fourth invention is dependent on any one of the first to third inventions, and the inclination angle of the first inclined portion with respect to the horizontal direction is 60 degrees or more and 80 degrees or less, the inclination angle of the suppression portion with respect to the horizontal direction is 80 degrees or more and 90 degrees or less, the inclination angle of the second inclined portion with respect to the horizontal direction is 35 degrees or more and 55 degrees or less, and the length of the second inclined portion in the pumping direction is 5.0 mm or more and 7.0 mm or less.

A fifth invention is dependent on any one of the first to fourth inventions, and the gap between the upper end of the second inclined portion and the developing roller is 1.0 mm or more and 2.0 mm or less, and the angle between the pumping pole and the regulating pole is 55 degrees or more and 65 degrees or less.

A sixth invention is according to any one of the first to fifth inventions, wherein the second inclined portion is formed into a curved surface that is concave downward.

A seventh invention is according to any one of the first to fifth inventions, wherein a connection portion between the suppression portion and the second inclined portion is formed into an upwardly convex curved shape.

An eighth aspect of the present invention is an image forming apparatus including the developing device according to any one of the first to seventh aspects of the present invention.

According to this invention, the lower end of the inclined surface is positioned lower than the upper end of the second transport member, and a suppression section that rises in a substantially vertical direction is formed in the central portion of the inclined surface in the direction in which the developer is pumped up. This makes it possible to properly guide the developer to the pumping pole of the developing roller while suppressing the accumulation of the developer. In other words, the pumping of the developer is stabilized, and the developer can be properly pumped up from the stirring transport member to the developing roller.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments given below with reference to the drawings.

1 is a schematic cross-sectional view showing an internal structure of an image forming apparatus according to a first embodiment of the present invention; FIG. 2 is a perspective view showing a developing device included in the image forming apparatus of FIG. 1 . FIG. 3 is a cross-sectional view showing the developing device of FIG. 2 . 3 is an enlarged cross-sectional view showing the periphery of a developing roller of the developing device of FIG. 2. 3 is an enlarged schematic view showing an inclined surface portion of a developing tank provided in the developing device of FIG. 2; FIG. FIG. 11 is a schematic diagram showing an inclined surface of a developing tank provided in a developing device according to a second embodiment of the present invention; FIG. 13 is a schematic diagram showing an inclined surface of a developing tank provided in a developing device according to a third embodiment of the present invention; 10A is a schematic diagram showing an inclined surface at the longitudinal center of a developing tank provided in a developing device of a fourth embodiment of the present invention, and FIG. 10B is a schematic diagram showing inclined surfaces at both longitudinal ends of the developing tank.

[First embodiment]
1, an image forming apparatus 10 according to an embodiment of the present invention is a multifunction peripheral (MFP) having a copying function, a printer function, a scanner function, a facsimile function, etc. As will be described in detail later, the image forming apparatus 10 includes a developing device 34, and forms a multicolor or monochrome image on a sheet (recording medium) by an electrophotographic method.

First, the basic configuration of the image forming device 10 will be briefly described. Note that in this first embodiment, the surface facing the position of the user operating the image forming device 10, i.e., the surface on which the operation panel is provided, is defined as the front (front), and the front-to-rear direction (depth direction) of the image forming device 10 and its components are defined. In addition, the left-to-right direction (horizontal direction) of the image forming device 10 and its components are defined based on the state in which the image forming device 10 is viewed by the user.

As shown in FIG. 1, the image forming device 10 includes a device main body 12 equipped with an image forming unit 30 and the like, and an image reading device 14 disposed above the device main body 12.

The image reading device 14 has a document placement platform 16 made of a transparent material. A document pressing cover 18 is attached above the document placement platform 16 via a hinge or the like so that it can be opened and closed freely. This document pressing cover 18 is provided with an ADF (automatic document feeder) 24 that automatically feeds documents placed on a document placement tray 20 one sheet at a time to an image reading position 22. Although not shown in the figure, an operation panel equipped with a touch panel display and operation buttons that accepts input operations such as printing instructions from the user is provided on the front side of the document placement platform 16.

The image reading device 14 also has a built-in image reading unit 26 that includes a light source, multiple mirrors, an imaging lens, and a line sensor. The image reading unit 26 exposes the document surface to the light source, and guides the light reflected from the document surface to the imaging lens using multiple mirrors. The imaging lens then focuses the reflected light on the light receiving element of the line sensor. The line sensor detects the luminance and chromaticity of the reflected light focused on the light receiving element, and generates image data based on the image of the document surface. A CCD (Charge Coupled Device) or a CIS (Contact Image Sensor) is used as the line sensor.

The device body 12 includes a control unit (not shown) including a CPU, memory, etc., and an image forming unit 30. The control unit transmits control signals to each part of the image forming device 10 in response to input operations to an operation unit such as a touch panel display, and causes the image forming device 10 to perform various operations.

The image forming section 30 includes an exposure unit 32, a developing device (developing unit) 34, a photoconductor drum 36, a cleaner unit 38, a charger 40, an intermediate transfer unit 42, a transfer roller 44, and a fixing unit 46, and forms an image on paper conveyed from a paper feed tray 48, etc., and discharges the paper with the image formed on it to a paper discharge tray 50. As image data for forming an image on the paper, image data read by the image reading section 26 or image data sent from an external computer, etc., is used.

The image data handled by the image forming device 10 corresponds to color images of four colors: black (K), cyan (C), magenta (M), and yellow (Y). For this reason, four of each of the developing devices 34, photoconductor drums 36, cleaner units 38, and chargers 40 are provided to form four types of latent images corresponding to each color, and these constitute four image stations.

The photoconductor drum 36 is an electrostatic latent image carrier in which a photosensitive layer is formed on the surface of a cylindrical conductive base body, and is rotatable around its axis by a drive unit (not shown). The charger 40 is a member that charges the surface of the photoconductor drum 36 to a predetermined potential. The exposure unit 32 is configured as a laser scanning unit (LSU) equipped with a laser emission unit and a reflecting mirror, etc., and exposes the charged surface of the photoconductor drum 36 to light to form an electrostatic latent image on the surface of the photoconductor drum 36 according to the image data. The cleaner unit 38 removes and collects toner remaining on the surface of the photoconductor drum 36 after the toner image is transferred to the intermediate transfer belt 54.

The developing device 34 visualizes (forms a toner image) the electrostatic latent image formed on the surface of the photoconductor drum 36 with four color (YMCK) toners, and includes a developing roller 76 that supplies toner to the photoconductor drum 36. A developer (two-component developer) consisting of toner and carrier is contained in a developing tank 80 of the developing device 34, and the toner contained in this developer is supplied to the photoconductor drum 36 via the developing roller 76. The specific configuration of the developing device 34 will be described later.

The intermediate transfer unit 42 includes an intermediate transfer belt 54, a drive roller 56, a driven roller 58, and four intermediate transfer rollers 60, and is disposed above the photosensitive drums 36. The intermediate transfer belt 54 is disposed so as to contact each photosensitive drum 36, and the intermediate transfer rollers 60 are used to transfer the toner images of each color formed on each photosensitive drum 36 to the intermediate transfer belt 54 in a sequentially overlapping manner, thereby forming a multi-color toner image on the intermediate transfer belt 54. In addition, a transfer roller 44 is disposed near the drive roller 56, and the toner image formed on the intermediate transfer belt 54 is transferred to the paper by the paper passing through the nip area between the intermediate transfer belt 54 and the transfer roller 44.

The fixing unit 46 includes a heat roller and a pressure roller, and is disposed above the transfer roller 44. The heat roller is set to a predetermined fixing temperature, and as the paper passes through the nip area between the heat roller and the pressure roller, the toner image transferred to the paper is melted, mixed, and pressed against the paper, thereby thermally fixing the toner image to the paper.

In the device body 12, a first paper transport path L1 is formed for sending paper transported from the paper feed tray 48, etc., via the registration rollers 62, transfer roller 44, and fixing unit 46 to the paper output tray 50. In addition, when performing double-sided printing on the paper, a second paper transport path L2 is formed for returning the paper after single-sided printing is completed and the paper has passed through the fixing unit 46 to the first paper transport path L1 upstream of the transfer roller 44 in the paper transport direction. In the first paper transport path L1 and the second paper transport path L2, a plurality of transport rollers 64 are appropriately provided to provide auxiliary propulsion force to the paper.

Next, the configuration of the developing device 34 will be described with reference to Figures 2 to 5. As shown in Figures 2 and 3, the developing device 34 includes a first transport member 72, a second transport member (agitation transport member) 74, a developing roller 76, and a doctor blade (layer thickness regulating member) 78, which are held together in a predetermined arrangement by the developing housing 70.

Specifically, a developer tank 80 is formed inside the developer housing 70. The developer tank 80 is formed in a generally elongated box shape extending in the front-rear direction. Inside the developer tank 80, a first transport member 72 and a second transport member 74 are provided so that their respective rotation axes are parallel, and a developer mixed with toner and carrier is stored. However, the developer is not shown. In addition, a rectangular plate-shaped boundary wall 82 is provided between the first transport member 72 and the second transport member 74 in the developer tank 80 to separate the internal space of the developer tank 80. As a result, a first transport path 84 through which the developer is transported by the first transport member 72 is formed in the developer tank 80, and a second transport path 86 through which the developer is transported by the second transport member 74 is formed. The first transport path 84 and the second transport path 86 are connected at both ends of the developer tank 80 in the longitudinal direction.

The first transport member 72 and the second transport member 74 are auger screws with helical blades formed on the outer circumferential surface of a cylindrical rotating shaft (screw shaft). The first transport member 72 and the second transport member 74 circulate the developer in a predetermined direction in the developer tank 80 by transporting the developer while stirring it. The second transport member 74 is also a member for transporting (pumping up) the developer in the developer tank 80 toward the developing roller 76. In other words, the second transport member 74 is an agitating transport member that pumps up the developer to the developing roller 76.

In addition, inside the developing tank 80, a developing roller 76 is provided diagonally above the second transport member 74. The developing roller 76 functions as a developer carrier and is disposed in a position facing the photosensitive drum 36 (see FIG. 1). The developing roller 76 includes a magnet roller 76a and a developing sleeve 76b.

The magnet roller 76a is a multi-pole magnetized magnet roller in which multiple bar magnets are arranged in a radial pattern, and is supported by the development housing 70 so that it cannot rotate. In this embodiment, the magnet roller 76a has five magnetic poles, namely, magnetic pole N1, magnetic pole S1, magnetic pole N2, magnetic pole N3, and magnetic pole S2. Here, magnetic pole S1 is also called the regulating pole, and is positioned opposite the doctor blade 78. Magnetic pole N2 is also called the pumping pole, and is positioned opposite the second transport member 74.

The developing sleeve 76b is a cylindrical member made of a non-magnetic material and is fitted onto the magnet roller 76a. The developing sleeve 76b is rotatably supported by the developing housing 70 and rotated by a driving means (not shown).

Such a developing roller 76 carries on its surface the developer in the developing tank 80 that has been pumped up by the second transport member 74, and supplies the toner contained in the carried developer to the surface of the photosensitive drum 36.

In addition, a doctor blade 78 is fixed inside the development housing 70 so as to have a predetermined gap with respect to the surface of the development roller 76. The doctor blade 78 is a plate-shaped member that extends in the axial direction of the development roller 76. This doctor blade 78 regulates the amount of developer carried by the development roller 76 to a predetermined amount.

In this first embodiment, an inclined wall 80a is provided on the upper part of the right side wall of the developer tank 80 below the developing roller 76, and an inclined surface 90 is formed on the inner surface of the inclined wall 80a, which extends diagonally upward to the right toward the doctor blade 78. The inclined surface 90 forms a path for drawing up the developer from the second transport member 74 to the developing roller 76.

Referring to Figures 3 to 5, the lower end of this inclined surface 90 is located below the upper end of the second transport member 74. Furthermore, a suppression portion 90a that rises in a step shape in a substantially vertical direction is formed in the central portion of the inclined surface 90 in the direction in which the developer is pumped up. That is, the inclined surface 90 has, in the direction in which the developer is pumped up, the suppression portion 90a formed in the central portion, a first inclined portion 90b formed on the upstream side of the suppression portion 90a, and a second inclined portion 90c formed on the downstream side of the suppression portion 90a so as to face the developing roller 76.

In this type of developing device 34, the path for pumping the developer from the second transport member 74 to the developing roller 76 is formed by the inclined surface 90, and since the lower end of this inclined surface 90 is located lower than the upper end of the second transport member 74, the amount of developer pumped up by the second transport member 74 that collides with the right side wall of the developing tank 80 is reduced, making it difficult for the developer to stagnate. In addition, since the inclined surface 90 has a suppression portion 90a, the developer picked up by the second transport member 74 is prevented from directly reaching the S1 pole (regulation pole) of the developing roller 76, and the developer is appropriately guided to the N2 pole (pumping pole) of the developing roller 76 by this suppression portion 90a. The developer properly pumped up by the N2 pole of the developing roller 76 has a sufficiently uniform density before passing through the S1 pole, so that no defects in the output image are generated.

Here, it is preferable that the upper end (downstream end in the pumping direction) of the suppression portion 90a of the inclined surface 90 is located above the upper end of the second transport member 74. If the upper end of the suppression portion 90a is at a height position below the upper end of the second transport member 74, a flow of developer will occur that flows toward the S1 pole without passing through the suppression portion 90a, whereas if the upper end of the suppression portion 90a is at a height position above the upper end of the second transport member 74, the developer transported by the centrifugal force of the second transport member 74 will smoothly reach the N2 pole of the developing roller 76, and the transport of the developer will be stabilized. However, if the upper end of the suppression portion 90a is too close to the developing roller 76, a narrow portion will be generated in the gap (gap) between the second inclined portion 90c and the outer peripheral surface of the developing roller 76 (developing sleeve 76b), which may hinder the transport of the developer, so the height position of the upper end of the suppression portion 90a is set within a range in which the gap between the second inclined portion 90c and the outer peripheral surface of the developing roller 76 maintains a predetermined size.

Furthermore, it is preferable that the lower end of the inclined surface 90 (i.e., the upstream end of the first inclined portion 90b) is located on the doctor blade 78 side of the central axis of the developing roller 76 in the left-right direction, which is the width direction of the developing device 34. This is because it allows the developing device 34 to be made smaller in the width direction. Also, it is possible to shorten the length of the inclined surface 90 in the developer transport direction, i.e., the movement distance of the developer transported along the inclined surface 90, and it is possible to reduce the effect of changes in the rotation speed of the second transport member 74 on the developer transport performance, and developer transport is stabilized.

Furthermore, it is preferable that the inclination angle θb of the first inclined portion 90b with respect to the horizontal direction is greater than the inclination angle θc of the second inclined portion 90c with respect to the horizontal direction. This is because the developer wound up by the second transport member 74 is more appropriately prevented from directly reaching the S1 pole of the developing roller 76.

Furthermore, the inclination angle θb of the first inclined portion 90b with respect to the horizontal direction is preferably 60 degrees or more and 80 degrees or less, the inclination angle θa of the suppression portion 90a with respect to the horizontal direction is preferably 80 degrees or more and 90 degrees or less, and the inclination angle θc of the second inclined portion 90c with respect to the horizontal direction is preferably 35 degrees or more and 55 degrees or less. In addition, the length Lc of the second inclined portion 90c in the pumping direction is preferably 5.0 mm or more and 7.0 mm or less. By setting the dimensions of each portion of the inclined surface 90 within these ranges, the amount of developer transported is stabilized, and the density of the developer reaching the S1 pole of the developing roller 76 is more appropriately uniformed.

That is, when the inclination angle θb is less than 60 degrees, the flow of the developer along the inclined surface 90 moves away from the N2 pole of the developing roller 76 and approaches the S1 pole, which may lead to problems in pumping from the S1 pole. On the other hand, when the inclination angle θb is greater than 80 degrees, it may lead to the stagnation of the developer. Also, when the inclination angle θa is less than 80 degrees, the developer transport suppression effect of the suppression section 90a may not be fully exerted. On the other hand, when the inclination angle θa is greater than 90 degrees, the developer transport suppression effect of the suppression section 90a becomes too large, and the flow of the developer may be stagnated, which may affect the pumping performance. Furthermore, when the inclination angle θc is less than 30 degrees, the gap between the S1 pole of the developing roller 76 and the second inclined section 90c widens, and the transport resistance of the developer decreases, making it easier for the developer to flow to the S1 pole of the developing roller 76. On the other hand, if the inclination angle θc is greater than 55 degrees, the height dimension and length of the suppression portion 90a (i.e., the step between the first inclined portion 90b and the second inclined portion 90c) will be small, and the effect of suppressing the flow of developer transported to the S1 pole of the developing roller 76 may not be fully exerted. Furthermore, if the length Lc is less than 5.0 mm, the effect of suppressing the transport of developer may not be fully exerted, and if the length Lc is greater than 7.0 mm, it may lead to obstruction of the transport of developer.

In this first embodiment, the inclination angle θb is 70 degrees, the inclination angle θa is 90 degrees, the inclination angle θc is 40 degrees, and the length Lc is 6 mm.

The gap D between the upper end of the second inclined portion 90c and the outer circumferential surface of the developing roller 76 is preferably 1.0 mm or more and 2.0 mm or less. Furthermore, the angle θ between the S1 pole and the N2 pole of the developing roller 76 is preferably 55 degrees or more and 65 degrees or less. By setting the gap D and the angle θ within these ranges, the separation accuracy between the developer transport function from the second transport member 74 to the N2 pole of the developing roller 76 and the developer amount control function by the doctor blade 78 and the S1 pole of the developing roller 76 is improved, and the developer is pumped up and transported more stably.

That is, if the gap D is less than 1.0 mm, the resistance to developer transport in front of the S1 pole (upstream side) of the developing roller 76 increases, which may cause transport problems. On the other hand, if the gap D is greater than 2.0 mm, the developer will tend to flow toward the S1 pole side of the developing roller 76. Also, if the angle θ is less than 55 degrees, the two poles are too close, and the functions of pumping and regulating cannot be fully separated, so some of the developer may be pumped up on the S1 pole side. On the other hand, if the angle θ is greater than 65 degrees, the distance between the developer stirring portion (second transport member 74) and the regulating portion (doctor blade 78) increases, and the developer travels a long distance. In this first embodiment, the gap D is 1.7 mm, and the angle θ is 60 degrees.

As described above, according to the first embodiment, the lower end of the inclined surface 90 is positioned below the upper end of the second transport member 74, and a suppression portion 90a that rises in a substantially vertical direction is formed in the central portion of the inclined surface 90 in the direction in which the developer is pumped up. This makes it possible to properly guide the developer to the N2 pole of the developing roller 76 while suppressing the accumulation of the developer in the developing tank 80. In other words, the pumping of the developer is stabilized, and the developer can be properly pumped up from the second transport member 74 to the developing roller 76. The developer properly pumped up by the N2 pole of the developing roller 76 has a sufficiently uniform density before passing through the S1 pole, preventing poor output images.

[Second embodiment]
Next, a developing device 34 provided in an image forming apparatus 10 according to a second embodiment of the present invention will be described with reference to FIG. 6. In this second embodiment, the configuration of an inclined surface 90 provided in a developing tank 80 differs from that of the first embodiment described above. Since the other parts are similar, the same reference numbers are used for parts common to the first embodiment described above, and duplicated descriptions will be omitted or simplified. The same applies to the third and fourth embodiments described below.

In the second embodiment, the second inclined portion 90c of the inclined surface 90 is formed as a curved surface concave downward. In this case, it is preferable that the second inclined portion 90c extends along the outer peripheral surface of the developing roller 76, i.e., is concentric with the outer peripheral surface of the developing roller 76, and is formed so that the radius of curvature is slightly larger than that of the outer peripheral surface of the developing roller 76. In this second embodiment, the inclination angle θb is 70 degrees, the inclination angle θa is 90 degrees, the inclination angle θc is 40 degrees, and the length Lc is 6 mm.

In this second embodiment, the second inclined portion 90c is formed in a curved shape that is concave downward, so that the distance between the developing roller 76 and the developing tank 80 in the path for drawing up the developer near the doctor blade 78 is constant, and the transport speed and density of the developer are more stable.

[Third Example]
7, a developing device 34 provided in an image forming apparatus 10 according to a third embodiment of the present invention will be described. In this third embodiment, the configuration of an inclined surface 90 provided in a developing tank 80 is different from that in the first embodiment described above.

In the third embodiment, the connecting portion 90d between the suppression portion 90a and the second inclined portion 90c of the inclined surface 90 is formed into a curved surface that is convex upward. In this third embodiment, the inclination angle θb is 70 degrees, the inclination angle θa is 80 degrees, the inclination angle θc is 45 degrees, and the length Lc is 6 mm.

In this third embodiment, the connecting portion 90d between the suppression portion 90a and the second inclined portion 90c is formed into a smooth curved surface, which reduces the flow resistance of the developer slightly and makes the flow of the developer more stable from pumping to transport to the doctor blade 78.

[Fourth embodiment]
Next, a developing device 34 provided in an image forming apparatus 10 according to a fourth embodiment of the present invention will be described with reference to Fig. 8. In this fourth embodiment, the configuration of an inclined surface 90 provided in a developing tank 80 is different from that in the first embodiment described above.

In the fourth embodiment, the shape of the suppression portion 90a of the inclined surface 90 is changed depending on the position in the longitudinal direction (i.e., the axial direction of the second transport member 74), and the developer pumping suppression ability of the suppression portion 90a is set to be greater in the center than at both ends in the axial direction of the second transport member 74. Specifically, the inclination angle θa of the suppression portion 90a with respect to the horizontal direction is set to be greater in the center than at both ends in the axial direction of the second transport member 74. This is because the front end and rear end of the developer tank 80 are the turning back portions of the developer, which reduces the circulation speed of the developer and makes it easier for the developer to stagnate, so that the developer is made to move more easily toward the developing roller 76 at the front end and rear end of the developer tank 80. In this fourth embodiment, as shown in FIG. 8(A), the central portion of the inclined surface 90 in the axial direction of the second transport member 74 has an inclination angle θb of 70 degrees, an inclination angle θa of 90 degrees, an inclination angle θc of 55 degrees, and a length Lc of 6 mm. On the other hand, as shown in FIG. 8(B), both ends (front end and rear end) of the inclined surface 90 in the axial direction of the second conveying member 74 have an inclination angle θb of 70 degrees, an inclination angle θa of 80 degrees, an inclination angle θc of 35 degrees, and a length Lc of 5 mm.

In order to increase the developer pumping prevention capacity of the suppression section 90a in the center compared to the both ends, instead of or in addition to making the inclination angle θa of the center of the suppression section 90a larger than that of the both ends, it is also possible to make the upper end position of the center of the suppression section 90a higher than the upper end positions of the both ends, or to make the inclination angle θc of the center of the second inclined section 90c larger than that of the both ends.

In the fourth embodiment, the inclined surface 90 is formed so that the developer pumping prevention capability of the suppression portion 90a is greater in the center than at both ends, so that the developer can be more appropriately pumped from the second transport member 74 to the developing roller 76.

In the above-described embodiments, the image forming device 10 is exemplified as a multifunction device that combines a copier, a facsimile, a printer, etc., but the image forming device 10 may be any one of a copier, a facsimile, a printer, etc., or a multifunction device that combines at least two of these. The image forming device 10 may also be a monochrome device.

The internal configuration of the developing device 34 can also be modified as appropriate. For example, the first transport member 72, the second transport member 74, and the developing roller 76 may be arranged in a left-right reversed manner compared to the first embodiment described above. In this case, the inclined surface 90 is formed so as to extend diagonally upward to the left below the developing roller 76.

Furthermore, the specific numerical values and part shapes given above are merely examples and can be changed as necessary according to the product specifications, etc.

REFERENCE SIGNS LIST 10 image forming apparatus 12 apparatus main body 14 image reading apparatus 30 image forming section 34 developing apparatus 36 photosensitive drum 70 developing housing 72 first transport member 74 second transport member (agitation transport member)
76 ... developing roller 78 ... doctor blade (layer thickness regulating member)
80: developing tank 90: inclined surface 90a: suppressing portion 90b: first inclined portion 90c: second inclined portion

Claims (8)

a developer tank for containing a developer;
A developing roller provided in the developing tank;
a stirring and transporting member that is provided in the developer tank at a position diagonally below the developing roller, for transporting the developer in the developer tank in the axial direction while stirring the developer, and for pumping the developer up to the developing roller; and a layer thickness regulating member that regulates a layer thickness of the developer carried on the outer peripheral surface of the developing roller,
the developing roller has a regulating pole provided at a position facing the layer thickness regulating member, and a drawing-up pole provided at a position facing the stirring and conveying member, for drawing the developer in the developing tank to the developing roller,
the developer tank is provided below the developing roller so as to extend obliquely upward, and has an inclined surface that forms a path for drawing up the developer from the agitating and conveying member to the developing roller;
a lower end of the inclined surface is located below an upper end of the agitating and conveying member,
a suppression portion that rises in a substantially vertical direction is formed at a central portion of the inclined surface in a direction in which the developer is scooped up,
the inclined surface has the suppression portion, a first inclined portion formed on an upstream side of the suppression portion in the pumping direction, and a second inclined portion formed on a downstream side of the suppression portion in the pumping direction,
an inclination angle of the first inclined portion with respect to the horizontal direction is larger than an inclination angle of the second inclined portion with respect to the horizontal direction;
an inclination angle of the second inclined portion with respect to the horizontal direction is smaller than an inclination angle of the first inclined portion with respect to the horizontal direction over the entire length in the pumping direction;
A developing device , wherein the developer pumping-up suppression capacity of the suppression section is greater at a center portion than at both ends of the suppression section in an axial direction of the agitation/transport member . The developing device according to claim 1, wherein the upper end of the suppression portion is located above the upper end of the agitation conveying member. The developing device according to claim 1 or 2, wherein the lower end of the inclined surface is located closer to the layer thickness regulating member than the central axis of the developing roller in the width direction of the developing device. The inclination angle of the first inclined portion with respect to the horizontal direction is equal to or greater than 60 degrees and equal to or less than 80 degrees,
The inclination angle of the suppression portion with respect to the horizontal direction is equal to or greater than 80 degrees and equal to or less than 90 degrees,
The inclination angle of the second inclined portion with respect to the horizontal direction is equal to or greater than 35 degrees and equal to or less than 55 degrees,
4. The developing device according to claim 1, wherein the length of the second inclined portion in the drawing direction is not less than 5.0 mm and not more than 7.0 mm. a gap between an upper end of the second inclined portion and the developing roller is 1.0 mm or more and 2.0 mm or less;
5. The developing device according to claim 1, wherein an angle between the draw-up pole and the regulating pole is equal to or greater than 55 degrees and equal to or less than 65 degrees. The developing device according to any one of claims 1 to 5, wherein the second inclined portion is formed into a curved surface that is concave downward. The developing device according to any one of claims 1 to 5, wherein the connecting portion between the suppressing portion and the second inclined portion is formed into an upwardly convex curved surface. An image forming apparatus comprising the developing device according to claim 1 .

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