JP3888405B2 - Developing device and image forming apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device that visualizes an electrostatic latent image on a latent image carrier using a developer and an image forming apparatus using the same, and more particularly, development using a non-magnetic one-component developer. The present invention relates to an apparatus and an image forming apparatus using the same.
[0002]
[Prior art]
As a conventional non-magnetic one-component developing device, since it is impossible to carry and transport developer (toner) by magnetic force, a developing housing that opens to face a latent image carrier such as a photosensitive drum , A developing roll arranged to face the opening of the developing housing and carrying and transporting a non-magnetic one-component developer, a developer supply roll that is pressed against the developing roll and supplies the developer, and a developing roll There are already provided ones that are provided with a layer-forming blade that forms a layer of the supplied developer to a predetermined thickness and is triboelectrically charged (for example, Japanese Patent Laid-Open Nos. 5-61245, 7-128977, and 6-6-1). No. 43742, JP-A-6-3966).
[0003]
Further, as the layer forming blade, a so-called wiper method in which the fixed end to the developing housing is located upstream in the rotation direction of the developing roll and the free end is pressed against the developing roll, or a fixed end to the developing housing is used. A so-called doctor method is already known, in which a free end is positioned in pressure contact with the developing roll and is located downstream in the rotation direction of the developing roll.
[0004]
[Problems to be solved by the invention]
By the way, the doctor type layer forming blade can provide a constant pressure with less pressure than the (1) wiper type. (2) In order to adjust the developer layer thickness, the blade protrusion amount ( The distance from the contact point of the blade to the developing roll to the tip) can be used as a parameter, and it is superior to the wiper method in that the developer layer thickness can be controlled more easily than the wiper method using only the contact pressure as a parameter. .
[0005]
Therefore, when using a doctor type layer forming blade, as shown in FIG. 6A, the free length L of the layer forming blade 200 (for example, a mode in which the soft elastic member 202 is fixed to the tip of the leaf spring 201) is set. In order to ensure sufficient capacity, the layer forming blade 200 must be disposed at a position that does not interfere with the developer supply roll 205 and the developer agitator 206 disposed obliquely below the developing roll 204. Due to the above restrictions, the vertical dimension of the developing housing 203 increases, and the developing device itself becomes large.
On the other hand, if priority is given to downsizing the developing device, the free length L of the layer forming blade 200 cannot be sufficiently secured as shown in FIG.
In fact, with a well-known general layout, when a doctor-type layer forming blade is used in an ultra-thin developing device having a thickness of 40 mm or less, it is quite difficult to introduce a layer forming blade having a sufficient free length. It is.
[0006]
Further, if the developing device is to be miniaturized, as shown in FIG. 6B, the space between the layer forming blade 200 and the developer supply roll 205 becomes narrow, and the space for circulating the developer is very small. Thus, a technical problem has been found that it is difficult to keep the developer circulation well.
[0007]
The present invention has been made in order to solve the above technical problem, and achieves both a reduction in the thickness of the apparatus itself and the securing of the free length of a so-called doctor-type layer forming blade, and the circulation of the developer. The present invention provides a developing device and an image forming apparatus using the same.
[0008]
[Means for Solving the Problems]
That is, according to the present invention, as shown in FIG. 1, a developing housing 3 that opens to face a latent image carrier 1 on which an electrostatic latent image is formed, and an opening of the developing housing 3 are disposed. And a developer roll 4 that carries and conveys a non-magnetic one-component developer, a developer supply member 5 that is pressed against the developer roll 4 to supply the developer, and a fixed end to the development housing 3 is the developer roll 4. And a layer forming member 6 whose free end is disposed in pressure contact with the developing roll 4 to form a developer layer, and the developer supply member 5 is a horizontal line passing through the central axis of the developing roll 4. The whole is disposed in the upstream area in the rotation direction of the developing roll 4 with the vertical line v passing through the lowest point and the central axis of the developing roll 4 in contact with the lower peripheral surface located below h. The layer forming member 6 is from the horizontal line h of the developing roll 4. It is characterized in that and are disposed on the peripheral surface of the rotating direction of the downstream side of the vertical line v in the way.
[0009]
In such technical means, the present embodiment, since the developer supplying member 5 is disposed in the developer recovery downward of the current image roll 4, will be recovered direction of the developer coincides with the direction of gravity, Spilling of developer is prevented .
Further, when this type of developing device 2 is incorporated in an image forming apparatus, the latent image carrier 1 is arranged so as to face the upper peripheral surface located above a horizontal line h passing through the central axis of the developing roll 4. You can do it.
[0010]
Furthermore, in a so-called tandem type image forming apparatus in which a plurality of image forming units in which this type of developing device 2 is incorporated are arranged in the vertical direction, for example, recording is carried and circulated along the arrangement direction of the image forming units. A recording transport body 8 (shown by phantom lines in FIG. 1) such as a material transport belt and an intermediate transfer belt is provided, and the recording transport body 8 and the latent image carrier 1 of each image forming unit, the developing roll 4 and the developer. A mode in which the space 9 is formed between the supply member 5 and the supply member 5 is preferable.
In this aspect, since the scattered developer is trapped in the space portion 9, the developer used in the upper image forming unit is scattered and dropped on the lower image forming unit. Such a situation is preferable because it is effectively prevented.
[0011]
Next, the operation of the technical means described above will be described.
In FIG. 1, a developer supply member 5 and a layer forming member 6 are disposed in pressure contact on a lower peripheral surface located below a horizontal line h passing through the central axis of the developing roll 4.
At this time, if the lower peripheral surface of the developing roll 4 is effectively used, the developer supplying member 5 and the layer forming member 6 can be arranged separately.
For example, the developer supply member 5 is disposed in pressure contact on the upstream side in the rotation direction of the developing roll 4 with the vertical line v passing through the lowest point and the central axis of the developing roll 4, and the layer forming member 6 on the downstream side. Is a mode of pressure-contact arrangement.
Therefore, by arranging the layer forming member 6 obliquely, the vertical dimension H of the developing housing 3 is suppressed to a short size, and the free length L of the layer forming member 6 is secured sufficiently large.
Further, a wide space for the developer to circulate is secured between the developer supply member 5 and the layer forming member 6.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows an embodiment of a developing device to which the present invention is applied.
In FIG. 1, a developing device 20 adopts a non-magnetic one-component developing system, and includes a developing housing 21 that opens to face a latent image carrier 11 such as a photosensitive drum, and an opening portion of the developing housing 21. A developing roll 22 disposed facing 211, a developer supply roll 23 that is pressed against the developing roll 22 to supply a non-magnetic one-component developer (toner), and is pressed against the developing roll 22. The so-called doctor-type layer forming blade 24 for forming the developer on the developing roll 22 to a predetermined layer thickness, and the developer accumulated in the developing housing 21 are agitated to convey the developer forward. Also, an agitator 25 that conveys excess developer to the rear, and a developer that is disposed at an intermediate position between the agitator 25 and the developing roll 22 and that is stirred and conveyed by the agitator 25 is supplied to the developer supply roller. Transported to the Le 23 side, whereas, and a conveying member 26 for conveying the developer recovered by the developer supplying roller 23 to the agitator 25 side.
[0013]
In the present embodiment, the developer supply roll 23 has a surface covered with an elastic layer, and rotates in a direction opposite to the rotation direction of the development roll 22 at a portion facing the development roll 22.
As shown in FIG. 3, the developer supply roll 23 is on the lower peripheral surface located below the horizontal line h passing through the central axis of the development roll 22 and the lowest point of the development roll 22. In addition, the developing roller 22 is disposed in pressure contact with the vertical line v passing through the central axis on the upstream side in the rotation direction.
[0014]
The layer forming blade 24 is made of, for example, a leaf spring. The base end of the layer forming blade 24 is fixed to the upper edge of the opening 211 of the developing housing 21 via holders 241 and 242 to form a layer. The front end portion (free end portion) of the blade 24 is on the lower peripheral surface located below the horizontal line h passing through the central axis of the developing roll 22 and is perpendicular to the lowest point and the central axis of the developing roll 22. The developing roller 22 is disposed in pressure contact with the line v on the downstream side in the rotation direction.
In the present embodiment, the layer forming blade 24 is inclined at a predetermined inclination angle θ (for example, 35 °) with respect to the horizontal plane so as to ensure a sufficient free length L.
[0015]
Further, in this embodiment, a span s between the contact portion of the developer supply roll 23 and the contact portion of the layer forming blade 24 with respect to the developing roll 22 is secured to some extent.
For example, in a mode in which the diameter dimension of the developing roll 22 is φ10 and the diameter dimension of the developer supply roll 23 is φ10, the span s is set to about 3 to 5 mm.
[0016]
Furthermore, as shown in FIG. 3 , the developing device 20 according to the present embodiment is on an upper peripheral surface located above a horizontal line h passing through the central axis of the developing roll 22, and on the developing roll 22. A portion located on the upstream side in the rotation direction of the developing roll 22 across the vertical line v passing through the lowest point and the central axis is disposed to face the latent image carrier 11, and this facing portion functions as the developing region m. It is like that.
A developing bias (not shown) is applied to the developing roll 22 at a predetermined timing.
[0017]
Therefore, according to the developing device according to the present embodiment, for example, even when the vertical dimension H of the developing housing 21 is about 40 mm, it is confirmed that the free length L of the layer forming blade 24 is sufficiently secured. .
[0018]
Further, although the layout of the developer supply roll 23 is greatly changed compared to the conventional one, since a space (based on the span s) between the developer supply roll 23 and the layer forming blade 24 is widely secured, The space where the developer can circulate is widened, and accordingly, the state where the same developer remains around the layer forming blade 24 is avoided, and the developer supply operation by the developer supply roll 23 is stabilized.
[0019]
Further, in the present embodiment, the residual developer on the developing roll 22 is peeled off at the contact portion with the developer supplying roll 23 and returned to the developing housing 21 through the peripheral surface of the developer supplying roll 23.
At this time, the collecting direction of the residual developer on the developing roll 22 is naturally moved downward along the direction of gravity, so that the developer is removed from the developing housing 21 during the collecting operation of the developer. The situation of spilling is effectively avoided.
[0020]
Embodiment 2
FIG. 4 shows an embodiment of an image forming apparatus to which the present invention is applied.
In the figure, the image forming apparatus is a so-called tandem type color image forming apparatus, and an image forming unit 122 (specifically, black, yellow, magenta, and cyan in this embodiment) is provided in a main body housing 121. 122a to 122d) are arranged in the vertical direction, and a paper feed cassette 123 for storing paper for supply is disposed below the paper feed cassette 123, and a paper feed cassette 123 is provided at a position corresponding to each image forming unit 122. A sheet conveyance path 124 serving as a conveyance path for a sheet (not shown) from the sheet is arranged in the vertical direction.
[0021]
In the present embodiment, the image forming unit 122 (122a to 122d) forms toner images for black, yellow, magenta, and cyan in order from the upstream side of the paper transport path 124. A cartridge 30 and an exposure unit 40 that emits light based on an image signal are provided.
Here, the photoconductor cartridge 30 includes, for example, a photoconductor drum 31, a charging roll 32 that precharges the photoconductor drum 31, and a static image formed by exposure on the charged photoconductor drum 31 by the exposure unit 40. The developing device 20 that develops the electrostatic latent image with corresponding color toner (for example, negative polarity in this embodiment) and the cleaner 34 that removes the residual toner on the photosensitive drum 31 are integrally formed into a cartridge. .
[0022]
Further, in the present embodiment, as shown in FIG. 4, a conveyance belt 80 that circulates along the paper conveyance path 124 is disposed at a position corresponding to each photosensitive drum 31 of each image forming unit 122. Yes.
The conveyor belt 80 is made of a belt material (rubber or resin) that can electrostatically adsorb paper (not shown), and is stretched between a pair of metal tension rolls 81 and 82. In the embodiment, the upper tension roll 82 is a drive roll, and the lower tension roll 81 is a driven roll.
[0023]
Furthermore, a transfer roll 50 is disposed on the back side of the conveyance belt 80 corresponding to the photosensitive drum 31 of each image forming unit 122, and the transfer roll 50 and the photosensitive drum 31 are arranged on the conveyance belt 80. The sheet is held in the nip. A transfer bias power source (not shown) is connected to the transfer roll 50 so that a predetermined transfer bias is applied at an appropriate timing.
[0024]
Further, in the present embodiment, the paper feed cassette 123 is provided with a paper feed roll 61 that sends out paper at a predetermined timing, and between the paper feed roll 61 and the transfer portion of the most upstream image forming unit 122a. A paper feed path 62 for paper delivery is provided in the paper transport path 124 located.
Further, a fixing device 64 is provided in the paper conveyance path 124 located on the downstream side of the most downstream image forming unit 122d, and a discharge roll 66 for discharging paper is provided on the downstream side of the fixing device 64. The discharged paper is stored in a storage tray 67 formed at the top of 121. In FIG. 4, reference numeral 65 denotes a paper guide for guiding the paper sent from the conveyance belt 80 to the fixing device 64.
[0025]
The developing device 20 in each image forming unit 122 (122a to 122d) adopts a non-magnetic one-component developing system, and as shown in FIG. 5, a developing housing 21 that opens to face the photosensitive drum 31. A developing roll 22 disposed facing the opening 211 of the developing housing 21, and a developer supply roll 23 that is disposed in pressure contact with the developing roll 22 and supplies a nonmagnetic one-component developer (toner). A so-called doctor-type layer forming blade 24 that is disposed in pressure contact with the developing roll 22 to form the developer on the developing roll 22 with a predetermined layer thickness, and is disposed on the back side of the developing housing 21 to store the accumulated developer. The agitator 25 that agitates and conveys the developer forward, and conveys the excess developer rearward, and an intermediate position between the agitator 25 and the developing roll 22 are disposed. Embodiment 1 includes a transport member 26 that transports the developer stirred and transported in 25 to the developer supply roll 23 side, and transports the developer collected by the developer supply roll 23 to the agitator 25 side. It is configured in the same way.
[0026]
In particular, in the present embodiment, the developing roller 22 has a vertical line v (see FIG. 3) across the vertical line v (see FIG. 3) on the upstream circumferential surface in the rotation direction of the developing roller 22, and the horizontal line h of the developing roller 22. The photosensitive drum 31 is disposed opposite to the circumferential surface on the upstream side in the rotation direction of the developing roller 22 (see FIG. 3), and the developer supply roller 23 is disposed in pressure contact with the circumferential surface on the downstream side in the rotation direction of the developing roller 22. ing.
Therefore, a space 100 is formed between the conveyance belt 80 and the photosensitive drum 31 of each image forming unit 122, the developing roll 22 of the developing device 20, and the developer supply roll 23.
[0027]
Therefore, according to the present embodiment, the sheet sent out from the sheet feeding cassette 123 is conveyed while being electrostatically attracted to the conveying belt 80, and sequentially passes through the transfer portions of the image forming units 122 (122a to 122d). Then, the color component toner images on the photosensitive drum 31 are sequentially transferred onto the paper by the transfer electric field by the transfer roll 50. Thereafter, when the leading end of the paper enters the fixing device 64 and finishes passing, the paper on which the unfixed image is fixed is discharged to the storage tray 67 through the discharge roll 66.
[0028]
In such an image forming process, in the developing device 20 of each image forming unit 122, there is a concern that the developer may scatter during the recovery operation of the residual developer from the developing roll 22, but even if the developer scatters, The scattered developer is trapped in the space 100.
For this reason, a situation where the developer used in the upper image forming unit 122U (for example, 122b) is scattered and dropped in the lower image forming unit 122L (for example, 122a) does not occur.
[0029]
In the image forming apparatus according to the present embodiment, since the ultra-thin developing device 20 is used, the vertical dimension of the device itself is set to be very short.
[0030]
【The invention's effect】
As described above, according to the developing device according to the present invention, the device itself is thinned by devising the layout with respect to the developing roll of the layer forming member and the developer supplying member, which are components of the non-magnetic one-component developing device. In addition to ensuring the free length of the so-called doctor-type layer forming member, it is also possible to maintain good developer circulation.
In addition, according to the image forming apparatus of the present invention, it is possible to maintain a good developing performance such as a layer forming performance with a thin developing device, so that the image forming performance is improved while downsizing the apparatus. Can keep.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of a developing device and an image forming apparatus using the developing device according to the invention.
FIG. 2 is an explanatory diagram showing an embodiment (Embodiment 1) of a developing device to which the invention is applied.
FIG. 3 is an explanatory diagram showing a positional relationship of main parts according to the first embodiment.
FIG. 4 is an explanatory diagram showing an embodiment (Embodiment 2) of an image forming apparatus to which the invention is applied.
5 is an explanatory diagram showing details of an image forming unit according to Embodiment 2. FIG.
6A is an explanatory diagram showing an example of a conventional non-magnetic one-component developing device, and FIG. 6B is an explanatory diagram showing an example in which the developing device of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Latent image carrier, 2 ... Developing apparatus, 3 ... Developing housing, 4 ... Developing roll, 5 ... Developer supply member, 6 ... Layer forming member, 8 ... Recording conveyance body, 9 ... Space part

Claims (3)

A developing housing that opens to face a latent image carrier on which an electrostatic latent image is formed;
A developing roll disposed facing the opening of the developing housing and carrying and transporting a non-magnetic one-component developer;
A developer supply member that is disposed in pressure contact with the developing roll and supplies the developer;
A fixed end portion to the developing housing is positioned on the downstream side in the rotation direction of the developing roll, and a free end portion is arranged in pressure contact with the developing roll to form a layer of developer,
The developer supply member is in contact with the lower peripheral surface located below the horizontal line passing through the central axis of the developing roll, and on the upstream side in the rotation direction of the developing roll across the lowest line of the developing roll and the vertical line passing through the central axis 2. A developing apparatus according to claim 1, wherein the entire layer is disposed in the region, and the layer forming member is disposed on the peripheral surface of the developing roll below the horizontal line and downstream of the vertical line in the rotational direction . A latent image carrier on which an electrostatic latent image is formed, and the developing device according to claim 1,
An image forming apparatus, wherein a latent image carrier is disposed oppositely on an upper peripheral surface located above a horizontal line passing through a central axis of the developing roll. A latent image carrier on which an electrostatic latent image is formed, and the developing device according to claim 1,
A plurality of image forming units in which a latent image carrier is opposed to each other on an upper peripheral surface located above a horizontal line passing through the central axis of the developing roll are arranged in a vertical direction,
A recording carrier that is circulated and conveyed along the arrangement direction of the image forming units is disposed,
An image forming apparatus, wherein a space is formed between the recording / conveying member and a latent image carrier, a developing roll, and a developer supply member of each image forming unit.

Images