Patent Application
20090232560
This application claims priority under 35 U.S.C. §119 from Japanese Patent Application No. 2008-063454, filed on Mar. 13, 2008. The entire subject matter of the application is incorporated herein by reference.
1. Technical Field
Aspects of the present invention relate to an image formation device and a developer supplying device.
2. Related Art
Developer supplying devices configured to supply developer (e.g., dry type developer (dry type toner)) to a supply target for developer (e.g., a photosensitive drum) have been widely used. Image formation devices employing such a developer supplying device have also been widely used.
Examples of such image formation devices or developer supplying devices are disclosed in Japanese Patent Provisional Publication No. SHO 63-13069A, Japanese Patent Examined Publication HEI 5-31146, Japanese Patent Provisional Publication No. HEI 5-19616A, and Japanese Patent Provisional Publication No. 2008-40045A (hereafter, referred to as JP2008-40045A).
Among the image formation devices or the developer supplying devices disclosed in the above described publications, the developer carrying device disclosed in JP2008-40045A is configured to employ two developer carrying units located to face with respect to each other. More specifically, the device disclosed in JP2008-40045A is provided with a carrying printed circuit board on which a plurality of carrying electrodes are formed and an opposite printed circuit board on which a plurality of opposite electrodes are formed. Between the carrying printed circuit board and the opposite printed circuit board, a predetermined gap is formed. To the plurality of carrying electrodes of the carrying printed circuit board and the plurality of opposite electrodes of the opposite printed circuit board, voltages for carrying the developer in a predetermined developer carrying direction are respectively applied.
To achieve suitable image formation on such image formation devices, it is necessary to carry developer smoothly.
Aspects of the present invention are advantageous in that at least one of a developer supplying device and an image formation device capable of carrying developer smoothly in a predetermined direction with a traveling waveform electric field is provided.
According to an aspect of the invention, there is provided an image formation device, comprising: a developer holding body having a developer holding surface which is parallel with a main scanning direction and which holds thereon developer including a number of minute particles; a developer supplying unit configured to carry charged developer to the developer holding body along a developer carrying path. In this configuration, the developer supplying unit comprises: a plurality of first carrying electrodes arranged along the developer carrying path, the plurality of first electrodes serving to carry the developer in a developer carrying direction intersecting with the main scanning direction when a first carrying voltage formed in a traveling waveform is applied to the plurality of first electrodes; a plurality of second carrying electrodes which are arranged along the developer carrying path to face the plurality of first electrodes while sandwiching the developer carrying path between the plurality of first and second electrodes, the plurality of second electrodes serving to carry the developer in the developer carrying direction when a second carrying voltage formed in a traveling waveform is applied to the plurality of second electrodes; a first carrying voltage applying unit configured to apply the first carrying voltage having a first frequency to the plurality of first carrying electrodes; and a second carrying voltage applying unit configured to apply, to the plurality of second carrying electrodes, the second carrying voltage having a second frequency different from the first frequency of the first carrying voltage.
Since the second carrying voltage of which frequency is different from the frequency of the first carrying voltage is applied to the second electrodes, the developer can be carried smoothly in the developer carrying direction. That is, the developer can be carried smoothly through a traveling waveform electric field.
According to another aspect of the invention, there is provided a developer supplying device, comprising: a plurality of first carrying electrodes arranged along a developer carrying path, the plurality of first electrodes serving to carry the developer in a developer carrying direction intersecting with a main scanning direction when a first carrying voltage formed in a traveling waveform is applied to the plurality of first electrodes; a plurality of second carrying electrodes which are arranged along the developer carrying path to face the plurality of first electrodes while sandwiching the developer carrying path between the plurality of first and second electrodes, the plurality of second electrodes serving to carry the developer in the developer carrying direction when a second carrying voltage formed in a traveling waveform is applied to the plurality of second electrodes; a first carrying voltage applying unit configured to apply the first carrying voltage having a first frequency to the plurality of first carrying electrodes; and a second carrying voltage applying unit configured to apply, to the plurality of second carrying electrodes, the second carrying voltage having a second frequency different from the first frequency of the first carrying voltage.
Since the second carrying voltage of which frequency is different from the frequency of the first carrying voltage is applied to the second electrodes, the developer can be carried smoothly in the developer carrying direction. That is, the developer can be carried smoothly through a traveling waveform electric field.
It is noted that various connections are set forth between elements in the following description. It is noted that these connections in general and unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. Aspects of the invention may be implemented in computer software as programs storable on computer-readable media including but not limited to RAMs, ROMs, flash memory, EEPROMs, CD-media, DVD-media, temporary storage, hard disk drives, floppy drives, permanent storage, and the like.
Hereafter, an embodiment according to the invention will be described with reference to the accompanying drawings.
On a sheet supply tray (not shown) provided in the printer 1, a stack of sheets of paper P is placed. The sheet carrying mechanism 2 is configured to carry a sheet of paper P along a predetermined paper supply path PP.
On an outer circumferential surface of the photosensitive drum 3, a latent image formation surface LS is formed as a holding surface for developer. The latent image formation surface LS is formed as a cylindrical surface positioned to be parallel with a main scanning direction (z-direction in
The photosensitive drum 3 is rotated about a center axis C in a rotational direction indicated by an arrow in
The term “auxiliary scanning direction” means one of directions perpendicular to the main scanning direction. Typically, the auxiliary scanning direction is defined as a direction intersecting with a vertical axis. In other words, the auxiliary scanning direction is defined as a direction parallel with a back-and-forth direction (i.e., x-direction which is perpendicular to a width direction of the sheet of paper and a direction of the height of the stack of sheets of paper).
The charger 4 is placed to face the latent image formation surface LS. The charger 4 is, for example, a corotron type charger or a scorotron type charger. The charger 4 is configured to charge uniformly the latent image formation surface LS.
The scanning unit 5 is configured to emit a laser beam LB modulated based on image data. That is, the scanning unit 5 emits the laser beam LB which has a predetermined wavelength band and is on/off modulated in accordance with presence or absence of an image pixel in the image data.
The scanning unit 5 is configured to converge the laser beam LB at a scanning position SP on the latent image formation surface LS. In this case, the scanning position SP is defined at a downstream side position along a rotation direction of the photosensitive drum 3 (i.e., a rotational direction (clockwise direction) indicated by an arrow in
Further, the scanning unit 5 is configured to form a latent image on the latent image formation surface FS by moving the position at which the laser beam LB is converged on the latent image formation surface LS, in the main scanning direction at a constant speed.
The toner supplying unit 6 is located to face the photosensitive drum 3. The toner supplying unit 6 is configured to supply charged toner (which is dry type developer) to the latent image formation surface LS. The toner supplying unit 6 is described in detail later.
Hereafter, each internal unit in the printer 1 is described.
The sheet carrying mechanism 2 includes a pair of registration rollers 21 and a transfer roller 22. The registration roller 21 is configured to feed the sheet of paper P toward gap between the photosensitive drum 3 and the transfer roller 22 at predetermined timing.
The transfer roller 22 is located to face the photosensitive drum 3 to sandwich the sheet of paper P between the transfer roller 22 and the latent image formation surface LS at a transfer position TP. Further, the transfer roller 22 is rotated in a rotational direction indicated by an arrow in
The transfer roller 22 is connected to a bias power circuit (not shown). That is, between the transfer roller 22 and the photosensitive drum 3, a transfer bias voltage is applied to transfer toner (developer) adhered to the latent image formation surface LS to the sheet of paper P.
The photosensitive layer 32 is provided to cover an outer surface of the drum body 31. The photosensitive layer 32 is formed of a photosensitive layer which has a positive electrostatic property and exhibits an electronic conduction property by exposure to laser light having a predetermined wavelength.
The latent image formation surface LS is formed by the outer circumferential surface of the photosensitive layer 32. That is, the latent image formation surface LS (i.e., the photosensitive layer 32) is configured such that a latent image L1 formed of a positively charged pattern is formed by scanning the laser beam LB at the scanning position SP after the latent image formation surface LS is charged positively and uniformly by the charger 4.
The toner supply unit 6 according to the embodiment is configured to supply charged toner T (developer) to the latent image formation surface LS while carrying the charged toner T along a toner transport path TTP. The toner supply unit 6 is explained in detail below.
The toner supply unit 6 includes a toner box 61 serving as a casing. The toner box 61 is a box-shaped member and is configured to accommodate therein the toner T which is fine-grained dry type developer. In this embodiment, the toner T is single-component nonmagnetic black toner which has a positive electrostatic property.
A top plate 61a of the toner box 61 is located to face the photosensitive drum 3. The top plate 61 a has a plate-like rectangular shape when viewed as a plan view and is located to be parallel with a horizontal plane.
As shown in
The toner through hole 61a1 is located at a position where the top plate 61a is closest to the photosensitive layer 32. In addition, the toner through hole 61a1 is located such that the center of the toner through hole 61a1 substantially coincides with the development position DP.
In the toner box 61, a toner electric field carrying body 62 is provided. The toner electric field carrying body 62 has a toner transport surface TTS. The toner transport surface TTS is a surface facing the toner transport path TTP in the toner electric field carrying body 62, and is configured to be parallel with the main scanning direction.
The toner electric field carrying body 62 is located such that the toner transport surface TTS faces the latent image formation surface LS in a state where the toner transport surface TTS is closest to the latent image formation surface LS at the development position DP. In other words, the toner electric field carrying body 62 is located such that the closest position where the toner transport surface TTS is closest to the latent image formation surface LS coincides with the development position DP.
The toner electric field carrying body 62 is a plate-like member having a predetermined thickness. The toner electric field carrying body 62 is configured to carry the toner T on the toner transport surface TTS in a predetermined toner transport direction TTD. The toner transport direction TTD is parallel with the toner transport surface TTS and is perpendicular to the main scanning direction (z-direction). That is, the toner transport direction TTD is a direction along the auxiliary scanning direction (x-direction).
The toner electric field carrying body 62 has a carrying printed circuit board 63. The carrying printed circuit board 63 is located to face the latent image formation surface LS while sandwiching the top plate 61a of the toner box 61 and the toner through hole 61a1 between the carrying printed board 63 and the latent image formation surface LS. For example, the carrying printed circuit board 63 has a structure like a flexible printed circuit board.
In the toner electric field carrying body 62, a plurality of carrying electrodes 63a are formed. Each of the carrying electrodes 63a is formed to be a linear patter having a longitudinal direction parallel with the main scanning direction (i.e., perpendicular to the auxiliary scanning direction). More specifically, the carrying electrode 63a is formed of copper foil and has the thickness of approximately several tens of micrometers. The carrying electrodes 63a are arranged to be parallel with each other. Further, the carrying electrodes 63a are arranged along the auxiliary scanning direction and are located along the toner transport surface TTS. That is, the carrying electrodes 63a are located near the toner transport surface TTS.
The toner carrying electrodes 63a are formed on a carrying electrode support film 63b. The carrying electrode support film 63b is a flexible film made of insulating synthetic resin, such as polyimide resin.
A carrying electrode coating layer 63c is made of insulating synthetic resin. The carrying electrode coating layer 63c is provided to cover the carrying electrodes 63a and the surface of the carrying electrode support film 63b on which the carrying electrodes 63a are formed.
On the carrying electrode coating layer 63c, a carrying electrode overcoating layer 63d is provided. That is, the carrying electrode coating layer 63c is formed between the carrying electrode overcoating layer 63d and the carrying electrodes 63a. The toner transport surface TTS is formed as a surface of the carrying electrode overcoating layer 63d, and is formed to be a smooth surface on which almost no bumps and dips are formed.
The toner electric field carrying body 62 is further provided with a carrying circuit board support member 64. The carrying circuit board support member 64 is a plate-like member formed of synthetic resin, and is located to support the carrying printed circuit board 63 from the bottom side.
On the inner surface of the top plate 61a of the toner box 61 (i.e., a surface of the top plate 61a facing space in which the toner T is accommodated), an opposite printed circuit board 65 is attached. The opposite printed circuit board 65 is located to face the toner transport surface TTS while sandwiching predetermined space between the opposite printed circuit board 65 and the toner transport surface TTS. The opposite printed circuit board 65 has the same structure as that of the carrying printed circuit board 63.
More specifically, the opposite printed circuit board 65 has an opposite circuit board surface CS which is parallel with the main scanning direction. The opposite circuit board surface CS is located to face the toner transport surface TTS while sandwiching the toner transport path TTP between the opposite circuit board surface CS and the toner transport surface TTS. Along the opposite circuit board surface CS, a plurality of opposite electrodes 65a are provided. That is, the opposite electrodes 65a are located near the opposite circuit board surface CS.
Each of the opposite electrodes 65a is formed to be a linear patter having a longitudinal direction parallel with the main scanning direction (i.e., perpendicular to the auxiliary scanning direction). More specifically, each opposite electrode 65a is formed of copper foil and has the thickness of approximately several tens of micrometers. The opposite electrodes 65a are arranged to be parallel with each other. Further, the opposite electrodes 65a are arranged along the auxiliary scanning direction.
The opposite electrodes 65a are formed on an opposite electrode support film 65b. The opposite electrode support film 65b is a flexible film made of insulating synthetic resin, such as polyimide resin.
An opposite electrode coating layer 65c is made of insulating synthetic resin. The opposite electrode coating layer 65c is provided to cover the opposite electrodes 65a and the surface of the opposite electrode support film 65b on which the opposite electrodes 65a are formed.
On the opposite electrode coating layer 65c, an opposite electrode overcoating layer 65d is provided. That is, the opposite electrode coating layer 65c is formed between the opposite electrode overcoating layer 65d and the opposite electrodes 65a. The opposite circuit board surface CS is formed as a surface of the opposite electrode overcoating layer 65d, and is formed to be a smooth surface on which almost no bumps and dips are formed.
The carrying electrodes 63a are connected to a first carrying voltage applying unit 66 which includes four power circuits VA1, VB1, VC1 and VD1. The carrying electrodes 63a arranged in the auxiliary scanning direction are connected to the first carrying voltage applying unit 66 such that the carrying electrodes 63a are connected to the same power circuit at every four intervals. More specifically, the carrying electrode 63a connected to the power circuit VA1, the carrying electrode 63a connected to the power circuit VB1, the carrying electrode 63a connected to the power circuit VC1 and the carrying electrode 63a connected to the power circuit VD1 are repeatedly arranged in the arrangement of the carrying electrodes 63a.
Each of the power circuits VA1, VB1, VC1 and VD1 outputs substantially the same alternating voltage (carrying voltage). The power circuits VA1, VB1, VC1 and VD1 output the alternating voltages such that each of waveforms of the alternating voltages has a phase shift of 90°. More specifically, in the order of the power circuits VA1, VB1, VC1 and VD1, a next alternating voltage has the phase shift of 90° with respect to a preceding alternating voltage.
Similarly, the opposite electrodes 65a are connected to a second carrying voltage applying unit 67 which includes four power circuits VA2, VB2, VC2 and VD2. The opposite electrodes 65a arranged in the auxiliary scanning direction are connected to the second carrying voltage applying unit 67 such that the opposite electrodes 65a are connected to the same power circuit at every four intervals. More specifically, the opposite electrode 65a connected to the power circuit VA2, the opposite electrode 65a connected to the power circuit VB2, the opposite electrode 65a connected to the power circuit VC2 and the opposite electrode 65a connected to the power circuit VD2 are repeatedly arranged in the arrangement of the opposite electrodes 65a.
Each of the power circuits VA2, VB2, VC2 and VD2 outputs substantially the same alternating voltage (carrying voltage). The power circuits VA2, VB2, VC2 and VD2 output the alternating voltages such that each of waveforms of the alternating voltages has a phase shift of 90°. More specifically, in the order of the power circuits VA2, VB2, VC2 and VD2, a next alternating voltage has the phase shift of 90° with respect to a preceding alternating voltage.
In this embodiment, the first and second carrying voltage applying units 66 and 67 output alternating voltages whose frequencies are different from each other. For example, the frequency of the output voltage of the first carrying voltage applying unit 66 and the frequency of the output voltage of the second carrying voltage applying unit 67 are set such that one of the frequency of the first and second carrying voltage applying units 66 and 67 is not an integral multiple of the frequency of the other of the first and second carrying voltage applying units 66 and 67.
Operations of the printer 1 configured as described above will now be explained. As shown in
While the sheet of paper P is carried to the transfer position TP, an image of the toner T is formed on the latent image formation surface LS as described below.
First, the latent image formation surface LS of the photosensitive drum 3 is charged positively and uniformly by the charger 4.
The latent image formation surface LS is then moved, in the auxiliary scanning direction, to the scanning position SP where the latent image formation surface LS faces the scanning unit 5, through rotations of the photosensitive drum 3 in the direction indicated by an arrow in
As shown in
The latent image LI formed on the latent image formation surface LS moves to the development position DP which faces the toner supply unit 6, through rotations of the photosensitive drum 3 in the rotational direction indicated by an arrow in
In the above described configuration, a voltage having a form of a traveling wave is applied to the plurality of carrying electrodes 63a. Therefore, a predetermined traveling electric field is formed on the toner transport surface TTS. Through the traveling wavelength electric field, the toner T (positive charge) is carried on the toner transport surface TTS in the toner transport direction TTD.
As shown in
That is, at the time t1, an electrostatic force having a direction opposite to the toner carrying direction acts on the positive toner T between the positions A and B. Between the positions A and B and between the positions B and C and, almost no electric static force acts on the toner T along the toner carrying direction. Between the positions C and D, an electrostatic force having a direction equal to the toner carrying direction acts on the positive toner T.
Therefore, at the time t1, the positive toner T gathers between the positions D and A. Similarly, at a time t2 (see
That is, the position where the toner T gathers moves on the toner transport surface TTS in the toner carrying direction with the passage of time. As described above, by applying voltages shown in
As shown in
Near the development position DP, the latent image LI formed on the latent image formation surface LS is developed with the toner T. That is, the toner T adheres to the portion from which the positive charges are removed from the latent image LI, by which an image formed by the toner T (hereafter, frequently referred to as a “toner image”) is held on the latent image formation surface LS.
As shown in
<Calculation Conditions>
Calculation Space Range: 1.6 mm in x-direction, 0.5 mm in y-direction, 0.03 mm in z-direction
(Toner Carrying Surface: y=0, Opposite Circuit Board Surface: y=0.5)
Width of each electrode in x-direction: 0.1 mm
Gap between adjacent electrodes in x-direction: 0.1 mm
Total Number of particles: 2000, Diameter of a toner particle: 10 μm
Charge of a toner particle: 2 fC, Density of a toner particle: 1.3 g/cm3
Applied Voltage: ±300V (sine wave)
Calculation time range: 0.01 seconds
Each of
As described above, in this embodiment, the toner T has the positive electrostatic property. However, typically, toner having an inverse electrostatic property (a negative electrostatic property in this embodiment) is also produced. For this reason,
There is a case where toner having the positive electrostatic property and toner having the negative electrostatic property are mixed at predetermined proportions, for example, as disclosed in Japanese Patent Provisional Publication No. HEI 5-19616A. For this reason,
For reference purposes,
If the toner T has no inverse electrostatic property toner, there is no substantive difference between the case where the frequency of the voltage from the carrying electrodes and the frequency of the voltage from the opposite electrodes are equal to each other and the case where the frequency of the voltage from the carrying electrodes and the frequency of the voltage from the opposite electrodes are different from each other. Rather, in this case, it appears that the case where the frequency of the voltage from the carrying electrodes and the frequency of the voltage from the opposite electrodes are equal to each other exhibits a suitable carrying condition of the toner T.
However, as shown in
By contrast, according to the embodiment, since the frequency of the voltage applied by the carrying electrode is set to be different from the frequency of the voltage applied by the opposite electrode (particularly by setting one of the frequencies not to be an integral multiple of the other of the frequencies), the concentration of the toner T in the y-axis direction can be reduced. Therefore, even if the toner T contains the inverse electrostatic property toner, the toner T can be carried suitably.
As described above according to the embodiment, the toner T can be carried smoothly in the toner transport direction TTD through the traveling waveform electric filed applied by the carrying printed circuit board 63 and the opposite printed circuit board 65.
The carrying performance of the toner T enhances dramatically particularly when positive electrostatic minute particles and negative electrostatic minute particles are mixed intentionally at predetermined proportions, when the positive electrostatic toner and the negative electrostatic toner are mixed intentionally at predetermined proportions, or when the positive electrostatic discharging material and the negative electrostatic discharging material are mixed intentionally at predetermined proportions.
Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible.
In the following, variations of the above described embodiment are explained. It should also be understood that the present invention is not limited to the variations described below, and feature of a part or all of the variations may be combined.
Image formation devices to which the technical feature of the above described embodiment is applied is not limited to the monochrome laser printer. The technical feature of the above described embodiment may be applied to various types of image formation devices employing an electrophotographic process, such as a color laser printer, a monochrome or color facsimile device. In this case, a photosensitive body may have various types of shapes. That is, the photosensitive body may have a shape other than a cylindrical shape. For example, the photosensitive body may have a plate-like shape or a shape of an endless belt.
In the above described embodiment, the photosensitive drum 3 is used as a developer holding body. However, the developer holding body is not limited to such an example (i.e., a photosensitive drum).
For example, an image formation device may adopt, as a developer holding body, a development roller or a development sleeve which is provided with a cylindrical toner holding surface for holding the toner T as a thin film and which is located to face a photosensitive drum.
Alternatively, the technical feature of the above described embodiment may be applied to image formation devices having an imaging scheme (e.g., a toner jet scheme not using a photosensitive body, an ion flow scheme, or a multi-stylus electrode scheme) other than the above described electrophotographic process. In this case, a drum-like or a belt-like intermediate transfer body may be used as a developer holding body.
The structure of the carrying printed circuit board 63 and the opposite printed circuit board 65 is not limited to the above described embodiment. For example, the carrying electrode overcoating layer 63d or the opposite electrode overcoating layer 65d may be omitted.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-063454 | Mar 2008 | JP | national |
