Patent Grant
9069283
This application claims priority based on 35 USC 119 from prior Japanese Patent Application No. 2012-094825 filed on Apr. 18, 2012, entitled “IMAGE FORMATION UNIT AND IMAGE FORMATION APPARATUS”, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The disclosure relates to an image formation unit and an image formation apparatus improved to solve problems of a deficiency in the amount of developer and an uneven distribution of the developer.
2. Description of Related Art
Image formation apparatuses having a function to solve problems of a deficiency of the amount of a developer, and an uneven distribution of the developer in an image formation unit, are generally known. Japanese Patent Application Publication No. 2005-221859 (Patent Document 1) is an example of such image formation apparatuses.
In the image formation apparatus of Patent Document 1, a stirring member is provided, in a longitudinal direction, in a portion of an image formation unit. The stirring member has functions to detect the amount of toner in the image formation unit and to stir the toner. The stirring member stirs the toner supplied through a toner supply port which is provided at the center, in the longitudinal direction, of the image formation unit. In other words, the stirring member detects the amount of toner as well as solves the problem of an uneven distribution of toner.
Even the conventional image formation apparatus of the above configuration cannot sufficiently solve the problem of uneven distribution of toner in some cases. In this case, image quality may be degraded.
A first aspect of the invention is an image formation unit that includes: a developer storage configured to store developer; an image carrier on which an electrostatic latent image is formed; a developer carrier being in contact with the image carrier and configured to transfer developer to the electrostatic latent image; a developer housing portion located below the developer storage and above the image carrier and configured to house the developer from the developer storage; a supply port provided above the developer housing portion to communicate with the developer storage and configured to supply the developer in the developer storage into the developer housing portion; a developer amount detection member rotatably disposed in the developer housing portion at a position below the supply port; and protrusions disposed on the developer amount detection member.
This aspect can bring the distribution of developer in the image formation unit close to being even, thus improving image quality.
Descriptions are provided hereinbelow for embodiments based on the drawings. In the respective drawings referenced herein, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents is omitted. All of the drawings are provided to illustrate the respective examples only.
Hereinbelow, an image formation unit and an image formation apparatus according to embodiments of the invention are described. Note that, in this specification, an image formation apparatus incorporating an image formation unit is described.
First of all, a first embodiment of the invention is described.
Tray 3 is disposed below image formation units 1K, 1Y, 1M, 1C, and medium 4 is stored in tray 3. Medium 4 is conveyed on a conveyance path formed by feed roller 5, conveyance rollers 6, and the like. Along the conveyance path for medium 4, there are disposed: image formation units 1K, 1Y, 1M, 1C; transfer belt 7 on which to transfer, onto medium 4, images formed by image formation units 1K, 1Y, 1M, 1C; fixing unit 8 configured to fix images transferred onto medium 4; ejection rollers 9, 10 configured to eject medium 4 outside the apparatus; and stacker cover 11 on which to keep ejected medium 4.
In addition, toner storage container 12, as a developer storage configured to store developer, is provided in an upper portion of each of image formation units 1K, 1Y, 1M, 1C. Toner storage containers 12 of image formation units 1K, 1Y, 1M, 1C store therein toners K, Y, M, and C of four colors, respectively.
Since image formation units 1K, 1Y, 1M, 1C have the same configuration and toner storage containers 12 have the same configuration, only one set of these is hereinafter described. Specifically, a set of image formation unit 1K of color K (black) and toner storage container 12 of image formation unit 1K is described.
Image formation unit 1K includes, in the inside: toner amount detection member 16 as a developer amount detection member; stirring members 17, 18; toner feed roller 19; and development roller 20 as a developer carrier.
Each of stirring members 17, 18 is a member for stirring toner 13. Stirring members 17, 18 are arranged inside developer housing portion S of image formation unit 1K in parallel with the longitudinal direction of developer housing portion S. Each of stirring members 17, 18 is rotatable. Toner 13 is stirred by rotation of stirring members 17, 18.
Toner feed roller 19 is a roller configured to feed toner 13 to development roller 20. Development roller 20 is a roller configured to hold, on its surface, a thin layer of toner 13 to be transferred to an electrostatic latent image on photosensitive drum 22. Development roller 20 transfers developer to the electrostatic latent image by contacting photosensitive drum 22. Development blade 21 is disposed in contact with development roller 20. Development blade 21 is a member configured to thin a layer of toner 13 on development roller 20, fed from toner feed roller 19. Photosensitive drum 22 is a roller on whose surface an electrostatic latent image can be formed. Charging roller 23 is a roller for charging the surface of photosensitive drum 22. Cleaning blade 24 is a member configured to scrape off toner 13 attached on the surface of photosensitive drum 22. Discarded toner conveyance member 25 is a device configured to discharge, to the outside, toner 13 scraped off of the surface of photosensitive drum 22 by cleaning blade 24.
Photosensitive drum 22 is disposed in contact with development roller 20. Charging roller 23 and cleaning blade 24 are disposed in contact with photosensitive drum 22. Discarded toner conveyance member 25 is disposed facing cleaning blade 24.
Next, toner amount detection member 16 is described.
Toner amount detection member 16 is a device configured to detect the amount of toner based on its rotation which varies in accordance with the amount of toner inside developer housing portion S. As shown in
Toner amount detection member 16 is in the form of a paddle having a flat surface that protrudes from its rotational axis toward one side in a radial direction. Thereby, toner amount detection member 16 has a configuration where its center of gravity is eccentric from the rotational axis toward the paddle. To put it differently, toner amount detection member 16 is a member which generates a moment of inertia to rotate toner amount detection member 16 in such a way that the center of gravity of toner amount detection member 16 is moved to its lowest point. This moment of inertia is a moment to rotate toner amount detection member 16 in such a way that the center of gravity of toner amount detection member 16 is moved to its highest point as toner amount detection member 16 is rotated, and is moved to the lowest point under the weight of the center of gravity once passing the highest point.
As shown in
Shaft portion 16a is a member serving as the rotational axis of toner amount detection member 16. Shaft portion 16a is rotatably provided in developer housing portion S of image formation unit 1K. Later-described drive gear 31 (see
Plate-shaped portion 16b is a member being in direct contact with toner 13 and is configured to change a rotation stop position in accordance with the amount of toner. Plate-shaped portion 16b includes crimping portion 16b1 and paddle portion 16b2. Crimping portion 16b1 is a member for joining shaft portion 16a and plate-shaped portion 16b integrally. Shaft portion 16a and plate-shaped portion 16b are joined together by crimping crimping portion 16b1 into grooves 16a1 of shaft portion 16a. Paddle portion 16b2 is a member for stirring toner 13, making the center of gravity eccentric, and supporting protrusions 27, 28. Paddle portion 16b2 is formed of a plate-shaped member having a flat surface. More specifically, paddle portion 16b2 is formed of a flat plate extending in a rotational axis direction of toner amount detection member 16 and protruding in the radial direction thereof. Toner 13 is stirred by making plate-shaped paddle portion 16b2 rotate about shaft portion 16a.
Paddle portion 16b2 is a member for making eccentric the center of gravity of toner amount detection member 16. Toner amount detection member 16 is configured in such a way that paddle portion 16b2, where the center of gravity is located, is rotated about shaft portion 16a by a drive source and, once passing the highest point, paddle portion 16b2 rotates irrespective of the drive source to move to the lowest point by the action of the moment of inertia (under the weight of paddle portion 16b2 (the weight of the center of gravity)). In addition, by the rotation under its own weight, paddle portion 16b2 contacts toner 13 as well as changes the rotation stop position in accordance with the amount of toner. More specifically, paddle portion 16b2 stops its rotation at a position close to the lowest point when the amount of toner is small, and at a position far from the lowest point when the amount of toner is large.
Protrusions 27, 28 function to spread toner 13, in a longitudinal direction, in a central portion of toner amount detection member 16, toward two sides thereof in the longitudinal direction. Protrusions 27, 28 are each a member configured to scoop the toner with the rotation of toner amount detection member 16, and they work in conjunction with one another to spread toner 13, which is supplied through toner supply port 15, toward the two ends, in the longitudinal direction, of toner amount detection member 16. Multiple protrusions 27, 28 are arranged in paddle portion 16b2 of toner amount detection member 16 in parallel with one another at equal intervals. Protrusions 27, 28 together act like a screw to convey and spread toner 13, which is supplied to the vicinity of the center, in the longitudinal direction, of image formation unit 1K (developer housing portion S), toward the two ends thereof in the longitudinal direction. To this end, protrusions 27 are arranged on one side of image formation unit 1K and protrusions 28 are arranged on the other side thereof with respect to the center, in the longitudinal direction, of image formation unit 1K. Thereby, protrusions 27, 28 are capable of spreading toner 13 in the center, in the longitudinal direction, of image formation unit 1K toward the two sides thereof. As shown in
In addition, as shown in
As shown in
As shown in
As shown in
As shown in
The image formation apparatus having the above configuration operates as follows.
In
The development process in each of image formation units 1K, 1Y, 1M, 1C is described based on
In the meantime, the surface of photosensitive drum 22 rotated in a direction indicated by arrow 22R is charged by charging roller 23. Photosensitive drum 22 is then exposed by exposure head 2, whereby an electrostatic latent image is formed on photosensitive drum 22. Toner 13 on development roller 20 moves to this electrostatic latent image, and thereby the exposed part is developed. After that, the image is transferred to medium 4. Toner 13 left on photosensitive drum 22 is scraped off by cleaning blade 24. Toner 13 thus scraped off is conveyed and discharged to the outside by discarded toner conveyance member 25.
Next, operations of toner amount detection member 16 and of the toner supply are described.
As shown in
In the state where the amount of toner 13 in image formation unit 1K is small (such a state is termed as “toner low”) and the level of toner upper surface 34a is low as shown in
If judging that image formation unit 1K is in the state of “toner low”, controller C issues a toner supply instruction. Upon issue of this instruction, rotatable shutter member 15a is rotated by a drive unit (not illustrated). By this rotation, toner 13 drops from toner storage container 12 and is supplied to image formation unit 1K. In this event, since toner supply port 15 is provided in the vicinity of the center, in the longitudinal direction, of image formation unit 1K, toner 13 is supplied to the vicinity of the center, in the longitudinal direction, of image formation unit 1K. Then, since multiple protrusions 27 (27a, 27b . . . ) are rotated as shown in
In this operation, enclosure member 26 covers a lower part of the rotation trajectory of protrusions 27, 28, and temporarily holds toner 13. In this manner, enclosure member 26 suppresses the influence of stirring members 17, 18 located near toner amount detection member 16 and thus enables protrusions 27, 28 of toner amount detection member 16 to convey toner 13 smoothly.
In the same way, multiple protrusions 28 rotate and produce a force in an opposite direction from push force 27F of multiple protrusions 27, and thereby convey toner 13 toward the other side, in the longitudinal direction, of toner amount detection member 16 (in a direction indicated by arrow 33 in this example).
In addition, as shown in
As the amount of supplied toner 13 accumulating on enclosure member 26 becomes larger, toner amount detection member 16 receives more pressure from toner 13. Accordingly, toner amount detection member 16 rotates in conjunction with locking protrusion 311 of drive gear 31 without dropping under its own weight.
Hence, stay period T2 in which toner amount detection member 16 stays at the lowest point becomes shorter as the amount of accumulating toner increases (i.e., stay period T2 becomes shorter as the time passes since the start of the toner supply). If stay period T2 becomes shorter than set period Tlow as shown in
As shown in
As shown in
As described above, protrusions 27, 28 are provided to toner amount detection member 16 in this embodiment. Hence, toner 13 can be stirred and conveyed by the protrusions 27, 28 even in the case where the fluidity of toner 13 is reduced due to deterioration of toner 13 or the like. Thus, toner 13 can be distributed evenly. This makes it possible to prevent toner 13 from accumulating near toner supply port 15, and thereby to keep a good toner amount detection accuracy while preventing a deterioration thereof.
In addition, the problems of a deficiency of the amount of toner and an uneven distribution of toner are solved. Thereby, it is possible to keep a good image quality while preventing a deterioration thereof.
Further, the stir/conveyance of toner 13 and the toner amount detection can be carried out by the single component (toner amount detection member 16), making it possible to reduce the number of components and cost.
On the other hand, in the case of the conventional image formation apparatus having no protrusions 27, 28, it is sometimes impossible to sufficiently solve the problem of an uneven distribution of toner caused when the fluidity of toner is reduced due to a deterioration of the toner or the like. To put it differently, when the fluidity of toner is reduced in the conventional image formation apparatus due to a deterioration of the toner or the like, toner is likely to accumulate near a toner supply port and, therefore, it is sometimes impossible to keep a good toner amount detection accuracy of image formation units. If a good toner amount detection accuracy cannot be kept, a deficiency in the amount of toner and an uneven distribution of toner in the image formation units occur, which in turn deteriorates the image quality.
Next, a second embodiment of the invention is described. The overall configuration of an image formation apparatus of this embodiment is almost the same as that of the image formation apparatus of the first embodiment. Thus, the same components are given the same reference numerals and are not described again.
Toner amount detection member 16 of this embodiment has variations in intervals at which protrusions 27, 28 are arranged. Specifically, unlike in the first embodiment where all protrusions 27, 28 are arranged at equal intervals, protrusions 27, 28 of this embodiment are arranged in such a way that their arrangement interval gradually increases. More specifically, arrangement interval L increases away from toner supply port 15. As shown in
L1<L2<L3. The configuration of the apparatus of this embodiment is the same as that of the first embodiment except for this point.
The image formation apparatus having the above configuration operates as follows. Note that, since the overall operation of the apparatus is the same as that of the first embodiment, the operation of protrusions 27, 28 is mainly described here.
As in the first embodiment, toner 13 is conveyed in the axial directions of toner amount detection member 16 by the rotation of toner amount detection member 16 and protrusions 27, 28. In this event, because the arrangement interval of protrusions 27, 28 is small near toner supply port 15, toner 13 can reach next protrusions 27, 28 quickly. Thus, the amount of toner which can be conveyed is large.
By contrast, the arrangement interval of protrusions 27, 28 is large at positions far from toner supply port 15. Accordingly, portions with no protrusions 27, 28 are each large, making it difficult to convey toner 13 in the axial directions. Thus, the amount of toner which can be conveyed becomes smaller away from supply port 15.
The operations of the apparatus of this embodiment are the same as those of the first embodiment except for the above.
In the first embodiment, the toner distribution which is uneven immediately after the toner supply, as shown in
On the other hand, in this embodiment where the arrangement interval of protrusions 27, 28 is adjusted, the toner distribution, which is uneven immediately after the toner supply as shown in
In both the first and second embodiments, the distribution of toner 13 becomes uneven after the elapse of period Tb to a degree not adversely affecting a print image. However, since the amount of toner which can be conveyed varies because of the variations in the interval of protrusions 27, 28, the toner distribution difference inside image formation unit 1K in these embodiments results in h1>h2. Thus, the second embodiment enables the toner distribution to be kept closer to an even distribution when evenly distributed toner is further stirred. As a result, it is possible to keep a good toner amount detection accuracy while more effectively preventing a deterioration thereof, and also to keep a good image quality while more effectively preventing deterioration thereof due to a deficiency in the amount of toner and an uneven distribution of the toner.
It should be noted that the invention relates to an image formation unit which is applicable to various image formation apparatuses. For example, the image formation unit of the invention is applicable to image formation apparatuses used as copiers, LED printers, laser printers, facsimiles, MFPs, and the like.
In addition, although the arrangement interval L of protrusions 27, 28 is increased gradually away from toner supply port 15 in the second embodiment, this arrangement interval L may be set more exactly. Specifically, since toner 13 has fluidity, and even deteriorated toner has fluidity to some extent, arrangement interval L of protrusions 27, 28 may be adjusted accordingly. More specifically, arrangement interval L of protrusions 27, 28 may be adjusted so that the amount of toner 13 flowing toward the center, in the longitudinal direction, of toner amount detection member 16 attributable to the fluidity of a deteriorated toner balances with the amount of toner conveyed toward the two sides thereof in the longitudinal direction by toner amount detection member 16 of the second embodiment. The amount of toner 13 to flow toward the center of toner amount detection member 16 that is attributable to the fluidity of deteriorated toner varies depending on various conditions, such as the degree of deterioration of toner 13. Accordingly, in a practical case, the values of the fluidity of toner according to these conditions are determined through experiments. Then, arrangement interval L of protrusions 27, 28 is adjusted so as to balance with the fluidity of the toner. Thereby, the toner distribution difference h2 can be reduced to a value close to 0. Further, angles θ, α of protrusions 27, 28 may be adjusted instead of, or together with, the adjustment of arrangement interval L of protrusions 27, 28.
The apparatus in each of the embodiments has a configuration where toner supply port 15 is provided to the central portion, in the longitudinal direction, of developer housing portion S and protrusions 27, 28 of toner amount detection member 16 spread toner 13 in the central portion thereof in the longitudinal direction toward the two sides thereof. However, the apparatus may have another configuration. Specifically, toner supply port 15 may be disposed, not in the central portion in the longitudinal direction of developer housing portion S, but in a portion slightly shifted left or right from the central portion, or in a portion largely shifted left or right from the central portion. In this case, a set of protrusions 27 and a set of protrusions 28 are arranged left and right about a position immediately under toner supply port 15. In the case where toner supply port 15 is provided at left or right ends of toner amount detection member 16, only protrusions 27 or only protrusions 28 are provided. In either case, the same working effect as those of the above embodiments can be achieved.
Moreover, although the four image formation units are provided for color printing in the above embodiments, only one image formation unit is provided in the case of monochrome printing. The invention is also applicable to this case.
In addition, the invention is not limited to the above embodiments, but may be embodied by modifying the constituents thereof within a range not departing from the spirit of the invention in a practical phase. Further, various aspects of the invention can be provided by appropriately combining two or more of the constituents disclosed in the above embodiments.
For example, some of the constituents out of all the constituents in the above embodiments and modifications may be combined or deleted. Furthermore, constituents according to another embodiment may be used in combination as appropriate.
The invention includes other embodiments in addition to the above-described embodiments without departing from the spirit of the invention. The embodiments are to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. Hence, all configurations including the meaning and range within equivalent arrangements of the claims are intended to be embraced in the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-094825 | Apr 2012 | JP | national |
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| 20110026974 | Kunihiro et al. | Feb 2011 | A1 |
| 20130022372 | Bucks et al. | Jan 2013 | A1 |
| 20130308965 | Tsuchiya et al. | Nov 2013 | A1 |
| Number | Date | Country |
|---|---|---|
| 2005-221859 | Aug 2005 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20130279925 A1 | Oct 2013 | US |
