Patent Application
20110158707
1. Field of the Invention
The present invention relates to a restricting blade for restricting the thickness of a developer agent staying on a developing roller, and a developing device using the same.
2. Description of the Related Art
As a developing device for supplying a developer agent onto an image carrier has been conventionally known a developing device comprising a developing roller and a restricting blade for restricting the thickness of a developer agent staying on the developing roller. In more recent years, a restricting blade obtained by punching a metallic plate made of phosphor bronze, stainless steel, or the like has been used to satisfactorily apply a frictional charge to a developer agent and further reduce the thickness of the developer agent staying on the developing roller. Incidentally, Japanese Patent Application Laid-open No. 2002-372858 discloses the related art.
However, the above-described configuration in the prior art raises the following problems.
An object of the present invention is to provide a restricting blade obtained by punching a metallic plate, the restricting blade being capable of uniformly restricting the thickness of a developer agent so as to prevent any occurrence of streaks on an image, and a developing device.
In order to achieve the above-described object, a restricting blade for restricting the thickness of a developer agent borne on a developing roller in contact with the developing roller includes: a metallic plate subjected to punching; a contact surface perpendicular to a thickness direction of the metallic plate, the surface being positioned upstream in a punch direction and brought into contact with the developing roller; an end surface of the metallic plate, formed by the punching, the surface being positioned at the metallic plate upstream in a rotational direction of the developing roller; and a coating layer formed in such a manner as to cover the end surface and a surface on the side of the end surface, positioned opposite to the contact surface in the thickness direction of the metallic plate with a resin or an elastomer.
In order to achieve the above-described object, a developing device includes: a developing roller for developing an electrostatic latent image with a developer agent borne thereon; and a restricting blade for restricting the thickness of the developer agent borne on the developing roller in contact with the developing roller, wherein the restricting blade includes: a metallic plate subjected to punching; a contact surface perpendicular to a thickness direction of the metallic plate, the surface being positioned upstream in a punch direction and brought into contact with the developing roller; an end surface of the metallic plate, formed by the punching, the surface being positioned at the metallic plate upstream in a rotational direction of the developing roller; and a coating layer formed in such a manner as to cover the end surface and a surface on the side of the end surface, positioned opposite to the contact surface in the thickness direction of the metallic plate with a resin.
A detailed description will be illustratively given below of preferred embodiments for embodying the present invention with reference to the attached drawings. Here, the dimensions, materials, shapes, and relative arrangement of component parts described in the preferred embodiments shall not limit the scope of the invention to the embodiments, as long as not specifically stated.
Referring to
The image forming apparatus is a laser beam printer of an electrophotographic system, including a photosensitive drum 1 (i.e., an image carrier) which can be rotated in a direction indicated by an arrow in
With this configuration, when a charging voltage is applied to the charging roller 2, the surface of the photosensitive drum 1 is uniformly charged to the same polarity as that of a developer agent. When the exposing device 5 scans and exposes the charged surface with and to the laser beam, an electrostatic latent image is formed on the photosensitive drum 1. Thereafter, the developing device 4 supplies the developer agent to the electrostatic latent image, thereby developing the electrostatic latent image as a developer agent image. The developer agent image developed in this manner is transferred onto a sheet material at a transfer nip defined between the photosensitive drum 1 and the transferring roller 6. The sheet material having the developer agent image transferred thereonto is transported to a fixing device 7. The sheet material, to which the developer agent image is heated and fixed in the fixing device 7, is discharged to a discharge unit 8 disposed at the upper portion of an apparatus body. A plurality of sheet materials can be stacked on a sheet cassette 9. Upon start of image formation, the sheet materials are transported one by one to the transfer nip through a feed roller 10 and a pair of transportation rollers 11 from the sheet cassette 9 while counting a timing.
After the developer agent image is transferred, the developer agent which has not transferred onto the sheet material remains on the photosensitive drum 1. In view of this, the cleaner 3 is provided in the image forming apparatus, for removing the remaining developer agent from the surface of the photosensitive drum 1. The cleaner 3 includes a cleaning blade 3a obtained by forming urethane rubber or silicon rubber into a blade shape and a cleaning container 3b. Here, the tip edge of the cleaning blade 3a is brought into contact with the surface of the photosensitive drum 1. With the above-described configuration, the cleaning blade 3a is counterclockwise brought into contact with the surface of the photosensitive drum 1 being rotated, so that the developer agent can be scraped off from the surface of the photosensitive drum 1 at the tip edge of the cleaning blade 3a. Furthermore, the scraped developer agent is contained in the cleaning container 3b.
The configuration of the image forming apparatus, to which the developing device 4 in the present preferred embodiment is applicable, is not limited to the above-described configuration. Specifically, an intermediate transfer system may be adopted in which after the developer agent image may be primarily transferred onto an intermediate transfer belt from the surface of the photosensitive drum 1, it may be secondarily transferred onto the sheet material; or, a transportation belt system may be adopted in which the sheet material is electrostatically adsorbed onto a transportation belt, and then, it is transported to the transfer nip. Alternatively, the developing device 4 may be configured to be detachably attached with respect to the apparatus body of the image forming apparatus, or the developing device 4, the charging roller 2, and the cleaner 3 may be held integrally with each other in a process cartridge.
Referring to
The developing device 4 includes a cylindrical developing roller 4a for supplying the developer agent onto the photosensitive drum 1 in contact with the surface of the photosensitive drum 1 and a supply roller 4b for supplying the developer agent onto the developing roller 4a in contact with the surface of the developing roller 4a. The developing roller 4a is exposed to the entire region in a direction of a rotary shaft of the photosensitive drum 1 from an opening formed at a frame of the developing device 4, and is brought into contact with the surface of the photosensitive drum 1 under a predetermined contact pressure. Moreover, the developing device 4 includes a restricting blade 4c which is brought into face contact with the surface of the developing roller 4a in such a manner that its longitudinal direction is substantially parallel to the axial direction of the developing roller 4a, for restricting the thickness of the developer agent to be supplied onto the developing roller 4a.
The developing roller 4a is configured such that a development voltage can be applied thereto from a power source, not shown. A predetermined DC voltage as the development voltage is applied, thus electrostatically supplying the developer agent onto the photosensitive drum 1 from the surface of the developing roller 4a. The developer agent supply roller 4b is an elastic roller made of urethane sponge or the like, and is provided in a rotatable manner in the same direction as that of the developing roller 4a. With this configuration, the developer agent contained in a developer agent container 4d can be supplied from the surface of the developer agent supply roller 4b to the surface of the developing roller 4a. Here, the developer agent which has not been supplied to the surface of the photosensitive drum 1 but remains on the developing roller 4a can be scraped off by the developer agent supply roller 4b.
A metallic blade obtained by “punching,” that is, punching a metallic plate is used as the restricting blade 4c (the shape of the tip surface after the punching is the same as that shown in
The restricting blade 4c is fixed to a support member 4e disposed at one end thereof in the frame of the developing device 4 in such a manner as to follow the rotation of the developing roller 4a. Moreover, the restricting blade 4c is brought into contact with the surface of the developing roller 4a while a surface opposite to that in a direction in which the punching is performed, that is, the surface at which the “round face” explained with reference to
Additionally, in the present preferred embodiment, the restricting blade 4c is connected to a power source, not shown. A voltage of the same polarity as that of an electric charge of a developer agent is applied to the restricting blade 4c, so that a satisfactory friction charge can be applied to the developer agent. As a consequence, it is possible to enhance the development performance of the developing device 4, and further, to prevent the developer agent from being fused to the restricting blade 4c. Incidentally, the material for the support member 4e for supporting the restricting blade 4c is not particularly limited, and therefore, it may be selected from metal, ceramic, a resin, and the like.
Referring to
The restricting blade 4c in the present preferred embodiment is featured in that its tip surface formed by punching and at least a region in the vicinity of the tip surface at the reverse are covered with the coating layer 4c1. In
In the present preferred embodiment, the above-described coating layer 4c1 is formed by “injection molding.”
In the state in which the restricting blade 4c is fed to the die and the die is swaged, clearances (i.e., metallic cavities) are formed between the tip surface and reverse of the restricting blade 4c and the die. The molten resin or elastomer is injected into the clearances, followed by cooling, so that the coating layer 4c1 can be formed at the tip of the restricting blade 4c and at least the region in the vicinity of the tip surface of the reverse. As shown in
When the thickness of the developer agent is restricted at the surface of the developing roller 4a by using the above-described restricting blade 4c, the developer agent flows as shown in
Referring to
<Thickness of Coating Layer (μm)>
The thickness of the coating layer should be preferably 10 μm or more and 1000 μm or less. More preferably, it should be 20 μm or more and 1000 μm or less. If it is 20 μm or more, the sheared face can be securely covered even at a portion at which the sheared face projects in the direction of the reverse, and further, even if a “burr” remains at the reverse, the “burr” can be securely covered with the coating layer 4c1. Consequently, the shape of the tip surface of the restricting blade 4c can be made uniform. In contrast, if the thickness is 1000 μm or less, the thickness of the developer agent can be stably restricted at the surface of the developing roller 4a.
<Distance X (μm)>
As shown in
<Maximum Thickness (Maximum Length) t (μm)>
As shown in
As the value ΔX/t is smaller, the shape variation at the tip surface of the restricting blade 4c becomes smaller. That is to say, the thickness of the developer agent can be uniformly restricted without any occurrence of a streak on an image, thus achieving the high quality of an image. The earnest study by the inventors of the present invention revealed that when the value ΔX/t is ⅛ or less (ΔX≦t/8) the flow of the developer agent need not be varied in the coating layer 4c1, so that there is least possibility that a streak occurs on an image. In other words, as long as this condition is satisfied, it is construed that the tip surface of the restricting blade 4c is smooth.
<Arithmetic Mean Roughness Ra (μm)>
In the present preferred embodiment, an arithmetic mean roughness Ra (μm) at the position P in
The preferred embodiments will be described by way of examples in the case where the dimension and arithmetic mean roughness of the above-described coating layer 4c1 are varied.
In the present example, a stainless steel plate having a thickness T of 0.08 mm was used as the metallic plate. The difference ΔX of the above-described “distance X (μm)” was 75 μm, the “maximum thickness t (μm)” was 600 μm, and the “arithmetic mean roughness Ra (μm)” was 0.3 μm. With these dimensions, ΔX=t/8. The coating layer 4c1 was formed at the tip surface and at least in the vicinity of the tip surface of the reverse of the restricting blade 4c by welding and injecting a polyamide elastomer (Trade name: Diamide E40), which was formed at a die temperature of 40° C., at a temperature from 200° C. to 270° C., followed by cooling.
In the present example, a stainless steel plate having a thickness T of 0.08 mm was used as the metallic plate. The difference ΔX of the above-described “distance X (μm)” was 15 μm, the “maximum thickness t (μm)” was 300 μm, and the “arithmetic mean roughness Ra (μm)” was 0.5 μm. With these dimensions, ΔX=t/20. Here, the coating layer 4c1 was formed in the same manner as Example 1.
In the present example, a stainless steel plate having a thickness T of 0.08 mm was used as the metallic plate. The difference ΔX of the above-described “distance X (μm)” was 50 μm, the “maximum thickness t (μm)” was 300 μm, and the “arithmetic mean roughness Ra (μm)” was 0.3 μm. With these dimensions, ΔX=t/6. Here, the coating layer 4c1 was formed in the same manner as Example 1.
In the present example, the restricting blade 4c was formed by extrusion molding in a manner different from Examples 1 to 3. Specifically, a stainless steel plate having a thickness T of 0.08 mm was put into a die, and then, a polyimide elastomer was dissolved at a temperature from 200° C. to 270° C., followed by sequentially injecting into a die cavity while traveling with the restricting blade 4c inside of an extrusion molder, thereby obtaining the coating layer 4c1. Here, the difference ΔX of the above-described “distance X (μm)” was 10 μm, the “maximum thickness t (μm)” was 100 μm, and the “arithmetic mean roughness Ra (μm)” was 0.3 μm. With these dimensions, ΔX=t/10.
In the present example, a stainless steel plate having a thickness T of 0.15 mm was used as the metallic plate. The difference ΔX of the above-described “distance X (μm)” was 100 μm, the “maximum thickness t (μm)” was 1000 μm, and the “arithmetic mean roughness Ra (μm)” was 0.3 μm. With these dimensions, ΔX=t/10. The coating layer 4c1 was formed by injection-molding a polyester elastomer in the present example.
In order to verify the effects of the present preferred embodiment, the thickness of the developer agent was restricted by using the restricting blades 4c in Examples 1 to 5 described above and restricting blades in Comparative Examples 1 to 4 below, and then, the occurrence of a streak on an image and the restriction degree of the developer agent were examined in each of Examples. Hereinafter, explanation will be made on the conditions of Comparative Examples 1 to 4 and the comparison result.
In this comparative example, the developer agent was restricted by using a conventional restricting blade without the above-described coating layer. In the same manner as in Examples 1 to 4, a stainless steel plate having a thickness T of 0.08 mm was used as a metallic plate. The numerical values of the “distance X,” the “maximum length t,” and the “arithmetic mean roughness Ra” were those of the metallic plate. Here, the difference ΔX of the above-described “distance X” was 20 μm, the “maximum thickness t” was 80 μm, and the “arithmetic mean roughness Ra” was 0.5 μm. With these dimensions, ΔX=t/4.
In this comparative example, the developer agent was restricted by using a conventional restricting blade without the above-described coating layer. In the same manner as in Examples 1 to 4, a stainless steel plate having a thickness T of 0.08 mm was used as a metallic plate. The numerical values of the “distance X,” the “maximum length t,” and the “arithmetic mean roughness Ra” were those of the metallic plate. Here, the difference ΔX of the above-described “distance X” was 20 the “maximum thickness t” was 80 μm, and the “arithmetic mean roughness Ra” was 0.4 μm. With these dimensions, ΔX=t/4.
In this comparative example, the same metallic plate as that in Example 1 was used, and further, the same material was subjected to injection-molding, thereby forming the coating layer. The difference ΔX of the above-described “distance X” was 200 μm, the “maximum thickness t” was 600 μm, and the “arithmetic mean roughness Ra” was 1.0 μm. With these dimensions, ΔX=t/3.
In this comparative example, a stainless steel plate having a thickness T of 0.15 mm was used as a metallic plate. A coating layer was formed by the injection-molding in the same manner as Comparative Example 3. The difference ΔX of the above-described “distance X” was 200 μm, the “maximum thickness t” was 2000 μm, and the “arithmetic mean roughness Ra” was 0.3 μm. With these dimensions, ΔX=t/10.
The evaluation result is shown below in Table 1.
As is found from Table 1, Examples 1, 2, 4, and 5 satisfy that ΔX/t is ⅛ or less (i.e., ΔX≦t/8). Therefore, the restricting blade could uniformly restrict the developer agent on the developing roller 4a from the beginning of image formation till exhaustion, thereby producing no streak on an image. Incidentally, in Example 3, ΔX/t is larger than ⅛. However, the arithmetic mean roughness Ra (μm) is 0.3 or less (the same in Examples 1, 4, and 5). This means the formation of the smooth coating layer 4c1, and therefore, no streak occurs on an image from the beginning of image formation till exhaustion.
To the contrary, no coating layer is formed in Comparative Examples 1 and 2 in the same manner as conventional. As a consequence, the shape is varied at the tip surface of the restricting blade in the longitudinal direction (it is found from the large value of ΔX/t), and therefore, a steak occurs on an image from the beginning of image formation till exhaustion. In contrast, although the coating layer was formed in Comparative Example 3, ΔX/t is larger than ⅛ and the arithmetic mean roughness Ra (μm) is larger than 0.3, and therefore, a steak occurs on an image. Moreover, although the coating layer was formed with ΔX/t being ⅛ or less and the arithmetic mean roughness Ra (μm) being 0.3 or less in Comparative Example 4, the maximum thickness t (μm) of the tip surface is large, and therefore, the contact pressure between the restricting blade and the surface of the developing roller locally becomes large. As a consequence, although no streak occurs on an image, deficiency occurs in restriction of the developer agent.
As described above, the present preferred embodiment can provide the restricting blade obtained by punching the metallic plate, capable of uniformly restricting the thickness of the developer agent so as to prevent any occurrence of a streak on, an image, and the developing device using the same.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2009-292604, filed on Dec. 24, 2009, which is hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-292604 | Dec 2009 | JP | national |
