Embodiments described herein relate generally to an image forming apparatus.
An image forming apparatus includes one or more image forming units. An image forming unit includes a photoconductive body, a charging device, an optical device, a developing device, and a transfer device. The charging device includes a charging roller and a cleaning roller. The cleaning roller contacts the charging roller and cleans the surface of the charging roller. It is desirable to sufficiently clean the surface of the cleaning roller.
An image forming apparatus according to an embodiment includes a photoconductive drum on which a toner image is to be formed; a charging roller positioned to contact a surface of the photoconductive drum and configured to charge the surface of the photoconductive drum; and a cleaning member configured contact a surface of the charging roller. The cleaning member includes a shaft extending along a rotational axis and a spiral portion spiraling around the shaft along a length of the shaft parallel to the rotational axis. A width of the spiral portion at a central region of the cleaning member is greater than a width of the spiral portion at an end region of the cleaning member. In general, the spiral portion satisfies at least one of following conditions: (1) A width of the spiral portion at the central region, along the rotational axis length, is greater than a width of the spiral portion at the end region(s) along the rotational axis length; (2) A pitch of the spiral portion at the central region is less than a pitch of the spiral portion at the end region(s).
Image forming units and image forming apparatuses according to example embodiments are described below with reference to the drawings. In the figures, the same components are denoted by the same reference numerals and symbols. For clarity in description, in some instances of the figures, dimensions and shapes of components may be exaggerated or simplified.
As illustrated in
The image forming station 20 includes a photoconductive drum 22, an electrostatic charger 23, an exposure scanning head 24, a developing device 26, and a photoconductive cleaner 27.
In the photoconductive drum 22, also referred to as a photoconductive body, a photoconductive layer is coated on the surface of a conductive cylindrical supporting body. The electrostatic charger 23, also referred to as ac charging device, applies electric charge to the photoconductive drum 22 to charge the surface of the photoconductive drum 22. The exposure scanning head 24, which is also referred to as an optical device, irradiates the photoconductive drum 22 with light to form an exposed latent image. The developing devices 26 of the image forming stations 20Y, 20M, 20C, and 20K respectively include two-component developers including the toners of Y (yellow), M (magenta), C (cyan), and K (black) and a carrier. The developing device 26 develops the exposed latent image with the developer. The photoconductive cleaner 27 removes the toners remaining on the photoconductive drum 22.
The printer section 11 includes a backup roller 18a, a driven roller 18b, a tension roller, the intermediate transfer belt 18, a plurality of primary transfer rollers 28, and a secondary transfer roller 30. The backup roller 18a, the driven roller 18b, and the tension roller support the intermediate transfer belt 18. The intermediate transfer belt 18 rotates in an arrow m direction. The primary transfer rollers 28 are respectively provided in positions opposed to the photoconductive drum 22 via the intermediate transfer belt 18. The secondary transfer roller 30 is provided in a position opposed to the backup roller 18a via the intermediate transfer belt 18.
A paper feeding section that supplies sheets is provided below the printer section 11. The printer section 11 includes a registration roller 31a, a fixing device 32, and a paper discharge roller pair 33. The registration roller 31a, the secondary transfer roller 30, the fixing device 32, and the paper discharge roller pair 33 are provided in a conveyance path on which the sheets are conveyed.
The primary transfer roller 28 primarily transfers a toner image formed on the photoconductive drum 22 onto the intermediate transfer belt 18. The primary transfer rollers 28 of the image forming stations 20Y, 20M, 20C, and 20K sequentially superimpose toner images of Y (yellow), M (magenta), C (cyan), and K (black) to form a color toner image on the intermediate transfer belt 18.
The secondary transfer roller 30 rotates following the intermediate transfer belt 18. The secondary transfer roller secondarily transfers the color toner image on the intermediate transfer belt 18 onto the supplied sheet.
The structure of the electrostatic charger 23 is described in detail below.
As illustrated in
The charging roller 41 rotates according to rotation of the photoconductive drum 22. Electric discharge occurs across a very small space between the charging roller 41 and the photoconductive drum 22, whereby the surface of the photoconductive drum 22 is charged.
As illustrated in
The shaft section 51 is formed in a circular shape in a cross section orthogonal to the center axis direction of the shaft section 51. The shaft section 51 has a fixed outer diameter. The line C1 (center axis C1) indicates the center axis of the shaft section 51. For example, the shaft section 51 is desirably made of a metal material such as stainless steel or a free-cutting steel material. If the shaft section 51 is made of metal material, sufficient mechanical strength can be given to the shaft section 51. Therefore, it is possible to prevent a bending of the shaft section 51 during cleaning. If the shaft section 51 is made of the metal material to have the fixed outer diameter, cost can be reduced.
The outer diameter of the shaft section 51 is desirably 4 mm to 6 mm. If the outer diameter of the shaft section 51 is 4 mm or more, sufficient mechanical strength can be given to the shaft section 51. Therefore, it is possible to prevent a bending of the shaft section 51 during cleaning. If the outer diameter of the shaft section 51 is 6 mm or less, manufacturing cost can be reduced. The length of the shaft section 51 is desirably 250 mm or more. If the length of the shaft section 51 is 250 mm or more, it is possible to clean a wide range of the charging roller 41 using a single cleaning member 42. Therefore, the structure of the electrostatic charger 23 can be simplified.
The shaft section 51 is disposed along the length direction of the charging roller 41. The shaft section 51 is disposed in parallel to the charging roller 41.
The contact member 52 is a wire body member spirally formed around the center axis C1 on an outer circumferential surface of the shaft section 51, and may be referred to as a spiral portion. A traveling distance in the length direction of the shaft section 51 (the center axis C1 direction) at the time when a twisting angle around the center axis C1 of the contact member 52 changes 360° is referred to as “pitch”. For example, a track of the contact member 52 can be represented as x=r cos θ (an X coordinate), y=r sin θ (a Y coordinate), and z=aθ (a Z coordinate) in an XYZ rectangular coordinate system, where r is a constant and is the distance between the contact member 52 and the center axis C1 on an XY plane, θ is a rotation angle centering on the center axis C1, and the value “a” is a constant and can be any real number.
A cross-sectional shape of the contact member 52 orthogonal to its length direction is, for example, substantially rectangular, that is, thin slices of the contact member 52 are substantially rectangular. An inner circumferential surface 52a of the contact member 52 is in contact with the outer circumferential surface of the shaft section 51 over the entire length of the contact member 52. The contact member 52 spirals along the length direction of the shaft section 51. An outer circumferential surface 52b of the contact member 52 can come into contact with an outer circumferential surface of the charging roller 41. The contact member 52 projects from the outer circumferential surface of the shaft section 51 in a radial outward direction.
The contact member 52 is desirably an elastically compressible-deformable material. If the contact member 52 is elastically compressible-deformable, then the contact member 52 can come into contact with the charging roller 41 in a state in which the contact member 52 has been elastically deformed in the thickness direction of the contact member 52 (that is, the radial direction of the shaft section 51). Therefore, the contact member 52 comes into contact with the charging roller 41 while in a compressed state an provides a physically repulsive force against the charging roller 41. Accordingly, it is possible to improve contact between the contact member 52 and the charging roller 41 and improve a cleaning effect.
At least a surface layer portion of the contact member 52 is desirably made of resin (e.g., foamed resin or foam rubber). As the resin, melamine resin and polyurethane can be used. For example, foamed melamine resin and foamed polyurethane (foamed urethane) are suitable. As the resin, polystyrene and polyolefins (polyethylene, polypropylene, etc.) can also be used.
A distribution of widths of the outer circumferential surface 52b of the contact member 52 is described below.
The shaft section 51 can be divided into two end portion ranges 61 and one intermediate range 62. A first end portion range 61A of the two end portion ranges 61 is a length range including one end 51a (first end portion) of the shaft section 51. For example, the first end portion range 61A is a length range equivalent to 10% to 40% with respect to the entire length of the shaft section 51. The length range of the first end portion range 61A is desirably 25% to 40%.
A second end portion range 61B of the two end portion ranges 61 is a length range including the end 51b (second end portion) of the shaft section 51. For example, the second end portion range 61B is a length range equivalent to 10% to 40% with respect to the entire length of the shaft section 51. The length range of the second end portion range 61B is desirably 25% to 40%.
The length of the first end portion range 61A and the length of the second end portion range 61B may be the same or may be different from each other.
The intermediate range 62 is a length range between the two end portion ranges 61A and 61B. For example, the intermediate range 62 is a length range equivalent to 20% to 80% with respect to the entire length of the shaft section 51. The length range of the intermediate range 62 is desirably 33% to 50%.
In the contact member 52, portions formed in one of the end portion ranges 61 are referred to as “end side portions 71”. In the contact member 52, portions formed in the first end portion range 61A and the second end portion range 61B are respectively referred to as a first end side portion 71A and a second end side portion 71B.
The width (hereinafter sometimes referred to as line width) of the outer circumferential surface 52b in the end side portions 71 is represented as “w1”. The width of the outer circumferential surface 52b of the first end side portion 71A and the width of the outer circumferential surface 52b of the second end side portion 71B may be the same or may be different from each other. A pitch of the contact member 52 in the end side portions 71 is represented as “p1”. A pitch of the first end side portion 71A and a pitch of the second end side portion 71B may be the same or may be different from each other.
For the contact member 52, a portion formed in the intermediate range 62 is referred to as “intermediate portion 72”. The width (hereinafter sometimes referred to as line width) of the outer circumferential surface 52b of the contact member 52 in the intermediate portion 72 is represented as “w2”. A pitch of the contact member 52 in the intermediate portion 72 is represented as “p2”.
The line widths w1 and w2 may be averages of line widths of the outer circumferential surface 52b of the contact member 52 in the relevant ranges (the end portion ranges 61 and the intermediate range 62). The pitches p1 and p2 may be averages of pitches of the contact member 52 in the relevant ranges (e.g., the end portion ranges 61 and the intermediate range 62).
As illustrated in
Each end portion of the shaft section 51 of the cleaning member 42 (see
As illustrated in
As illustrated in
An area of the outer circumferential surface 52b per unit length of the contact member 52 in the intermediate portion 72 is desirably larger than an area of the outer circumferential surface 52b per unit length of the contact member 52 in at least one end side portion 71. Consequently, it is possible to reduce deviations of the contact area and the pressing force of the contact member 52 in the length direction of the cleaning member 42. Therefore, it is possible to sufficiently clean the charging roller 41 in a wide range in the length direction.
The cleaning member 42 can be easily manufactured by winding two kinds of contact members 52 having different line widths on the shaft section 51. Accordingly, the image forming station 20 is excellent in easiness of manufacturing and manufacturing cost.
If the voltage applied to the charging roller 41 by the power supply 43 illustrated in
As illustrated in
A distribution of pitches of the contact member 152 is described below.
In the contact member 152, portions formed in the end portion ranges 61 are referred to as “end side portions 171”. In the contact member 152, portions formed in the first end portion range 61A and the second end portion range 61B are respectively referred to as a first end side portion 171A and a second end side portion 171B. A pitch of the contact member 152 in the end side portions 171 is represented as “p11”. A pitch of the first end side portion 171A and a pitch of the second end side portion 171B may be the same or may be different from each other.
In the contact member 152, a portion formed in the intermediate range 62 is referred to as “intermediate portion 172”. A pitch of the contact member 52 in the intermediate portion 172 is referred to as “p12”.
The pitch p12 of the intermediate portion 172 is smaller than the pitch p11 of at least one end side portion 171. The pitch p12 of the intermediate portion 172 only has to be smaller than the pitch p11 of any one end side portion 171. The pitch p12 of the intermediate portion 172 is desirably smaller than the pitch p11 of both the end side portions 171.
A magnitude relation between the line width of an outer circumferential surface 152b of the intermediate portion 172 and the line width of outer circumferential surfaces 152b of the end side portions 171 is not particularly limited. In
In the image forming station 120, since the pitch p12 of the intermediate portion 172 is smaller than the pitch p11 of the end side portions 171, even in the intermediate portion 172, it is possible to secure a contact area of the contact member 152 with the charging roller 41 and a pressing force of the contact member 152 against the charging roller 41. Therefore, it is possible to reduce deviations of the contact area and the pressing force of the contact member 152. Therefore, it is possible to sufficiently clean the charging roller 41 in a wide range along the length direction. Accordingly, it is possible to reduce defects of images due to charging unevenness of the charging roller 41 and obtain satisfactory image quality. Since the charging roller 41 can be sufficiently cleaned, it is possible to suppress occurrence of noise due to resonance.
An area of the outer circumferential surface 152b per unit length of the contact member 152 in the intermediate portion 172 is desirably larger than an area of the outer circumferential surface 152b per unit length of the contact member 152 in at least one end side portion 171. Consequently, it is possible to reduce deviations of the contact area and the pressing force of the contact member 152 along the length direction of the cleaning member 142. Therefore, it is possible to sufficiently clean the charging roller 41 in a wide range in the length direction.
The cleaning member 142 can be manufactured by winding the contact member 152 on the shaft section 51 while changing the winding pitches in the end side portions 171 and the intermediate portion 172. Accordingly, the image forming station 120 is excellent in easiness of manufacturing and manufacturing cost.
If the voltage applied to the charging roller 41 by the power supply 43 illustrated in
As illustrated in
The cleaning member 242 has the same configuration as the configuration of the cleaning member 42 illustrated in FIG. 3 except that the outer diameter of an intermediate portion 272 is larger than the outer diameter of end side portions 271.
The cleaning member 242 can reduce deviations of a contact area and a pressing force of the contact member 252. Therefore, it is possible to sufficiently clean the charging roller 41 in a wide range in the length direction. Accordingly, it is possible to reduce defects of images due to charging unevenness of the charging roller 41 and obtain satisfactory image quality. Since the charging roller 41 can be sufficiently cleaned, it is possible to suppress noise occurrence due to resonance.
The image forming station 20 including the electrostatic charger 23 illustrated in
The image forming station 120 including the electrostatic charger 123 illustrated in
The image forming station 120 including the electrifying electrostatic charger 123 illustrated in
As illustrated in Table 1, in the examples 1 to 4, it has been found that occurrence of concentration unevenness and vertical streaks can be suppressed.
The cross-sectional shape of the contact member orthogonal to its length direction is not limited to a rectangular shape. The cross-sectional shape of the contact member may be a or comprise a circular shape, an elliptical shape, a triangular shape, or the like.
If the contact member satisfies the condition (1) described above, the pitch of the contact member may be smaller in a portion closer to the center of the shaft section along the length direction. If the contact member satisfies the condition (2) described above, the width of the outer circumferential surface of the contact member may be larger in a portion closer to the center in the length direction of the shaft section.
The image forming apparatus may be a monochrome image forming apparatus. The number of image forming stations is not particularly limited. The image forming apparatus may be of a type that transfers a toner image onto a sheet directly from the photoconductive body rather than by an intermediate transfer belt or the like. The image forming apparatus may include a plurality of printer sections.
According to at least one embodiment described above, it is possible to secure a contact area of the contact member with the charging roller and a pressing force of the contact member against the charging roller even in the intermediate (central) portions of the charging roller. Therefore, it is possible to reduce deviations of the contact area and the pressing force of the contact member along the length direction of the cleaning member. Therefore, it is possible to sufficiently clean the charging roller in a wide range along the length direction. Accordingly, it is possible to reduce defects in images due to charging unevenness of the charging roller and obtain satisfactory image quality. Since the charging roller can be sufficiently cleaned, it is possible to suppress occurrence noise due to resonance.
While certain embodiments have been described these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.
Number | Name | Date | Kind |
---|---|---|---|
20110170901 | Kawai | Jul 2011 | A1 |
20170219988 | Yada | Aug 2017 | A1 |
20170219989 | Yada | Aug 2017 | A1 |
Number | Date | Country |
---|---|---|
2007127770 | May 2007 | JP |
2017-078817 | Apr 2017 | JP |