Patent Grant
10228639
Technical Field
Aspects of this disclosure relate to an image forming apparatus.
Related Art
An electrophotographic image forming apparatus includes, for example, a belt-shaped image bearer to rotate with an image borne thereon, a transferer disposed opposing the image bearer, and a transfer section between the image bearer and the transferer to transfer the image from image bearer onto a recording medium delivered. Such an image forming apparatus may include a guide member upstream from the transfer section in a delivery direction of the recording medium, to guide entry of the recording medium into the transfer section. A recording medium is guided with the guide toward the transfer section. When the recording medium passes the guide, the leading or trailing end of the recording medium may contact the image bearer. Such contact of the leading or trailing end of the recording medium against the image bearer may inwardly displace the image bearer in rotation, depending on the degree of contact, thus causing unnecessary vibration.
In an aspect of this disclosure, there is provided an image forming apparatus that includes a belt-shaped image bearer, a transferer, a guide unit, and a plurality of contact members. The belt-shaped image bearer has an image bearing surface to bear an image thereon. The transferer forms a transfer section between the transferer and the image bearer, to transfer the image onto a recording medium. The guide unit is disposed upstream from the transfer section in a delivery direction of the recording medium, to guide the recording medium toward the transfer section. The plurality of contact members are disposed side by side at positions opposing the guide unit and in contact with a non image bearing surface of the image bearer opposite to the image bearing surface.
The aforementioned and other aspects, features, and advantages of the present disclosure would be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve similar results.
Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable.
Below, embodiments and variations of the present disclosure are described with reference to drawings. In the embodiments and variations described below, the same reference numerals are given to components having the same functions and configuration, and the descriptions thereof are omitted as needed. In the drawings attached, components may partially be omitted for ease of understanding. It is to be noted that suffixes Y, M, C, and K denote colors yellow, magenta, cyan, and black, respectively. These suffixes may be omitted unless otherwise specified.
Below, a description is given of an image forming apparatus 100 according to an embodiment of the present disclosure. In this embodiment, the image forming apparatus 100 is illustrated as an electrophotographic color printer. Below, a configuration of an image forming apparatus 100 according to an embodiment of the present disclosure is described with reference to
The photoconductor 2 includes a drum-shaped base and an organic photosensitive layer on a surface of the base. The photoconductor 2 is rotated in a clockwise direction indicated by arrow RD in
The uniformly charged surface of the photoconductor 2 by the charging roller 7 is scanned by exposure light such as a light beam projected from the optical writing unit 101, thereby forming an electrostatic latent image for black on the surface of the photoconductor 2. The electrostatic latent image on the photoconductor 2 is developed with toner T of the respective color by the developing device 8. Accordingly, a visible image, also known as a toner image, is formed. The toner image formed on the photoconductor 2 is transferred primarily onto an intermediate transfer belt 31 formed into an endless loop.
The photoconductor cleaner 3 removes residual toner remaining on the surface of the photoconductor 2 after a primary transfer process, that is, after the photoconductor 2 passes through a primary transfer nip between the intermediate transfer belt 31 and the photoconductor 2. The photoconductor cleaner 3 includes a cleaning brush roller 4 which is rotated and a cleaning blade 5. The cleaning blade 5 is cantilevered, that is, one end thereof is fixed to a housing of the photoconductor cleaner 3, and the other end is a free end that contacts the surface of the photoconductor 2. The cleaning brush roller 4 rotates and brushes off the residual toner from the surface of the photoconductor 2 while the cleaning blade 5 scraping off the residual toner from the surface. The static eliminator may employ a known static eliminating device and removes residual charge remaining on the photoconductor 2 after the surface thereof is cleaned by the photoconductor cleaner 3 in preparation for the subsequent imaging cycle. The surface of the photoconductor 2 is initialized by the charge removing operation in preparation for the subsequent imaging cycle.
The developing device 8 includes a developing section 12 and a developer conveyor 13. The developing section 12 includes a developing roller 9 inside thereof. The developer conveyor 13 stirs and transports the developing agent. The developer conveyor 13 includes a first chamber equipped with a first screw 10 and a second chamber equipped with a second screw 11. The first screw 10 and the second screw 11 are rotatably supported by, e.g., a casing of the developing device 8. The first screw 10 and the second screw 11 are rotated to deliver the developing agent to the developing roller 9 while circulating the developing agent.
As illustrated in
Referring back to
The intermediate transfer belt 31 has a front surface 31a serving as an image bearing surface to bear a toner image thereon. The intermediate transfer belt 31 is looped around and stretched taut between the plurality of rollers, i.e., the drive roller 32, the secondary-transfer back surface roller 33, the cleaning auxiliary roller 34, the four primary transfer rollers 35Y, 35M, 35C, and 35K, and the rollers 36 and 37. The drive roller 32 is rotated in the clockwise direction by a driving device, such as a drive motor, and rotation of the drive roller 32 causes the intermediate transfer belt 31 to rotate in the same direction. In the transfer unit 30, the intermediate transfer belt 31 is looped around the plurality of rollers, thereby delivering a recording medium P.
The intermediate transfer belt 31 is interposed between the primary transfer rollers 35Y, 35M, 35C, and 35K, and the photoconductors 2Y, 2M, 2C, and 2K, thereby forming primary transfer nips serving as transfer sections for each color between a front surface 31a or an image bearing face of the intermediate transfer belt 31 and the photoconductors 2Y, 2M, 2C, and 2K. A primary transfer bias is applied to the primary transfer rollers 35Y, 35M, 35C, and 35K by a transfer bias power source. Accordingly, a primary transfer electric field is formed between the primary transfer rollers 35Y, 35M, 35C, and 35K, and the toner images of yellow, magenta, cyan, and black formed on the photoconductors 2Y, 2M, 2C, and 2K,
An yellow toner image formed on the photoconductor 2Y enters the primary transfer nip for yellow as the photoconductor 2Y rotates. Subsequently, the yellow toner image is primarily transferred from the photoconductor 2Y to the intermediate transfer belt 31 by the transfer electric field and the nip pressure. The intermediate transfer belt 31, on which the yellow toner image has been transferred, passes through the primary transfer nips of magenta, cyan, and black. Subsequently, a magenta toner image, a cyan toner image, and a black toner image on the photoconductors 2M, 2C, and 2K, respectively, are superimposed on the yellow toner image which has been transferred on the intermediate transfer belt 31, one atop the other in the primary transfer process, Accordingly, a composite toner image, in which the toner images of four different colors are superimposed on one atop the other, is formed on the surface of the intermediate transfer belt 31 in the primary transfer process. According to the present embodiment, roller-type primary transferors, that is, the primary transfer rollers 35Y, 35M, 35C, and 35K, are employed as primary transferors, Alternatively, a transfer charger and a brush-type transferer may be employed as the primary transferer.
The secondary transfer unit 41 is disposed outside the loop of the intermediate transfer belt 31. A nip forming roller 400 of the transfer unit 30 is disposed outside the loop formed by the intermediate transfer belt 31, opposite to the secondary-transfer back surface roller 33. The intermediate transfer belt 31 is interposed between the secondary-transfer back surface roller 33 and the nip forming roller 400, thereby forming a secondary transfer nip N serving as a transfer section at which the front surface 31a of the intermediate transfer belt 31 contacts the secondary transfer belt 404. A secondary transfer bias is applied to the secondary-transfer back surface roller 33 by a secondary-transfer bias power source 39 (hereinafter referred to as power source 39). With this configuration, a secondary-transfer electrical field is formed between the secondary-transfer back surface roller 33 and the secondary transfer belt 404 so that the toner T having a negative polarity is moved electrostatically from the secondary-transfer back surface roller 33 to the secondary transfer belt 404. In other words, the secondary transfer belt 404 serving as secondary transferor forms the secondary transfer nip N between the secondary transfer belt 404 and an image bearing surface 21A, to transfer a toner image on a recording medium P.
As illustrated in
In the transfer unit 30, the intermediate transfer belt 31 is an endless looped belt serving as an image bearer to bear a toner image transferred thereon. In the transfer unit 30, the intermediate transfer belt 31 is looped around and supported with the plurality of rollers, i.e., the drive roller 32, the secondary-transfer back surface roller 33, the cleaning auxiliary roller 34, and the rollers 36 and 37. Accordingly, the transfer unit 30 acts as a belt unit to deliver the toner images transferred on the intermediate transfer belt 31 to the secondary transfer nip N serving as a transfer section at which the toner image is transferred from the intermediate transfer belt 31 to the recording medium P in the secondary transfer process.
In the secondary transfer nip N, the recording medium P tightly contacts the composite toner image on the front surface 31a of the intermediate transfer belt 31, and the four-color superimposed toner images are collectively transferred onto the recording medium P by a secondary transfer electric field and a nip pressure applied thereto, thereby forming a full-color toner image in combination with white color of the recording medium P. After passage of the secondary transfer nip N, untransfered residual toner remains on the intermediate transfer belt 31. The residual toner is removed from the intermediate transfer belt 31 by the belt cleaning device 38 which contacts the front surface 31a of the intermediate transfer belt 31. The cleaning auxiliary roller 34 inside the loop formed by the intermediate transfer belt 31 supports the cleaning operation performed by the belt cleaning device 38. A potential sensor 63 is disposed outside the loop formed by the intermediate transfer belt 31. More specifically, of the entire circumferential area of the intermediate transfer belt 31, the potential sensor 63 is disposed opposite to a portion of the intermediate transfer belt 31 wound around the drive roller 32 with a predetermined gap between the potential sensor 63 and the intermediate transfer belt 31. The surface potential of the toner image primarily transferred onto the intermediate transfer belt 31 is measured with the potential sensor 63 when the toner image comes to a position opposite to the potential sensor 63.
A post-nip delivery path 65b is disposed downstream of the secondary transfer nip N in a direction of delivery of a recording medium P indicated by arrow B (hereinafter, the delivery direction B). Hereinafter, the downstream side in the delivery direction B of the recording medium P is referred to as a downstream, side in the delivery direction. The downstream side in the delivery direction means a left side of the secondary transfer nip Nin
In the apparatus body 100A, the secondary transfer unit 41 is supported with a first support assembly 40. The first support assembly 40 detachably supports the secondary transfer unit 41. The secondary transfer unit 41 is replaceable independently as a single unit. The secondary transfer unit 41 includes the nip forming roller 400 serving as a rotator and a transferer disposed opposite to the secondary-transfer back surface roller 33 via the intermediate transfer belt 31. The secondary transfer unit 41 includes three rollers 401, 402, and 403 serving as three rotators, and a secondary transfer belt 404 looped around the nip forming roller 400 and three rollers 401, 402, and 403. The secondary transfer belt 404 serves as an image bearer and a transferer. In other words, the secondary transfer unit 41 is a belt conveyor unit in which the secondary transfer belt 404 is an endless looped belt serving as an image bearer, and is looped around the plurality of rollers, i.e., the nip forming roller 400 and the rollers 401, 402, and 403. The nip forming roller 400 is also referred as a secondary transfer roller.
The nip forming roller 400 secondarily transfers the toner image from the front surface 31a of the intermediate transfer belt 31 onto the recording medium P. The nip forming roller 400 is disposed inside the belt loop of the secondary transfer belt 404, facing to the secondary-transfer back surface roller 33. The intermediate transfer belt 31 and the secondary transfer belt 404 are interposed between the nip forming roller 400 and the secondary-transfer back surface roller 33. The nip forming roller 400 is biased against the secondary transfer belt 404 so as to pressingly contact the secondary transfer belt 404, thereby forming the secondary transfer nip N between the intermediate transfer belt 31 and the secondary transfer belt 404.
In this embodiment, the power source 39 applies bias for secondary transfer (secondary transfer bias) to the secondary-transfer back surface roller 33. In some embodiments, the power source 39 applies secondary transfer bias to the nip forming roller 400. In a case in which the secondary transfer bias is applied to the nip forming roller 400, the secondary transfer bias having a polarity opposite that of the toner is applied to the nip forming roller 400. In a case in which the secondary transfer bias is applied to the secondary-transfer back surface roller 33, the secondary transfer bias having the same polarity as that of the toner is applied to the secondary-transfer back surface roller 33. The roller 401 is to strip the recording medium P, which is electrostatically attracted to the secondary transfer belt 404, from the secondary transfer belt 404 by self stripping along the curvature of the roller 401.
Next, a description is given of a configuration of an upstream side from the secondary transfer nip N in the delivery direction B.
When the recording medium P is further delivered, the leading end Pa is guided into the secondary transfer nip N. The front surface 31a of the intermediate transfer belt 31 and the recording medium P tightly contact each other and enter the secondary transfer nip N. After a trailing end Pb of the recording medium P passes the upper guide 500, as illustrated in
Hence, in this embodiment, as illustrated in
The guide unit 50 includes the mount 53 made of metal and the first guide 51 and the second guide 52 mounted on the mount 53. The first guide 51 and the second guide 52 are film members made of resin. As illustrated in
As illustrated in
As illustrated in
As illustrated in
In this embodiment, as illustrated in
The first guide 51 and the second guide 52 are dimensioned to satisfy d1≥d2, where d1 is the thickness of the first guide 51 in the adjoin-separation direction F and d2 is the thickness of the second guide 52. The thickness d2 of the second guide 52 includes a thickness d3 of the sheet 521 and a thickness d4 of the sheet 522. Note that the relation of d1>d2 is preferable to allow the trailing end. Pb of the recording medium P to more smoothly move from the second guide 52 to the first guide 51.
The configuration of the multiple sheets 521 and 522 laminated facilitates adjustment of the thickness of the second guide 52. In other words, the first guide 51 presses the leading end Pa or the entire of the recording material P during passage, at a position upstream from the secondary transfer nip N in the delivery direction B. Accordingly, the first guide 51 has a hardness sufficient to prevent contact with the front surface 31a of the intermediate transfer belt 31 even when the first guide 51 is elastically deformed by contact with the recording medium P. By contrast, the second guide 52 has a flexibility, rather than a hardness, sufficient to elastically deform by contact with the trailing end Pb of the recording medium P. Accordingly, it may be more difficult to set the thickness d2 with a single sheet, Hence, in this embodiment, the multiple sheets are preferably laminated to obtain the desired thickness d2. Thus, the thickness d1 of the first guide 51 and the thickness d2 of the second guide 52 are set to satisfy the relation of d1≥d2. Note that the number of sheets constituting the second guide 52 is not limited to two and may be two or more. Alternatively, if proper elastic deformation is obtained, the second guide may be made of a single sheet.
Next, a description is given of a configuration of the mount 53. As illustrated in
As illustrated in
As described above, the formation of the mount 53 by joining multiple metal members preferably obtains a desired hardness while securing the predetermined gap D1 between the first guide 51 and the second guide 52. In addition, as illustrated in
Next, action of the guide unit 50 is described with reference to
As the leading end Pa of the recording medium P enters the secondary transfer nip N, the recording medium P more warps. However, the first guide 51 has a desired hardness, thus preventing the first guide 51 from being excessively bent toward the intermediate transfer belt 31. Accordingly, since the contact of the front surface 31a with the first guide 51 is prevented, the vibration of the intermediate transfer belt 31 is reduced, thus preventing occurrence of an abnormal image due to disturbance of a toner image borne on the front surface 31a.
When the recording medium P is further delivered, the leading end Pa is guided into the secondary transfer nip N. The front surface 31a of the intermediate transfer belt 31 and the recording medium P tightly contact each other and enter the secondary transfer nip N. As illustrated in
The leading end 52c of the second guide 52 is disposed to be inclined relative to the delivery direction B in an area from the end 52a to the other end 52b in the lateral direction X. In other words, the leading end 52c of the second guide 52 is inclined so that a projecting amount t1 of the end 52a beyond the downstream end 53c is greater than a projecting amount t2 of the other end 52b beyond the downstream end 53c. Accordingly, as the recording medium P is delivered in the delivery direction B, the contact area of the second guide 52 with the recording medium P increases. Such a configuration moderates deformation of the second guide 52 toward the first guide 51. As illustrated in
The warping of the trailing end Pb of the recording medium P at the first guide 51 is reduced by deformation of the second guide 52 than when the trailing end Pb of the recording medium P arrives at the lower portion of the guide unit 50, thus moderating the restoring action. In such a state, when the recording medium P moves in the delivery direction B, the first guide 51 elastically deforms in a direction to approach the intermediate transfer belt 31. Accordingly, after the trailing end Pb passes below the first guide 51, as illustrated in
If the first guide 51 is heavily bent and contacts the front surface 31a, the roller 37 disposed inside the loop of the intermediate transfer belt 31 prevents the intermediate transfer belt 31 from being shifted toward the inside of the loop. Accordingly, vibration of the intermediate transfer belt 31 is reduced, thus more reliably preventing occurrence of an abnormal image on the recording medium P.
As illustrated in
As the leading end P1a of the recording medium P1 enters the secondary transfer nip N, the recording medium P1 more warps. However, the first guide 51 has a desired hardness, thus preventing the first guide 51 from being excessively bent toward the intermediate transfer belt 31. Accordingly, since the contact of the front surface 31a with the first guide 51 is prevented, the vibration of the intermediate transfer belt 31 is reduced, thus preventing occurrence of an abnormal image due to disturbance of a toner image borne on the front surface 31a.
When the recording medium P is further delivered, the leading end Pa is guided into the secondary transfer nip N. The front surface 31a of the intermediate transfer belt 31 and the recording medium P tightly contact each other and enter the secondary transfer nip N. As illustrated in
The leading end 52c of the second guide 52 is disposed to be inclined relative to the delivery direction B in an area from the end 52a to the other end 52b in the lateral direction X. In other words, the leading end 52c of the second guide 52 is inclined so that a projecting amount t1 of the end 52a beyond the downstream end 53c is greater than a projecting amount t2 of the other end 52b beyond the downstream end 53c. Accordingly, as the recording medium P1 is delivered in the delivery direction B, the contact area of the second guide 52 with the recording medium P1 increases, thus moderating deformation of the second guide 52 toward the first guide 51. Thus, as illustrated in
The warping of the trailing end P lb of the recording medium P1 at the first guide 51 is reduced by deformation of the second guide 52 than when the trailing end Pb of the recording medium P arrives at the lower portion of the guide unit 50, thus moderating the restoring action. In such a state, when the recording medium P1 moves in the delivery direction B, the first guide 51 elastically deforms in a direction to approach the intermediate transfer belt 31. Accordingly, after the trailing end P1b passes below the first guide 51, as illustrated in
Next, a description is given of the dimension of the guide unit 50 in this embodiment. In this embodiment, the gap GP of the opposing face 51d of the first guide 51 and the front surface 31a of the intermediate transfer belt 31 is disposed within a range of 0.5 mm to 2 mm from the front surface 31a. For the second guide 152, the projecting amount of the other end 52b beyond the end 52a is not greater than 5 mm. The predetermined gap D1 between the first guide 51 and the predetermined gap D1 is not greater than 2 mm. The thickness d1 of the first guide 51 is 0.35 mm in consideration of the hardness and the contact with the front surface 31a of the intermediate transfer belt 31. The thickness d1 can be greater. However, if the thickness d1 is greater, the first guide 51 would he closer to the front surface 31a and might contact the front surface 31a. Therefore, in consideration of the balance between the thickness and the gap GP, the thickness d1 is set to be 0.35 mm. The thickness d2 of the second guide 52 is not limited to 0.35 mm. However, if the thickness d2 is relatively smaller, the second guide 52 would have a relatively lower hardness and might be broken by contact with the recording medium P or P1. Accordingly, in consideration of endurance, the thickness d2 of the second guide 52 is set to be at least 0.125 mm. Such a thickness prevents breakage of the second guide 52 and causes the second guide 52 to be sufficiently bent, thus allowing smooth movement of the recording medium P from the second guide 52 to the first guide 51. The degree of bending and the contact state of each of the first guide 51 and the second guide 52 vary with the delivery speed of recording media R. Therefore, the above-described test of the thickness d2 of the second guide 52 is conducted with a maximum delivery speed of recording media in a test apparatus.
In delivery, typically, the strong recording medium P, a thick sheet of paper, contacts both the first guide 51 and the second guide 52, and the weak recording medium P1, a thin sheet of paper, contacts only the first guide 51 or the second guide 52. However, when the thin recording medium P1 is conveyed at a high speed, the thin recording medium P1 may contact both the first guide 51 and the second guide 52. Accordingly, recording media P to contact and be guided with the first guide 51 and the second guide 52 are not limited to thick sheets of paper and thin sheets of paper, and any suitable types of recording material to be delivered toward the secondary transfer nip N. In this embodiment, the first guide 51 and the second guide 52 are made of resin film(s). Note that, since the first guide 51 does not necessarily need bendability, the first guide 51 may be made of a single metal plate, instead of the resin film(s).
Next, a description is given of the configuration and arrangement of the rollers 36 and 37 serving as two rotators. As illustrated in FIG, 11, the rollers 36 and 37 are disposed side by side in a belt travel direction A of the intermediate transfer belt 31, at a position upstream from the secondary transfer nip N in the delivery direction B of the recording medium P (the belt travel direction A of the intermediate transfer belt 31) and opposing the guide unit 50. The rollers 36 and 37 contact the back surface 31b serving as the non image bearing face of the inter mediate transfer belt 31, which is disposed at an opposite side of the front surface 31a. The roller 37 is disposed closer to the secondary transfer nip N (the transfer section) than the roller 36. and serves as a first rotator. The roller 36 serves as a second rotator disposed upstream from the roller 37 in the belt travel direction A of the intermediate transfer belt 31. The roller 36 and the roller 37 are rotatably supported with mount brackets 70 and 71 opposing each other. The roller 36 is a metal roller, and the roller 37 adjacent to the secondary transfer nip N is an insulation roller to prevent leakage of secondary transfer bias. In this embodiment, the roller 37 is an insulation roller made of resin.
The intermediate transfer belt 31 is supported with a plurality of rollers including, e.g., the drive roller 32, the secondary-transfer back surface roller 33, and the cleaning auxiliary roller 34. The drive roller 32 supports the intermediate transfer belt 31 at a most upstream position (a right-side position in
The rollers 36 and 37 contact the back surface 31b of the intermediate transfer belt 31 at the transfer-entry-side stretched surface 31d. The intermediate transfer belt 31 wind around each of the rollers 36 and 37 at a certain amount. Each of the rollers 36 and 37 is disposed at a position upstream in the belt travel direction A from a position at which a leading end Pa of a recording medium P delivered from the pair of registration rollers 61 toward the secondary transfer nip N contacts the front surface 31a of the intermediate transfer belt 31. Each of the rollers 36 and 37 is disposed at a position closer to the secondary transfer nip N than the drive roller 32 in the transfer-entry-side stretched surface 31d, In other words, an interaxial distance La between the roller 36 disposed at the upstream side (hereinafter, also referred to as the upstream roller 36) and the roller 37 disposed at the downstream side (hereinafter, also referred to as the downstream roller 37) in the belt travel direction A is shorter than a distance Lc from the drive roller 32 to the upstream roller 36. A distance Lb from the downstream roller 37 to the secondary transfer nip N is shorter than the distance Lc from the drive roller 32 to the upstream roller 36. A total distance of La and Lb is set to be shorter than the distance Lc.
In other words, the front surface 31a of the intermediate transfer belt 31 is wound around the drive roller 32 that serves as an adjustment rotator disposed upstream from the transfer nip N in the belt travel direction A (a rotation travel direction of the intermediate transfer belt 31) to adjust the orientation of the intermediate transfer belt 31. Accordingly; the front surface 31a of the intermediate transfer belt 31 is divided into the image-formation-side stretched surface 31c upstream from the drive roller 32 in the belt travel direction A and the transfer-entry-side stretched surface 31d between the drive roller 32 and the secondary transfer nip N, La represents a distance (inter-rotational-center distance) between a rotation center J3 of the roller 36 and a rotation center J4 of the roller 37. Lb is a distance from the rotation center J4 of the roller 37 serving as the first rotator disposed closer to the secondary transfer nip N, of the rollers 36 and 37, and the secondary transfer nip N. Lc is a distance from the rotation center J3 of the roller 36 serving as the second rotator disposed further away from the secondary transfer nip N than the roller 37, of the rollers 36 and 37, and the rotation center J5 of the drive roller 32. The rollers 36 and 37 and the drive roller 32 are disposed to satisfy the relations of La<Lc, Lb<Le, and La+Lb<Lc.
As described above, as compared with a configuration in which only the roller 36 is disposed at the transfer-entry-side stretched surface 31d, the arrangement of the rollers 36 and 37 on the transfer-entry-side stretched surface 31d reduces the shift (referred to as shock jitter) of the transfer position of a toner image at the primary transfer section, which is formed at an opposing portion at which the photoconductors oppose the front surface 31a of the intermediate transfer belt 31, due to transmission of an impact (shock) of a contact of the recording medium P with the front surface 31a of the intermediate transfer belt 31 to the image-formation-side stretched surface 31c. The arrangement of the rollers 36 and 37 at a position closer to the secondary transfer nip N than the drive roller 32 reliably reduces flutter or vibration of the intermediate transfer belt 31 due to a contact of a leading end Pa or a trailing edge Pb of a recording medium P with the intermediate transfer belt 31.
As illustrated in
At a position upstream from the secondary transfer nip N, the intermediate transfer belt 31 is wound around the secondary transfer belt 404 by the downstream roller 37. An imaginary surface Q1 is defined as a stretched surface of the intermediate transfer belt 31 between the secondary transfer nip N and the upstream roller 36, assuming that the downstream roller 37 is not provided. In the area of the imaginary surface Q1, the intermediate transfer belt 31 is wound around the secondary transfer belt 404 by the upstream roller 36, at a position upstream from the secondary transfer nip N.
Such arrangement of the rollers 36 and 37 allows the rollers (in particular, the roller 36 at the upstream side in the belt travel direction A) to apply tension to the intermediate transfer belt 31, thus reducing the fluttering or vibration of the intermediate transfer belt 31 and allowing more stable rotation of the intermediate transfer belt 31.
In this embodiment, a triangle is defined by the rotation center J1 of the nip forming roller 400, the rotation center J2 of the secondary-transfer back surface roller 33, and the rotation center J3 of the upstream roller 36. At this time, the downstream roller 37 is disposed such that the rotation center J4 is located within a range of the triangle (within the triangle). Such arrangement prevents the downstream roller 37 from excessively projecting toward the front surface 31a of the intermediate transfer belt 31 (downward in
When the recording material P is a thick sheet of paper, the bending amount of the first guide 51 or the second guide 52 of the guide unit 50 is relatively large, the distance (the gap GP) between the guide unit 50 and the front surface 31a of the intermediate transfer belt 31, more preferably, the first guide 51 and the front surface 31a is preferably larger. However, if the distance (the gap GP) between the front surface 31a and the first guide 51 is increased, as described above, a trailing end Pb of the recording medium P would more strongly flip up after passage of the first guide 51 and cause vibration in the intermediate transfer belt 31, thus resulting in a reduction in image quality. Therefore, in the case of the thick sheet of paper, the roller 37 is pushed further downward than in the case of a thin sheet of paper, to reduce the distance (the gap GP). In other words, the projection amount of the roller 37 is greater in the case of the thick sheet of paper than in the case of the thin sheet of paper.
Hence, in this embodiment, as illustrated in
In this embodiment, when the mount brackets 70 and 71 swing counterclockwise around the shaft 72, the roller 37 moves in a direction to approach the guide unit 50. By contrast, when the mount brackets 70 and 71 swing clockwise around the shaft 72, the roller 37 moves in a direction to separate from the guide unit 50.
As described above, the position of the roller 37 is movable to a position at which the intermediate transfer belt 31 is placed adjacent to the guide unit 50 and to a position at which the intermediate transfer belt 31 is placed away from the guide unit 50, thus allowing adjustment of the projecting amount of the roller 37 in accordance with the thickness of the recording medium P. In other words, the distance (the gap GP) between the guide unit 50 and the front surface 31a is adjustable, and the position of the front surface 31a of the intermediate transfer belt 31 is adjustable to an optimal position suitable for the recording medium P. Such a configuration reduces vibration of the intermediate transfer belt 31, thus preventing a reducing in image quality. In
In the above-described embodiment, the roller 37 is supported to be swingable relative to the guide unit 50 to adjust the distance (the gap GP) between the front surface 31a of the intermediate transfer belt 31 and the guide unit 50 (the opposing face 51d of the first guide 51). In an embodiment illustrated in
In the above-described embodiment, the multiple rollers 36 and 37 serving as a plurality of rotators and a plurality of contact members are rotatably supported with the mount brackets 70 and 71. However, in some embodiments, as illustrated in
The plurality of contact members are not limited to the configurations of the rollers 36 and 37 or the contact members 360 and 370 and may be any other suitable type of members. For example, as illustrated in FIG, 22, as the plurality of contact members, a first contact member 370A and a second contact member 360A of a block shape are disposed opposing the intermediate transfer belt 31. The first contact member 370A and the second contact member 360A have a flat contact face 370Aa and a flat contact face 360Aa, respectively, to contact a front surface 31a serving as an image bearing surface of the intermediate transfer belt 31 serving as the image bearer. The number of the contact member having the flat contact face is not limited to two. At least one of the first contact member 370A and the second contact member 360A may be the contact member having the flat contact face. For example, one of the first contact member 370A and the second contact member 360A may be disposed in combination with one of the rollers 36 and 37 or one of the contact members 370 and 360 in the above-described embodiment. For example, as illustrated in
The stationary (nonrotatable) contact member 370, the first contact member 370A, or the first contact member 370B may be employed instead of the roller 37. Such a configuration reduces unnecessary vibration of the intermediate transfer belt 31, serving as a belt-shaped image bearer, upstream from the secondary transfer nip N, serving as the transfer section, in the delivery direction of a recording medium P. Alternatively, the stationary (nonrotatable) contact member 360, the second contact member 360A, or the first contact member 360B may be employed instead of the roller 36. Such a configuration reduces unnecessary vibration of the intermediate transfer belt 31, serving as a belt-shaped image bearer, upstream from the secondary transfer nip N, serving as the transfer section, in the delivery direction of a recording medium P. The number of contact members (rotators) disposed side by side at positions opposing the guide unit 50 serving as a guide unit is not limited to two. In some embodiments, three or more contact members (rotators) may be disposed at positions opposing the guide unit 50 serving as a guide unit.
Like the rollers 36 and 37, the contact member 360 and, the contact member 370, the first contact member 370A and the second contact member 360A, the first contact member 370B and the second contact member 360B may be disposed opposing a guide unit 50 including two guides, the first guide 51 and the second guide 52. Alternatively, in some embodiments, the guide unit 50 includes a single guide.
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, but a variety of modifications can naturally be made within the scope of the present disclosure. For example, the image forming apparatus is not limited to a color printer and may also be a printer, a facsimile machine, a plotter printer, or a multifunction peripheral having capabilities of a scanner and at least one of a printer, a facsimile machine, a plotter printer, or a copier. In the above-described embodiments, the guide unit 50 including two guides, the first guide 51 and the second guide 52, is disposed opposing the rollers 36 and 37. Alternatively, as described above, the guide unit 50 may be a guide unit including a single guide.
In the above descriptions, the image forming apparatus according to any of the above-described embodiments transfers images from the intermediate transfer belt 31 onto a recording medium P. Instead of such an image forming apparatus employing an intermediate transfer system, for example, the present invention is applicable to an apparatus (an image forming apparatus of a direct transfer system that directly transfers an image from an image bearer, such as a photoconductor drum or a photoconductor belt, onto a recording medium P. In the above-described embodiments, the secondary transfer belt 404 is employed as a transfer device. Alternatively, in some embodiments, instead of the secondary transfer belt 404, a secondary transfer roller may be employed as a transfer device. The transfer section may be a transfer device of a system having no transfer nip (e.g., a transfer charger of a charging system). In the above-described embodiments, the image forming apparatus conveys a recording medium P in a horizontal direction in the transfer section (the secondary transfer nip N). However, embodiments of this disclosure are not limited to the configuration of horizontal conveyance. For example, the present invention is applicable to an image forming apparatus that conveys a recording medium P in a transfer section upward, downward, diagonally upward, or diagonally downward.
The above-described effects of the embodiments and variations are only examples of effects obtained from the present invention, and the effects of the present invention are not limited to those described in the above-described embodiments and variations.
Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the above teachings, the present disclosure may be practiced otherwise than as specifically described herein. With some embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the present disclosure and appended claims, and all such modifications are intended to be included within the scope of the present disclosure and appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-253108 | Dec 2014 | JP | national |
| 2015-197986 | Oct 2015 | JP | national |
This application is a continuation of U.S. application Ser. No. 14/969,216, filed on Dec. 15, 2015, and is based upon and claims the benefit of foreign priority from Japanese Patent Application No. 2014-253108, filed on Dec. 15, 2014, and from Japanese Patent Application No. 2015-197986, filed on Oct. 5, 2015. The entire contents of each of the above applications are incorporated herein by reference in entirety.
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| Child | 15592006 | US |
