Patent Grant
11586131
The present invention relates to an image forming apparatus, such as a printer, a copying machine, a facsimile, or a multi-function machine, using electrophotography.
Conventionally, in order to form an image on a recording material, an image forming apparatus of an intermediary transfer type has been used. In the image forming apparatus of the intermediary transfer type, a toner image formed on a photosensitive drum is transferred onto an intermediary transfer belt in response to application of a primary transfer voltage. Thereafter, when a strong electric field is generated in response to application of a secondary transfer voltage in a transfer nip formed by an inner secondary transfer roller and an outer secondary transfer roller which are provided while sandwiching the intermediary transfer belt therebetween, the toner image on the intermediary transfer belt is transferred onto a recording material passing through the transfer nip. The recording material onto which the toner image is to be transferred is fed toward the transfer nip, and is controlled in attitude and guided by a pair of an inner guiding plate and an outer guiding plate which are disposed on a side upstream of the transfer nip with respect to a recording material feeding direction (Japanese Laid-Open Application (JP-A) 2016-170289).
In the case of an apparatus disclosed in JP-A 2016-170289, the outer guiding plate is provided in a transfer feeding unit rotatably supported by a supporting frame, and the inner guiding plate is fixed to the supporting frame so as to form one surface of a recording material feeding path between itself and the outer guiding plate. That is, the outer guiding plate is capable of being contacted to and separated from the intermediary transfer belt and the inner guiding plate in response to rotation of the transfer feeding unit. Further, the transfer feeding unit is provided with a pressing unit (pressing member) for rotating and positioning the outer guiding plate in order to form an interval (gap), appropriate for the toner image transfer, between the outer guiding plate and the intermediary transfer belt. The outer guiding plate is supported by the transfer feeding unit via the pressing unit. This is because in the case where the interval between the outer guiding plate and the intermediary transfer belt is not appropriate, when the recording material enters the transfer nip, an entrance angle is not stabilized and the recording material flutters and thus there is a liability that improper transfer such that the toner image is not properly transferred is caused to occur. Particularly, the improper transfer is liable to occur when the outer guiding plate is provided at a position spaced from the intermediary transfer belt.
However, conventionally, there was a liability that the outer guiding plate is not disposed at a position where the outer guiding plate is capable of forming the interval appropriate for the toner image transfer relative to the intermediary transfer belt since the outer guiding plate and the intermediary transfer belt are disposed on separate units by way of many component parts. That is, each of the supporting frame, the transfer feeding unit, and the pressing unit can cause component (part) tolerance. Therefore, a relative positional relationship between the intermediary transfer belt and the outer guiding plate which are mounted to the respective units is influenced by the component tolerances of the respective units. If so, for each of individual image forming apparatuses, there is a liability that in a state in which the outer guiding plate is spaced from the intermediary transfer belt in a distance more than an appropriate interval, the outer guiding plate is disposed relative to the intermediary transfer belt.
The present invention has been accomplished in view of the above-described problem. A principal object of the present invention is to provide an image forming apparatus in which an outer guiding plate for guiding a recording material to a transfer nip is capable of being provided at a position where an interval appropriate for toner image transfer is formed between the outer guiding plate and an intermediary transfer belt.
According to an aspect of the present invention, there is provided an image forming apparatus comprising: an endless image bearing belt rotatable while bearing a toner image transferred from an image bearing member; a first roller configured to stretch the image bearing belt; a second roller provided on a side upstream of the first roller with respect to a rotational direction of the image bearing belt and configured to stretch the image bearing belt in cooperation with the first roller; a rotatable member configured to form a transfer nip in which the toner image on the image bearing belt is transferred onto a recording material while nipping and feeding the recording material in cooperation with the first roller through the image bearing belt; a holding member configured to rotatably hold the second roller at opposite end portions with respect to a rotational axis direction of the second roller; a feeding unit configured to feed the recording material toward the transfer nip; a guiding member which is provided on a side downstream of the feeding unit and upstream of the transfer nip with respect to a recording material feeding direction at a position opposing a stretching portion stretched by the first roller and the second roller of the image bearing belt and which is configured to guide the recording material, to the transfer nip, fed by the feeding unit; and wherein the guiding member is fixed to the holding portion.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Parts (a) and (b) of
Part (a) of
<Image Forming Apparatus>
An image forming apparatus of this embodiment will be described using
As shown in
An outer secondary transfer roller 217 as a rotatable member is provided so as to sandwich the intermediary transfer belt 216 in cooperation with the inner secondary transfer roller 216a, and forms a secondary transfer nip T2 where the toner images on the intermediary transfer belt (image bearing belt) 216 are secondary-transferred onto the recording material S. In the secondary transfer nip T2, the recording material S is nipped and fed by the inner secondary transfer roller 216a and the outer secondary transfer roller 217. Further, in response to application of a secondary transfer voltage to, for example, the outer secondary transfer roller 217 by an unshown high-voltage source, the toner images on the intermediary transfer belt 216 are transferred onto the recording material S.
In this embodiment, on a side upstream of a pair of these inner secondary transfer roller 216a and outer secondary transfer roller 217, an inner guiding plate 290a and an outer guiding plate 290b are provided.
The inner guiding plate 290a and the outer guiding plate 290b are provided for guiding the recording material S, fed by a registration roller pair 270, to the secondary transfer nip T2, the inner guiding plate 290a and the outer guiding plate 290b will be described later (see
Below the image forming apparatus 201, one to a plurality of cassettes 231 in which recording materials S are accommodated are provided. The recording material S accommodated in the cassette 231 are supplied one by one from the cassette 231 to a feeding path 60 by a feeding roller 251 in conformity to an image forming timing. The recording material S is fed to the registration roller pair 270 disposed in the feeding path 60, and is subjected to oblique movement correction and timing correction by the registration roller pair 270 as a feeding unit, and then is fed toward the secondary transfer nip T2.
The four image forming portions PY, PM, PC and PK provided in the image forming apparatus 201 have the substantially same constitution except that colors of toners used in developing devices 214 included therein are different from each other. Accordingly, herein, the yellow image forming portion PY will be described as a representative, and other image forming portions PY, PC and PK will be omitted from description. In the image forming portion PY, a photosensitive drum 212 as an image bearing member is provided. The photosensitive drum 212 is a photosensitive member rotationally driven by an unshown motor. At a periphery of the photosensitive drum 212, a charging device 213, the developing device 214, and a primary transfer roller 219 are provided.
In the case where an image forming operation is started, first, a surface of the rotating photosensitive drum 212 is electrically charged uniformly by the charging device 213. Then, the photosensitive drum 212 is subjected to scanning exposure with laser light emitted from an exposure device 210 (for example, a laser scanner) used in common with the image forming portions PY, PM, PC and PK. By this, an electrostatic latent image depending on the image signal is formed on the photosensitive drum 212. The electrostatic latent image formed on the photosensitive drum 212 is developed into a toner image by toner (developer) accommodated in the developing device 214.
The toner image formed on the photosensitive drum 212 is primary-transferred onto the intermediary transfer belt 216 in a primary transfer portion formed between the photosensitive drum 212 and the primary transfer roller 219 disposed while sandwiching the intermediary transfer belt 216 therebetween. At this time, to the primary transfer roller 219, a primary transfer voltage is applied. Thus, the intermediary transfer belt 216 is rotated while bearing the toner image transferred from the photosensitive drum 212.
The operation as described above is sequentially performed in the image forming portions PY, PM, PC and PK for yellow, magenta, cyan and black, so that the toner images are capable of being formed on the intermediary transfer belt 216. For example, a single-color toner image can be formed, and a toner image of a desired color can be formed by appropriately superposing toners of some of the four colors. In conformity to a formation timing of such a toner image, the recording material S supplied from the cassette 231 is fed to the secondary transfer nip T2 via the registration roller pair 270. Further, for example, a secondary transfer voltage is applied to the outer secondary transfer roller 217, whereby the toner images on the intermediary transfer belt 216 are secondary-transferred onto the recording material S during passing of the recording material S through the secondary transfer nip T2.
The recording material S on which the toner images are transferred from the intermediary transfer belt 216 is fed to a fixing device 220. In the fixing device 220, heat and pressure are applied to the recording material S while nipping and feeding the recording material S, whereby the toner images are fixed on the recording material S. In the case of an operation in a one-side printing mode in which the toner images are formed on one surface, the recording material S on which the toner images are fixed by the fixing device 220 is discharged onto a recording material stacking portion 223. On the other hand, in the case of an operation in a double-side printing mode in which the toner images are formed on both surfaces of the recording material S, after the toner images are formed on one surface by the fixing device 220, the recording material S is turned upside down by switch-back feeding and passes through a double-side (printing) feeding path 61, and then is fed toward the registration roller pair 270. Thereafter, the recording material S is subjected to a similar process as the process in the case of the operation in the one-side printing mode, so that the toner image is formed on the other surface by the fixing device 220, and then, the recording material S is discharged onto the recording material stacking portion 223.
In the case of this embodiment, the intermediary transfer belt 216, the inner secondary transfer roller 216a, the tension roller 216b, the pre-secondary transfer roller 216c, the driving roller 216d, a plurality of primary transfer rollers 219, the inner guiding plate 290a, and the outer guiding plate 290b form an intermediary transfer unit 20. The intermediary transfer unit 20 is provided so as to be inserted in and extracted from the supporting frame 201A. The intermediary transfer unit 20 is provided slidably in a mounting direction (arrow Y direction) in
<Outer guiding plate and inner guiding plate>
Next, the outer guiding plate 290b and the inner guiding plate 290a will be described using
The inner guiding plate 290a and the outer guiding plate 290b guide the recording material S to the secondary transfer nip T2 while restricting a movement direction of the recording material S sent from the registration roller pair 270. The inner guiding plate 290a as a first guiding member guides one surface (transfer surface onto which the toner image is transferred from the intermediary transfer belt 216) of the recording material S so as to restrict motion such that the recording material S approaches the intermediary transfer belt 216. On the other hand, the outer guiding plate 290b as a second guiding member guides the other surface (surface opposite from the transfer surface) of the recording material S so as to restrict motion such that the recording material S is moved away from the intermediary transfer belt 216.
As shown in
Incidentally, in the case of this embodiment, the outer guiding plate 290b is disposed so that, a feeding path 150 formed by the upstream guiding portion 291 and the inner guiding plate 290a becomes narrow from an upstream toward a downstream. Further, the outer guiding plate 290b is disposed so that a feeding path 160 formed by the downstream guiding portion 292 and the intermediary transfer belt 216 becomes narrow from the upstream toward the downstream. <Conventional example>
Incidentally, the outer guiding plate 290b is used in pair with the inner guiding plate 290a or the intermediary transfer belt 216, so that a guiding function of the recording material S as described above is capable of being realized. Therefore, each of a positional relationship between the upstream guiding portion 291 and the inner guiding plate 290a and a positional relationship between the downstream guiding portion 292 and the intermediary transfer belt 216 has an influence on the feeding path (150, 160), so that the attitude of the recording material S fed to the secondary transfer nip T2 of the intermediary transfer belt 216 is capable of being changed.
Conventionally, the positional relationship between the upstream guiding portion 291 and the inner guiding plate 290a and the positional relationship between the downstream guiding portion 292 and the intermediary transfer belt 216 were liable to cause positional deviation due to the component tolerance. Therefore, the intervals of the feeding paths (150, 160) become narrow or broad and thus an interval such that the toner image is appropriately transferred is not provided, with the result that improper transfer onto the recording material S occurred. Particularly, on an upstream side of the secondary transfer nip T2, electric discharge is generated by broadening of the interval between the recording material S and the intermediary transfer belt 216, so that a charge polarity of the toner is reversed. By this, a part of the image is not transferred onto the recording material S, so that there was a liability that a phenomenon of a white void of the image as improper transfer occurs. In order to suppress this phenomenon, it is effective that on the upstream side of the secondary transfer nip T2, the recording material S and the intermediary transfer belt 216 are caused to move together. That is, it is known that narrowing of the interval between the outer guiding plate 290b and the intermediary transfer belt 216 is effective. The conventional example is shown in
As shown in
As shown in part (a) of
In response to a closing operation of the door 400, the engaging portion 601 of the transfer feeding unit 600 contacts a free end (on a side opposite from the rotation shaft 560a) of the lock lever 560 provided on the supporting frame 450. Then, the door 400 is closed in a state in which the engaging portion 601 abuts against the lock lever 560, so that the lock lever 560 is rotated about the shaft 560a. The door 400 is closed as it is, as shown in
In the above-described transfer feeding unit 600, as shown in
In such a conventional example, there are many interposed component parts regarding the positioning of the outer guiding plate 610 and the intermediary transfer unit 500. For that reason, due to tolerances of the respective members, the interval (gap) between the intermediary transfer belt 501 and the outer guiding plate 610 is liable to become different, so that there was a liability that the above-described improper transfer is caused to occur. Particularly, on an upstream side of the secondary transfer nip T2 (in a stretching portion of the intermediary transfer belt 501 where the intermediary transfer belt 501 is stretched by the inner secondary transfer roller 502 and the pre-secondary transfer roller 503), electric discharge is generated by broadening of the interval between the recording material S and the intermediary transfer belt 501, so that the charge polarity of the toner is reversed. By this, a part of the image is not transferred onto the recording material S, so that there was a liability that a phenomenon of a white void of the image as improper transfer occurs. Therefore, in this embodiment, as described hereinbelow, at a position where an interval appropriate for transfer of the toner image is formed between the outer guiding plate 290b and the intermediary transfer belt 216, the outer guiding plate 290b was capable of being positionally disposed relative to the intermediary transfer belt 216. In the following, a positioning constitution of the outer guiding plate 290b relative to the intermediary transfer belt 216 will be described.
<Positioning Constitution of Outer Guiding Plate Relative to Intermediary Transfer Belt>
As shown in
On the other hand, the outer guiding plate 290b is fixed to the bearing 295 which is an example of a holding portion as shown in
The outer guiding plate 290b is fixed to the bearing 295 at a position outside, a feeding region of the recording material S fed by the registration roller pair 270, in the rotational axis direction of the pre-secondary transfer roller 216c. In order to fix the outer guiding plate 290b with the screw 300, at each of opposite end portions outside a width of a feedable maximum-width recording material S, as shown in
Thus, by fixing the outer guiding plate 290b to the bearing 295 of the pre-secondary transfer roller 216c for stretching the intermediary transfer belt 216, at a position where the interval between the outer guiding plate 290b and the intermediary transfer belt 216 becomes the interval appropriate for the toner image transfer, the outer guiding plate 290b can be positioned and disposed. That is, by directly fixing the outer guiding plate 290b to the bearing 295 supporting the pre-secondary transfer roller 216c, the number of interposed members relating to positioning of these guiding plates can be reduced. Therefore, the influence of component tolerances on the positioning can be suppressed, so that the interval of the feeding path 160 formed by the outer guiding plate 290b and the intermediary transfer belt 216 can be set at the interval appropriate for the toner image transfer.
As in the above-described conventional example, when the outer guiding plate 290b is disposed relative to the intermediary transfer belt 216 via six or more component parts, even when the component tolerances can be suppressed to about “0.1 mm” which is possible minimum level in manufacturing, the interval of the feeding path 160 can cause a variation of about “0.6 mm”. For example, it is preferable that in the feeding path 160, the interval at a narrowest position is “1.5 mm” (predetermined interval” and is constant with respect to the widthwise direction, but in the conventional example, for each image forming apparatus, a variation such that the interval is not constant in a range of “0.9 mm” to 2.1 mm” with respect to the widthwise direction occurred in some instances.
On the other hand, according to the above-described this embodiment, the variation in interval of the feeding path 160 formed by the outer guiding plate 290b and the intermediary transfer belt 216 can be suppressed to about “0.3 mm”. As regards a minimum interval of the feeding path 150 is set in general at a narrow interval such as about “1.5 mm” in order to prevent the improper transfer, and therefore, when the variation in interval can be suppressed from the conventional “0.6 mm” to about “0.3 mm”, a degree of contribution thereof is large. According to this embodiment, for example, in the case where it is desirable that the interval of the feeding path 160 at the narrowest position is “1.5 mm”, the variation in interval can be suppressed to a range of “1.2 mm to 1.8 mm” for each of individual image forming apparatuses.
As described above, according to this embodiment, the outer guiding plate 290b is fixed to the bearing 295 of the pre-secondary transfer roller 216c for stretching the intermediary transfer belt 216. By doing so, at positions where the interval of the feeding path 160 formed between the outer guiding plate 290b and the intermediary transfer belt 216 is formed at the interval appropriate for the toner image transfer, the outer guiding plate 290b can be disposed relative to the intermediary transfer belt 216 with a simple constitution. By this, when the recording material S enters the secondary transfer nip T2, a phenomenon that the entrance angle with respect to the intermediary transfer belt 216 is not stabilized and that the recording material S flutters does not occur, and thus improper transfer of the toner image from the intermediary transfer belt 216 onto the recording material S does not readily occur. That is, it is possible to suppress that the outer guiding plate 290b is disposed in a position spaced from the stretching portion 293, by the influence of the tolerances due to intervention of many members, of the intermediary transfer belt 216 stretched by the pre-secondary transfer roller 216c and the inner secondary transfer roller 216a. Therefore, electric discharge generated by broadening of the interval between the outer guiding plate 290b and the intermediary transfer belt 216 can be suppressed, so that it is possible to suppress the occurrence of improper transfer such that the white void of the image occurs due to that a part of the image is not transferred onto the recording material S.
Incidentally, in order that the interval of the feeding path 160 (see
Further, as described above, in the case where the interval of the feeding path 150 is made adjusted by the fastening degree of the screw 300, as shown in
Incidentally, in the above-described embodiment, an example in which the inner guiding plate 290a is disposed in a position set in advance in the supporting frame 201A was described, but the present invention is not limited thereto. For example, as shown in
Incidentally, in the image forming apparatus 201, a so-called jam such that the recording material S during the feeding is jammed at an intermediate portion of the feeding path during the image forming operation occurs in some instances. In the case where the jam occurs, the image forming apparatus 201 stops the feeding of the recording material S, but the recording material S stagnates in the feeding paths (150, 160, see
However, there is a need that the outer guiding plate 290b is disposed relative to the intermediary transfer belt 216 so as to form the interval appropriate for the toner image transfer between the outer guiding plate 290b and the intermediary transfer belt 216 in a state in which the outer guiding plate 290b is brought near to the intermediary transfer belt 216. A second embodiment for realizing such a constitution will be described using parts (a) and (b) of
As shown in parts (a) and (b) of
Then, on the free end side of the outer guiding plate 290b, in the case where the outer guiding plate 290b is in the closed position, an abutting portion 301 for providing an interval between the outer guiding plate 290b and the intermediary transfer belt 216 by being abutted against the bearing 295 is formed at each of the opposite end portions with respect to the widthwise direction. In the case where the outer guiding plate 290b is in the closed position, the abutting portion 301 is formed between the outer guiding plate 290b and the intermediary transfer belt 216 in a length such that the feeding path 160 (see
By doing so, even after the outer guiding plate 290b is moved away from the intermediary transfer belt 216 and the recording material S is removed by opening the feeding paths (150, 160), the feeding path 150 with the interval appropriate for the toner image transfer can be immediately reproduced between the outer guiding plate 290b and the intermediary transfer belt 216. Incidentally, the abutting portion 301 is not limited to the case where the abutting portion 301 is formed on the outer guiding plate 90b, but may also be formed on the bearing 295.
Incidentally, the registration roller portion 270 is rotationally driven by an unshown motor, but a rotational direction thereof is restricted only to one direction by a mechanism (not shown) such as a one-way clutch, for example. Further, at an end of a roller shaft of the registration roller pair 270, a gripping member 302 is provided (see
Thus, the operator can only pull out the recording material S, stagnated in the feeding paths (150, 160), from the downstream side with respect to the widthwise direction. By doing so, even when the toner image is transferred from the intermediary transfer belt 216 onto a part of the recording material S, a portion on which the toner image is transferred does not pass through the feeding paths (150, 160). That is, without contaminating the outer guiding plate 290b and the inner guiding plate 290a with the toner, the recording material S is removed from the feeding paths (150, 160).
Next, a third embodiment will be described. At the positions where the interval appropriate for the toner image transfer is formed, the outer guiding plate 290b and the inner guiding plate 290a are positioned in advance, and these guiding plates may also be integrally provided with the intermediary transfer unit. Such an intermediary transfer unit 20A will be described using
As shown in
Incidentally, in this embodiment, a type in which the door 400 (see
The intermediary transfer unit 20A as a transfer means includes the intermediary transfer belt 216, the inner secondary transfer roller 216a, the tension roller 216b, the pre-secondary transfer roller 216c, the driving roller 216d, the plurality of primary transfer rollers 219 (see
As shown in
Thus, in this embodiment, the inner guiding plate 290a and the outer guiding plate 290b are integrally provided as the intermediary transfer unit 20A. That is, the inner guiding plate 290a and the outer guiding plate 290b are fixed to the holding portion 201c for rotatably holding the inner secondary transfer roller 216a. Further, in the intermediary transfer unit 20A, each of the inner guiding plate 290a and the outer guiding plate 290b is fixed to the holding portion 201c which is a single component part at opposite end portions, so that the influence of component tolerances can be suppressed compared with the conventional example in which many component parts are interposed. Further, in this embodiment, at positions where the interval appropriate for the toner image transfer is formed between the inner guiding plate 290a and the outer guiding plate 290b, the inner guiding plate 290a and the outer guiding plate 290b are capable of being positioned and disposed. In addition, this embodiment is advantageous also in that a positional relationship between the inner guiding plate 290a and the outer guiding plate 290b is unchanged even when the intermediary transfer unit 20A is mounted and dismounted.
Incidentally, the inner guiding plate 290a is not limited to that the inner guiding plate 290a is fixed to the holding portion 201c, but may also be fixed to the outer guiding plate 290b by the screw 300 or the like. That is, as regards the intermediary transfer unit 20A, a constitution in which only the outer guiding plate 290b is fixed to the holding portion 201c and in which the inner guiding plate 290a can be separately mounted may also be employed.
According to the present invention, at a position where the interval appropriate for the toner image transfer is formed between the second guiding member and the image bearing belt which guide the recording material, onto which the toner image is to be transferred, to the secondary transfer nip, arrangement of the second guiding member relative to the image bearing belt can be realized by the simple constitution.
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 Applications Nos. 2021-028188 filed on Feb. 25, 2021, and 2022-013257 filed on Jan. 31, 2022, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2021 -028188 | Feb 2021 | JP | national |
| JP2022-013257 | Jan 2022 | JP | national |
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| Number | Date | Country |
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| Number | Date | Country | |
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| 20220269194 A1 | Aug 2022 | US |
