Patent Application
20220137536
The present disclosure relates to an image forming apparatus provided with a belt cleaning device which electrostatically cleans a belt carrying a toner image.
Conventionally, as an electrophotographic image forming apparatus, there is known an image forming apparatus provided with a photosensitive drum corresponding to each color (e.g., yellow, magenta, cyan, and black) and an intermediate transfer belt to which a toner image is transferred from the photosensitive drum.
In the image forming apparatus above, as a cleaning unit of the intermediate transfer belt, there is a method of performing a cleaning by bringing an elastic blade into contact with the intermediate transfer belt. There is a method of electrically collecting a toner, which adheres to the belt, by causing the toner adhere to a collection roller (electrostatic cleaning method). When the belt includes an elastic layer, the latter electrostatic cleaning method is generally used. Electrically collecting toner generally requires an application of a voltage of the order of several kilo volts (KV). In this case, polarity of the toner may be reversed by applying the voltage, and two application rollers are usually used so as to collect the toner having the reversed polarity.
Recently, in order to improve a cleaning property, a configuration in which a third cleaning roller (or brush) is added in addition to the conventional two cleaning rollers has been proposed. (Japanese Patent Application Laid-Open No. 2012-233946)
In the case of the electrostatic cleaning method, other than a fur brush as a cleaning member, a metal roller for applying the voltage to the fur brush and a blade for stripping the toner from the metal roller, or the like, are often provided. For this reason, as the number of cleaning members increases, the number of attached parts also increases, which tends to enlarge the belt cleaning device. In the case of a horizontal conveyance type image forming apparatus that conveys a recording material in a horizontal direction to the secondary transfer section, a sheet conveyance path for conveying a sheet that has passed through the secondary transfer section is usually provided below the cleaning device. Accordingly, as the cleaning device is enlarged, a space above the sheet conveyance path is occupied by the cleaning device, leaving an issue of making it difficult to secure a jam handling space and making it difficult to remove any jam that has occurred below the cleaning device.
In view of the above-described issue, there is a conceivable configuration in which an outer hang roller that stretches the belt from the outside is arranged and the belt arranged above the sheet conveyance path is bent inwardly thereby to reduce the stretched cross-sectional area of the belt and secure the jam handling space, but this leaves an issue of complicating the configuration.
The present disclosure is directed to providing an image forming apparatus in which a belt is electrostatically cleaned with a fur brush, in which a jam handling space can be secured with a simple configuration even if the number of fur brushes is increased, and in which a decrease in usability during the jam handling can be prevented. The above direction is achieved by the image forming apparatus according to the present disclosure.
According to an aspect of the present disclosure, an image forming apparatus includes an image forming unit configured to form a toner image, an intermediate transfer belt to which the toner image is transferred from the image forming unit at a primary transfer position and configured to transfer the transferred toner image to a recording material at a secondary transfer position, a first cleaning unit arranged downstream of the secondary transfer position and upstream of the primary transfer position in a conveyance direction of the intermediate transfer belt and configured to clean the intermediate transfer belt, wherein the first cleaning unit has a first fur brush and a second fur brush configured to contact the belt and electrostatically collect a toner, and a first container configured to collect the toner collected by the first fur brush and the second fur brush, a second cleaning unit arranged downstream of the secondary transfer position and upstream of the first cleaning unit in the conveyance direction of the intermediate transfer belt and configured to clean the intermediate transfer belt, wherein the second cleaning unit has a third fur brush configured to contact the belt and electrostatically collect the toner, and a second container configured to collect the toner collected by the third fur brush, a conveyance unit provided opposite to the first cleaning unit and the second cleaning unit at a position below the first cleaning unit and the second cleaning unit, and configured to convey the recording material which has passed through the secondary transfer position, wherein the first cleaning unit is arranged above the secondary transfer position, and is arranged in such a way that, in a vertical direction, a first space is formed between the first cleaning unit and the conveyance unit, and wherein the second cleaning unit is arranged at a position where the second cleaning unit does not overlap the first cleaning unit when viewed in the vertical direction, and, in the conveyance direction of the recording material, a second space adjacent to the first space is formed at a position located upstream of the first cleaning unit and downstream of the second cleaning unit, and a third space from which, when a jam occurs to the conveyance unit, the first space and the second space are accessible, with the conveyance unit being attached.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
An image forming apparatus according to the present exemplary embodiment will be described with reference to drawings. The dimensions, materials of the components of the image forming apparatus and the relative positions, etc., of the components are not intended to limit the scope of the present exemplary embodiment to them alone, unless otherwise specifically stated. Those marked with the same sign in each figure have the same configuration or operation, and any duplicate explanation of these items has been omitted as appropriate.
As illustrated in
Development devices 4Y, 4M, 4C, and 4K contain colored toners, that is, yellow (Y), magenta (M), cyan (C), and black (K) toners, respectively. The aforementioned electrostatic latent images are developed by the development devices 4Y, 4M, 4C, and 4K, and toner images are formed on the surfaces of the respective photosensitive drums 1Y, 1M, 1C, and 1K. A reversible development method is used, by which the toner is caused to adhere to an exposed section of the electrostatic latent image and is developed.
The intermediate transfer belt 6 is arranged to be in contact with the front side of the photoconductor drum 1. The intermediate transfer belt 6 is stretched by a plurality of tension rollers 20, 21, 22, 23, 25, 26 thereby to rotationally move at 150-470 mm/sec in a direction indicated by an arrow G. In the present exemplary embodiment, the tension roller 20 is a tension roller that controls the tension of the intermediate transfer belt 6 to be at a constant level. The tension roller 22 is a drive roller (downstream roller) of the intermediate transfer belt 6. The tension roller 21 is an opposing roller for a secondary transfer. The opposing roller 21 is provided in contact with an inner surface of the intermediate transfer belt 6 at a secondary transfer position, and cooperates with a secondary transfer roller 9 thereby to form a secondary transfer nip.
The secondary transfer roller 9 cooperates with the intermediate transfer belt 6 thereby to form the secondary transfer nip, and holds and conveys a transfer material. At the secondary transfer position (secondary transfer nip), the secondary transfer roller 9 secondarily transfers the toner image from the intermediate transfer belt 6 to the transfer material (recording material).
At a primary transfer position, primary transfer rollers 5Y, 5M, 5C, 5K primarily transfer, onto the intermediate transfer belt 6, the toner image on the respective photosensitive drums 1Y, 1M, 1C, and 1K. The primary transfer rollers 5Y, 5M, 5C, 5K are so arranged to oppose the respective photosensitive drums 1Y, 1M, 1C, and 1K via the intermediate transfer belt 6. A transfer bias having a polarity opposite to that of the toner image and a voltage controlled to be constant is applied to the primary transfer rollers 5Y, 5M, 5C, 5K.
A transfer roller, which includes an elastic layer of ion-conductive foam rubber and a core metal, has an outer diameter of 15 to 20 mm, and has a resistance value of 1E+5 to 1E+8Ω at 23° C., by 50% relative humidity (RH) environmental measurement, and with 2 KV application, is used as each of the primary transfer rollers 5Y, 5M, 5C, 5K.
A transfer roller, which includes an elastic layer of ion-conductive foam rubber and a core metal, has an outer diameter of 20 to 25 mm, and has a resistance value of 1E+5 to 1E+8Ω at 23° C., by 50% RH environmental measurement, and with 2 KV application, is used as the secondary transfer roller 9.
A transfer roller, which includes an electronically conductive rubber elastic layer and a core metal, has an outer diameter of 20 to 22 mm, and has a resistance value of 1E+5 to 1E+8Ω at 23° C., by 50% RH environmental measurement, and with 50 V application, is used as the tension roller 21.
A resist roller 8 supplies a transfer material 7 to the secondary transfer section in synchronization with the toner image on the intermediate transfer belt 6 being conveyed to the secondary transfer nip.
At this time, the transfer bias having the polarity opposite to that of the toner image and the voltage controlled to be constant is applied to the secondary transfer roller 9. For example, a transfer voltage of +1 to +7 KV and a current of +40 to +120 μA are applied to the secondary transfer roller 9, thereby to transfer, to the transfer material 7, the toner image on the intermediate transfer belt 6.
The transfer material 7 is conveyed and introduced to a fixing device 30 by a pre-fixing conveyance device 41 and a pre-fixing conveyance device 42 which form a conveyance path for conveying a sheet which has passed through the secondary transfer position, and the transfer material 7 undergoes a heat and pressure fixing process of the toner image. The pre-fixing conveyance devices 41 and 42 each have a belt body rotationally moving in the center section in the width direction, and the transfer material 7 is placed on the belt body and is conveyed. The belt body is made of a rubber material such as ethylene propylene diene methylene (EPDM) with a width of 100 to 110 mm and a thickness of 1 to 3 mm, and has holes with a diameter of 3 to 7 mm, and the belt body is sucked from the inside thereby to increase a force for carrying the transfer material 7 and stabilize conveyability. The pre-fixing conveyance devices 41 and 42 form a conveyance unit and are so configured as to be pulled out to the front side of a main body of the apparatus.
The pre-fixing conveyance device 41 is arranged below an electrostatic cleaning device 11. The upstream side of the pre-fixing conveyance device 41 in the recording material conveyance direction is arranged above the electrostatic cleaning device 11 and below the secondary transfer position. In this way, the transfer material 7 can be smoothly passed from the secondary transfer position to the pre-fixing conveyance device 41 while securing a space in which the electrostatic cleaning device 11 is arranged.
The electrostatic cleaning device 11 and an electrostatic cleaning device 12 electrostatically collect and clean a secondary transfer residual toner on the intermediate transfer belt 6. The cleaned intermediate transfer belt 6 is repeatedly used in the image forming and image making processes.
The configuration of the apparatus according to the present exemplary embodiment is divided into a first housing H and a second housing B which is provided with a waste sheet process unit including the fixing device 30, as illustrated in
As illustrated in
As illustrated in
The fur brush includes carbon-dispersed nylon fibers, acrylic fibers, or polyester fibers having a thread resistance value of 3E+5 to 1E+13 (Ω/cm) and a fiber thickness of 2 to 15 denier, planted on a metal roller at a planting density thereof of 50,000 to 500,000 fibers/inch2.
The above electrostatic fur brushes 112, 122, and 123 are slidably arranged while maintaining an intrusion amount of about 1.0 to 2.0 mm to the intermediate transfer belt 6, and are so formed as to rotationally move, by a drive motor not illustrated, in an arrow direction at a speed of 20 to 80% of a conveyance speed of the intermediate transfer belt 6. The metal rollers 113, 124, 125 are so arranged as to maintain an intrusion amount of 1.5 to 2.5 mm to the electrostatic fur brushes 112, 122, 123 and are so arranged as to rotate in an arrow direction at the same speed as the speed of the electrostatic fur brushes 112, 122, 123. The cleaning blades 114, 126, and 127 which come into contact with the metal rollers 113, 124, and 125 are plate-shaped rubber such as urethane. The cleaning blades 114, 126 and 127 each have a thickness of 1.6 to 2.2 mm and an international rubber hardness degrees (IRHD) hardness of 70 to 78° (23° C., 50% RH), and are arranged on the metal roller while maintaining an intrusion amount of 0.5 to 2.0 mm
Toner conveyance members 115 and 128 have screw shapes, are rotatably provided inside toner conveyance paths 141 and 142, respectively, and convey the toner along with the rotation.
In the electrostatic cleaning device 11, an opposing cleaning roller 24 is so provided as to oppose the electrostatic fur brush 112 in such a way that the intermediate transfer belt 6 is arranged between the opposing cleaning roller 24 and the electrostatic fur brush 112. A constant-current-controlled DC voltage of −20 μA in negative polarity is applied to the opposing cleaning roller 24 by a DC power supply (−20 μA in the present exemplary embodiment, but not limited thereto). With the voltage applied to the opposing cleaning roller 24, the electrostatic fur brush 112 arranged at the most upstream with respect to the rotational direction of the intermediate transfer belt 6 electrostatically cleans the toner remaining on the intermediate transfer belt 6.
The electrostatic fur brushes 122 and 123 provided in the electrostatic cleaning device 12 are arranged opposite the tension roller 22 in such a way that the intermediate transfer belt 6 is arranged between the electrostatic fur brushes 122 and 123 and the tension roller 22.
The electrostatic fur brush 122 is arranged next to the electrostatic fur brush 112 with respect to the rotational direction of the intermediate transfer belt 6. The electrostatic fur brush 122 is so configured as to be supplied with an electric current from the metal roller 124. The metal roller 124 is subjected to an application, by the DC power supply, of the constant-current-controlled DC voltage of −40 μA in negative polarity (−40 μA in the present exemplary embodiment, but not limited thereto). The electrostatic fur brush 123 is located at the most downstream with respect to the rotational direction of the intermediate transfer belt 6. A constant-current-controlled DC voltage of +20 μA in positive polarity is applied to the metal roller 125 by the DC power supply thereby to supply current to the electrostatic fur brush 123 (+20 μA in the present exemplary embodiment, but not limited thereto). A cleaning electric field suitable for cleaning is formed between the fur brushes 112, 122, and 123 and the intermediate transfer belt 6, and the transfer residual toner on the intermediate transfer belt 6 adheres to and collected by the fur brushes 112, 122, and 123. The adhering and collected toner is further transferred from the fur brushes 112, 122, 123 to the metal rollers 113, 124, 125 by an electric field, and scraped off by the cleaning blades 114, 126, 127. The scraped-off toner is conveyed to a collection container by the toner conveyance member.
The arrangement of the electrostatic cleaning device according to the present exemplary embodiment will be described.
As described above, the cleaning device illustrated in
The electrostatic cleaning device 11 is arranged upstream of the electrostatic cleaning device 12 in the conveyance direction of the intermediate transfer belt 6. Further, the electrostatic cleaning device 11 is located vertically below the lower surface of the electrostatic cleaning device 12.
In the present exemplary embodiment, the electrostatic cleaning device 11 is arranged upstream (on the right side of the sheet plane in
As illustrated in
In the present exemplary embodiment, an interval of the second jam handling space J2 (width in the left-right direction in
This is because, as illustrated in
To handle the jam, a jammed sheet needs to be pulled out to the right side of
The jam handling space J according to the present exemplary embodiment will be described. When the main body is in operation, the jam handling space J is blocked by a front cover (not illustrated) of the first housing H. In a case where the front cover is opened when a jam occurs, it can be observed that an opening section (third space) that is substantially identical with the jam handling space J is provided in an inner cover of the first housing H. For this reason, with the transfer unit and the conveyance units being mounted, the user can access the jam handling space J from the opening section.
In other words, when viewed in the width direction of the intermediate transfer belt 6, the opening section for the jam handling is formed at a position including an area where a first area defined by projecting the electrostatic cleaning device 12 in the vertical direction and a second area defined by projecting the electrostatic cleaning device 11 in the left-right direction overlap each other. The opening section for the jam handling is arranged below the electrostatic cleaning device 12, and is provided at a position that is downstream of the electrostatic cleaning device 11 and upstream of the downstream end of the electrostatic cleaning device 12, in the conveyance direction of the transfer material 7. The opening section for the jam handling is, in the horizontal direction orthogonal to the width direction of the intermediate transfer belt 6, provided in such a manner as to extend to an area between the electrostatic cleaning device 11 and the electrostatic cleaning device 12.
The need for the jam handling space J will be explained. As mentioned above, the apparatus according to the present exemplary embodiment includes the first housing H and the second housing B. If the transfer material 7 stops across the first housing H and the second housing B, it is necessary to pull out the transfer material 7 to the first housing H side. Concerning the pull-out direction, in the present exemplary embodiment, the transfer material 7 is pulled out to the right side. The reason for pulling out the transfer material 7 to the first housing H is that a section C (conveyance unit) in
If the conveyance rail is pulled out without removing the transfer material 7, the transfer material 7 may be jammed between the first housing H and the second housing B, e.g., the transfer material 7 may be damaged and part thereof may remain in the housing (B, H). For this reason, it is necessary to remove the transfer material T after removing the transfer material 7. Providing the jam handling space J makes it possible for the user to pull out the transfer material 7 without any problem.
A required size of the jam handling space J varies depending on a size of a hand or posture of the user, but in the present exemplary embodiment, there is provided a space of 15 cm in the vertical direction and 20 cm in the left-right direction. This makes it possible to pull out the transfer material 7 without any stress, regardless of the size of the hand or the posture. If the above space cannot be provided, it is desirable to have a space of at least 50 mm in the vertical direction and 100 mm in the left-right direction. That is, the size of the opening section is preferably 5 cm or more and 15 cm or less in a longitudinal direction and 10 cm or more and 20 cm or less in a lateral direction.
In the present exemplary embodiment, since the intermediate transfer belt 6 is directly above the jam handling space J, there is a risk of accidentally touching the intermediate transfer belt 6 when the user pulls out the transfer material 7 or grabs the transfer material 7. It is not desirable for the user to touch the intermediate transfer belt 6, because any sebum adhering onto the intermediate transfer belt 6 or scratching the front side would affect the image transferred to the intermediate transfer belt 6. Accordingly, in the present exemplary embodiment, a protective member 27 as a cover member is provided so that the user cannot touch the intermediate transfer belt 6. As illustrated in
In the present exemplary embodiment, the example has been illustrated in which, in the rotational direction of the intermediate transfer belt 6, the electrostatic cleaning device 12 is arranged downstream and the electrostatic cleaning device 11 is arranged upstream, but the respective cleaning units may be arranged in reverse. That is, even when the fur brushes 122, 123 are upstream and the fur brush 112 is downstream, the effect can be similarly obtained if the space obtained by dividing the cleaning units can be used as the jam handling space.
In the present exemplary embodiment, the example has been described in which the electrostatic cleaning device 11 is arranged below the lower plane of the electrostatic cleaning device 12, but the electrostatic cleaning device 11 may be below the electrostatic cleaning device 12. A part of the electrostatic cleaning device 11 may be positioned above the lower plane of the electrostatic cleaning device 12.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure 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 priority from Japanese Patent Application No. 2020-185332, filed Nov. 5, 2020, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-185332 | Nov 2020 | JP | national |
