Patent Application
20240051773
The present disclosure relates to a sheet conveyance apparatus, and more particularly, to a sheet conveyance apparatus for conveying sheets such as recording sheets and document sheets, mounted on image forming apparatuses such as printers, facsimiles, and copying machines.
A certain sheet conveyance apparatus is configured to bias one roller to the other roller to bring the rollers into contact with each other. In a known example of this configuration, the one roller is a drive roller rotating by a driving force of a drive source, and the other roller is a driven roller driven to rotate by the drive roller. Japanese Patent Application Laid-Open No. 2019-137517 discusses a configuration in which a driven roller holder for slidably and rotatably holding a driven roller is pressed by a spring, and the driven roller comes into contact with a drive roller.
The present disclosure is directed to providing a sheet conveyance apparatus effectively using the space around rollers while restricting a large change of the sheet conveyance direction.
According to an aspect of the present disclosure, a sheet conveyance apparatus includes a roller pair configured to convey a sheet and including a first roller and a second roller, a biasing member, a roller holder configured to hold the first roller and to be biased by the biasing member so that the first roller is biased toward the second roller, wherein the roller holder includes a guided portion and the guided portion includes a first guided portion and a second guided portion positioned upstream of the first guided portion in a biasing direction of the biasing member, and a guiding portion including a first guide and a second guide, wherein the first guide is configured to movably support and guide the first guided portion, the second guide is configured to movably support and guide the second guided portion, and the guiding portion is configured to movably guide the roller holder so that the first and second rollers can take a first state where the first roller comes into contact with the second roller with a contact force that is a predetermined force and take a second state where the contact force is reduced from the predetermined force, wherein a first direction in which the first guide guides the first guided portion is inclined relative to a second direction in which the second guide guides the second guided portion, and wherein, when viewed in a rotational axis direction of the first roller in a case where the first and second rollers are in the first state, an angle formed by a straight line passing through rotational centers of the first and second rollers and the first direction is smaller than an angle formed by the straight line and the second direction.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
In the configuration illustrated in
The conveyance roller pair (conveyance rollers 23b′ and 24′) illustrated in
The roller holder 31′ is provided with two pairs of bosses 25a′ and 25b′ in the direction perpendicular to the nip line. While sliding with a groove 30′ as a part of a frame 29′, the roller holder 31′ pressed by a spring (not illustrated) linearly moves in the direction of a nip pressure F. The groove 30′ is disposed so that the upstream boss 25a′ and the downstream boss 25b′ of the roller holder 31′ are disposed on the line connecting the centers of the conveyance roller 23b′ and the driven roller 24′.
The conveyance direction N of the conveyance roller pair (conveyance rollers 23b′ and 24′) has an angle relative to the horizontal direction H and conveys the sheet S in the obliquely upward direction. However, in this configuration, allocating a space for disposing the spring, the roller holder 31′, and the frame 29′ will increase the distance HD from the outer diameter edge of the driven roller 24′ of the frame 29′ for holding the roller holder 31′ in the horizontal direction H. The longer the distance HD, the higher the possibility that the trailing edge of the discharged sheet S is caught on the frame 29′.
In the configuration illustrated in
As a result, the driven roller 24′ relatively rotates counterclockwise around the conveyance roller 23b′. Therefore, the angle of the conveyance direction changes by the angle θ formed by the line connecting with the center of the conveyance roller pair (conveyance rollers 23b′ and 24′) drawn with a solid line, and the line connecting with the center of the conveyance roller pair (conveyance rollers 23b′ and 24′) drawn with a dotted line. Then, the conveyance direction changes from N1 to N2. Particularly if the outer diameter of the conveyance roller 23b′ is small, the conveyance direction largely changes, possibly preventing the sheets S from being normally stacked on the sheet discharge tray.
As an example of a configuration of the image forming apparatus according to a first exemplary embodiment, an electrophotographic laser printer will be described below. The following describes an overall configuration of the image forming apparatus according to the present exemplary embodiment, and then describes a configuration of a sheet discharge unit of the image forming apparatus according to the present exemplary embodiment.
An image forming apparatus 1 illustrated in
The image forming apparatus 1 includes a process cartridge 2 attachable to and detachable from the apparatus main body. The process cartridge 2 includes a process unit including a photosensitive drum 3, a developing unit (not illustrated), a charge roller (not illustrated), and the like. A scanner unit 4 disposed vertically above the process cartridge 2 emits light based on an image signal to the photosensitive drum 3 for exposure.
After the photosensitive drum 3 has been charged to a predetermined negative polarity potential by the charge roller (not illustrated), an electrostatic latent image is formed on the drum 3 by the scanner unit 4. The electrostatic latent image is applied with negative-polarity toner by the developing unit (not illustrated) in the process cartridge 2 for reversal development, and a toner image is formed.
The sheet feeding unit includes a sheet feeding unit 5a attached to the image forming apparatus 1, and a sheet feeding cassette 6a for storing sheets S attachable to and detachable from the image forming apparatus 1. The sheets S stored in the sheet feeding cassette 6a are separated and fed one by one from the sheet feeding cassette 6a by the sheet feeding unit 5a that is rotated by the power of a sheet feeding drive unit (not illustrated). A fed sheet S is conveyed to a registration roller pair 8 by a conveyance roller pair 7a, and subjected to skew correction and conveyed to a transfer unit by the registration roller pair 8.
A sheet feeding cassette 6b also stores sheets S with a different size from or the same size as the sheets S in the sheet feeding cassette 6a.
The transfer unit is configured to apply a positive-polarity bias to the transfer roller 9 by a bias application unit (not illustrated). Thus, a toner image is transferred as a non-fixed image onto the sheet S conveyed to the transfer unit.
The sheet S with the toner image transferred thereon is conveyed to the fixing apparatus 10 provided downstream of the transfer unit in the conveyance direction. The fixing apparatus 10 for fixing the toner image transferred on the sheet S includes a heat roller 11 as a fixing member heated by a heater as heating unit (not illustrated), and a pressure roller 12 as a pressurizing member rotating in pressure contact with the heat roller 11. The sheet S is conveyed while being pinched by a fixing nip portion formed by the heated roller 11 and the pressure roller 12. When the toner image is heated and pressurized, the toner image is fixed onto the surface of the sheet S.
Then, the sheet S with the toner image fixed thereto is discharged from the fixing apparatus 10 onto a sheet discharge tray 60 for stacking sheets S discharged by a sheet discharge roller pair 22 (described below) illustrated in
The sheet discharge unit 20 that characterizes the present exemplary embodiment will be described below with reference to
The sheet discharge roller pair 22 includes a sheet discharge roller 23 as a second roller rotatably driven by a driving source (not illustrated). The sheet discharge roller pair 22 further includes a sheet discharge driven roller 24 as a first roller driven to rotate by the rotation of the sheet discharge roller 23. The sheet discharge driven roller 24, when pressed by a pressing spring 26, comes into contact with the sheet discharge roller 23 to form a nip. As a result, the sheet S is conveyed while being pinched by the sheet discharge roller 23 and the sheet discharge driven roller 24. The sheet discharge driven roller 24 is positioned vertically below the sheet discharge roller 23.
The sheet discharge roller 23 includes a sheet discharge roller axis 23a, and two rubber rollers 23b along the direction of the sheet discharge roller axis 23a, and brings the sheet discharge driven roller 24 into contact with each of the rubber rollers 23b. The sheet discharge driven roller 24 is rotatably held to the roller holder 31. The roller holder 31 is provided with a projection 25 that engages with a groove 30 (described below) to be movably regulated. The roller holder 31 is attachable to and detachable from the apparatus main body together with the sheet discharge driven roller 24. The roller holder 31 has two different projections 25 (guided portions, to be guided portions): a first projection 25b (first guided portion), and a second projection 25a (second guided portion) positioned upstream of the first projection 25b in the biasing direction of a biasing member (the pressing spring 26 to be described below).
A sheet discharge frame 29 (guiding portion) is a part of the frame of the main body of the image forming apparatus 1. The sheet discharge frame 29 is provided with the groove 30 as an opening for storing the projections 25. The groove 30 includes a first groove 30b (first guide) for movably supporting and guiding the first projection 25b, and a second groove 30a (second guide) for movably supporting and guiding the second projection 25a. In other words, the first projection 25b and the second projection 25a are stored in the groove 30, and the first projection 25b and the second projection 25a are movably guided by a portion (plane) forming the first groove 30b and the second groove 30a, respectively.
Thus, the sheet discharge frame 29 allows the roller holder 31 to be movable so that the sheet discharge roller 23 and the sheet discharge driven roller 24 come into pressure contact with each other (pressure contact state or first state) and come out of pressure contact (released state or second state).
According to the present exemplary embodiment, in a state where the sheet discharge roller 23 and the sheet discharge driven roller 24 are in pressure contact with each other, the sheet S can be conveyed. In a state where the sheet discharge roller 23 and the sheet discharge driven roller 24 are out of pressure contact, the rollers 23 and 24 are separable. Although, according to the present exemplary embodiment, both rollers are configured to be separable in a state where the rollers 23 and 24 are out of pressure contact, the present exemplary embodiment is not limited thereto. The pressure contact force between the rollers may be reduced to an extent that sheet S jam recovery is possible, i.e., a light contact state.
The groove 30 further includes an intermediate groove 30c for connecting the first groove 30b and the second groove 30a. When the roller holder 31 is attached to the sheet discharge frame 29, the second projection 25a passes through the intermediate groove 30c. More specifically, the first groove 30b and the second groove 30a are provided at the portion where an opening is formed. Although, according to the present exemplary embodiment, a groove is provided as an opening on the sheet discharge frame 29, the opening may have any desired shape, for example an oblong hole, as long as the opening guides the projections.
The first groove 30b is inclined relative to the second groove 30a. More specifically, the direction (first direction) in which the first groove 30b guides the first projection 25b, i.e., the direction in which the first projection 25b moves in the first groove 30b is inclined relative to the direction (second direction) in which the second groove 30a guides the second projection 25a, i.e., the direction in which the second projection 25a moves in the second groove 30a.
In a relation where the first groove 30b is inclined relative to the second groove 30a, the angle formed by the first direction relative to the direction of the straight line passing through the rotational centers of the sheet discharge driven roller 24 and the sheet discharge roller 23 when viewed in the rotational axis direction of the sheet discharge driven roller 24 in a state where the sheet discharge driven roller 24 and the sheet discharge roller 23 are in pressure contact with each other is smaller than the angle formed by the second direction relative to the direction of the straight line.
Since the first groove 30b and the second groove 30a are not parallel to each other, the roller holder 31 and the sheet discharge driven roller 24 move along the groove 30, while rotating, relative to the apparatus main body. The moving locus of the sheet discharge driven roller 24 in this operation is different from the biasing direction and the directions of the first groove 30b and the second groove 30a. According to the present exemplary embodiment, the first groove 30b and the second groove 30a are formed so that the sheet discharge driven roller 24 moves toward the sheet discharge roller axis 23a.
More specifically, the angle formed by the lines A2 and A1 is smaller than the acute angle formed by the lines A1 and A3, where the line A1 is the line along the first direction, the line A2 is the line along the second direction, and the line A3 is the straight line passing through the rotational centers of the sheet discharge driven roller 24 and the sheet discharge roller 23. This means that the line A2 forms an angle closer to the vertical direction than the line A3. When the roller holder 31 and the sheet discharge driven roller 24 move, while rotating, relative to the apparatus main body based on this relation between the lines A1, A2, and A3, the sheet discharge driven roller 24 moves toward the sheet discharge roller axis 23a.
A more specific configuration of the lines A1, A2, and A3 will be described below. According to the present exemplary embodiment, the line A2 extends in the vertical direction. In other words, the second groove 30a extends in the vertical direction. Referring to
Referring to
These angular configurations may be suitably changed according to the direction in which the sheet discharge driven roller 24 is to be biased. The angular ranges are represented by 0°<x<90° and 0°≤y<90°.
The pressing spring 26 (compression spring) as a biasing member is held at one end by the sheet discharge frame 29 and held at the other end by the roller holder 31. Thus, the pressing spring 26 presses the sheet discharge driven roller 24 toward the sheet discharge roller 23 to bring the sheet discharge driven roller 24 and the sheet discharge roller 23 into pressure contact with each other. The biasing direction of the pressing spring 26 is in the vertically upward direction, and the angle relative to the extending direction of the second groove 30a is smaller than the angle relative to the extending direction of the first groove 30b. Although the present exemplary embodiment uses a compression spring as a biasing member, any member for pressing the roller holder 31 is suitably applicable.
A sheet discharge full load detection flag 27 is provided to be rotatable around a rotational center 27c, as illustrated by the arrow a. The sheet S conveyed by the sheet discharge roller pair 22 presses the sheet discharge full load detection flag 27 and is conveyed to the sheet discharge tray 60.
As illustrated in
As illustrated in
The above-described configuration enables the moving direction K of the sheet discharge driven roller 24 and the nip pressure direction F to be approximately in parallel. As a result, even if the sheet discharge roller axis 23a is bent by the nip pressure, the angle of the conveyance direction N of the sheet S remains unchanged, thus achieving stable conveyance. This makes it possible to use a molding material having a low rigidity instead of a highly rigid metal as the sheet discharge roller axis 23a, achieving cost reduction.
The inclination of the nip direction will be briefly described below with reference to
In a state where the sheet discharge driven roller 24 is in contact with the sheet discharge roller 23 as illustrated in
Referring to
Referring to
Referring to
Since the moving direction of the sheet discharge driven roller 24 is different from that in
In the above descriptions, the thick sheet S2 is used. The thicker the sheet S, the more markedly the effect of the present exemplary embodiment is exhibited. However, the effect that the conveyance direction of the sheet S is unlikely to change can be obtained even when the thin sheet S is used.
As illustrated in
The roller holder 31 is upwardly pressed by the force of the pressing spring 26, and the first projection 25b comes into contact with the groove 30′ at a point 25b′. Since the roller holder 31 receives the resistance of the nip pressure in the F′ direction, a moment M′=F′*L′ arises around the point 25b′, where L′ denotes the distance between the point 25b′ and the dotted line of the nip pressure direction F. As a result, the second projection 25a comes into contact with the groove 30′ at a point 25a′ and receives the moment M′.
Since a direction Z1 of the force by the moment M′ at the point 25a′ and a direction Z2 perpendicular to the surface receiving the force at the point 25a′ form an angle ε1, the upstream boss 25a generates a force to break into the groove 30′. Therefore, when the roller holder 31 moves downward, the sliding friction at the point 25a′ increases, making it hard for the roller holder 31 to move downward.
On the other hand, in the configuration illustrated in
According to a second exemplary embodiment, the configuration characterizing the present disclosure is applied to the sheet feeding unit 5a. The present exemplary embodiment will be described below with reference to
Referring to
The separation roller unit 100 includes a separation roller 102, a separation roller holder 104, a separation guide 105, and a pressure spring 107. The separation roller 102 is held by the separation roller holder 104 that is held by the separation guide 105. When the separation roller holder 104 is pressed toward the feed roller 101 by the pressure spring 107, the nip pressure between the feed roller 101 and the separation roller 102 is applied.
The moving direction of the downstream boss 104b toward the feed roller 101 is indicated by the arrow D, and the moving direction of the upstream boss 104a toward the feed roller 101 is indicated by the arrow U. According to the present exemplary embodiment, to achieve stable sheet feeding as in the first exemplary embodiment, the arrow D is inclined relative to the arrow U by an angle γ upstream in the conveyance direction N to bring the moving direction K of the separation roller 102 and the nip pressure direction F close to each other.
When viewed in the rotational axis direction of the separation roller 102 like the first exemplary embodiment, the angle formed by the arrow D relative to the direction of the straight line passing through the rotational centers of the separation roller 102 and the feed roller 101 is smaller than the angle formed by the arrow U relative to the direction of the straight line.
A guide path formed by the groove 106, the downstream boss 104b, and the upstream boss 104a is disposed upstream of the line of the arrow F in the sheet S conveyance direction. The use of this configuration enables reducing the downstream side of the separation roller 102 and the separation roller holder 104 in the horizontal direction H, making it possible to provide the conveyance path 120 as illustrated in
The sheet conveyance apparatus of the present disclosure can effectively use the space around the rollers while restricting a large change of the sheet conveyance direction.
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 Japanese Patent Application No. 2022-126812, filed Aug. 9, 2022, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-126812 | Aug 2022 | JP | national |
