The present invention relates to a sheet feeding apparatus having a detection unit configured to detect sheets stacked in a sheet stacking portion.
As a sheet feeding apparatus of an image forming apparatus, there is known a configuration in which sheets stacked in a sheet stacking portion are separated one by one by a paper feeding roller and each sheet is fed to an image forming portion. When the paper feeding roller operates in a state in which no sheet is present in the sheet stacking portion, an excessive frictional force is generated between the paper feeding roller and the sheet stacking portion, and there is a possibility that the paper feeding roller and the sheet stacking portion may be damaged. By providing a detection unit configured to detect the presence or absence of the sheet in the sheet stacking portion, it is possible to prevent the damage caused by idle feeding.
In Japanese Patent Application Publication No. 2000-177855, a rack is provided at a position which is exposed in the case where no sheet is present in a sheet stacking portion (cassette), and an idler gear is coupled to a swing arm which supports a feeding roller. In the case where no sheet is present, the rack, the idler gear, and a gear provided on a rotation shaft of the feeding roller are engaged with each other. When no sheet is present, the driving force of a motor which drives the feeding roller is transmitted to the rack, and the sheet stacking portion is discharged to the outside of a main body.
In Japanese Patent Application Publication No. 2006-182463, a through hole is provided in a bottom portion of a detachable sheet stacking portion (cassette), and a lever is installed at a position below the sheet stacking portion in an image forming apparatus so as to pass through the through hole and project upward from the sheet stacking portion. This lever detects the presence or absence of a sheet in the sheet stacking portion.
In Japanese Patent Application Publication No. 2000-177855, in the case where a foreign object is present on an installation surface for an image forming apparatus and the sheet stacking portion runs on the foreign object in the vicinity of the rack, the position of the rack becomes higher than expected. As a result, when no sheet is present, the rack, the idler gear, and the gear of the feeding roller are not engaged with each other properly, the sheet stacking portion is not discharged even when no sheet is present, and there is a possibility that the presence or absence of the sheet may not be detected. In addition, while the sheet stacking portion is often manufactured by injection molding, in a component manufactured by injection molding, a warp occurs due to heat shrinkage of a molding material and molding conditions. Also in the case where deformation such as a warp caused by injection molding is present in the sheet stacking portion, when no sheet is present, the rack, the idler gear, and the gear of the feeding roller are not engaged with each other properly, and there is a possibility that the presence or absence of the sheet may not be detected.
In Japanese Patent Application Publication No. 2006-182463, the sheet stacking portion is detachable, space in which the sheet stacking portion is mounted is provided in the image forming apparatus, and the lever for performing sheet detection is provided at a bottom portion of the space. Consequently, the lever can operate even when the sheet stacking portion is detached from the image forming apparatus. Accordingly, even in the case where the sheet is placed directly in the space, it follows that the presence of the sheet is detected and, when a sheet feeding command is issued, a sheet feeding operation is executed. The sheet subjected to the sheet feeding operation in a state in which the sheet stacking portion is detached is not conveyed properly, and there is a possibility that feed failures such as double feed and non-feed, and jamming may occur.
An object of the present invention is to detect the presence or absence of sheets stacked in a sheet stacking portion with high accuracy.
A sheet feeding apparatus according to the present invention comprising:
a sheet stacking portion having a stacking surface on which a sheet is stacked;
a feeding unit configured to come into contact with the sheet placed in the sheet stacking portion and to feed the sheet to a conveyance path; and
a detection unit provided to be movable with respect to the sheet stacking portion and configured to detect the sheet by causing a contact portion to come into contact with an uppermost sheet stacked on the stacking surface, wherein
a bottom portion of the sheet stacking portion forms a part of a bottom portion of the sheet feeding apparatus,
the sheet stacking portion is provided with a through hole configured to be exposed in a case where no sheet is stacked on the stacking surface, the through hole penetrating the stacking surface to a bottom surface of the sheet stacking portion, and
the contact portion is positioned inside the through hole in the case where no sheet is stacked on the stacking surface.
According to the present invention, it is possible to detect the presence or absence of the sheets stacked in the sheet stacking portion with high accuracy.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
An embodiment of the present invention will be described. Herein, the embodiment in which the present invention is applied to an inkjet recording apparatus will be described, but the present invention is not limited to the inkjet recording apparatus.
The recording apparatus has the sheet feeding apparatus 10 which feeds the sheet to a recording head 102 which forms an image on the sheet with an inkjet system. The sheet feeding apparatus 10 has a case 100, and the sheet stacking portion 11 which is provided so as to form part of a bottom portion of the sheet feeding apparatus 10. Sheets stacked on a stacking surface of the sheet stacking portion 11 are fed to a first conveyance path 104 by a feeding roller 12. The feeding roller 12 comes into contact with the sheets stacked in the sheet stacking portion 11 and feeds the sheets to the first conveyance path 104. Each sheet fed to the first conveyance path 104 is conveyed to the recording head 102 by a conveyance roller 101. The recording head 102 records an image based on image data on the sheet. The sheet feeding apparatus 10 has a second conveyance path 105 for reversing an image recording target surface of the sheet in the case where images are to be recorded on both surfaces of the sheet. The conveyance roller 101 conveys the sheet in which image recording on the front surface is completed to the second conveyance path 105, and the sheet conveyed to the second conveyance path 105 is conveyed to the recording head 102 through the first conveyance path 104 again, and image recording on the back surface is performed.
The sheet feeding apparatus 10 has a separation slope 16 for separating the sheets fed by the feeding roller 12, and the detection lever 13 for coming into contact with the sheet placed in the sheet stacking portion 11 to detect the presence or absence of the sheet. The feeding roller 12 is provided at a tip of an arm which is rotatable about a rotation shaft 121 provided in the case 100 of the sheet feeding apparatus 10, and feeds the sheets placed in the sheet stacking portion 11 one by one into a recording apparatus main body. The detection lever 13 is provided to be movable relative to the sheet stacking portion 11 of the sheet feeding apparatus 10, and has a roller 132 which serves as a contact portion which is configured to come into contact with the uppermost sheet of the stacked sheets in the case where the sheets are stacked on a stacking surface 21. In the present embodiment, the detection lever 13 is provided to be rotatable about a rotation shaft 131 provided in the case 100 of the sheet feeding apparatus 10, and the roller 132 is provided at a tip of the detection lever 13 to face the sheet stacking portion 11. While the sheet is fed into the recording apparatus main body by the feeding roller 12, the detection lever 13 comes into contact with the sheet via the roller 132, and hence an increase in the conveyance resistance of the sheet caused by the contact of the detection lever 13 with the sheet is suppressed. The presence or absence of the sheet placed in the sheet stacking portion 11 is detected by the detection lever 13.
The sheet stacking portion 11 is fixed to the sheet feeding apparatus 10. Note that the present invention can also be applied to the sheet feeding apparatus having a detachable sheet stacking portion. In the stacking surface 21 of the sheet stacking portion 11, the through hole 14 which is configured to be exposed in the case where no sheet is stacked on the stacking surface 21, the through hole 14 penetrating the stacking surface 21 to a bottom surface of the sheet stacking portion 11 is provided. The roller 132 of the detection lever 13 is provided so as to be positioned inside the through hole 14 in the case where no sheet is stacked on the stacking surface 21. The through hole 14 is provided at a location to which the roller 132 at the tip of the detection lever 13 is close. The roller 132 of the detection lever 13 is provided at a position which is offset in the width direction of the sheet (X direction) with respect to the feeding roller 12. Specifically, the detection lever 13 is provided at a position about 40 mm away in a −X direction from the feeding roller 12 positioned at a central portion of the sheet stacking portion 11 in the X direction. This allows the detection lever 13 to operate without interfering with the feeding roller 12. With regard to a relationship among sizes of the detection lever 13, the roller 132, and the through hole 14 in the X direction, if it is assumed that the size of the roller 132 in the X direction is 1, the size of the detection lever 13 in the X direction is 1.6, and the size of the through hole 14 in the X direction is 2.1. Herein, the size of the through hole 14 in the X direction corresponds to a size between tips of ribs 141 provided at both ends of the through hole 14 in the X direction. The size (height) of the rib 141 in the Z direction is configured to narrow an opening portion of the through hole 14 by setting the size of the rib 141 to a size which does not allow the detection lever 13 and the rib 141 to interfere with each other in a state in which the detection lever 13 is at a position at which the detection lever 13 detects the absence of the sheet. Note that an offset amount of the roller 132 with respect to the feeding roller 12 and the sizes of the roller 132, the detection lever 13, and the through hole 14 are only examples, and are not limited to the offset amount thereof and the sizes thereof mentioned above.
As shown in
The detection lever 13 is provided to be rotatable about the rotation shaft 131. The detection lever 13 rotates in an arrow R direction by its own weight in a state in which an external force does not act, and the position of the roller 132 in the Z direction is lowered. The sheet feeding apparatus 10 has a regulation unit for regulating a range of movement of the detection lever 13 such that the roller 132 does not move to a position below a predetermined position inside the through hole 14 in the case where no sheet is stacked on the stacking surface 21 of the sheet stacking portion 11. Specifically, a posture holding portion 133 is provided in the detection lever 13, and a posture holding portion 134 is provided in the case 100. When the detection lever 13 rotates in the R direction and the position of the roller 132 in the Z direction is lowered to a predetermined position, the posture holding portion 133 and the posture holding portion 134 come into contact with each other, and further rotation of the detection lever 13 in the R direction is regulated. When the posture holding portion 133 and the posture holding portion 134 come into contact with each other, the tip portion of the detection lever 13 is at the reachable lowest point. A position Z1 in the Z direction when the tip portion of the detection lever 13 is at the lowest point is lower than a position Z2 of the stacking surface 21 of the sheet stacking portion 11 in the Z direction. A state in which the tip portion of the detection lever 13 is at the position Z1 of the lowest point corresponds to a state in which the detection lever 13 is at the sheet absence detection position. Note that the lowest point which the tip portion of the detection lever 13 can reach is at a position higher than an installation surface for the sheet feeding apparatus 10.
As shown in
The sheet feeding apparatus 10 has a sensor 136 constituted by an optical sensor. The sensor 136 outputs a signal corresponding to light incident from the outside to a control portion 30. The detection lever 13 has a light-shielding portion 135 which is an opening-closing unit configured to open and close an optical path to the sensor 136 on a side opposite to the side of the roller 132 with the rotation shaft 131 interposed between the light-shielding portion 135 and the roller 132. The light-shielding portion 135 switches between opening and closing of the optical path according to whether the roller 132 is at the predetermined position inside the through hole or at a position higher than the stacking surface 21 of the sheet stacking portion 11. In the present embodiment, the light-shielding portion 135 blocks the optical path to the sensor 136 when the detection lever 13 is at the sheet absence detection position, and opens the optical path to the sensor 136 when the detection lever 13 is at the sheet presence detection position. When the control portion 30 receives a signal indicating that light is detected from the sensor 136, the control portion 30 determines that the sheets stacked in the sheet stacking portion 11 are present. When the control portion 30 receives a signal indicating that light is not incident from the sensor 136, the control portion 30 determines that the sheets stacked in the sheet stacking portion 11 are absent.
Note that, according to the presence or absence of the sheet in the sheet stacking portion 11, the position of the tip portion of the detection lever 13 in the Z direction changes, and an angle of rotation of the detection lever 13 changes. Consequently, in addition to the method which detects the presence or absence of the sheet based on opening and closing of the optical path of the sensor 136 caused by the rotation of the detection lever 13, the position of the tip portion of the detection lever 13 in the Z direction or the angle of rotation of the detection lever 13 may be measured, and the presence or absence of the sheet may be detected based on the measurement.
In the case where the sheets are stacked on the stacking surface 21 of the sheet stacking portion 11, a position at which the feeding roller 12 comes into contact with the sheet is on an upstream side in the conveyance direction of the sheet of a position at which the roller 132 of the detection lever 13 comes into contact with the sheet. Specifically, as shown in
An inner wall surface of the through hole 14 is configured to has a shape which does not allow the inner wall surface to interfere with the roller 132 in the range of movement of the roller 132 of the detection lever 13 irrespective of the position of the bottom surface of the sheet stacking portion 11 in a direction perpendicular to the installation surface for the sheet feeding apparatus 10. In the present embodiment, as shown in
By using
As shown in
A component which is one of the separation portion 15 and the sheet stacking portion 11 and is disposed on an upper side in the joint portion 25 has a shape in which a warp caused by molding is protruded downward, and a component which is one of the separation portion 15 and the sheet stacking portion 11 and is disposed on a lower side in the joint portion 25 has a shape in which a warp caused by molding is protruded upward. For example, the component which is disposed on the upper side in the joint portion 25 has a shape in which a rib projects downward from a plane, and the component which is disposed on the lower side in the joint portion 25 has a shape in which a rib projects upward from a plane. In the present embodiment, as shown in
Herein, each of the sheet stacking portion 11 and the separation slope base 17 is a component manufactured by injection molding. In the injection molding, molding is performed by pouring a plastic material into a mold including a cavity (female mold) and a core (male mold). During the molding, a warp occurs in a molded component due to a mold shape and a molding condition. In a molded component having a shape in which a rib projects from a plane such as, e.g., the sheet stacking portion 11 or the separation slope base 17 in
On the other hand, as shown in
In the present embodiment, as shown in
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 Application No. 2021-118866, filed on Jul. 19, 2021, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2021-118866 | Jul 2021 | JP | national |