JP3634543B2 - Paper feeder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device mounted on a copying machine, a printer, or the like, and in particular, a sheet feeding device that includes a sheet feeding cassette or a sheet feeding tray and feeds cut sheets stacked in the inside one by one to an image forming unit. About.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine or a printer, a detachable paper feed cassette or a pullable paper feed tray (collectively referred to as a paper feed tray) is mounted on a paper feed unit of the apparatus body to feed paper. A paper feeding device is provided that feeds a plurality of cut sheets stacked inside the tray one by one to the image forming unit.
As an example of the paper feeding device, a feeding roller for feeding cut sheets one by one to the image forming unit is normally provided at a position separated from the uppermost portion of the cut paper so as to contact only during paper feeding. During feeding, the feed roller is moved to a predetermined position where it abuts on the top of the cut sheet. Further, in the paper feed tray, by providing a moving means for moving the cut sheet loaded on the cut sheet so that the uppermost part is always located at a predetermined position, the uppermost part of the cut sheet is always located at a fixed position so that the movement is performed. A constant pressure is applied to the feed roller. As a control method, the position of the uppermost part of the cut sheet is detected by a position sensor, and the position of the uppermost part of the cut sheet is controlled to be the first predetermined position based on the detection signal. That is, every time the image is consumed by image formation, the top of the cut sheet is lowered, and the position sensor detects that the top is lowered, and the bottom plate on which the cut sheet is stacked is raised.
Conventionally, a part of the bottom plate on which the cut paper is stacked is pivoted to raise the cut paper. For example, a metal plate in which one end abuts the lower surface of the bottom plate and the other end is pivotable. The bottom plate is moved by.
[0003]
Such a paper feeder needs to maintain the top of the cut sheet in a very accurate position. For this reason, the feed roller is made of elastically deformed rubber or sponge and comes into contact with the top of the cut sheet that has reached a predetermined position with uniform pressure to pull out the cut sheet from the paper feed tray to prevent double feed. It is sent out to the image forming unit via a roller.
[0004]
[Problems to be solved by the invention]
However, in the paper feeding device described above, the detection accuracy of the position sensor that detects the position of the uppermost portion of the cut paper is not strict. That is, since the minimum detection amount of the position sensor is larger than the paper thickness, the position sensor cannot detect the uppermost lowering amount with respect to pulling out a small number of cut sheets. For example, when the minimum detection amount of the position sensor is 0.5 mm and the thickness of the cut sheet is 0.1 mm, the uppermost part of the cut sheet can be obtained only by drawing a few sheets of cut sheet to the image forming unit. The position sensor cannot detect the lowered amount. For this reason, the height of the uppermost part of the cut sheet is not constant, the pressure applied between the uppermost part of the cut sheet and the feed roller is not stable, and there is a problem that the paper feeding operation is not performed reliably.
[0005]
The present invention has been made in view of the above-described problems. When the cut paper is pulled out from the paper feeding device, the height of the top of the cut paper is always kept constant so that the top of the cut paper It is an object of the present invention to provide a paper feeding device in which the pressure between the feeding rollers is substantially constant.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention has a detection unit that detects the uppermost portion of a cut sheet, and moves a plurality of cut sheets stacked on a bottom plate in a paper feed tray based on a detection signal from the detection unit. The uppermost part of the cut sheet is moved by the moving means that enables the uppermost part of the cut sheet to be in the first predetermined position, and the uppermost sheet of the cut sheet is provided by a feed roller provided so as to be able to contact and separate from the uppermost part of the cut sheet In the paper feeding device that feeds the toner toward the image forming unit, the moving means has a substantially triangular shape with one end abutting on the lower surface of the bottom plate, pivoting about the other end, and having the other end as a base. A leaf spring is provided, and the uppermost portion of the cut sheet is moved to the first predetermined position by the pivot of the leaf spring based on the detection signal from the detection means, and the feed roller transmits the drive. First transmission member and delivery b And a second transmission member fixed to the frame, and supported pivotably about the first transmission member, and between the first transmission member and the second transmission member. Urging means for urging the feeding roller in a direction away from the uppermost portion of the cut sheet is provided, and the first predetermined position is opposed to the action of the urging means by driving the first transmission member. The delivery roller is pivoted toward a second predetermined position set at a lower position, and the pressing force when the delivery roller reaches the second predetermined position becomes stronger than the elastic force of the leaf spring. Features.
[0008]
Furthermore, the leaf spring has a substantially triangular shape with the other end as a base.
[0009]
In such a configuration, the position sensor detects that the cut sheet is consumed by image formation and the uppermost part of the cut sheet is lowered. Based on this detection signal, the bottom plate is moved so as to pivot about the one end side of the leaf spring so that the uppermost portion of the cut sheet is at the first predetermined position. Even if the cut sheet is consumed and the uppermost position of the cut sheet is changed, the cut sheet is fed at the second predetermined position. However, the leaf spring is elastically deformed so that the pressing force is kept substantially constant. The paper is fed from the paper feeding unit to the image forming unit.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a sheet feeding device 1 in a state where a sheet feeding operation is not performed according to the present invention, and a sheet feeding tray 2 that can be pulled out from the image forming apparatus, and a stack in the sheet feeding tray 2. A feed roller 4 that pulls out the uppermost portion of the cut sheet 3 to the image forming unit, a position sensor 5 that detects the position of the uppermost portion of the cut sheet 3, and a double feed prevention roller pair 6 that prevents double feed of the cut sheet 3. Have
In the embodiment, the paper feed tray 2 is provided so as to be drawn out in a direction perpendicular to the conveyance direction of the cut paper 3 with respect to the image forming apparatus main body, and the cut paper 3 is replenished with the paper feed tray 2 pulled out. Then, it is loaded into the image forming apparatus.
[0011]
As shown in FIG. 1, a plurality of cut sheets 3 are stacked on a frame body 7 and a bottom plate 8 in the sheet feed tray 2. The bottom plate 8 is pivotable in the direction of arrow A about the fulcrum 9. Below the bottom plate 8, there is provided a leaf spring 11 having one end in contact with the lower surface of the bottom plate 8 and pivoted by a drive source (not shown) around a pivot 10 provided on the other end side. The leaf spring 11 is interlocked with a position sensor 5 that detects the height of the uppermost portion of the cut paper 3, and the position sensor 5 indicates that the uppermost position of the cut paper 3 has changed due to the consumption of the cut paper 3. Based on this detection signal, the leaf spring 11 is pivoted in the direction of arrow B, the bottom plate 8 is pivoted in conjunction with this, and the uppermost portion of the cut sheet 3 is moved to the first predetermined position.
[0012]
The position sensor 5 is configured by a combination of an actuator 12 and a photosensor 13. The leading end side of the actuator 12 is brought into contact with the uppermost part of the cut sheet 3, and the actuator 12 is swung around the fulcrum 14 as the uppermost part of the cut sheet 3 moves, and the other end side of the actuator 12 blocks the photosensor 13. . The position of the uppermost part of the cut sheet 3 is detected based on the degree of the blockage.
[0013]
A gear 15 indicated by a broken line is fixed to the delivery roller 4 as a first transmission member. A gear 16 as a second transmission member is connected to the gear 15. The gear 16 is provided on a fixed shaft 17, and the feed roller 4 is provided so as to be pivotable in the direction of arrow C along the outer periphery of the gear 16 around the shaft 17. For this reason, the delivery roller 4 pivots in the direction of arrow C or rotates in the direction of arrow D based on the action of an urging means described later by rotating the gear 16.
[0014]
The feed roller 4 is separated from the uppermost part of the cut paper 3 when the paper feeding operation is not performed, and is fed to the uppermost part of the cut paper 3 when the paper feed operation is performed. An urging means 18 is provided for abutting the surface of the urging member. The biasing means 18 is provided on the shaft 17 and can be rotated when a set force is applied, and one end side is locked to the torque limiter 19, and the other end side is locked to the shaft 20 of the feed roller 4. And a coil spring (not shown) that urges the feed roller 4 in a direction away from the uppermost portion of the cut sheet 3.
One end side of the coil spring is fixed to the sheet feeding device 1, and the other end side is locked to the support member 21.
[0015]
The first predetermined position where the uppermost portion of the cut sheet 3 is located is set to be higher than the second predetermined position where the outer peripheral surface of the feed roller 4 is located, and the difference is the minimum detection range of the position sensor 5. If it is within. That is, it is only necessary that the feed roller 4 is always in contact with the uppermost portion of the cut paper 3 during paper feeding, and the feed roller 4 can press the uppermost portion of the cut paper 3 with the pressure set by the torque limiter 19.
[0016]
The double feed prevention roller pair 6 includes a feed roller 23 that is driven to rotate in the direction of arrow E, and a double feed prevention roller 24 that is fixed or rotates in a direction opposite to the feed roller 23. The surface of the feed roller 23 is set to have a frictional resistance higher than that of the surface of the double feed prevention roller 24, and only one sheet can be fed into the image forming unit even when the double feed is performed.
[0017]
FIG. 3 shows a view of the leaf spring 11 as viewed from above, and the leaf spring 11 is fixed to the pivot 10 with screws 22 or the like. The shape of the leaf spring 11 is appropriately selected according to the weight and thickness per unit of the cut paper to be used, and preferably a substantially triangular shape with the base portion on the pivot 10 side of the leaf spring as shown in the figure. Used for. When the leaf spring has a substantially triangular shape, it is possible to reliably feed the cut sheet to the sheet feeding unit in response to a slight change in the pressing force by the feeding roller.
[0018]
The operation will be described with such a configuration.
In FIG. 1, first, the uppermost position of the cut sheet 3 is controlled to be the first predetermined position. The position sensor 5 detects the position of the uppermost portion of the cut paper 3 in a state where the feed roller 4 is not in contact with the uppermost portion of the cut paper 3, and the leaf spring 11 is pivoted about the pivot 10 based on this detection signal. Let The bottom plate 8 on which the cut paper 3 is loaded is pivoted about the fulcrum 9 by the pivot of the leaf spring 11, and the cut paper 3 moves. The pivoting of the leaf spring 11 is performed until the uppermost part of the cut sheet 3 reaches the first predetermined position.
[0019]
When image formation is performed, the feed roller 4 starts operating based on the paper feed signal. The gear 16 is rotated by a driving source (not shown) at the timing of paper feeding. By this rotation, the feed roller 4 acting so as to be separated from the uppermost part of the cut sheet 3 is pivoted in the direction of arrow C by the support member 21 against the action of the coil spring 22, and the feed roller 4 is moved to the second position. Pivot to a predetermined position.
In FIG. 2, the feed roller 4 comes into contact with the uppermost portion of the cut sheet 3 and further pivots until a force exceeding the set value is applied to the torque limiter 19. For this reason, the leaf spring 11 is elastically deformed, the uppermost position of the cut sheet 3 is lowered, and the feed roller 4 is pressed against the uppermost part of the cut sheet. In this state, more force than the setting is applied to the torque limiter 19, so that the gear 15 connected to the gear 16 rotates, rotates the feed roller 4, and pulls the cut sheet 3 toward the double feed prevention roller pair.
[0020]
Each time the cut paper 3 is pulled out, the paper feed signal is released, and the feed roller 4 pivots to a position away from the uppermost portion of the cut paper 3 by the action of the coil spring locked to the support member 21 again. The leaf spring 11 elastically deformed by this operation returns to its original state.
[0021]
Each time the above operation is repeated, the position of the uppermost portion of the cut sheet 3 changes, and when the change is detected by the position sensor 5, the leaf spring 11 is pivoted about the pivot 10 and cut to the first predetermined position. The uppermost part of the paper 3 is moved to the first predetermined position.
[0022]
【The invention's effect】
The sheet feeding device of the present invention can maintain the height of the uppermost portion of the cut sheet constantly by the action of the leaf spring when the cut sheet is pulled out from the sheet feeding device. The pressure between them became almost constant, and paper feeding errors were drastically reduced.
[0026]
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a paper feeding device according to the present invention.
FIG. 2 is a schematic cross-sectional view of a paper feeding device during paper feeding according to the present invention.
FIG. 3 is a view showing an example of a shape of a leaf spring.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Paper feeder 2 Paper feed tray 3 Cut paper 4 Feed roller 5 Position sensor 6 Double feed prevention roller pair 7 Frame 8 Bottom plate 9 Supporting point 10 Axis 11 Leaf spring 12 Actuator 13 Photo sensor 14 Supporting point 15 Gear 16 Gear 17 Gear 18 Force means 19 Torque limiter 20 Shaft 21 Support member 22 Screw 23 Feed roller 24 Double feed prevention roller

Claims (1)

The uppermost part of the cut sheet has a detecting unit that detects the uppermost part of the cut sheet, and the moving unit is configured to move a plurality of cut sheets stacked on the bottom plate in the paper feed tray based on a detection signal from the detecting unit. Is moved so as to be at the first predetermined position, and a sheet feeding device that feeds the uppermost sheet of the cut sheet toward the image forming unit by a feed roller provided so as to be able to contact and separate from the uppermost part of the cut sheet The moving means includes a leaf spring having a substantially triangular shape with one end abutting against the lower surface of the bottom plate, pivoting about the other end, and having the other end as a base. The leaf spring pivots on the basis of the detection signal from the first sheet to move the uppermost portion of the cut sheet to the first predetermined position, and the feed roller is fixed to the first transmission member and the feed roller for transmitting the drive. To the second transmission member Are connected to each other, are pivotally supported around the first transmission member, and the feeding roller is disposed between the first transmission member and the second transmission member at the top of the cut sheet. A second predetermined position provided with a biasing means for biasing in a direction away from the first predetermined position and set at a position lower than the first predetermined position against the action of the biasing means by driving the first transmission member; The paper feeding device is characterized in that the feeding roller is pivoted toward the side, and the pressing force when the feeding roller reaches the second predetermined position is stronger than the elastic force of the leaf spring .

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