JP3885004B2 - Sheet feeding apparatus and image forming apparatus provided with the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet feeding apparatus and an image forming apparatus including the sheet feeding apparatus, and more particularly to a configuration of a detection unit that detects the presence or absence of a sheet stored in a sheet storage unit.
[0002]
[Prior art]
2. Description of the Related Art In recent years, image forming apparatuses such as printers, copiers, and facsimiles are provided with a sheet feeding device for separating sheets one by one and feeding them to an image forming unit. As such a sheet feeding device, for example, the pickup roller can be moved up and down, the sheet is fed by lowering the pickup roller to the sheet side when feeding, and the pickup roller is raised at times other than feeding. Some lift-up systems are designed to be separated from the seat.
[0003]
Here, in such a conventional lift-up type sheet feeding apparatus, when the sheet feeding cassette is mounted, the middle plate incorporated in the sheet feeding cassette is lifted from the lowest position by driving on the apparatus body side. Thus, when the middle plate rises as described above, the pickup roller comes into contact with the uppermost sheet eventually, and when the middle plate further rises, the pickup roller also rises.
[0004]
Thereafter, when the pickup roller is raised to a predetermined position, the intermediate plate is stopped. The position where the middle plate stops is a position where an appropriate sheet feeding pressure is applied to the upper surface of the sheet by the pickup roller during feeding, and the sheet is reliably fed out by stopping the middle plate at such a position. Will be able to.
[0005]
By the way, such a conventional sheet feeding apparatus is provided with a detecting means for detecting the presence or absence of a sheet stored in the sheet storing means, and the sheets are sequentially fed, and the sheet is supplied to the sheet storing means. When the sheet no longer exists, this is detected by the detection means, and the operator is notified that the sheet is no longer present in the sheet storage means.
[0006]
FIG. 5 is a diagram showing the configuration of such a conventional sheet presence / absence detection device that detects the presence / absence of a sheet. In FIG. 5, reference numeral 41 is provided in a sheet feeding cassette 4 that is a sheet storage means. An intermediate plate 50 is a sheet presence / absence detection device including an actuator 51 and a sensor (not shown). Reference numeral 41 a denotes a slit formed in the intermediate plate 41, and the slit 41 a is formed at a position facing the actuator 51.
[0007]
Here, when there is a sheet in the paper feed cassette 4 (on the middle plate 41), the actuator 51 comes into contact with the sheet and stops at the position shown in FIG.
[0008]
On the other hand, when the sheet on the intermediate plate 41 runs out, the actuator 51 passes through the slit 41a of the intermediate plate 41 and descends to a position indicating that there is no sheet on the intermediate plate 41 shown in FIG. It has become. Here, when the actuator 51 is lowered to such a position, a sensor (not shown) is turned on. When the sensor is turned on in this way, the control unit (not shown) causes the paper feed cassette 4 (on the middle plate 41). It is determined that there is no sheet, and the operator is notified of the absence of the sheet by a buzzer or a display.
[0009]
[Problems to be solved by the invention]
By the way, in the conventional sheet feeding device provided with the sheet presence / absence detection device having such a configuration, the actuator 51 is biased downward by a spring (not shown) in order to ensure the detection operation by the actuator 51. Yes. However, if the actuator 51 is urged downward by the spring in this way, the actuator 51 collides with, for example, the edge of the slit 41a when the sheet disappears and descends to the position shown in FIG. It becomes like this.
[0010]
And when it collides with the edge of the slit 41a in this way, the actuator 51 rebounds upward due to the impact, and thereafter, an impact force that directs the actuator 51 upward and a spring that directs the actuator 51 downward. It vibrates in the vertical direction by the urging force of.
[0011]
Here, when the actuator 51 vibrates in this way, the output of the sensor becomes unstable, and the control unit may start a sheet feeding operation even when there is no sheet on the intermediate plate 41. Is a paper feed failure.
[0012]
Accordingly, the present invention has been made in view of such a current situation, and provides a sheet feeding apparatus capable of reliably detecting the presence or absence of a sheet with a simple configuration and an image forming apparatus including the sheet feeding apparatus. It is intended.
[0013]
[Means for Solving the Problems]
The present invention relates to a sheet feeding apparatus in which a sheet stored in the sheet storage means is sent out by the sheet feeding means, and abuts on the sheet stored in the sheet storage means, and the sheet is stored in the sheet storage means The sheet storage means has a lever member that moves to a position indicating that there is no sheet, and detecting means for detecting the presence or absence of the sheet in the sheet storage means according to the position of the lever member; Biasing means for urging the lever member in the direction of the sheet; and brake means for reducing a moving speed when the lever member moves to a position indicating that the sheet is absent. Is.
[0014]
Further, the invention is characterized in that the brake means generates a frictional force with the lever member as the lever member moves.
[0015]
In the invention, it is preferable that the brake means generates the frictional force by an elastic force.
[0016]
Further, the present invention is characterized in that the urging means and the brake means are integrated.
[0017]
Further, the present invention is characterized in that the urging means integrated with the brake means is arranged between the lever member and the frame of the detecting means.
[0018]
According to the present invention, in a sheet feeding device in which the sheet stored in the sheet storing unit is sent out by the sheet feeding unit, the sheet is mounted on the shaft so as to be swingable, and the sheet stored in the sheet storing unit An abutting actuator that swings to a position indicating that there is no sheet in the sheet storage means when there is no sheet in the sheet storage means, and a sheet of the sheet storage means according to the swing position of the actuator. A detecting means for detecting presence / absence; a fixing member fixed to the shaft; and the actuator, arranged on the shaft, one end engaged with the fixing member and the other end engaged with the actuator. A rotational biasing force is applied to the actuator, and the actuator is arranged in a compressed state between the fixed member and the actuator. It is characterized in that and a torsion coil spring for generating a frictional force between the.
[0019]
According to another aspect of the present invention, an image forming apparatus includes the image forming unit that forms an image on a sheet, and the sheet feeding device according to any one of the above that feeds the sheet to the image forming unit. To do.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
FIG. 1 is a diagram showing a schematic configuration of a laser beam printer which is an example of an image forming apparatus provided with a sheet feeding apparatus according to an embodiment of the present invention.
[0022]
In FIG. 1, reference numeral 1 denotes a laser beam printer. The laser beam printer 1 includes an image forming unit 2 that forms an image, a sheet feeding device 5 that separates and feeds sheets P one by one to the image forming unit 2, and the like. It has.
[0023]
Here, the image forming unit 2 includes a process cartridge 7 that can be attached to and detached from a laser beam printer main body (hereinafter referred to as an apparatus main body) 1A, a transfer roller 9, and the like, and the sheet feeding device 5 is a sheet storage for stacking and storing sheets. A sheet separating and feeding unit including a sheet feeding cassette 4 as a means, a pickup roller 6 as a sheet feeding means, a feed roller 14 and a retard roller 15 is provided. The process cartridge 7 includes a photosensitive drum 8, a charging roller 20, a developing unit 22, a cleaning unit (not shown), and the like.
[0024]
The charging roller 20 is provided in contact with the photosensitive drum 8 so as to be driven to rotate by the photosensitive drum 8, and is used to uniformly charge the surface of the photosensitive drum when the photosensitive drum 8 rotates. The developing means 22 supplies toner to the developing area of the photosensitive drum 8 and develops the latent image formed on the photosensitive drum 8.
[0025]
In the figure, 12 is a laser scanner unit, 10 is a fixing unit, 13 is a sheet discharge roller for discharging the sheet P to the sheet discharge stacking table 16, 1B is a cassette storage section provided in the apparatus main body 1A, and 11 is a control. Part.
[0026]
Next, an image forming operation of the laser beam printer 1 configured as described above will be described.
[0027]
When image information is sent from a personal computer (not shown) and a controller board (not shown) that performs image formation processing of this image information issues a print signal, it is loaded on a paper feed cassette 4 that is detachably attached to the apparatus body 1A. The sheets P are fed one by one by the pickup roller 6 and the sheet separating and feeding unit, and sent to the nip between the photosensitive drum 8 and the transfer roller 9 in the process cartridge 7.
[0028]
On the other hand, based on the image information together with this print command, the laser scanner unit 12 irradiates the photosensitive drum with a bit image of the image information (laser light), and a latent image is formed on the surface of the photosensitive drum 8 according to the bit image. It is formed. Further, by developing this latent image, a toner image is formed on the photosensitive drum.
[0029]
The toner image thus formed on the photosensitive drum is then transferred to the sheet P fed into the nip between the photosensitive drum 8 and the transfer roller 9. Further, the sheet P on which the toner image is transferred is sent to the fixing unit 10 and is heated and pressed by the fixing unit 10, whereby the toner image is fixed semipermanently. Further, thereafter, the sheet P on which the toner image is fixed is discharged to the sheet discharge stack 16 by the discharge roller 13.
[0030]
In the figure, reference numeral 41 denotes a middle plate of the paper feed cassette 4. The middle plate 41 is provided on the paper feed cassette 4 so as to be rotatable (movable) in the vertical direction with a locking portion 41a as a fulcrum. Reference numeral 42 denotes a side plate that is suspended from one end of a push-up plate 43 provided below the intermediate plate 41 and has a rack 42a formed at the upper end. 44 is a motor (not shown) provided in the apparatus main body. It is a pinion that rotates.
[0031]
When the paper feed cassette 4 is mounted in the cassette housing portion 1B (see FIG. 1) provided in the apparatus main body 1A, the rack 42a of the side plate 42 meshes with the pinion 44. After that, the control unit 11 drives the motor to rotate the push-up plate 43 upward, thereby pushing up the intermediate plate 41 so that the upper surface of the sheet P has a substantially constant height at which appropriate pressure is applied when feeding. I try to raise it.
[0032]
FIG. 2 shows the configuration of the sheet feeding device 5. In FIG. 2, reference numeral 45 denotes a sheet presence / absence detection device which is detection means for detecting the presence / absence of sheets in the sheet feeding cassette 4. FIGS. 3A to 3C are a side view, a front view, and a perspective view of the sheet presence / absence detection device 45, respectively.
[0033]
Here, the sheet presence / absence detecting device 45 is arranged above the sheet feeding cassette 4 (the middle plate 41) as shown in FIG. 2, and an actuator 46, which is a lever member, as shown in FIG. A sensor 47 that detects the position of the actuator 46 by being turned on and off by a flag 46 b provided on the shaft 46 a of the actuator 46 is provided. In the present embodiment, an optical sensor having a light emitting unit and a light receiving unit (not shown) is used as the sensor 47.
[0034]
When there is a sheet on the intermediate plate 41, the actuator 46 comes into contact with the sheet and stops at the position shown in FIG. When the sheet runs out, it turns downward, passes through the slit 41a of the intermediate plate 41, and descends to a position indicating the absence of the sheet shown in FIG.
[0035]
Here, when the actuator 46 is lowered to such a position, it is shielded by the flag 46b and the sensor 47 is turned on. When the sensor 47 is turned on in this way, the control unit 11 determines that there is no sheet in the sheet feeding cassette 4 (on the middle plate 41), and informs the operator that there is no sheet by a buzzer or a display.
[0036]
Incidentally, as shown in FIG. 4, the actuator 46 has a torsion coil spring as an urging means whose one end is locked to a frame 45 a as a fixing member of the detection device 45 and the other end is locked to the upper surface of the actuator 46. 48 is biased downward. The actuator 46 is urged downward by the torsion coil spring 48 in this way, so that the detection operation by the actuator 46 is ensured.
[0037]
By the way, in this embodiment, the torsion coil spring 48 is compressed between the actuator 46 and the frame 45a of the sheet presence / absence detecting device 45 as shown in FIG. Is attached.
[0038]
Here, by arranging the torsion coil spring 48 in a compressed state between the actuator 46 and the frame 45a of the sheet presence / absence detection device 45 as described above, when the actuator 46 descends, the torsion coil spring 48 and the actuator 46 are moved downward. A frictional force is generated between them. As a result, the speed when the actuator 46 descends becomes slow.
[0039]
That is, by arranging the torsion coil spring 48 in a compressed state between the actuator 46 and the frame 45a of the detection device 45, the torsion coil spring 48 acts as a brake means, and the actuator 46 is in a position indicating that there is no seat. The moving speed when moving is reduced.
[0040]
And when the speed at the time of descending becomes slow in this way, when the actuator 46 runs out of the sheet on the intermediate plate 41 and descends to the position shown in FIG. 5 (b), the actuator 46 collides with the edge of the slit 41a. The impact is reduced, and as a result, the vertical vibration of the actuator 46 is reduced.
[0041]
When the vibration of the actuator 46 is reduced in this way, the output of the sensor 47 is stabilized, and the control unit 11 can reliably determine that there is no sheet on the intermediate plate 41. As a result, the sheet feeding operation is not started even though there is no sheet on the intermediate plate 41, and as a result, the occurrence of sheet feeding defects is eliminated.
[0042]
In this way, the actuator 46 is biased in the direction of the seat by the spring 48, and the moving speed when the actuator 46 moves to a position indicating that there is no seat is reduced by the torsion coil spring 48 that also serves as a brake means. The vertical vibration of the actuator 46 can be prevented. Accordingly, it is possible to reliably detect the presence of a sheet with a simple configuration, and it is possible to prevent the occurrence of a paper feed failure.
[0043]
The present invention is not limited to the configuration of this embodiment. For example, in this embodiment, the urging means and the brake means are combined with a torsion coil spring. You may comprise with another member.
[0044]
【The invention's effect】
As described above, according to the present invention, the lever member that contacts the sheet stored in the sheet storage means and moves to a position indicating that there is no sheet when there is no sheet in the sheet storage means. By energizing in the direction of the sheet, the brake member reduces the moving speed when the lever member moves to a position indicating that there is no sheet in the sheet storage means, thereby reliably confirming the presence or absence of the sheet with a simple configuration. Can be detected.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a laser beam printer which is an example of an image forming apparatus including a sheet feeding device according to an embodiment of the present invention.
FIG. 2 is a perspective view of a main part for explaining a configuration of a sheet feeding device of the laser beam printer.
FIG. 3 is a diagram illustrating a configuration of a sheet presence / absence detection device provided in the sheet feeding device.
FIG. 4 is a partial cross-sectional side view of the sheet presence / absence detection device.
FIG. 5 is a diagram illustrating a configuration of a sheet presence / absence detection device that is a detection unit that detects the presence / absence of a sheet.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser beam printer 2 Image formation part 4 Paper feed cassette 5 Sheet feeding apparatus 41 Middle board 45 Sheet presence / absence detection apparatus 46 Actuator 47 Sensor 45a Frame 48 Torsion coil spring

Claims (7)

In the sheet feeding apparatus in which the sheet stored in the sheet storing means is sent out by the sheet feeding means,
A lever member that contacts the sheet stored in the sheet storage means and moves to a position indicating that there is no sheet in the sheet storage means when there is no sheet in the sheet storage means; Detecting means for detecting the presence or absence of a sheet in the sheet storing means according to the position of,
Biasing means for biasing the lever member in the direction of the sheet;
Brake means for reducing the moving speed when the lever member moves to a position indicating that there is no sheet;
A sheet feeding apparatus comprising: 2. The sheet feeding apparatus according to claim 1, wherein the brake means generates a frictional force with the lever member as the lever member moves. The sheet feeding apparatus according to claim 2, wherein the brake means generates the frictional force by an elastic force. The sheet feeding apparatus according to claim 1, wherein the urging unit and the brake unit are integrated. 5. The sheet feeding apparatus according to claim 4, wherein an urging unit integrated with the brake unit is disposed between the lever member and a frame of the detection unit. In the sheet feeding apparatus in which the sheet stored in the sheet storing means is sent out by the sheet feeding means,
Swingably mounted on the shaft, abuts on the sheet stored in the sheet storage means, and swings to a position indicating that there is no sheet in the sheet storage means when there is no sheet in the sheet storage means An actuator to
Detection means for detecting the presence or absence of a sheet in the sheet storage means according to the swing position of the actuator;
Arranged on the shaft between a fixing member fixed to the shaft and the actuator, one end engages with the fixing member, the other end engages with the actuator and applies a rotational biasing force to the actuator; A torsion coil spring for generating a frictional force between the fixing member and the actuator by being arranged in a compressed state;
A sheet feeding apparatus comprising: An image forming apparatus comprising: an image forming unit that forms an image on a sheet; and the sheet feeding device according to any one of claims 1 to 6 that feeds the sheet to the image forming unit. apparatus.

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