JPH04243748A - Sheet feeder - Google Patents

Abstract

PURPOSE:To surely feed sheets P by using a rear-end detection sensor 25 to detect the rear end of a sheet conveyed from a sheet feeder 3 to an image forming apparatus 1, and performing the drive control of both a feed roller 10 adapted to feed sheets and a pair of conveying rollers 16. CONSTITUTION:Sheets P loaded are fed from the lowermost one by a feed roller 10 and when the sheets P are conveyed by a pair 16 of conveying rollers the rear end of a sheet Pa being fed is detected by a rear-end detection sensor 25. The drive control for the feed roller 10 and the pair 16 of conveying rollers is carried out in response to a signal indicative of detection of the rear end Pb of the sheet. The feed roller 10 is thus rotated correspondingly to the length of each of the sheets P loaded, whereby different sheets P are surely fed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is capable of being detachably connected to an image forming apparatus such as a copying machine or a laser beam printer.
The present invention relates to a sheet feeding device that feeds sheets one by one to an image forming section of the image forming apparatus.

0002

2. Description of the Related Art Conventionally, a device for feeding sheet materials one by one from outside the device to an image forming apparatus such as a laser beam printer has been used as a feeding means (hereinafter referred to as a feeding means) for feeding sheet materials stacked on a sheet stacking table. a pressure member that presses the sheet against the feeding roller; a conveying means (hereinafter referred to as a pair of conveying rollers) that conveys the fed sheet material into the image forming apparatus; 2. Description of the Related Art Devices are known that include a drive unit and the like for driving a pair of conveyance rollers.

[0003] In such a sheet feeding device, the feeding of the sheet by the feeding roller is performed based on a preset time period for the trailing edge of the sheet being fed to reach the trailing edge of the feeding roller. During this time, the feeding roller is driven.

0004

SUMMARY OF THE INVENTION However, the above-mentioned conventional sheet feeding device has the following problems.

1. If the drive time of the feed roller is set as the time it takes for the trailing edge of a relatively short sheet to touch the feed roller, when feeding a relatively long sheet, the driving time for the feed roller is set as the time it takes for the trailing edge of a relatively short sheet to hit the feed roller. Sometimes the sheet cannot be fed because the feeding roller stops driving.

2. If the drive time of the feed roller is set as the time required for the trailing edge of a relatively long sheet to reach the feed roller, when feeding a relatively short sheet, even if the trailing edge of the sheet passes the feed roller, Since the feeding roller continues to be driven, the next sheet is fed, resulting in double feeding of sheets. Therefore, the present invention provides a trailing edge detection sensor for detecting the trailing edge of the sheet to be fed, and a trailing edge detection sensor for detecting the trailing edge of the sheet to be fed is provided on the sheet stacking table, and the first conveying means An object of the present invention is to provide a sheet feeding device that solves the above-mentioned problems by driving a feeding roller (feeding roller).

[0007]

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned circumstances. For example, as shown with reference to FIGS. A device main body (5), a sheet loading table (6) provided in the sheet feeding device main body (5) and capable of loading a plurality of sheets (P), and a top plate of the sheets (P). A first conveyance means (10) that feeds the lower sheet (Pa), and a sheet (Pa) that is fed by the first conveyance means (10).
) into the image forming apparatus (1); a trailing edge detection sensor (25) which detects the trailing edge (Pb) of the sheet (Pa) and is disposed upstream of the first conveyance means (10); ), the drive control means (31) controls the rotational operation of the first feeding operation (10) and the second conveying means (16) by detecting the trailing edge (Pb) of the sheet. It is characterized by

Further, the trailing edge detection sensor (25) is detected during the feeding by the jumping action of the trailing edge (Pb) of the sheet from the diving board (26) which separates the sheet (P) from above the sheet stacking table (6). It is characterized in that only the rear end (Pb) of the sheet (Pa) is detected.

[0009]

[Operation] Based on the above configuration, when an instruction to feed a sheet (P) is transmitted from the image forming apparatus 1 to the sheet feeding device (3), the sheet (P) stacked on the sheet stacking table (6) is transmitted.
The lowest sheet (P) of the first conveying means (10
), and is further fed by a second conveying means (1
6) is transported to the image forming apparatus (1).

When the sheet (Pa) is conveyed by the first conveying means (10) and the second conveying means (16), the trailing edge (Pb) of the sheet (Pa) is detected by the trailing edge detection sensor (2).
5) is detected. Upon detection of this trailing edge (Pb), the drive to the feeding roller (10) is released, and only the pair of conveying rollers 16 is driven to convey the sheet (Pa) to the image forming apparatus (1). This makes it possible to control the drive of the first conveyance means (10) in accordance with the length of the sheet (P) stacked on the sheet stacking table (6) in the conveyance direction. ) is realized.

Further, the trailing edge detection sensor (25) detects that the trailing edge (Pb) of the sheet (Pa) being fed is the diving board (26).
) from the rear end of the seat (Pb
) is detected, and this causes the sheet being fed (
Even if a sheet (Pa) other than Pa) is loaded on the sheet stacking table (6), the sheet (Pa) being fed
The rear end (Pb) of the chisel can be reliably detected.

Note that the above-mentioned symbols in parentheses are shown for reference to the drawings, and do not limit the structure of the present invention in any way.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

In FIGS. 1 and 2, reference numeral 1 designates an image forming apparatus such as a copying machine or a laser beam printer, which includes an image forming section 2 for forming an image on a sheet, which will be described later. . This image forming apparatus 1 includes an apparatus main body 5 of a sheet feeding apparatus 3 which is used as an option.
is attached removably.

As shown in FIG. 2, the apparatus main body 5 houses a sheet stacking table 6 on which a plurality of sheets P are stacked, and a drive section, which will be described later, provided at the end of this sheet loading table 6. It has a hollow side wall portion 7. The sheets P are aligned by having one side pressed against the wall surface 7a of the side wall portion 7 by a regulating plate 9 that is reciprocally movable along the width direction of the sheet stacking table 6.

As shown in FIG. 1, below the sheet stacking table 6, a first conveying means (hereinafter referred to as a feeding roller) is rotatably supported by a support shaft 11. 10 has an upper circumferential surface extending upward from a hole formed in the sheet stacking table 6 and comes into contact with the lowest sheet Pa of the stacked sheets P. Also, at the top of the sheet P,
A pressure member 12 having an appropriate weight is placed to press the lowest sheet Pa against the feeding roller 10.

A support shaft 1 is provided on the downstream side of the feed roller 10.
The lower conveying roller 1 is pivotally supported by 3 and rotates in the direction of the arrow.
A second conveying means (hereinafter referred to as a pair of conveying rollers) 16 is provided, which includes a second conveying means 6a and an upper conveying roller 16b that comes into contact with the upper conveying roller 16b and rotates in the direction of the arrow. The above upper conveyance roller 16b
is attached to the support shaft 15 via a torque limiter (not shown), and when the number of sheets P fed by the feeding roller 10 is two or more, it rotates in the direction of the arrow to Separate into one piece. The sheet P transported to the image forming apparatus 1 by the transport roller pair 16 is transported between the transport roller 17 provided in the image forming apparatus 1 and the sheet P transported to the transport roller 1.
The guide member 19 that presses the image forming section 7 is conveyed to the image forming section 2 .

In FIG. 2, inside the side wall portion 7 are a drive motor 20 for driving the above-mentioned feeding roller 10, the pair of conveying rollers 16, etc.; A gear unit 21 connected to the drive motor 20, the gear unit 21, and the like constitute a drive section 22.

Next, a detection means for detecting the trailing edge of the sheet P being fed will be explained. As shown in FIG. 1, a trailing edge detection sensor 25 is located near the upstream side of the feeding roller 10.
The details of this rear end detection sensor 25 are shown in FIG.

In the figure, a diving board 26 having a stepped portion 26a facing toward the feeding roller 10 is provided near the upstream side of the feeding roller 10. As shown in FIG. This diving board 26 is arranged along the width direction of the feeding roller 10 to make it easier to detect the rear end of the sheet P.
a is the trailing edge detection line of the sheet P.

[0021] A rear end detection sensor 25 consisting of a photosensor 25a containing a light emitting diode and a light receiving element and a detection lever 25b is disposed in a notch provided at a suitable location in the diving board 26. The above detection lever 25
As shown in FIG. 4, b is rotatable by a support shaft 27, and a flag 25c for blocking the optical path of the photosensor 25a is provided at its inner end.

FIG. 5 shows a block diagram of the control section in this embodiment.

In the figure, reference numeral 31 is a control unit (CPU) for controlling the sheet feeding device, 32 is a motor driver for driving the drive motor 20, and 33 is a CPU for communicating with the image forming apparatus 1. A communication circuit, 35 is a control bus with the image forming apparatus 1, 36 is an operation instruction signal as a result of analyzing the communication control information from the image forming apparatus 1, 37 is a motor control signal that controls the motor driver 32, 39 is a drive motor A motor drive signal for driving 20 is shown, and 40 is a sensor signal from the trailing edge detection sensor 25 when the trailing edge of the sheet P is detected.

Next, the operation of this embodiment will be explained with reference to the block diagram of FIG. 5 and the flowchart of FIG. 6.

The control section 31 in the sheet feeding device 3 is waiting for an operation instruction signal 36 from the image forming apparatus 1, and the operation instruction signal 36 from the image forming apparatus 1 is sent to the communication circuit via the control bus 35. After being analyzed by the same circuit 33, a motor drive instruction is given to the control unit 31 using an operation instruction signal 36. The control unit 31 outputs a motor control signal 37 and an excitation pattern to control the motor driver 32. The excitation pattern at this time is
This is a pattern in which the feeding roller 10 is rotated in the normal direction, that is, a pattern in which the feeding roller 10 is rotated in the direction of the arrow in FIG.

Next, the motor driver 32 amplifies the motor control signal 37 from the control section 31 and outputs a motor drive signal 39 to drive the drive motor 20. When the drive motor 20 rotates forward, the gear unit 21 (
The feeding roller 10 and the pair of conveying rollers 16 are rotated in the direction of the arrow by the driving force transmitted through the roller (see FIG. 2) (S2).

By the rotation of the feed roller 10, the lowest sheet Pa is conveyed on the conveyance path 6a on the side wall portion 7 in the direction of arrow 41. Here, when the rear end of the sheet Pa conveyed by the feeding roller 10 is located upstream of the diving board 26 shown in FIG. 3, the sheet Pa does not press the detection lever 25b because it is obstructed by the diving board 26. Therefore, the flag 25c of the rear end detection sensor 25 remains in a state where the optical path of the photosensor 25a remains blocked, as shown in FIG. 4(a).

When the rear end of the sheet Pa being fed passes the diving board 26, the rear end Pb of the sheet Pa falls from the stepped portion 26a of the diving board 26, and the stepped portion 26a moves toward the rear end as shown in FIG. Detection lever 25b of detection sensor 25
Press and rotate it in the direction of the arrow. By the rotation of the detection lever 25b and the flag 25c integrated therewith, the optical path of the detection lever 25b is opened, and the passage of the rear end Pb of the sheet Pa is detected (S3).

When the trailing edge detection sensor 25 detects the trailing edge Pb of the sheet Pa, an excitation pattern is outputted from the control section 31 in order to rotate the drive motor 20 in the reverse direction, thereby causing the drive motor 20 to rotate in the reverse direction. .

Note that the feed roller 1 is connected from the gear unit 21 to
A one-way rotation clutch (not shown) is provided in the transmission path that transmits the driving force to the feed roller 10, and transmits the driving force to the feeding roller 10 only when the drive motor 20 rotates in the normal direction. The driving force is not transmitted to the feeding roller 10 during reverse rotation. Further, the conveyance roller pair 16 is configured to be driven by two drive paths having a one-way rotation clutch (not shown) included in the gear unit 21, so that the drive motor 20 rotates forward and backward. It always rotates in the direction of the arrow (S4
).

The sheet Pa conveyed by the conveying roller pair 16 is conveyed to the image forming section 2 by the conveying roller 17 and guide member 19 in the image forming apparatus 1, and an image is formed thereon. When the conveyance of the sheet Pa is detected by a sensor (not shown) in the image forming apparatus 1 due to the conveyance of the sheet Pa by the pair of conveyance rollers 16 described above, the image forming apparatus 1 causes the motor driver 32 to control the motor via the control bus 35. A stop instruction is output (S5). The control unit 31 includes a communication circuit 33,
When the motor stop instruction is recognized via the operation instruction signal 36, the excitation pattern output is stopped to the motor driver 32 via the motor control signal 37, the motor drive signal 39 is also stopped, and the operation in the sheet feeding device 3 is completed. (S
6).

As mentioned above, in this embodiment, FIG.
As shown in FIG. 3, the detection lever 25b of the trailing edge detection sensor 25 is rotated by the trailing edge of the sheet Pa to ensure detection of the trailing edge Pb of the sheet Pa. By controlling the backward movement of the roller 1 and the drive motor 20 to control the rotational operations of the feeding roller 10 and the pair of conveying rollers 16, it is possible to reliably feed sheets of different sizes.

Note that even if another switch is used to detect the rear end Pb of the sheet Pa in place of the photo sensor used as the rear edge detection sensor 25 in the above embodiment, the same operation as in the above embodiment can be achieved. It is possible to realize this.

Next, a second embodiment of the present invention will be explained with reference to FIGS. 7 and 8. Components having the same functions as those shown in FIG. 5 are denoted by the same reference numerals, and their explanation will be omitted.

In FIG. 6, reference numeral 51 indicates the electromagnetic clutch 5.
2 shows a clutch drive circuit for driving 2. The electromagnetic clutch 52 is provided in the gear unit 21 shown in FIG.
This is a clutch for different operations. When this clutch drive circuit 51 is driven, the feeding roller 10 is disengaged from the gear unit 21, and the rotational force is lost, and only the pair of conveying rollers 16 begins to rotate. Further, when the clutch drive circuit 51 is released (turned OFF), the feeding roller 10 also starts rotating together with the pair of conveying rollers 16 which are still rotating.

Next, the operation of this embodiment will be explained with reference to FIG.

In the figure, a control section 31 in the sheet feeding device 3 is waiting for an operation instruction signal 36 from the image forming device 1. When the communication circuit 33 receives the start operation instruction signal 36 from the image forming apparatus 1 via the control bus 35 (S1), the control unit 31 controls the clutch drive circuit 51
A clutch drive signal 53 is output to release the clutch. At this time, the electromagnetic clutch 52 in the gear unit 21 is OF
The state is set to F, and the drive to the feeding roller 10 is released.

Next, the control unit 31 sends a motor control signal 3 to the motor driver 32 in order to drive the drive motor 20.
Get 7. Here, when controlling the drive of the feeding roller 10 using the electromagnetic clutch 52, the drive motor 20
The drive motor 20, which uses a DC motor, will be explained as an example because it is not a motor that can rotate forward and backward like a stepping motor, but can only rotate in the same direction like a DC motor.

The motor drive of the control section 31 does not require sending out an excitation pattern every time the sheet P is fed, as is the case with a stepping motor, and the motor control signal 37 can be used only at the time of startup, so that Until the trailing edge Pb of the sheet Pa is detected by the trailing edge detection sensor 25, it is in a standby state.

When the control section 31 detects the rear end Pb of the sheet Pa by the rear end detection sensor 25, the clutch drive signal 53 is sent to the clutch drive circuit 5 to turn on the electromagnetic clutch 52.
Output for 1. When the electromagnetic clutch 52 is turned on, a gear (not shown) in the drive system of the feeding roller 10 is disengaged, and the feeding roller 10 stops rotating, so that only the pair of feeding rollers 16 can be driven.

Next, the control section 31 waits until an operation stop signal is received from the image forming apparatus 1. When the control unit 31 receives the operation stop instruction, the control unit 31 stops the drive motor 2.
0 is stopped, and the control of the feeding operation of the lowest sheet Pa is completed.

As described above, this embodiment is effective when a DC motor, which cannot rotate forward or backward, is used as the drive motor 20, like the stepping motor in the first embodiment. Furthermore, even if a stepping motor is used as the drive motor 20 in this embodiment, it is of course possible to control the drive of the feeding roller 10 and the conveying roller pair 16.

Next, a third embodiment of the present invention is shown in FIG.

In this embodiment, the first and second
As in the embodiment, the control unit (CPU) 31 controls the motor,
The sensor recognition and clutch control that were previously performed are now performed by the control section 31a, which is a control circuit.

The operation of this embodiment will be explained below. When a start operation instruction is sent from the image forming apparatus 1 to the control section 31a of the sheet feeding device 3 via the motor control signal 61, the control section (control circuit) 31a starts the operation even if the trailing edge detection sensor 25 is OFF. For example, a signal corresponding to clutch OFF is output to the clutch drive circuit 51, and the rear end detection sensor 2
5 is ON, a signal corresponding to clutch ON is output to the clutch drive circuit 51.

The motor control signal 61 outputs a motor control signal 37 that controls the motor driver 32. That is, when an operation instruction corresponding to motor start is received from the image forming apparatus 1, a signal corresponding to motor start is output as the motor control signal 37, and then an operation instruction corresponding to motor stop is output to the image forming apparatus 1. When this happens, a signal corresponding to stop is sent out as the motor control signal 37.

As explained above, in this embodiment, the operation instructions of the drive motor 20 and the electromagnetic clutch 52, the transmission of sensor signals, and the electromagnetic There is a feature that the clutch 52 is driven immediately.

[0048]

[Effects of the Invention] As explained above, according to the present invention,
A first conveying means (feeding roller) that feeds the lowest sheet of the stacked sheets and a second conveying means (a pair of conveying rollers) that conveys the fed sheet to the image forming apparatus are driven. By detecting and controlling the trailing edge of the lowest sheet being fed by a trailing edge detection sensor, the first conveying means can be driven in accordance with the length of the sheet in the conveying direction.
The sheet feeding operation can be carried out reliably without having to set a particular drive time for the conveyance means or having the set time affect the sheet feeding operation.

Furthermore, even if sheets with different lengths in the conveying direction are mixedly loaded on the sheet stacking table, the sheets can be conveyed to the image forming apparatus without being affected by the mixed loading condition, which improves the operability of the paper feeding operation. can be improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of a sheet feeding device showing one embodiment of the present invention.

FIG. 2 is a rear view as well.

FIG. 3 is an enlarged side view of the rear end detection sensor section.

[Figure 4] (a) is a side view of the rear end detection sensor, (b)
is a plan view of the rear end detection sensor.

FIG. 5 is a block diagram similarly showing control.

FIG. 6 is a flowchart as well.

FIG. 7 is a block diagram showing control of a sheet feeding device showing a second embodiment of the present invention.

FIG. 8 is a flowchart as well.

FIG. 9 is a block diagram showing control of a sheet feeding device according to a third embodiment of the present invention.

[Explanation of symbols]

P...sheet, Pa...lowest seat,
Pb...rear end of sheet, 1...image forming device,
3... Sheet feeding device, 5... Apparatus main body of sheet feeding device, 6... Sheet loading platform, 10... First conveying means (feeding roller), 16... Second conveying means (conveying roller pair), 20 ...drive motor,
25... Rear end detection sensor, 26... Diving board, 31, 31a... Drive control means (control unit)
.

Claims (2)

[Claims] 1. A sheet feeding device main body that is detachably attachable to an image forming apparatus, a sheet loading table provided in the sheet feeding device main body and capable of stacking a plurality of sheets, and a sheet feeding device main body that is detachable from an image forming apparatus; a first conveying means for feeding from a lower level;
a second conveying means for conveying the sheet fed by the first conveying means into the image forming apparatus; a trailing edge detection sensor that detects the trailing edge of the sheet and is disposed on the upstream side of the first conveyance means;
A sheet feeding device comprising: drive control means for controlling the feeding operation of the second conveying means and the rotating operation of the second conveying means. 2. The trailing edge detection sensor detects only the trailing edge of the sheet being fed by a jumping motion of the trailing edge of the sheet from a diving board that separates the sheet from above the sheet stacking table. Item 1. The sheet feeding device according to item 1.