JP2001026337A - Paper feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent development of creak in a paper sheet and to positively determine the transporting position of the paper sheet. SOLUTION: A sensor 13 for the extremity of a paper sheet is placed at a given position between an image forming part 1 and a transporting roller 10. The paper sheet 6 in a paper feeding mode is passed between a spaced transporting roller 10 and a pinch roller 11. A paper feeding roller 18 is halted when the sensor 13 for the extremity of the paper sheet detects the extremity of the paper sheet 6. This allows paper feeding without slacking the paper sheet 6 to prevent development of creak in the paper sheet 6 and to positively determine the resist position of the paper sheet 6 regardless of the presence or absence of the slippage of the paper sheet 6 and the presence or absence of double deeding. In addition, paper feeding is allowed toward an image forming part 1 without delaying timing with the paper sheet 6 positively sandwiching between the transporting roller 10 and the pinch roller 11. Thus, the transporting position of the paper sheet 6 is positively determined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeding device for feeding paper to a printing device.

[0002]

2. Description of the Related Art Conventionally, as described in, for example, JP-A-5-305707, a guide plate is provided between a paper feed roller for feeding paper stacked on a paper feed table and an image forming section. The paper feed path includes a paper leading edge sensor that detects the leading edge of a sheet, and a pair of registration rollers disposed downstream of the paper leading edge sensor. There is a device.

In such a paper feeder, when paper loaded on a paper feed table is separated and fed one by one by a paper feed roller, the leading edge of the paper is taken into account by taking into account slippage of the paper. When it is detected by, by taking allowance in the amount of paper feeding from the detection position to the registration roller, the paper is slackened and the leading end abuts against the nip of the registration roller to synchronize with the operation of the image forming unit. By rotating the registration roller, non-feeding is prevented.

[0004]

In the paper feeding device, as described above, the paper may slip with respect to the paper feeding roller depending on the state and may be delayed. Therefore, the paper leading edge sensor in front of the registration roller detects the leading edge of the paper. Allowance for the amount of paper to be fed from the position where has arrived to the registration roller. Therefore, when the paper advances too much, such as in the case of double feed, the slack of the paper increases, and when the loose state of the paper is eliminated, a loud noise is generated as noise. The squealing sound becomes louder as the paper becomes stiffer and further increases in proportion to the printing speed, which goes against the demands of the times.

Further, when the sheet is abutted against the nip portion of the registration roller and the registration roller is driven to feed the sheet to the image forming section, the timing of feeding the sheet due to slip between the registration roller and the sheet is determined. In some cases, the image may not be printed at a desired position on the sheet.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet feeder which prevents the occurrence of a popping sound of a sheet at the time of sheet feeding and accurately determines a registration position of the sheet.

Another object of the present invention is to provide a sheet feeding device capable of preventing skew of a sheet during sheet feeding.

[0008]

According to the first aspect of the present invention,
A paper feed roller that is driven by a paper feed drive unit to feed paper stacked on a paper feed table, a transport roller disposed between the paper feed roller and the image forming unit, A pinch roller that is freely supported, a transport driving unit that drives at least one of the transport roller and the pinch roller, and a length of the paper that is shorter than the length of the sheet relative to the transport roller downstream of the transport roller. A sheet leading edge sensor that is arranged at a fixed position at a distance and outputs a sheet reaching signal when the leading end of the sheet reaches, and drives the sheet feeding driving unit in synchronization with an image forming operation of the image forming unit to drive the sheet feeding unit. Paper feed drive control means for stopping the paper feed drive when the paper leading edge sensor outputs a paper arrival signal; and causing the pinch roller to coincide with the transport roller for a fixed time after the paper feed drive is stopped. Comprising a pinch roller moving means, and a transfer drive control means for driving a predetermined time the transfer drive after stopping of the sheet feed driving unit.

Therefore, the paper on the paper feed table is fed by the paper feed roller, and is conveyed to the image forming section through the space between the conveyance roller and the pinch roller which are separated from each other. When the leading edge of the sheet reaches the sheet leading edge sensor, the sheet leading edge sensor outputs a sheet reaching signal. Since the paper feed drive unit is stopped by the paper arrival signal, the registration position of the paper becomes constant regardless of the occurrence of slippage of the paper and the occurrence of double feed. When the paper feed drive unit stops, the pinch roller is matched with the transport roller for a fixed time, and the transport drive unit is driven for a fixed time. Therefore, the timing is delayed in a state where the paper is securely sandwiched between the transport roller and the pinch roller. The paper is fed to the image forming unit without any processing.

According to a second aspect of the present invention, in the first aspect of the present invention, a sheet abutting plate disposed between the transport roller and the sheet feeding roller for abutting the leading end of the sheet is provided. A sheet abutting plate control means for causing the sheet abutting plate to advance into the sheet feeding path immediately after the start of the sheet and retracting the sheet abutting plate from the sheet feeding path after a predetermined time has elapsed.

Therefore, since the sheet abuts on the sheet abutment plate on the way to the transport roller, if the sheet is skewed, the skew is corrected.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the paper feed roller is disposed at a predetermined position on the upstream side of the transport roller at a distance shorter than the length of the paper with respect to the paper feed roller. And an intermediate sheet leading edge sensor for outputting a sheet reaching signal when the leading end of the sheet arrives, and an arrival time from the start of sheet feeding until the intermediate sheet leading edge sensor outputs the sheet reaching signal. A comparing unit that compares the value with a predetermined theoretical value, and the sheet leading edge sensor outputs the sheet reaching signal after the intermediate sheet leading edge sensor outputs the sheet reaching signal according to a comparison result by the comparing unit. A sheet feed speed change control unit that changes the rotation speed of the sheet feed drive unit until the output is performed.

Therefore, it is possible to correct the paper feeding speed in the latter half of the paper feeding process according to the high and slow speed of the paper feeding speed in the first half of the paper feeding process.

[0014]

FIG. 1 shows a first embodiment of the present invention.
A description will be given with reference to FIG. FIG. 1 is a side view of the sheet feeding device, and FIG. 2 is a plan view thereof. In the figure, reference numeral 1 denotes an image forming unit. The image forming unit 1 includes, as main components, a printing drum 2 around which a prepressed master (not shown) is wound in this example, and a press roller 3 provided to be able to approach and separate from the printing drum 2. I have. A transmission type paper feed start sensor 4 is provided at a fixed position on an end face side of the print drum 2, and a light shielding plate 5 for turning on and off the paper feed start sensor 4 is fixedly provided on the print drum 2.

The paper 6 fed between the printing drum 2 and the press roller 3 is stacked on a paper feed table 7. The paper feed table 7 is driven up and down so that the uppermost sheet 6 is positioned at a certain level. A separation pad 9 is pressed against a paper feed roller 8 for drawing out the uppermost sheet 6. A transport roller 10 and a pinch roller 11 supported so as to be able to contact and separate from the transport roller 10 between the paper feed roller 8 and the image forming unit 1.
And a guide plate 12 that defines a paper feed path for the paper 6 is provided between the transport roller 10 and the pinch roller 11 and the paper feed roller 8. When the leading edge of the paper 6 reaches a certain position between the conveying roller 10 and the pinch roller 11 and the image forming unit 1, the state is optically detected and a paper arrival signal (ON signal) is output. A paper leading edge sensor 13 is provided.

The pinch roller 11 is configured to come into contact with and separate from the transport roller 10 in synchronization with the rotational movement of the printing drum 2. In this example, an arm (not shown) for rotatably supporting the pinch roller 11 is connected to a drive source such as a solenoid described later to control the operation timing of the solenoid, but the pinch roller 11 is rotatable. Alternatively, a mechanism that contacts and separates from the transport roller 10 may be employed by displacing the arm that is supported by the cam that rotates at the same time as the print drum 2 rotates.

As shown in FIG. 2, the paper feed roller 8 is connected to a rotating shaft 14 via a one-way clutch (not shown) provided at the center, and the rotating shaft 14 is supplied via gears 15 and 16. It is connected to a paper feed motor (stepping motor) 17 which is a paper drive unit.

Next, the electrical connection configuration will be described with reference to FIG. Reference numeral 18 denotes a control unit.
A feed motor 17, a transport motor 19 that is a transport drive unit that drives the transport roller 10, a drum drive motor 20 that drives the print drum 2, a solenoid 21 that drives an arm that rotatably supports the above-described pinch roller 11, Paper speed sensor 4, paper edge sensor 13, printing speed input means 22 for selecting and specifying printing speed (image forming speed)
Etc. are connected. This printing speed input means 22
Is performed by, for example, key input.

The control unit 18 controls each of the motors 17, 19, 20.
A driver (not shown) that independently drives each of
RO where fixed data including program is written
M, RAM for writing variable data such as work data in an updatable manner, C for monitoring the operation of each unit and executing programs
It has a PU and the like. The low-speed drive data, the constant-speed drive data, and the high-speed drive data for driving the paper feed motor 17 are data from the through-up to the expected maximum speed and are written in a storage medium such as a ROM of the control unit 18. .

Here, the drum driving motor 2 is used for printing.
When the print drum 2 around which the master having been made is wound is rotated clockwise, the paper feed start sensor 4 is turned on at the moment the light shielding plate 5 is separated. The paper feed motor 17 is driven by this ON signal, so that the paper feed roller 8
Rotates to feed paper.

Next, a paper feed control process executed in parallel with the printing process will be described with reference to a flowchart shown in FIG. In this paper feed control process, first, the CPU of the control unit 18 calls the low speed drive data, the constant speed drive data, and the high speed drive data of the paper feed motor 17 from the ROM of the control unit 18 and sets them in the paper feed motor drive routine ( S1). This is data corresponding to the printing speed input by the operator operating the printing speed input means 22. When the feed start sensor 4 is turned on by the rotation of the printing drum 2 (S
2), the paper feed motor 17 is driven (S3), and the paper feed roller 8 is rotated to start the paper feed operation. In the paper feeding process during this time, if the leading edge of the paper 6 reaches the paper leading edge sensor 13, the paper leading edge sensor 13 outputs a paper arrival signal (ON) (Y in S4). 17 is stopped (S5), and the sheet 6 is stopped.

After the feed motor 17 is stopped, the solenoid 21 is excited, and the arm for rotatably supporting the pinch roller 11 is displaced downward, so that the pinch roller 1 is displaced.
1 is matched with the transport roller 10 for a predetermined time (S6), and the transport motor 19 is driven for a predetermined time (S7), and the paper 6 is sent out between the printing drum 2 and the press roller 3. At this time, the press roller 3 is kept separated from the printing drum 2, and presses the sheet 6 against the printing drum 2 when the leading end of the sheet 6 passes. As a result, the ink in the printing drum 2 oozes out of the master and is transferred to the paper 6. That is, printing is performed. Since the present invention relates to paper feeding, the flow of the printing process is omitted.

When a certain period of time has passed after the pinch roller 11 is brought into contact with the transport roller 10, the solenoid 21 is de-energized, and the pinch roller 11 is separated from the transport roller 10 in preparation for the next paper feed (S8).

Each time one sheet is printed, it is determined whether or not there is a feed end command signal. If there is no feed end command signal (N in S9), the process proceeds to step 2 for the next feed. If there is a paper feed end command signal (Y in S9), the paper feed operation ends.

As described above, when the paper 6 on the paper feed table 7 is fed by the paper feed roller 8 toward the image forming unit 1,
Since the paper 6 passes between the transport roller 10 and the pinch roller 11 which are separated from each other, the paper 6 can be fed without being loosened. As a result, it is possible to prevent the generation of the sound of the paper 6.

The paper feed roller 8 is stopped by recognizing the state that the paper 6 has reached the predetermined position based on the paper arrival signal output from the paper front end sensor 13 disposed at the predetermined position and stopping the paper feed roller 8. 6, regardless of the presence or absence of slippage and the presence of double feed, the registration position of the paper 6 can be accurately determined. Further, as a paper feed drive unit for driving the paper feed roller 8, a paper feed motor 17 by a stepping motor is used.
, The feed motor 17 can be stopped immediately at an accurate position. Thereby, the registration position of the sheet 6 can be determined more accurately.

Further, since the sheet leading edge sensor 13 is arranged at a fixed position downstream of the conveying roller 10 with a distance shorter than the length of the sheet 6 from the conveying roller 10,
When the paper feed motor 17 is stopped, the transport rollers 10
In this state, the rear end of the paper 6 does not pass through between the paper and the pinch roller 11. Therefore, in this state, the pinch roller 11 is made to coincide with the transport roller 10 for a certain period of time, and the transport roller 10 is driven for a certain period of time, so that the timing is delayed while the paper 6 is securely sandwiched between the transport roller 10 and the pinch roller 11. The sheet can be fed to the image forming unit 1 without any need. Therefore, the position of the image to be printed on the paper 6 can be accurately determined.

In FIG. 4, steps S2 to S5 are performed when the paper feed motor (paper feed drive) 17 is driven in synchronization with the image forming operation of the image forming section 1 and the paper leading edge sensor 13 outputs a paper arrival signal. Function as a paper feed drive unit control means for stopping the paper feed motor 17. Steps S6 and S8 are
After the paper feed motor 17 stops, the pinch roller 11
Function as a pinch roller contacting / separating unit that matches with the transport roller 10. Step S7 functions as a transport drive unit control unit that drives the transport motor (transport drive unit) 19 for a fixed time after the paper feed motor 17 stops.

Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 5 is a side view of the sheet feeding device, and FIG. 6 is a plan view thereof.

In the present embodiment, in addition to the configuration of the above-described embodiment, a sheet striking plate 23 disposed between the transport roller 10 and the sheet feeding roller 8 and an operation of the sheet striking plate 23 are described. Paper abutting plate control means (not shown) for control. The sheet striking plate control means advances the sheet striking plate 23 into the sheet feeding path of the sheet 6 immediately after the start of sheet feeding, and retracts the sheet striking plate 23 from the sheet feeding path of the sheet 6 after a predetermined time has elapsed.
In this example, the sheet abutment plate 23 is connected to a solenoid (not shown).
And the like, and is configured to control the operation timing of this solenoid. However, the paper abutment plate 23 is displaced by a cam that rotates simultaneously with the rotation of the printing drum 2, thereby conveying the paper 6. Advance to the route,
A retracting mechanism may be employed.

Next, a paper feed control process executed in parallel with the printing process will be described with reference to a flowchart shown in FIG. First, the CPU of the control unit 18 stores the low speed data, constant speed data, and high speed data of the sheet feeding motor 17 in the ROM of the control unit 18.
And set it in the sheet feeding motor driving routine (S21). This is because the operator can set the print speed input means 22
Is the data corresponding to the printing speed input by operating. When the paper feed start sensor 4 is turned on by the rotation of the printing drum 2 (Y in S22), the paper feed motor 17 is driven (S23), and the paper feed roller 8 is rotated to start the paper feed operation.

When the drive of the paper feed motor 17 is recognized,
By energizing the solenoid, the sheet abutment plate 23 is advanced to the sheet feeding path of the sheet 6, that is, above the guide plate 12 (S2).
4) When it is recognized that a certain time has elapsed (S25)
Y), the solenoid is de-energized and the paper abutment plate 23
Is retracted below the guide plate 12 (S26). During the period in which the sheet abutment plate 23 is advanced, the leading edge of the sheet 6 abuts on the sheet abutment plate 23 and is still fed by the paper feed roller 8. It is loosened until it hits the butting plate 23. Thus, even if skew occurs at the beginning of sheet feeding, the skew can be corrected.

When the sheet abutment plate 23 is retracted (S2
6) The paper 6 is stretched between the transport roller 10 and the pinch roller 11 due to its stiffness.
The paper is fed. When the leading edge of the paper 6 reaches the paper leading edge sensor 13, the paper leading edge sensor 13 outputs a paper arrival signal (ON) (Y in S27). When this output is recognized, the paper feeding motor 17 is stopped ( S28) The paper 6 is stopped.

After the feed motor 17 is stopped, the solenoid 21 (see FIG. 3) is excited, and the arm that rotatably supports the pinch roller 11 is displaced downward, so that the pinch roller 11 is fixed to the transport roller 10. The time is matched (S29), and the transport motor 19 is driven for a fixed time (S29).
30), the paper 6 is sent out between the printing drum 2 and the press roller 3. When a certain period of time elapses after the pinch roller 11 is matched with the transport roller 10, the solenoid 21 is de-energized, and the pinch roller 11 is separated from the transport roller 10 in preparation for the next sheet feeding (S31).

Each time one sheet is printed, it is determined whether there is a paper feed end command signal, and if there is no paper feed end command signal (S32).
N), the process proceeds to step S22 for the next sheet feeding, and when there is a sheet feeding end command signal (Y in S32), the sheet feeding operation is ended.

In this embodiment, similarly to the above-described embodiment, the state in which the sheet 6 has reached the certain position is recognized by the sheet arrival signal output from the sheet leading end sensor 13 disposed at the certain position, and the sheet feeding roller 8 to stop
Can be accurately determined. Further, the sheet 6 having the registered position can be fed to the image forming section 1 without delaying the timing in a state where the sheet 6 is securely held between the transport roller 10 and the pinch roller 11.

When a sheet is abutted against the nip portion of a pair of registration rollers which is generally used to determine the registration position of the sheet and correct the skew, the leading end of the sheet is placed between the outer circumferences of the pair of registration rollers. Since the sheet has to be pushed into the wedge-shaped gap, it is necessary to increase the excessive feed amount of the sheet and to hit the sheet to the nip portion with a strong force. Thereby, the tension of the paper increases when the registration roller is driven.

In this embodiment, the sheet 6 is abutted against the sheet abutment plate 23 on the way to the transport roller 10, so that if the sheet 6 is skewed during feeding, the skew is corrected. be able to. In this case, the registration position of the paper 6 does not need to be determined by the paper abutment plate 23.
The leading edge of the sheet 6 can be abutted against the sheet-shaped sheet abutment plate 23 with a small force. Thus, in the process of abutting the sheet 6 against the sheet abutment plate 23, it is not necessary to feed the sheet 6 excessively to increase the slack amount. Therefore, when the sheet abutment plate 23 retreats, it is possible to suppress the generation of the squealing sound due to the expansion of the sheet 6.

The sheet abutment plate 23 may be advanced before the sheet 6 reaches the transport roller 10. A sensor for detecting the leading end of the sheet 6 may be provided upstream of the sensor, and the sheet abutting plate 23 may be advanced when the sensor detects the leading end of the sheet 6.

In FIG. 7, steps S22, S23,
In steps S27 and S28, the sheet feeding motor (sheet feeding driving unit) 17 is driven in synchronization with the image forming operation of the image forming unit 1 and the sheet feeding motor 1 is output when the sheet leading edge sensor 13 outputs a sheet reaching signal.
7 functions as a sheet feed drive unit control unit that stops the operation of the sheet feeding unit 7. Steps S23 to S26 are performed immediately after the sheet feeding is started.
The sheet advancing plate 3 functions as a sheet abutment plate control unit that causes the sheet abutment plate 23 to retreat from the paper supply path of the sheet 6 after a predetermined time has elapsed. Steps S29 and S31
Functions as a pinch roller contact / separation unit that matches the pinch roller 11 with the transport roller 10 for a certain period of time after the paper feed motor 17 stops. In step S30, the feed motor 17
Functions as a transport drive unit control unit that drives the transport motor (transport drive unit) 19 for a certain period of time after the stop of the operation.

Next, a third embodiment of the present invention will be described with reference to FIGS. The same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 8 is a side view of the sheet feeding device. In the present embodiment, in addition to the configuration of the above-described embodiment, an intermediate sheet leading edge sensor 24 is provided at a fixed position at a distance shorter than the length of the sheet 6 with respect to the sheet feeding roller 8 on the upstream side of the transport roller 10. Have. The intermediate sheet leading end sensor 24 outputs a sheet reaching signal (ON signal) when the leading end of the sheet 6 reaches.

In this embodiment, the arrival time from the start of sheet feeding until the intermediate sheet leading edge sensor 24 outputs a sheet arrival signal is actually measured, and the measured value is compared with a predetermined theoretical value. The comparing means (not shown) and the feed motor 17 between the time when the intermediate sheet leading edge sensor 24 outputs the sheet reaching signal and the time when the sheet leading edge sensor 13 outputs the sheet reaching signal according to the comparison result by the comparing means. Paper feed speed change control means (not shown) for changing the rotation speed.
In this case, the theoretical value of the arrival time required from the start of sheet feeding until the intermediate sheet leading edge sensor 24 outputs the sheet arrival signal is written in a storage medium such as a ROM of the control unit 18.

Here, as described above, the paper feed start sensor 4
Is turned on, the paper feed motor 17 is driven to rotate the paper feed roller 8 to feed paper. The operation of the paper feed start sensor 4, the paper feed motor 17, and the intermediate paper leading edge sensor 24 at this time is shown in FIG. 10 is shown in the time chart. The time from when the paper feed start sensor 4 is turned on to drive the paper feed motor 17 to when the intermediate paper front end sensor 24 detects the front end position of the paper 6 and turns on is determined by the paper feed roller 8 and the separation pad. 9 depends on the state at the time of sheet separation.

That is, as shown in FIG. 10, when there is no slippage or double feed at the time of sheet separation (a), the arrival time at which the intermediate sheet leading edge sensor 24 is turned on coincides with the theoretical value. When there is a double feed at the time of sheet separation (b), the sheet 6 advances because the driving force by the sheet feeding roller 8 is large, and the arrival time is shortened. When there is slippage during sheet separation (c), the arrival time is long because the sheet 6 is delayed.

The above-mentioned constant-speed drive data of the feed motor 17 corresponds to the state shown in FIG. 10A, the low-speed drive data corresponds to the state shown in FIG. 10B, and the high-speed drive data corresponds to the state shown in FIG.
It is set corresponding to the state of (c) of 0.

Based on the above, the paper feed control process will be described with reference to the flowchart shown in FIG. First, the CPU of the control unit 18 calls the low-speed drive data, the constant-speed drive data, and the high-speed drive data of the paper feed motor 17 from the ROM of the control unit 18 and sets them in the paper feed motor drive routine. The theoretical value of the time it takes for the leading edge of No. 6 to reach the intermediate sheet leading edge sensor 24 is R
Called from OM and set in comparison routine (S4
1). When the feed start sensor 4 is turned on by the rotation of the printing drum 2 (Y in S42), the feed motor 17
Is driven (S43), and the paper feeding roller 8 is rotated to start the paper feeding operation. The processing so far is the same as the processing in steps S1 to S3 in FIG.

In the paper feeding process during this time, when the leading edge of the paper 6 reaches the intermediate paper leading edge sensor 24, the intermediate paper leading edge sensor 24
Is turned on, and the CPU of the control unit 18 recognizes this state (Y in S44). The arrival time from the start of sheet feeding to the output of the sheet arrival signal (ON signal) by the intermediate sheet leading edge sensor 24 is actually measured by a method such as counting clocks by the control unit 18. The value is compared (S45).

As a result of this comparison, if the theoretical value> the arrival time, as shown in FIG.
Is advanced, the feed motor 17 is driven by the low-speed drive data (S46), and the feed amount until the leading end of the sheet 6 reaches between the transport roller 10 and the pinch roller 11 is corrected to be small.

FIG. 10A shows a case where the theoretical value is equal to the arrival time.
As shown in (4), since the paper 6 is being conveyed with the arrival time according to the theoretical value without slipping or double feeding, the paper feed motor 17 is driven by the constant speed drive data (S47).

If the theoretical value is less than the arrival time, FIG.
As shown in FIG. 7, since the paper 6 is delayed due to slippage or the like, the paper feed motor 17 is driven by the high-speed drive data (S
48), the feed amount until the leading edge of the sheet 6 reaches between the transport roller 10 and the pinch roller 11 is slightly corrected.

While the paper feed motor 17 is being driven, the paper 6 further advances, and when the leading edge reaches the paper leading edge sensor 13, the paper leading edge sensor 13 outputs a paper arrival signal (ON) (Y in S49). When it is recognized, the paper feed motor 17 is stopped (S50), and the paper 6 is stopped.

After the feed motor 17 is stopped, the solenoid 21 is excited, and the arm for rotatably supporting the pinch roller 11 is displaced downward, whereby the pinch roller 1 is displaced.
1 is matched with the transport roller 10 for a predetermined time (S51), and the transport motor 19 is driven for a predetermined time (S52).
Is sent out between the printing drum 2 and the press roller 3. At this time, the press roller 3 is kept separated from the printing drum 2, and presses the sheet 6 against the printing drum 2 when the leading end of the sheet 6 passes. As a result, the ink in the printing drum 2 oozes out of the master and is transferred to the paper 6. That is, printing is performed. Since the present invention relates to paper feeding, the flow of the printing process is omitted.

When a certain period of time has elapsed after the pinch roller 11 is brought into contact with the transport roller 10, the solenoid 21 is de-energized, and the pinch roller 11 is separated from the transport roller 10 in preparation for the next paper feed (S53).

Each time one sheet is printed, it is determined whether or not there is a feed end command signal. If there is no feed end command signal (S54).
N), the process proceeds to step S42 for the next sheet feeding, and if there is a sheet feeding end command signal (Y in S54), the sheet feeding operation is ended. Steps S49 to S54
Is the same as the processing in steps S4 to S9 in FIG.

Also in the case of this embodiment, in the process of feeding the paper 6 on the paper feed table 7 toward the image forming unit 1 by the paper feed roller 8, the paper 6 is pinched with the transport roller 10 separated from each other. Since the sheet passes between the rollers 11, the sheet can be fed without being slackened. As a result, it is possible to prevent the generation of the sound of the paper 6. Then, the sheet leading edge sensor 1 disposed at a certain position
In order to recognize the state in which the sheet 6 has reached a certain position based on the sheet arrival signal output by the sheet 3 and stop the sheet feeding roller 8,
The registration position of the paper 6 can be accurately determined regardless of the presence or absence of a slip between the paper feed roller 8 and the paper 6 and the presence or absence of double feed.

When the leading edge of the paper 6 is detected by the leading edge sensor 13 (S49), the feeding motor 1
7 is stopped (S50), the transport motor 19 is driven for a certain period of time (S52), and the transport roller 10 is rotated to transport the paper 6 toward the print drum 2, and the top of the master wound around the print drum 2 is rotated. In order to print an image at a fixed position on the sheet 6, the timing at which the transport motor 19 is driven is synchronized with the rotational movement of the printing drum 2. By allowing some margin for the timing of driving the transport motor 19, even if the arrival time of the paper 6 at the position of the paper leading edge sensor 13 is slightly delayed due to slippage between the paper feed roller 8 and the paper 6, etc. By the time the transport motor 19 is driven, the leading end of the sheet 6 can reach the position of the sheet leading end sensor 13.

However, it is conceivable that the arrival time of the sheet 6 until the sheet 6 is detected by the sheet leading edge sensor 13 may be unexpectedly delayed.
The paper feeding speed in the latter half of the paper feeding process (after the intermediate paper leading edge sensor 24 is turned ON) in accordance with the fast and slow feeding speed in the first half of the paper feeding process (until the intermediate paper leading edge sensor 24 is turned ON). Can be corrected, so that the time from the start of paper feeding until the leading edge of the paper 6 reaches the paper leading edge sensor 13 can be set to a small allowable range. If the paper feeding speed in the first half of the paper feeding process is high, when the paper leading edge sensor 13 detects the leading edge of the paper 6, the paper feeding motor 17
Is stopped, and the paper 6 is stopped at the target position, so that there is no problem. Therefore, even if the paper 6 is considerably delayed due to slippage of the paper 6 with respect to the paper feed roller 8 at the beginning of the paper feeding, the paper 6 is finally supplied in synchronization with the rotational movement of the printing drum 2. Can be paper.

As described above, the correction of the sheet feeding speed in accordance with the advance of the sheet 6 can be achieved by, as shown in FIG. Also, the present invention can be applied to a configuration arranged between them. In this case, the sheet abutment plate 23 is advanced before step S44 in FIG. 11 (step S44 in FIG. 7).
24), step 4 in FIG.
Before step 9, the sheet abutment plate 23 is retracted (similar processing to step S26 in FIG. 7).

In FIG. 11, steps S42, S43
In steps S49 and S50, the sheet feeding motor (sheet feeding drive unit) 17 is driven in synchronization with the image forming operation of the image forming unit 1 and the sheet feeding motor 17 is turned on when the sheet leading edge sensor 13 outputs a sheet reaching signal. It functions as a sheet feed drive unit control unit for stopping. Steps S51 and S53 correspond to the sheet feeding motor 17
The pinch roller 11 is moved for a certain time after the
It functions as a pinch roller contact / separation unit that matches 0.
Step S52 functions as a transport drive unit control unit that drives the transport motor (transport drive unit) 19 for a fixed time after the paper feed motor 17 stops. Step S45 functions as comparison means for actually measuring the arrival time from the start of sheet feeding until the intermediate sheet leading edge sensor 24 outputs the sheet arrival signal, and comparing the measured value with a predetermined theoretical value. The processing in steps S46, S47, and S48 is performed by controlling the feed motor 17 from when the intermediate sheet leading edge sensor 24 outputs the sheet reaching signal to when the sheet leading edge sensor 13 outputs the sheet reaching signal according to the comparison result by the comparing means. It functions as paper feed speed change control means for changing the rotation speed.

In the above embodiment, the transport roller 10
Although only the driving of the pinch roller 11 supported by the transport roller 10 is described in the present invention, only the pinch roller 11 supported by the transport roller 10 may be driven by the transport motor 19. In this case, the driving force of the transport motor 19 may or may not be transmitted to the transport roller 10.

[0061]

According to the first aspect of the present invention, the paper leading edge sensor is disposed at a fixed position between the image forming section and the transport roller for transporting the paper fed from the paper feed roller and the pinch roller. When the paper on the paper feed tray is fed toward the image forming unit, the paper passes between the transport roller and the pinch roller in the separated state, and the paper leading edge sensor detects the leading edge of the paper and sends a paper arrival signal. Since the paper feed roller is configured to stop when output is performed, paper can be fed without slackening the paper and the occurrence of the noise of the paper can be prevented.
The registration position of the sheet can be accurately determined regardless of the presence or absence of slippage of the sheet and the presence or absence of double feed. Further, after stopping the paper feed drive unit, the pinch roller is made to coincide with the transport roller for a certain time in a state where the rear end of the paper does not pass through the transport roller, and to drive the transport drive unit for a certain time, the paper is conveyed to the transport roller The sheet can be fed to the image forming section without delaying the timing in a state where the sheet is securely held between the pinch rollers. Therefore, the position of the image to be printed on the paper can be accurately determined.

According to the second aspect of the present invention, in the first aspect of the present invention, the sheet abutment plate is disposed between the transport roller and the sheet supply roller, and the sheet abutment plate is provided immediately after the start of sheet supply. The paper abutment plate control means is provided to advance the paper abutment plate from the paper supply path after a certain period of time. By doing so, if skew has occurred during paper feeding, the skew can be corrected. In this case, the registration position of the paper does not need to be determined by the paper abutment plate,
Further, since the leading edge of the sheet can be abutted against the plate-shaped sheet abutment plate with a small force, the sheet is excessively fed in the process of abutting the sheet against the sheet abutment plate to increase the slack amount. No need. Therefore, when the sheet abutment plate is retracted, it is possible to suppress the generation of the squealing sound due to the expansion of the sheet.

According to the third aspect of the present invention, in the first or second aspect of the present invention, the intermediate sheet leading edge sensor is disposed upstream of the transport roller, and the intermediate sheet leading edge sensor is set to the leading end of the sheet from the start of sheet feeding. It is configured to measure the arrival time until detecting the arrival signal and output the arrival signal, and to change the rotation speed of the sheet feeding drive unit according to the result of comparing the measured value with a predetermined theoretical value. In addition, the paper feeding speed in the latter half of the paper feeding process can be corrected in accordance with the higher and slower paper feeding speed in the first half of the paper feeding process. Therefore, if a severe restriction is imposed on the timing of driving the transport roller, even if the paper is considerably delayed due to slippage of the paper relative to the paper feed roller at the initial stage of paper feed, even if the paper is finally delayed, Paper can be fed accurately within a set time.

[Brief description of the drawings]

FIG. 1 is a side view of a sheet feeding device according to a first embodiment of the present invention.

FIG. 2 is a plan view of the sheet feeding device.

FIG. 3 is a block diagram showing an electrical connection structure.

FIG. 4 is a flowchart illustrating a sheet feeding control process.

FIG. 5 is a side view of a sheet feeding device according to a second embodiment of the present invention.

FIG. 6 is a plan view of the sheet feeding device.

FIG. 7 is a flowchart illustrating a sheet feeding control process.

FIG. 8 is a side view of a sheet feeding device according to a third embodiment of the present invention.

FIG. 9 is a block diagram showing an electrical connection structure.

FIG. 10 is a time chart illustrating a sheet feeding operation.

FIG. 11 is a flowchart illustrating a sheet feeding control process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming part 6 Paper 7 Paper feed stand 8 Paper feed roller 10 Transport roller 11 Pinch roller 13 Paper edge sensor 17 Paper feed drive 19 Transport drive 23 Paper abutment plate 24 Intermediate paper edge sensor S2 to S5 Paper feed drive Control means S6, S8 Pinch roller contact / separation means S7 Transport drive section control means S22, S23, S27, S28 Paper feed drive section control means S23 to S26 Paper abutment plate control means S29, S31 Pinch roller contact / separation means S30 Transport drive section Control means S42, S43, S49, 50 Feeding drive control means S45 Comparison means S46, S47, S48 Feeding speed change control means S51, S53 Pinch roller contact / separation means S52 Transport drive control means

Claims (3)

[Claims] A paper feed roller driven by a paper feed drive unit to feed paper stacked on a paper feed table; a transport roller disposed between the paper feed roller and an image forming unit; A pinch roller supported by a transport roller so as to be able to freely contact and separate from the transport roller, a transport drive unit that drives at least one of the transport roller and the pinch roller, and a sheet downstream of the transport roller with respect to the transport roller. A paper leading edge sensor which is arranged at a fixed position separated by a distance shorter than the length of the paper and outputs a paper arrival signal when the leading edge of the paper arrives, and the paper feed driving in synchronization with an image forming operation of the image forming unit. A paper feed drive unit control means for driving the paper feed unit to stop the paper feed drive unit when the paper leading edge sensor outputs the paper arrival signal; and the pinch roller for a predetermined time after the paper feed drive unit is stopped. A sheet feeding device comprising: a pinch roller contact / separation unit that matches a conveyance roller; and a conveyance driving unit control unit that drives the conveyance driving unit for a predetermined time after the sheet feeding driving unit stops. 2. A sheet abutting plate disposed between the transport roller and the sheet feeding roller for abutting the leading edge of the sheet, and the sheet abutting plate is supplied with the sheet immediately after the start of sheet feeding. 2. The sheet feeding device according to claim 1, further comprising a sheet hitting plate control unit that advances to a sheet path and retracts the sheet hitting plate from the sheet feeding path after a predetermined time has elapsed. 3. A paper arrival signal is output when a leading end of the paper arrives at a fixed position on the upstream side of the transport roller and at a distance shorter than the length of the paper with respect to the paper feed roller. An intermediate sheet leading edge sensor, and comparing means for actually measuring the arrival time from the start of sheet feeding until the intermediate sheet leading edge sensor outputs the sheet reaching signal, and comparing the measured value with a predetermined theoretical value; A feeder for changing the rotation speed of the paper feed drive unit from when the intermediate sheet leading edge sensor outputs the sheet reaching signal to when the sheet leading edge sensor outputs the sheet reaching signal according to the comparison result by the comparing means. 3. The paper feeding device according to claim 1, further comprising a paper speed change control unit.