JP2000302294A - Sheet feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce stretching noises following the avoidance of the slackening of sheets without impairing the function of resist rollers for accurately determining the resist position of sheets. SOLUTION: In this device, when the condition that the ends of sheets 6 at starting feeding arrive at a predetermined position in front of resist rollers 10, 11 is detected, the rotating speed of a feeding motor is changed in response to the length of an actually measured value for an arrival time required so far. In this way, the slackening of the sheets 6 is determined to a required minimum, before the sheets are abutted to the nips of the resist rollers 10, 11. Stretching noises following the avoidance of the slackening of the sheets 6 can be effectively reduced without impairing the function of the resist rollers 10, 11 having advantage of accurately determining the resist position of the sheets 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a sheet feeder provided with a registration roller.

[0002]

2. Description of the Related Art Conventionally, a paper feed path having a guide plate disposed opposite to a paper feed roller for feeding paper stacked on a paper feed table and an image forming section is provided. There is a paper feeder provided with a paper edge sensor for detecting the edge of the paper and a pair of registration rollers. Such a paper feeder,
When the paper loaded on the paper feed table is separated and fed one by one by the paper feed roller, the paper slip is considered, and when the leading edge of the paper is detected by the paper leading edge sensor, By allowing the paper to be fed to the registration rollers, the paper is slackened, the leading edge of the paper is brought into contact with the nip of the registration rollers, and the registration rollers are rotated in synchronization with the operation of the image forming unit. This is to prevent occurrence.

Further, as disclosed in Japanese Patent Application Laid-Open No. 9-142703, a registration roller is detected by detecting the progress of a sheet to be fed and controlling the sheet feeding speed in accordance with the detection result. There has been a proposal to manage the registration position of a sheet without using a sheet.

Further, as described in Japanese Patent Application Laid-Open No. 8-332969, as a paper feeding device of a printing machine, a paper fed by a paper feeding roller is not stopped temporarily at a pair of feeding rollers. There is a proposal to reduce the load on the feed roller by carrying the sheet between the plate cylinder and the impression cylinder, and to correct the registration position of the sheet.

[0005]

SUMMARY OF THE INVENTION A paper feeder provided with a registration roller can increase the accuracy of the registration position of a sheet. On the other hand, the paper may slip with respect to the paper feed roller depending on the state, and may be delayed. Therefore, allowance is provided for the paper feed amount from the position where the leading edge of the paper reaches the paper leading edge sensor in front of the registration roller to the registration roller. In. 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 stiffness of the paper increases as the paper becomes stiffer and increases in proportion to the printing speed.

The proposals described in Japanese Patent Application Laid-Open Nos. 9-142703 and 8-332697 do not generate the above-mentioned noise in the paper. However, it does not have a function of a registration roller for making the registration position more accurate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet feeder which includes a registration roller for making the registration position more accurate and which can prevent the occurrence of a popping sound of a sheet.

[0008]

According to the first aspect of the present invention,
A paper feed roller driven by a paper feed motor to feed paper stacked on a paper feed table; and a paper feed roller disposed between the paper feed roller and the image forming unit, and rotated in synchronization with the operation of the image forming unit. A pair of driven registration rollers, a sheet feeding motor driving unit that drives the sheet feeding motor in synchronization with an image forming operation of the image forming unit, and a tip of the sheet fed by the sheet feeding roller. A paper leading edge detecting means for detecting the paper leading edge at a fixed position before the registration roller, and an arrival time from the start of paper feeding until the leading edge of the paper is detected by the paper leading edge detecting means, and the actual measurement value is determined in advance. A comparison unit for comparing with the theoretical value, and a rotation speed of the sheet feeding motor from when the sheet is detected by the sheet front end detection unit to when the sheet is transferred to the nip portion of the registration roller, and an actually measured value of the arrival time. The theory And a paper feed speed change control means for changing in accordance with the difference between.

Therefore, the paper feed roller is driven by the paper feed motor to feed the paper on the paper feed table. In the paper feeding process, when the state in which the leading end of the paper has reached the home position is detected, the rotation speed of the paper feeding motor is changed according to the length of the actually measured value of the required arrival time. Thus, it is possible to set the slack of the sheet to a necessary minimum and make the sheet come into contact with the nip portion of the registration roller.

According to a second aspect of the present invention, in the first aspect, the paper feed speed change control means changes the rotation speed of the paper feed motor in accordance with a designated image forming speed.

Therefore, it is possible to change the rotation speed of the sheet feeding motor according to the designated image forming speed.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the sheet feeding speed change control means sets the sheet to the sheet when the measured value of the arrival time is shorter than the theoretical value. The rotation speed of the paper feed motor from the time of detection by the leading edge detection means to the time of delivery to the nip portion of the registration roller is controlled to be low.

Therefore, even if the arrival time of the paper is short due to the occurrence of double feeding during paper feeding or the like, when the pair of registration rollers come and go, the paper is registered at the timing before the registration rollers come into contact with each other. It does not reach the roller, which makes it possible to prevent deviation of the registration position.

According to a fourth aspect of the present invention, in the first or the second aspect of the present invention, the sheet feeding speed change control means sets the sheet to the sheet when the measured value of the arrival time is longer than the theoretical value. The rotation speed of the paper feed motor from detection by the leading edge detection means to transfer to the nip portion of the registration roller is controlled at a high speed.

Therefore, even when the speed of the paper is low due to slippage of the paper feed roller with respect to the paper at the time of paper feeding, the leading end of the paper can be abutted against the nip portion of the registration roller.

[0016]

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 master (not shown), which has been made in this example, is wound, and a press roller 3 which is provided so as to be able to contact 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 loaded 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 guide plate 12 for guiding the paper 6 is provided between the paper feed roller 8 and the registration rollers 10, 11. Above the guide plate 12, the presence or absence of the paper 6 at a fixed position before the registration rollers 10, 11. There is provided a paper leading edge sensor 13 whose operation is switched by the operation. Note that the registration roller 10 is connected to the printing drum 2.
It is configured to come into contact with and separate from the registration roller 11 in synchronization with the rotational movement of. Specifically, the registration roller 1 is rotated by a cam that rotates at the same time as the print drum 2 rotates.
1. Of course, it may be made to contact and separate by a drive source such as a solenoid.

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 motor (stepping motor) 17.

Next, the electrical connection configuration will be described with reference to FIG. Reference numeral 18 denotes a control unit.
A paper feed motor 17, a registration motor 19 for driving the registration roller 11, a drum drive motor 20 for driving the print drum 2, a paper feed start sensor 4, a paper edge sensor 13, and a printing speed (image forming speed) are selected and designated. The printing speed input means 21 and the like are connected. This printing speed input means 21 is performed by, for example, key input or the like.

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, constant-speed, and high-speed drive data for driving the paper feed motor 17 is data from a through-up to the expected maximum speed, and is written in a storage medium such as a ROM of the control unit 18. Also, from the start of paper feeding,
The controller 18 also calculates the theoretical value of the time required for the leading edge of the paper 6 to reach the fixed position where the paper leading edge sensor 13 is provided.
On a storage medium such as a ROM.

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 print start sensor 4 is turned on at the moment when 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. The operation of the paper feed start sensor 4, the paper feed motor 17, the paper leading edge sensor 13, and the registration rollers 10, 11 at this time is shown in the time chart of FIG. The time required from when the paper feed start sensor 4 is turned on to when the paper front end sensor 13 detects the front end position of the paper 6 to be turned on from the start of paper feed is determined by the paper feed roller 8 and the separation pad 9. It changes according to the state of time.

That is, as shown in FIG. 4, when there is no slippage or double feed at the time of sheet separation (a), the arrival time at which the sheet leading edge sensor 13 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 constant speed data of the feed motor 17 described above is
4A, the low-speed data corresponds to the state of FIG. 4B, and the high-speed data corresponds to the state of FIG.

Based on the above, the paper feed control process will be described with reference to the flowchart shown in FIG. First, the low speed data, constant speed data, and high speed data of the paper feed motor 17 are called from the ROM of the control unit 18 and set in the paper feed motor drive routine. The theoretical value of the arrival time until arrival is called from the ROM and set in the comparison routine (S1). As the print drum 2 rotates,
When the paper feed start sensor 4 is turned on (Y in S2), the paper feed motor 17 is driven (S3), and the paper feed roller 8 is rotated to start the paper feed operation. Subsequently, the registration rollers 10, 1
1 is matched (S4). This means that the upper registration roller 10 contacts the lower registration roller 11 in synchronization with the rotational movement of the printing drum 2 as described above. In the paper feeding process during this time, when the leading edge of the paper 6 reaches the paper leading edge sensor 13, the paper leading edge sensor 13 is turned on, and the CPU of the control unit 18 recognizes this state (Y in S5).

The arrival time at which the leading end of the sheet 6 reaches the sheet leading end sensor 13 from the start of sheet feeding is actually measured by a method such as counting a clock by the control unit 18, and the actually measured arrival time and theoretical value are calculated. A comparison is made (S6). Theoretical value>
In the case of the arrival time, as shown in FIG. 4B, since the paper 6 is advanced by multifeed or the like, the paper feed motor 17 is driven by the low speed data (S7), and the registration rollers 10, 1 are driven.
The feed amount until the leading end of the sheet 6 reaches the nip portion of the first sheet is corrected to be small.

When the theoretical value is equal to the arrival time, as shown in FIG. 4A, the paper 6 is conveyed with the arrival time according to the theoretical value without slipping or double feeding. Driving is performed with constant speed data (S8).

When the theoretical value is smaller than the arrival time, as shown in FIG. 4C, the sheet 6 is delayed due to slippage or the like.
The paper feed motor 17 is driven by the high-speed data (S9), and the feed amount until the leading end of the paper 6 reaches the nip portion between the registration rollers 10 and 11 is corrected to be larger.

In any case, when it is determined that the paper feed motor 17 has been driven by the predetermined number of feed steps (S1).
0, Y), the registration motor 20 is driven for a predetermined time (S11), and the registration rollers 10, 11 are rotated to convey the paper 6 toward the printing drum 2. At this time, the press roller 3 is kept separated from the printing drum 2,
When the leading end of the paper 6 passes, the paper 6 is pressed against the printing drum 2. 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 print processing flow is omitted.

In this printing, after the paper reaches the nip portion between the printing drum 2 and the press roller 3, the printing drum 2
The registration roller 10 is separated from the registration roller 11 in synchronism with the rotational movement of (S12). Note that the registration roller 10 is separated from the registration roller 10 until the trailing edge of the sheet passes, but then contacts the registration roller 11 for the next paper feeding.

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 (S13).
N), the process proceeds to step 2 for the next sheet feeding, and if there is a sheet feeding end command signal (Y in S13), the sheet feeding operation is ended.

As described above, when the state in which the leading end of the sheet 6 has reached the home position from the start of sheet feeding is detected, the feeding motor 17 is controlled in accordance with the length of the actually measured value of the time required until that time. The rotation speed can be changed in three stages by low speed data, constant speed data, and high speed data. Thereby, the paper 6
Rollers 10 and 11 are set so that the slack of the rollers is minimized.
Can be brought into contact with the nip portion. Therefore, it is possible to effectively suppress the generation of the squealing noise when the looseness of the paper 6 is eliminated without impairing the functions of the registration rollers 10 and 11 that can accurately determine the registration position of the paper 6.

Further, when the double feed occurs, the arrival time of the sheet to the sheet leading edge sensor 13 is shortened. If the sheet is fed as it is, in the conventional case, the sheet is interposed between the separated registration rollers 10 and 11. May reach the registration roller 11 after the arrival, and the registration position of the sheet may be shifted. However, according to the present invention, the rotation speed of the paper feed motor 17 can be reduced in such a case, so that the registration roller 10 can be brought into contact with the registration roller 11 before the paper arrives. Thus, the registration position of the sheet can be correctly determined.

In this embodiment, as shown in FIG. 3, the printing speed input means 21 for selecting and specifying the printing speed (image forming speed) is provided, but the printing speed is fixed (for example, the highest speed). And the paper feed control process is described with the print speed maintained.

A paper feed control process when a desired print speed is designated by the print speed input means 21 shown in FIG. 3 will be described as a second embodiment of the present invention with reference to FIG. 1 to 4 are the same in the present embodiment.

However, low-speed, constant-speed, and high-speed drive data for driving the paper feed motor 17 are set for each printing speed and written in a storage medium such as a ROM of the control unit 18. The theoretical value of the time required for the leading edge of the sheet 6 to reach the fixed position where the sheet leading edge sensor 13 is provided from the start of sheet feeding is also set for each printing speed, and is stored in the ROM or the like of the control unit 18. Written on the medium.

In the paper feed control process according to the present embodiment, when the print speed is input by the print speed input means 21, the control unit 18 sets the input print speed (sets it in the RAM) (S20).

Subsequently, low-speed data, constant-speed data, and high-speed data of the paper feed motor 17 corresponding to the set print speed are called from the ROM of the control unit 18 and set in the paper feed motor drive routine. Paper from time 6
The theoretical value of the arrival time until the leading end of the sheet reaches the leading end sensor 13 is called from the ROM and set in the comparison routine (S21). Subsequent processes are the same as steps S2 to S13 in FIG.

Step S3 in FIG. 5 and FIG.
Functions as a sheet feeding motor driving unit that drives the sheet feeding motor in synchronization with the image forming operation of the image forming unit 1.

Step S5 functions as a paper leading edge detecting means for detecting the leading edge of the paper 6 fed by the paper feeding roller 8 at a fixed position before the registration rollers 10 and 11.

Step S6 is a comparing means for actually measuring the arrival time from the start of paper feeding until the leading edge of the paper 6 is detected by the leading edge detecting means and comparing the measured value with a predetermined theoretical value. Function.

In steps S7 to S9, the registration rollers 10 and 11
Functions as a paper feed speed change control unit that changes the rotation speed of the paper feed motor 17 until it is delivered to the nip portion according to the difference between the measured value of the arrival time and the theoretical value.

[0042]

According to the first aspect of the present invention, when it is detected that the leading edge of the sheet has reached a fixed position in front of the registration roller from the start of sheet feeding, the actual measured value of the arrival time required up to that point is detected. Since the rotation speed of the paper feed motor is changed according to the length of the paper feed roller, the slack of the paper can be set to a necessary minimum and can be brought into contact with the nip portion of the registration roller.
Therefore, it is possible to effectively suppress the generation of the squealing noise when the looseness of the paper is eliminated without impairing the function of the registration roller that can accurately determine the registration position of the paper.

According to the second aspect of the present invention, the paper feeding speed change control means changes the rotation speed of the paper feeding motor in accordance with the designated image forming speed. The rotation speed of the paper feed motor can be changed.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, the feeding speed change control means is provided at the nip portion of the registration roller when the measured value of the paper arrival time is shorter than the theoretical value. Since the rotation speed of the paper feed motor until transfer is controlled to a low speed, even if the arrival time of the paper is short due to the occurrence of double feed during paper feeding, the registration The sheet does not reach the registration rollers at the timing before the rollers come into contact with each other, thereby preventing the registration position from being misaligned.

According to a fourth aspect of the present invention, in the first or the second aspect of the present invention, the feeding speed change control means is provided at the nip portion of the registration roller when the measured value of the paper arrival time is longer than the theoretical value. Since the rotation speed of the paper feed motor until transfer is controlled at high speed, even if the paper speed is low due to slippage of the paper feed roller with respect to the paper during paper feeding,
The leading edge of the sheet can be abutted against the nip portion of the registration roller, thereby preventing occurrence of non-feeding.

[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 time chart illustrating a sheet feeding operation.

FIG. 5 is a flowchart illustrating a sheet feeding control process.

FIG. 6 is a flowchart illustrating a sheet feeding control process according to the second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 image forming unit 6 paper 7 paper feed table 8 paper feed roller 10, 11 registration roller 17 paper feed motor S3 paper feed motor driving means S5 paper leading edge detection means S6 comparison means S7-S9 paper feed speed change control means

Continued on the front page F-term (reference) 3F048 AA02 AB01 BA21 BB02 BD07 CC11 DA06 EB24 EB29 3F049 DA12 EA10 EA22 EA28 LA02 LB03 3F102 AA06 AB01 BA02 BB02 CA05 CB04 DA08 EA03 EC02 FA05 FA06 3F343 FA02 FB02 MA01 MB03

Claims (4)

[Claims] A sheet feed roller driven by a sheet feed motor to feed sheets stacked on a sheet feed table; and an operation of the image forming section disposed between the sheet feed roller and an image forming section. A pair of registration rollers that are driven to rotate in synchronization with a sheet feeding motor; a sheet feeding motor driving unit that drives the sheet feeding motor in synchronization with an image forming operation of the image forming unit; Paper leading edge detecting means for detecting the leading edge of the paper at a fixed position in front of the registration roller; and measuring the arrival time from the start of paper feeding until the leading edge of the paper is detected by the paper leading edge detecting means. A comparison unit that compares the value with a predetermined theoretical value; and a rotation speed of the sheet feeding motor from when the sheet is detected by the sheet leading end detection unit to when the sheet is transferred to the nip portion of the registration roller. Temporal Sheet feeding apparatus comprising a sheet feeding speed change control means for changing in accordance with the difference between the theoretical and Hakachi, the. 2. The sheet feeding device according to claim 1, wherein the sheet feeding speed change control unit changes the rotation speed of the sheet feeding motor in accordance with a designated image forming speed. 3. The paper feed speed change control means, when the measured value of the arrival time is shorter than the theoretical value, detects the paper by the paper leading edge detection means and then receives the paper at the nip portion of the registration roller. 3. The sheet feeding device according to claim 1, wherein the rotation speed of the sheet feeding motor until the transfer is controlled to a low speed. 4. The paper feed speed change control means, when the measured value of the arrival time is longer than the theoretical value, detects the paper by the paper leading edge detection means and then receives the paper at the nip portion of the registration roller. 3. The paper feeding device according to claim 1, wherein the rotation speed of the paper feeding motor until the transfer is controlled at a high speed.