JPH10329986A - Paper feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeder in which a power swing in a motor driving a conveying roller can be prevented and a proper loop quantity can be obtained. SOLUTION: When drive of a paper feeding motor M1 is started, a sheet S is fed out from a manual feed table 26 at a speed at which separating ability can be secured. For the duration from the start of the drive to the engagement of the sheet S with a vertical conveying roller 46, a conveying speed by means of the vertical conveying roller 46 is controlled to a speed substantially equal to the previously mentioned paper feeding speed, and after the lapse of time required for engagement between the sheet S and the vertical conveying roller 46 from the start of the drive, a conveying speed by means of the vertical conveying roller 46 is controlled to a speed which is higher than a paper feeding speed as required by a printer unit. When the tip of a sheet is detected by means of a sensor 50 previous to resisting, a drive continuing time for a vertical conveying motor M2 driving the vertical conveying roller 46 is decided according to the conveying speed in this detection, and the vertical conveying motor M2 is driven for the drive continuing time from the detection time, and as a result, a loop quantity optimum for correcting a skew in the sheet S can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeder, and more particularly, to a paper feeder used in an image forming apparatus such as a copying machine.

[0002]

2. Description of the Related Art In a conventional sheet feeding apparatus, the uppermost sheet of a sheet bundle is taken out by rotation of a pickup roller provided in pressure contact with a sheet bundle stored in a sheet feeding cassette, and is provided immediately downstream. The sheet is fed out to the feed roller. In order to prevent double feeding of sheets, a separating roller is provided on the feed roller in pressure contact with a predetermined force to constitute a separating mechanism. The separating roller is given a rotational load in a direction opposite to the sheet conveying direction by a torque limiter provided coaxially, and when the separating roller comes into direct contact with the feed roller (that is, when there is no sheet between both rollers). When only one sheet is fed between the two rollers, the sheet is driven by the feed roller against the above-mentioned rotational load. On the other hand, when two or more sheets are fed out and fed between the two rollers by so-called entrainment of the uppermost sheet, since the rotating load of the separating roller is larger than the frictional force between the sheets, the separating roller is used. Is stopped, whereby movement of the sheet on the separating roller side in the transport direction is prevented, and double feeding of the sheet is prevented.

[0003] Only the sheet that has been in contact with the feed roller separated by the separating mechanism is sent out to a transport roller provided downstream of the transport path toward the image forming section. Then, in order to improve the number of copies per unit time (CPM), the feed roller and the transport roller are driven to rotate as fast as possible. The sheet is further conveyed by a conveying roller, and the leading end of the sheet is abutted against a registration roller that is provided in front of the photosensitive drum of the image forming unit and is not rotating. By rotating the conveying roller for a predetermined time after the collision and feeding the sheet, the sheet buckles, forming a so-called loop, and the oblique feeding (skew) in the sheet conveying direction is corrected by the loop.

[0004]

However, in the above-mentioned separating mechanism, the sheet feeding speed of the sheet by the feed roller is limited in order to secure the separating property. , I have to lower it. For this reason, a speed difference occurs between the two rollers.For example, when a pulse motor is used as a drive source of the transport roller, the pulse motor is driven at the moment the recording sheet engages with the transport roller due to the speed difference. There is a problem that a load is impulsively applied, which causes a step-out of the pulse motor and hinders a smooth transport operation.

In order to solve this problem, it is necessary to wait until a predetermined time required for the sheet to engage with the conveying roller elapses from the start of sheet feeding, that is, from the start of driving of the sheet feeding motor for driving the pickup roller and the feed roller. Alternatively, a method in which the transport speed of the transport roller is controlled to be substantially the same as the transport speed of the feed roller and the transport speed of the transport roller is accelerated to a predetermined high speed after the predetermined time has elapsed. Thereby, when the sheet is engaged with the transport roller, there is no speed difference between the two rollers, it is possible to prevent the step-out, and the CPM can be maintained.

However, according to this method, if the sheet has already jumped out of the sheet cassette due to the accompanying feeding of the preceding sheet at the start of sheet feeding, the sheet reaches the registration roller in a shorter time than usual. As a result, the transport roller may abut against the registration roller before reaching a high speed (ie, during acceleration). In this case, even if the transport roller is rotated for the predetermined time after the collision, the specified loop amount cannot be obtained, and the skew correction becomes insufficient. This problem tends to occur in a copying machine or the like provided with a plurality of paper feed cassettes, particularly for sheets fed from a paper feed cassette near an image forming unit.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a sheet feeder which can prevent a motor driving a transport roller from stepping out and can obtain an appropriate loop amount.

[0008]

In order to achieve the above object, a sheet feeding apparatus according to the present invention receives a sheet supplied from a sheet storage section at a first speed at substantially the same speed as the first speed. A sheet feeder having a first conveying roller that starts accelerating to a second speed higher than the first speed and conveys the sheet to a second conveying roller that is in a stopped state in a rotation stopped state A detection sensor provided between the second conveyance roller and the first conveyance roller for detecting the presence or absence of a sheet; a timer for starting timing when the detection sensor detects the leading edge of the sheet; A sheet conveying speed detecting means for detecting the sheet conveying speed at the time when the leading edge of the sheet is detected by the sensor; and a driving of the first conveying roller in accordance with the sheet conveying speed detected by the sheet conveying speed detecting means. A drive continuing time determining means for determining a timer, characterized in that and a first conveying roller stopping means for stopping said first conveyor roller and record the determined drive continued time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a case where an embodiment of a paper feeding apparatus according to the present invention is applied to a digital copying machine will be described. FIG. 1 is a diagram showing an overall configuration of the digital copying machine (hereinafter, simply referred to as “copying machine”).

As shown in FIG. 1, the copying machine comprises a document reading section 100, a printer section 200, and a paper feeding section 300. The document reading unit 100 converts the reflected light from the document into an electric signal, performs necessary image processing such as density conversion and edge enhancement, and outputs the signal to the printer unit 200. The printer unit 200 forms an image. In the exposure scanning section 1 of the printer section 200, a laser diode (not shown) emits laser light in response to an output signal from the document reading section 100, and the laser light is reflected on a mirror surface of a polygon mirror (not shown) driven to rotate at a constant speed. Is reflected and deflected. The light path of the deflected laser beam is changed by the mirror 2 and the surface of the photosensitive drum 3 is exposed and scanned. Around the photosensitive drum 3, a charging charger 4, a developing device 5, a transfer charger 6, a separation charger 7, a cleaning device 8, and an eraser lamp 9 are provided.
Are arranged in this order along the drum rotation direction a, and a toner image is formed on the recording sheet conveyed from the sheet feeding unit 300 by a known electrostatic copying process such as charging, exposure, development, transfer, and separation. Transcribe The recording sheet onto which the toner image has been transferred is sent to the fixing device 11 by the transport belt 10, where it is fixed, and then discharged onto the tray 13 via the discharge roller 12.

The paper feeding section 300 feeds recording sheets to the printer section 200. The paper feed unit 300 includes paper feed cassettes 21 to 25 slidably held by guide rails (not shown) in the front of the drawing in cabinets 61 provided in two upper and lower stages, and feed cassettes along the right wall of the cabinet. And a transport path 70 for transporting the recording sheets from the paper cassettes 21 to 25. The starting end of the transport path 70 is branched by the number of paper feed cassettes 21 to 25, and the branch paths 71 to 75 are provided.
The paper feed mechanisms 31 to 35 for taking out the recording sheets one by one from the paper feed cassette are arranged at the ends of the paper feed cassette. Further, the paper feed unit 300 includes the manual feed table 26 and the paper feed mechanism 3.
6. The manual feed table 26 is provided so as to protrude from the cabinet 61 and serves as a mounting table for recording sheets to be manually inserted. The paper feed mechanism 36 takes out the recording sheets one by one from the loaded sheet bundle.

Since the configurations of the paper feed mechanisms 31 to 36 are the same, only the paper feed mechanism 36 will be described with reference to FIG. As shown in the figure, the paper feed mechanism 36 includes a pickup roller 36a, a paper feed roller 36b, and a separation roller 36.
c. The pickup roller 36a and the paper feed roller 36b are attached to their drive shafts via one-way clutches each allowing rotation only in the direction of the arrow. A torque limiter (not shown) is coaxially attached to the separating roller 36c. The pickup roller 36a and the paper feed roller 36b are driven to rotate in a direction shown by an arrow via a power transmission mechanism (not shown) using a paper feed motor M1 (FIG. 3) formed of a pulse motor as a driving source.

Pickup roller 36a and paper feed roller 3
When the recording sheet 6b is driven to rotate, the pickup roller 36a pressed against the recording sheet pays out the recording sheet S placed on the manual feed table 26 from the uppermost sheet, and the fed recording sheet is fed to the paper feed roller 36b. The sheet is further transported by the separating roller 36c. At this time, the separating roller 36
Since a predetermined torque is applied to c by the torque limiter as described above, when two or more recording sheets are fed out by so-called entrainment of the top sheet, only the top sheet is fed by the paper feed roller. The recording sheet conveyed by the sheet 36b and transported thereunder is prevented by the separating roller 36c from being conveyed. This prevents double feeding of the recording sheet S. In this way, only one recording sheet S taken out from the manual feed table 26 is transported by the paper feed roller 36b to the vertical transport roller 46 provided further downstream.

The other five paper feed mechanisms 31 to 35 (FIG. 1) are also driven by the paper feed motor M1 similarly to the paper feed mechanism 36, but are provided for each of the paper feed mechanisms 31 to 36. The driving force of the paper feeding motor M1 is intermittently driven by a paper feeding clutch (not shown) including a known electromagnetic micro clutch, and one of the six paper feeding mechanisms 31 to 36 is selectively driven. You. The transport path length between the pickup roller of each paper feed mechanism and the nearest vertical transport roller on the downstream side is at least
The length is set shorter than the length of the shortest recording sheet S in the transport direction among the recording sheets S that can be stored in the corresponding sheet feeding cassette.

Returning to FIG. 1, each paper feed roller 31b-36b
The vertical transport roller 4 is positioned at a predetermined distance from
In addition, a vertical transport roller 47 is disposed downstream of the vertical transport roller 41, and a vertical transport mechanism is configured by this. This vertical transport mechanism is driven by a vertical transport motor M2 (FIG. 3) composed of a pulse motor as a driving source via a power transmission mechanism (not shown) to rotate a recording sheet fed from a sheet cassette or a manual feed table. It is transported further downstream.

The leading end of the recording sheet conveyed by the vertical conveying roller is abutted against the registration roller 81 whose rotation has been stopped. After the abutment, the rotation of the vertical transport roller is continued for a predetermined time, and the sheet is conveyed by a predetermined distance to the rear end side of the sheet, so that the sheet buckles and a so-called loop is formed. Will be corrected.
Here, the predetermined distance is referred to as a “loop amount” as an amount indicating the degree of loop (buckling). The recording sheet that forms a loop and is on standby is conveyed to the transfer position of the photosensitive drum 3 by the registration roller 81 that is rotated and driven in synchronization with the image forming operation of the photosensitive drum 3 described above.

The registration roller 81 is driven by a registration motor M3 (FIG. 3) composed of a pulse motor, and detects that the recording sheet has reached immediately before the registration roller 81 immediately before the registration roller 81. Pre-resist sensor 50 is provided. An operation panel (not shown) is located at an easy-to-operate position on the front of the copier.
Is installed. The operation panel has various input keys such as a copy start key for instructing the start of copying, a numeric keypad for setting the number of copies, and a paper size key for specifying the size of the recording sheet, and a display unit for displaying the set contents. And so on. The document reading unit 10
0, the printer unit 200 and the paper feed unit 300 realize a smooth copy operation under the control of the main control unit 90.

FIG. 3 shows the configuration of the sheet feeding control section 390 for controlling the sheet feeding operation in the sheet feeding section 300. As shown in the drawing, the sheet feeding control unit 390 mainly includes a CPU 301 and a ROM 302, a RAM 303,
The excitation circuits 304, 305, and 306 are connected to the pre-registration sensor 50, and the CPU 301 controls according to a program stored in the ROM 302.

As shown in FIG. 4, the ROM 302 stores a pulse rate table 400 used for drive control of the vertical transport motor M2. Although pulse rate tables for the sheet feeding motor M1 and the registration motor M3 are also stored, they are not the main focus of the present invention, and thus description thereof is omitted. Pulse rate table 400
Stores pulse rates corresponding to the rate numbers 0 to 20. The pulse rate is 0 for the rate number.
, And are stored in ascending order. When the vertical transport motor M2 is driven at the pulse rate in this order, the transport speed of the sheet by the vertical transport roller is accelerated, and when the motor is driven at the reverse pulse rate, the speed is reduced. When driven at a pulse number of 1000 [PPS] with a rate number 15, the transport speed becomes a speed V1 substantially equal to the transport speed by the paper feed mechanism. In addition,
It is preferable that the transport speed by the paper feed mechanism and the speed V1 match, but it is difficult to completely match them, so it is sufficient that they match to the extent achievable with the current technology. Also, the pulse rate 1250 [P
PS], the transport speed becomes a speed required by the printer unit 200, that is, a speed V2 (V1 <V2) which is almost the same as the transport speed by the registration rollers 81. Rate numbers 15 to 20 correspond to each of the rates, and further, from when the leading edge of the recording sheet is detected by the pre-registration sensor to when the stop operation of the vertical transport motor is started to obtain a predetermined loop amount. Time T1 (hereinafter,
“Loop creation time T1”) is stored. That is, if the loop creation time T1 is kept constant, the loop amount is not constant when the leading end of the recording sheet comes into contact with the registration roller 81 during acceleration of the transport speed by the vertical transport roller, so that a stable loop amount is obtained. Therefore, the loop creation time T1 is set according to the transport speed at the start of the loop creation. Each transport speed (pulse rate)
Can be obtained through experiments or the like.

Although not shown, the ROM 302 further stores a certain time T2 from the start of sheet feeding, that is, the start of driving of the sheet feeding motor M1, to the start of acceleration of the transport speed by the vertical transport roller from V1 to V2. It is obtained and stored in advance. Time T2 is determined by the start of driving of the sheet feeding motor M1.
This is the time required for the recording sheet taken out from the paper feed cassette or the manual feed table to fully engage (be engaged) with the first transport roller located downstream.

The RAM 303 is a work area for executing a program, and has a motor drive flag and a motor speed flag. The motor drive flag is a flag for determining the drive / stop of the vertical transport motor M2. When 1 is set, the motor is driven, and when 0 is set, the motor is stopped. The motor speed flag is a flag for determining the number of revolutions (pulse rate) of the vertical transport motor M2. When 1 is set, the pulse speed corresponds to the transport speed V2, and when 0 is set, the transport speed V1 is set. Is driven at a pulse rate corresponding to.

The excitation circuits 304, 305, and 306 excite the respective phases of the sheet feeding motor M1, the vertical transport motor M2, and the registration motor M3 based on a control signal from the CPU 301. The CPU 301 controls the main control unit 90
Paper feed motor M according to an instruction from the
1. The drive control of the vertical conveyance motor M2 and the registration motor M3 and the ON / OFF control of a paper feed clutch (not shown) are performed.

FIGS. 5 and 6 are flowcharts showing the contents of the drive control of the vertical transport motor M2. FIG. 5 is a flowchart showing a routine for controlling drive timing such as starting, speed switching, and stop of the vertical transport motor M2.
5 is a flowchart showing a routine for controlling a rotation operation such as acceleration, constant speed, and deceleration of the vertical transport motor M2 according to timing controlled by the flowchart of FIG.

First, a description will be given with reference to the flowchart of FIG. Note that 0 is initially set for both the motor drive flag and the motor speed flag. First, it is determined whether or not a copy operation is currently being performed based on an output signal from the main control unit 90 (step S102). If the copy operation is not being performed, the vertical transport motor M2 does not need to be driven. The flag is set to 0 (maintained 0), and the process proceeds to the motor operation routine (step S200). If a copy operation is being performed, the main control unit 90 waits for a sheet supply start instruction. Step S1
06, YES), the motor drive flag is set to 1 in order to start the vertical transport motor M2, and the timing of the start of acceleration of the transport speed from V1 to V2 is measured.
Time T2 is set in the internal timer (step S10)
8).

When a paper feed start instruction is received from the main control unit 90, the conveyance of recording sheets from the paper feed cassette or the manual feed table is started. , Paper feed mechanisms 31 to 36
The description will be made assuming that the sheet feeding mechanism 36 is instructed. ) Is turned on, and the sheet feeding motor M1 is driven.

When the time T2 has elapsed (YES in step S110), it can be determined that the recording sheet taken out from the manual feed table 26 has engaged the vertical transport roller 46, and the transport speed of the vertical transport roller 46 is reduced to the speed V2.
, The motor speed flag is set to 1 (step S112). Subsequently, the control waits until the leading end of the recording sheet turns on the pre-registration sensor 50 (YES in step S114), and the loop creation time T1 corresponding to the same rate number as the counter value N of the counter described later is pulsed at that time. It reads from the rate table 400 (step S116), and sets the loop creation time T1 in an internal timer (step S118).

When the loop creation time T1 has timed out (YES in step S120), the motor drive flag is set to 0 to stop the vertical transport motor M2 and interrupt the transport of the recording sheet (step S122). The control unit 90 waits for the input of a registration signal urging the restart of conveyance of the recording sheet. When a registration signal is input (YES in step S124), vertical transport motor M2
, The motor drive flag is set to 1, and the motor speed flag is set to 1 to control the transport speed of the vertical transport roller to V2. At the same time as the input of the registration signal, the registration motor M3 is also started, and the registration roller 81 is driven to rotate so that the conveyance speed thereof becomes substantially equal to the speed V2. Therefore,
At this time, the recording sheet is conveyed while maintaining the initial loop until the trailing edge passes through the vertical conveyance roller 46.

When the trailing edge of the conveyed recording sheet is detected by the pre-registration sensor 50 (step S1).
(YES in step S28), the motor speed flag is set to 0 in order to make the vertical transport roller stand by at the transport speed V1 in preparation for the next paper feed (step S130). Next, the processing is performed in parallel with the above-described processing (steps S102 to S130).
FIG. 6 shows the rotation operation routine (step S200).
This will be described according to the flowchart shown in FIG.

First, it is determined whether or not the motor drive flag is 1 (step S202). If it is 1, then the state of the motor speed flag is determined (step S204). If the motor speed flag is 0, it is determined. , Pulse rate table 400
Referring to (FIG. 4), the rate number 15 corresponding to the speed V1 is stored as Nmax (step S206). On the other hand, if the motor speed flag is 1, the rate number 20 corresponding to the speed V2 is stored as Nmax with reference to the pulse rate table 400 (FIG. 4) (step S208).

Next, the counter value N is compared with Nmax (step S210). If the counter value N is smaller than Nmax (YES in step S210), the counter value is referred to the pulse rate table 400 (FIG. 4). At the pulse rate corresponding to the same rate number as the value N (step S21
2) The vertical transport motor M2 is driven until the time TM1 has elapsed (YES in step S214). When the time TM1 has elapsed, the counter is incremented (step S2).
16) The time TM1 is reset to a timer (step S218), and the process proceeds to step S220. This time TM
Reference numeral 1 denotes a driving time at each pulse rate shown in the pulse rate table 400 (FIG. 4) when the vertical transport motor M2 is accelerated. That is, the shorter the TM1, the greater the acceleration,
The longer the TM1, the lower the acceleration.

By the processing in steps S210 to S218, the transport speed of the vertical transport roller is changed from 0 to V1, V1
→ V2 or 0 → V2. Step S2
At 20, the counter value N is compared with Nmax (step S220). If the counter value N does not exceed Nmax (NO in step S220), the process proceeds to step S222, and the pulse rate table 400 (FIG. 4) is referred to. Then, the vertical transport motor M2 is driven at a pulse rate corresponding to the same rate number as the counter value N, and step S232 is performed.
(In this case, NO is always determined in step S232). That is, step S21
If NO is determined as 0 and NO is determined in step S220, the counter value N = Nmax. In this case, until the motor speed flag is changed in the flowchart of FIG. 5 (FIG. 5, step S112). , S122, 1
30), the vertical transport motor M2 is driven at a pulse rate having the same rate number as Nmax set in step S206 or step S208. Therefore, by this processing, the transport speed of the vertical transport roller is V1 or V2.
(N = Nmax), the vertical transport roller remains at V1 or V for a certain period of time until the motor speed flag is changed.
2 is driven at a constant speed.

On the other hand, at step S220, the counter value N
Is determined to exceed Nmax, the determination is:
After the rate number 20 corresponding to the speed V2 is stored as Nmax and the counter value N is incremented to 20, the motor speed flag is changed (step S in FIG. 5).
130), when the rate number 15 corresponding to the speed V1 is stored as Nmax (steps S204, S206). In this case, the pulse rate table 400
Referring to FIG. 4, at the pulse rate corresponding to the same rate number as the counter value N (step S224), the time T
The vertical transport motor M2 is driven until M2 elapses (YES in step S226). When the time TM2 elapses, the counter is decremented (step S228), and the timer TM is reset to time TM2 (step S230).
Proceed to step S232. This time TM2 is a drive time at each pulse rate shown in the pulse rate table 400 (FIG. 4) when the vertical transport motor M2 is decelerated. That is,
The shorter TM2, the more rapid deceleration, and the longer TM2, the more gentle deceleration.

This step S220, S224 to S23
0, the transport speed by the vertical transport roller becomes V2
→ The speed is reduced to V1. Subsequently, in step S232,
When it is determined that the motor drive flag is set to 0, this determination is made when the copy operation is not performed and the motor drive flag remains at the initial setting because the copy operation is not performed. (Steps S102 and S104 in FIG. 5), and the loop creation time T1 increases (step S12 in FIG. 5).
0), when the motor drive flag is changed to 0 (FIG. 5,
Step S122) is performed. In this case, if the counter value N is not 0 (NO in step S234), referring to the pulse rate table 400 (FIG. 4), at the pulse rate corresponding to the same rate number as the counter value N (step S236), The vertical transport motor M2 is driven until TM2 elapses (YES in step S238), and the time T
When M2 has elapsed, the counter is decremented (step S240), the time TM2 is reset to the timer (step S242), and the routine returns. On the other hand, when it is determined in step S234 that the counter value N is 0, the process skips steps S234 to S242 and returns.

By the processing of steps S234 to S242, the transport speed of the vertical transport roller is reduced from V2 to 0. FIG. 7 is an example of a time chart of control according to the flowcharts shown in FIGS. 5 and 6 described above. First, when there is a paper feed instruction from the main control unit 90, the motor drive flag is set to 1 (C1), and the vertical transport motor M2 is set.
(B1), and when the time T2 elapses, that is, when the time required for the recording sheet taken out by the paper feed mechanism to fully engage (be engaged) with the first vertical transport roller on the downstream side elapses, the vertical The transport speed by the transport roller is changed from V1 to V2
(B3 to B5).

The leading end of the recording sheet is a pre-registration sensor 5
When 0 is turned on (A1), the loop creation time T corresponding to the same rate number as the counter value N at that time is referred to the pulse rate table 400 to create a loop.
1, ie, when the loop creation time T1 corresponding to the transport speed (pulse rate) at that time has elapsed, the motor drive flag is set to 0 (C2), and the vertical transport motor M2 is decelerated and stopped (B6 to B6). B7).

In a state in which the recording sheet forms a loop, and the registration roller 81 is in a standby state with its leading end abutting,
When the registration signal is input, the motor drive flag is set to 1 (C3), and the vertical transport motor M2 is activated (B
8) Accelerate to the transport speed V2 (B9). When the trailing edge of the recording sheet turns off the pre-registration sensor 81 (A2), the motor speed flag is set to 0, and the speed V
The speed is reduced to 1 (B10 to B11) to prepare for the next sheet feeding.

As described above, according to the paper feeder of this embodiment, when the recording sheet is engaged with the vertical transport roller,
Since the recording sheet transport speed is the same speed V1 as the transport speed of the vertical transport roller, a smooth paper feed operation can be realized without step-out occurring in the pulse motor that drives the vertical transport roller. Further, when the time T2 has elapsed and the recording sheet is conveyed by the conveyance force of the vertical conveyance roller, the conveyance speed of the vertical conveyance roller is increased to the speed V2. Can be.

For example, in the conventional sheet feeding device, the conveying speed by the vertical conveying rollers is set to 500 mm / sec, which is the upper limit at which the separating operation can be ensured, and the conveying speed by the vertical conveying roller is set to 500 mm.
mm / sec, the step angle of the pulse motor used for driving the vertical conveyance roller is 1.8 °, and the pulse rate corresponding to the conveyance speed of 350 mm / sec is 1750 pp.
s, the pulse rate corresponding to the transport speed of 500 mm / sec is 2
Assuming that the load inertia of the paper feeding mechanism in the conventional paper feeding device is 0.5 kgf · cm ² , when the recording sheet is engaged with the vertical conveying roller, the conveying speed of the vertical conveying roller is To maintain the pressure at 500 mm / sec (to prevent loss of synchronism), an extra torque of Ta = 0.5 / 980.7 × 1.8 π / 180 × (2500-1750) /0.0004=30 [kgf · cm] In practice, it is not possible to withstand this load torque, and step-out occurs. However, as described above, the paper feeder according to the present embodiment avoids such a situation. You can.

In the above equation, 980.7 is the gravitational acceleration [cm / sec ² ], and 0.0004 (= 1/25)
00) is the time [sec] required for one step angle rotation during conveyance at a conveyance speed of 500 mm / sec (2500 pps). Further, according to the sheet feeding device according to the present embodiment, the loop is created with the loop creation time T1 according to the transport speed of the vertical transport roller when the recording sheet comes into contact with the registration roller. In addition, appropriate skew correction can be performed.

It should be noted that the present invention can be applied not only to a case where a step-out occurs due to a sudden load change in the drive source of the vertical transport mechanism but also to a case where another type of motor is used. It can be applied to realize a paper feeding operation. For example, when a DC motor is used, the rotation speed may be detected as a signal corresponding to the pulse rate of the above-described embodiment from an output signal of a rotary encoder attached to the rotation shaft. In the ROM 302, a table storing an optimum loop creation time T1 corresponding to the detected rotation speed is prepared as a table corresponding to the pulse rate table of the above-described embodiment. Then, when the pre-registration sensor 50 detects the leading edge of the recording sheet, the loop creation time T corresponding to the rotation speed specified from the output signal of the rotary encoder.
1 may be read from the table, and the motor may be stopped as in the above-described embodiment.

[0041]

As described above, according to the paper feeder of the present invention, the first transport roller feeds the sheet supplied from the sheet storage section at the first speed at substantially the same speed as the first speed. , The motor used as the drive source of the first transport roller can be prevented from stepping out, and a smooth paper feed operation can be realized. Also, after receiving, the second speed faster than the first speed
Acceleration to the speed of
PM can be maintained.

Further, when the leading edge of the sheet is detected by a detection sensor provided between the second conveying roller and the first conveying roller, a timer starts counting time, and the sheet conveying speed at the time of the detection is measured. When the timer counts the corresponding drive continuation time, the first transport roller is stopped, so that an appropriate loop amount is obtained for the sheet, and skew correction is surely performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a digital copying machine to which a sheet feeding device according to an embodiment is applied.

FIG. 2 is a diagram showing a configuration from a manual feed table to a registration roller in a paper feeding unit of the copying machine.

FIG. 3 is a diagram illustrating a configuration of a paper feed control unit that controls a paper feed unit of the copying machine.

FIG. 4 is a diagram showing a pulse rate table stored in a ROM of the paper feed control unit.

FIG. 5 is a flowchart showing control contents of a paper feed control unit of the copying machine.

FIG. 6 is a flowchart showing control contents of a paper feed control unit of the copying machine.

FIG. 7 is a diagram showing a time chart of an operation of a paper feeding unit of the copying machine.

[Explanation of symbols]

21, 22, 23, 24, 25 Paper cassette 26 Manual feed table 41, 42, 43, 44, 45, 46, 47 Vertical conveyance roller 50 Pre-registration sensor 81 Registration roller 90 Main control unit 301 CPU 302 ROM 303 RAM 305 Excitation Circuit 390 Paper feed controller 400 Pulse rate table M2 Vertical transport motor

Claims (1)

[Claims] A sheet fed from a sheet storage section at a first speed is received at substantially the same speed as the first speed, and thereafter, acceleration to a second speed higher than the first speed is started. , The second sheet waiting for the rotation of the sheet is stopped.
A sheet feeding device having a first conveyance roller for conveying to a conveyance roller, wherein a detection sensor provided between the second conveyance roller and the first conveyance roller to detect presence / absence of a sheet; A timer that starts timing when the leading edge is detected, sheet transport speed detecting means that detects the sheet transport speed when the leading edge of the sheet is detected by the detection sensor, and a sheet transport speed that is detected by the sheet transport speed detecting means A drive continuation time determining means for determining a drive continuation time of the first conveyance roller according to the following; and a first conveyance roller stopping means for stopping the first conveyance roller when a timer counts the determined drive continuation time. A paper feeding device comprising: