JPH10316256A - Paper feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeding device provided with a separation mechanism, capable of smooth paper supplying while maintaining CPM. SOLUTION: A sheet supplied from a supply paper cassette 21 is separated by a separation roller 31c provided abutting to a paper feeding roller 31b at such a paper feeding speed that separation performance can be assured, carrying speed by a vertical carrying roller 51 is controlled to be roughly similar to above paper feeding speed till a tip of one separated sheet is detected by a vertical carrying sensor 51, and after the tip of the sheet is detected by the vertical carrying roller 51, carrying speed by the vertical carrying roller 51 is controlled to be faster than the paper feeding speed as demanded by a printer part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a paper feeding apparatus, particularly an image forming apparatus such as a copying machine, and separates and takes out the sheets one by one from a paper feeding cassette in which a sheet bundle is set. The present invention relates to a sheet feeding device for feeding a forming unit.

[0002]

2. Description of the Related Art In a conventional paper feeding apparatus, a separating mechanism including a feed roller and a separating roller is provided to prevent double feeding of sheets. The separating roller is given a rotational load in a direction opposite to the sheet conveying direction by a torque limiter provided coaxially, and is pressed against the feed roller with a predetermined force. When the separating roller comes into direct contact with the feed roller (that is, when there is no sheet between the rollers), or when only one sheet is fed between the rollers, the separating roller feeds the sheet against the rotating load. The sheet is driven by the roller, but when a plurality of sheets are overlapped and sent between the rollers, the separating roller is stopped because the rotational load is larger than the frictional force between the sheets. Movement of the sheet in the transport direction is prevented, and double feeding of the sheet is prevented. The sheet separated by the separating mechanism is sent to a transport roller provided downstream of the transport path toward the image forming unit. 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.

[0003]

However, in the above-mentioned separating mechanism, there is a limit to the sheet feeding speed of the sheet by the feed roller in order to secure the separating property and prevent the skew of the recording sheet. However, the transport speed must be lower than the transport speed of the transport roller that does not require the separating action. Therefore, a speed difference occurs between the two rollers.For example, when a pulse motor is used as a drive source of the transport roller, an extra load is applied to the pulse motor due to the speed difference. The motor loses synchronism,
There is a problem that a smooth transport operation is hindered.

FIG. 7 is a view showing a moment when a recording sheet S taken out of a sheet feeding cassette (not shown) by a sheet feeding mechanism in a conventional sheet feeding device is engaged with a vertical conveying roller. Here, the transport speed by the paper feeding mechanism is the upper limit at which the separating action can be ensured in the conventional paper feeding device.
0mm / sec, transport speed by vertical transport roller is 500mm / s
ec, the step angle of the pulse motor used for driving the vertical conveying roller is 1.8 °, and the conveying speed is 35 °.
A pulse rate corresponding to 0 mm / sec is 1750 pps, and a pulse rate corresponding to a conveying speed of 500 mm / sec is 2500
pps, and assuming that the load inertia of the paper feeding mechanism in the conventional paper feeding device is 0.5 kgf · cm ² , the conveying speed of the vertical conveying roller when the recording sheet is engaged with the vertical conveying roller 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] However, in practice, it is not possible to withstand this load torque and step-out occurs.

In the above equation, 980.7 is the gravitational acceleration [cm / sec ² ], and is 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). The present invention has been made in view of the above circumstances, and has as its object to provide a paper feeding device capable of performing smooth paper feeding while maintaining CPM.

[0006]

In order to achieve the above object, a sheet feeding apparatus according to the present invention is a sheet feeding apparatus for feeding sheets stacked in a sheet storage section one by one, and comprises: A sheet feeding roller provided near the unit for feeding a sheet at a first speed; a separating member for cooperating with the sheet feeding roller to separate the sheet; and a sheet feeding roller driven by a first motor. A conveyance roller for conveying the sheet fed from the conveyance direction downstream, a detection unit provided downstream of the conveyance roller in the sheet feeding direction, and detecting the presence or absence of a sheet; and a sheet fed by the sheet feeding roller. Until the leading edge of the sheet is detected by the detecting means, the transport speed of the transport roller is substantially equal to the first speed, and the leading edge of the sheet fed by the paper feeding roller is detected by the detecting means. After the transfer roller Transport speed due to comprising the a conveying speed control means for controlling the first motor to be increased to second speed higher than the first speed.

Further, a second motor for driving the paper feed roller, a clutch for intermittently transmitting power from the second motor to the paper feed roller, and a control of the rotation speed of the second motor are provided. Paper feed control means for controlling engagement and disengagement of the clutch, wherein when the detection means detects the leading edge of the sheet, the clutch is disengaged and the rotation speed of the second motor is reduced to a second speed. It is characterized by performing control for maintaining the number of rotations corresponding to the speed of 1.

[0008]

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 once, 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 by a known electrostatic copying method. In the exposure scanning unit 1, a laser diode (not shown) emits a laser beam in response to an output signal from the document reading unit 100, The light is reflected and deflected by a mirror surface of a polygon mirror (not shown) driven to rotate at a constant speed. 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 separating charger 7, a cleaning device 8, and an eraser lamp 9 are arranged in this order along the drum rotating direction a. Then, the toner image of the read document is transferred onto the recording sheet fed from the sheet feeding unit 300 by a known electrostatic copying process such as charging, exposure, development, transfer, and separation. The recording sheet to which the toner image has been transferred is transported by the transport belt 10.
The sheet is fed into the fixing device 11, where it is fixed, and then discharged onto a tray 13 via a discharge roller 12.

The paper feed unit 300 holds the paper feed cassettes 21 to 25 slidably in the front of the drawing by guide rails (not shown) in cabinets 61 provided in two upper and lower tiers, and is mounted on the right wall of the cabinet. A transport path 70 for transporting the recording sheets from each of the paper feed cassettes 21 to 25 is formed along the transport path 70. 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 7 are provided.
Sheet feed mechanisms 31 to 35 for taking out recording sheets from the sheet feed cassette are arranged at the end of the branch road 5.

Since the configurations of the paper feed mechanisms 31 to 35 are the same, only the paper feed mechanism 31 will be described with reference to FIG. As shown in the figure, the paper feeding mechanism 31 includes a pickup roller 31a, a paper feeding roller 31b, a separating roller 31c,
And a paper feed sensor 31d. The pickup roller 31a and the paper feed roller 31b 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 31c. The pickup roller 31a and the paper feed roller 31b are
It is driven to rotate in a direction shown by an arrow via a power transmission mechanism (not shown) using a sheet feeding motor M1 (FIG. 1) composed of a pulse motor as a driving source.

Pickup roller 31a and paper feed roller 3
When the recording roller 1b is driven to rotate, the pickup roller 31a pressed against the recording sheet S draws out the recording sheet S in the sheet cassette 21 from the uppermost sheet, and the fed sheet S is separated from the sheet feeding roller 31b. Although the sheet is further conveyed by the roller 31c, a predetermined torque is applied to the separating roller 31c by the torque limiter as described above. Only the upper recording sheet S is the feed roller 31b
The recording sheet S thereunder is prevented from being conveyed by the separating roller 31c. This prevents double feeding of the recording sheet S. In this manner, only one recording sheet S taken out from the paper feed cassette 21
Is transported by a paper feed roller 31b to a vertical transport roller 41 provided further downstream.

The paper feed sensor 31d includes a separating roller 31c.
And the vertical conveyance roller 41, and detects the presence or absence of the recording sheet S conveyed on the branch path 71 at the measurement position. The other four paper feed mechanisms 32 to 35 (FIG. 1)
Are driven by a paper feed motor M1 similarly to the paper feed mechanism 31, but are provided by paper feed clutches 31e to 35e, each of which is a known electromagnetic micro clutch provided for each of the paper feed mechanisms 31 to 35.
(See FIG. 3), the driving force of the paper feed motor M1 is intermittent, and one of the five paper feed mechanisms 31 to 35 is selectively driven. Also, the transport path length between the paper feed roller of each paper feed mechanism and the nearest vertical transport roller on the downstream side is at least the shortest recording direction in the transport direction of the recording sheets S that can be stored in the corresponding paper feed cassette. The length is set shorter than the length of the sheet S.

Returning to FIG. 1, longitudinal transport rollers 41 to 45 are disposed on the transport path 70 at a predetermined distance from the paper feed sensors 31d to 35d toward the downstream side, thereby constituting a vertical transport mechanism. Have been. This vertical transport mechanism is driven to rotate by a vertical transport motor M2 composed of a pulse motor via a power transmission mechanism (not shown), and transports the recording sheet fed from the paper feed cassette further downstream. .

Further, immediately after the downstream side of each of the vertical conveying rollers 41 to 45, vertical conveying sensors 51 to 55 are provided, respectively, so that the presence or absence of the recording sheet conveyed on the conveying path 70 at the measurement position is detected. Is done. The distance on the transport path between adjacent vertical transport sensors is set shorter than the length of the shortest recording sheet to be transported.

The recording sheet conveyed by the vertical conveying roller is conveyed further downstream on the conveying path 70 by the intermediate roller 81, abuts against the registration roller 82, waits for a while, and then contacts the photosensitive drum 3. The photosensitive drum 3 is conveyed to the transfer position in synchronization with the image forming operation. An operation panel (not shown) is provided at a position on the front of the copying machine where the operation is easy. 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 100, the printer unit 200, and the paper feeding unit 300
Under the control of the main control unit 90, a smooth copying operation is realized.

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,
Excitation circuits 304 and 305, paper feed sensors 31d to 35d
The CPU 301 controls according to a program stored in the ROM 302.

The excitation circuits 304 and 305 are respectively C
Based on a control signal from the PU 301, the sheet feeding motor M1,
Excitation of each phase of the vertical transport motor M2 is performed. As a result, the feed motor M1 and the vertical transport motor M2 are driven, and the transport speed of the recording sheet by the paper feed mechanism is set to a speed V1 (for example, 350 mm / sec) at which the loosening action is guaranteed. Transfer speed V1 or speed V2 (for example, 50
0 mm / sec) (V1 <V2). In addition,
It is preferable that the speed V1 of the paper feeding mechanism and the speed V1 of the vertical transport mechanism match, but it is difficult to make them completely match. Therefore, it is sufficient that the speed V1 matches the level achievable with the current technology.

The CPU 301 responds to an instruction from the main control unit 90 or a detection signal from each sensor to control the feed motor M
1. Drive control of the vertical transport motor M2 and the paper feed clutch 31e
On-off control of .about.35e. Next, the control contents of the paper feed control unit 390 will be described with reference to the flowchart shown in FIG.

First, it is determined whether or not there is a feed instruction from the main control unit 90 (step S102). If so, the feed motor M1 is started and started up by a slow-up operation.
The rotation control is performed so that the conveyance speed of the recording sheet by the paper feeding mechanism becomes the speed V1 (step S104).
The driving of the vertical conveyance motor M2 is started, and the rotation of the vertical conveyance motor M2 is controlled so that the conveyance speed of the recording sheet by the vertical conveyance mechanism becomes the speed V2 (step S106).
When the feed motor M1 reaches the target rotation speed (the rotation speed at which the transport speed becomes V1), the feed mechanism specified by the main controller 90 (hereinafter, the feed mechanism among the feed mechanisms 31 to 35, The description will be made assuming that the mechanism 31 has been instructed.) The paper feed clutch 31e (FIG. 3) is turned on (step S10).
8).

When the paper feeding clutch 31e is turned on, one recording sheet is taken out from the corresponding paper feeding cassette 21, and the taken out recording sheet is further conveyed by the vertical conveyance roller 41 to the downstream side. When the vertical conveyance sensor 51 is turned on by the (leading edge) of the recording sheet being conveyed (Yes in step S110), it can be determined that the recording sheet has engaged (engaged) with the vertical conveyance roller 41, and as a result, Is reliably sent forward by the transport force of the vertical transport roller 41, the paper feed clutch 31e (FIG. 3) is turned off (step S112), and the transport speed of the recording sheet by the vertical transport mechanism is changed from V1 to V2. Then, the rotation speed of the vertical transport motor M2 is increased (step S114).

After the paper feed clutch 31e is turned off, the recording sheet is transported by the vertical transport roller 41,
The trailing end portion of the recording sheet engaged with the paper feed mechanism 31 advances while the pickup roller 31a and the paper feed roller 31b idle with respect to the drive shaft. Subsequently, when the trailing edge of the recording sheet passes through the detection area of the paper feed sensor 31d and the paper feed sensor 31d is turned off (Yes in step S116), it is necessary to feed more recording sheets from the paper feed cassette. (Yes at step S118)
s), the process proceeds to step S120, the paper feed clutch is turned on, and when the rear end of the recording sheet passes through the detection area of the vertical conveyance sensor 51 and the vertical conveyance sensor 51 is turned off (Yes in step S122), the vertical conveyance is performed. The vertical transport motor M is set so that the transport speed of the recording sheet by the mechanism is changed from V2 to V1.
2 is reduced (step S124), and step S1 is performed.
Return to 10.

On the other hand, if it is not necessary to feed the recording sheets from the paper feed cassette (No in step S118), the flow advances to step S126, in which the paper feed motor M1 is decelerated by the slowdown operation and stopped, and the vertical transport sensors 51 to 51 are stopped. When all 55 are turned off (Yes in step S128), the vertical transport motor M2 is stopped (step S128), and the process returns to step S102.

The conveyance of the recording sheet by the paper feeding mechanism and the vertical conveyance mechanism is temporarily interrupted by the instruction of the main control unit 90 in accordance with the timing when the preceding recording sheet comes into contact with the registration roller 82 and waits. However, since the description is complicated, the processing is omitted in the flowchart. FIG. 5 corresponds to FIG.
5 is a time chart relating to the control of the flowchart shown in FIG.

First, the driving of the paper feeding motor M1 and the driving of the vertical transport motor M2 are started (C1, D1), and the paper feeding mechanism 31 is started.
When the number of rotations at which the recording sheet is conveyed reaches V1 (C2), the paper feed clutch 31e is turned on (A1). In this state, the first recording sheet is taken out from the paper feed cassette 21 and is conveyed. The first recording sheet conveyed at the speed V1 (the leading end thereof) is a vertical conveyance sensor 5
1 (E1), and when it is confirmed that the recording sheet is engaged with the vertical conveyance roller 41, the sheet feeding clutch 3
1e is turned off (A2), and the rotation speed of the vertical conveyance motor M2 is increased to the rotation speed corresponding to the conveyance speed V2 (D3 to D3).
4).

When the trailing end of the first recording sheet conveyed at the speed V2 turns off the sheet feeding sensor 31d (B1), the sheet feeding clutch 31e is turned on (A3) and the second recording sheet is fed. Start. On the other hand, when the rear end of the first recording sheet is detected by the vertical conveyance sensor 51 (E2), the rotation speed of the vertical conveyance motor M1 is increased from the conveyance speed V2 to the conveyance speed V1.
(D5 to D6) to prepare for the conveyance of the second recording sheet.

When the leading edge of the second recording sheet is detected by the vertical transport sensor 51 (E3), the rotational speed of the vertical transport motor M2 is increased to the rotational speed corresponding to the transport speed V2 (D7 to D7).
D8) The trailing end of the second recording sheet is the feed sensor 31d
Is turned off (B2), since the recording sheet to be fed is the last, the feeding motor M1 is decelerated by the slowdown operation and stopped (C3 to C4). When the rear end of the second recording sheet turns off the vertical conveyance sensor 51 (E4), after confirming that all the vertical conveyance sensors are turned off, the vertical conveyance motor M2 is slowed down by a slowdown operation and stopped. (C9-C10).

As described above, according to the paper feeder of the present embodiment, as shown in FIG. 6, when the recording sheet S is engaged with the vertical transport roller, the recording sheet transport speed is increased by the vertical transport roller. Speed V1 (350 mm / sec)
c), a smooth paper feed operation can be realized without step-out occurring in the pulse motor for driving the vertical transport roller. When the leading edge of the recording sheet is detected by a vertical transport sensor provided immediately downstream of the recording sheet, the transport speed of the vertical transport roller is increased to V2 (500 mm / sec).
, The CPM can be maintained substantially the same as the conventional one.

Further, when the leading end of the recording sheet turns on the vertical conveyance sensor and it is confirmed that the recording sheet is engaged with the vertical conveyance roller, an electromagnetic micro clutch for transmitting power from the paper feeding motor M1 to the paper feeding mechanism. Is turned off and the sheet feeding motor M1 is put on standby without stopping, so that the next sheet feeding is started only by turning on the electromagnetic micro clutch. Distance can be shortened.

In this embodiment, a pulse motor is used as a drive source of the vertical transport mechanism. However, the present invention is not limited to this.
The present invention is applicable to a case where a motor that causes a step-out due to a sudden load change is used as a drive source of a vertical transport mechanism.

[0032]

As described above, according to the sheet feeding apparatus of the present invention, the sheet leading out of the sheet storage unit is detected until the leading end of the sheet is detected by the detecting means provided downstream of the conveying roller. Indicates that the paper feed speed by the transport rollers is
Since the sheet feeding speed is controlled to be substantially the same as the first speed which is the sheet feeding speed by the sheet feeding roller, when the sheet reaches the conveying means, the sheet feeding speed and the conveying speed are substantially the same, The step-out of the first motor caused by the difference between the two speeds can be prevented, and a smooth paper feeding operation can be realized. Further, after the leading edge of the sheet is detected by the detecting means, the conveying speed by the conveying roller is increased to the second speed, which is higher than the first speed, so that it is possible to maintain substantially the same CPM as the conventional one. Becomes

Further, when the detecting means detects the leading edge of the sheet, the clutch for interrupting the transmission of power from the second for driving the paper feed roller to the paper feed roller is disengaged, and the second motor is driven. Since the number of revolutions is maintained at the number of revolutions corresponding to the first speed, at the time of the next sheet feeding, sheet feeding can be started immediately just by engaging the clutch, the sheet feeding time can be reduced, and the CPM can be reduced. improves.

[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 one of the paper feeding mechanisms 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 flowchart showing control contents of a paper feed control unit of the copying machine.

FIG. 5 is a diagram showing a time chart of an operation of a paper feeding unit of the copying machine.

FIG. 6 is a diagram for explaining a sheet feeding device according to the embodiment of the present invention.

FIG. 7 is a diagram for explaining a sheet feeding device according to the related art.

[Description of Signs] 21, 22, 23, 24, 25 Paper cassette 31, 32, 33, 34, 35 Paper feed mechanism 31b Paper feed roller 31c Separation roller 31d Paper feed sensor 31e, 32e, 33e, 34e, 35e Electromagnetic Micro clutch 41, 42, 43, 44, 45 Vertical transport roller 51, 52, 53, 54, 55 Vertical transport sensor M1 Feed motor M2 Vertical transport motor 390 Feed control unit

Claims (2)

[Claims] 1. A sheet feeding device for feeding sheets stacked in a sheet storage unit one by one, comprising: a sheet feeding roller provided near the sheet storage unit for feeding sheets at a first speed. A separating member for separating sheets in cooperation with the sheet feeding roller; a conveying roller driven by a first motor to convey the sheet fed from the sheet feeding roller downstream in the sheet feeding direction; Detecting means for detecting the presence or absence of a sheet, which is provided on the downstream side in the sheet feeding direction, and adjusting the conveying speed of the conveying roller to a second speed until the leading end of the sheet fed by the sheet feeding roller is detected by the detecting means. A second speed at which the conveying speed of the conveying roller is higher than the first speed after the leading end of the sheet fed by the feed roller is detected by the detecting means. To be accelerated to 1
Feeding speed control means for controlling the motor. A second motor for driving the paper feed roller; a clutch for intermittently transmitting power from the second motor to the paper feed roller; and controlling a rotation speed of the second motor. And sheet feed control means for performing on / off control of the clutch. When the detection means detects the leading edge of the sheet, the sheet feed control means disengages the clutch and reduces the rotation speed of the second motor to the first. 2. The sheet feeding device according to claim 1, wherein control is performed to maintain the rotation speed corresponding to the speed of 1.