JPH09188442A - Paper conveying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve registering precision through restarting of conveyance of a paper sheet at an accurate timing and enhance a paper skew correction function, in a paper conveying device for a copying machine or a printer. SOLUTION: A paper conveying device conveys paper sheets by using a register roller pair 42 in such a manner that the forward end of a paper sheet is caused to coincide with the tip of an image forming region on a photoreceptor drum. A register upper roller 42a has a low friction factor and a register lower roller 42b has a high friction factor. The register upper roller 42a continues rotation during a paper conveyance mode and the lower register roller 42b is rotationally drive based on the generation of a synchronous signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus, and more particularly to a sheet conveying apparatus for conveying a sheet in an image forming apparatus such as an electrophotographic copying machine or a laser printer in synchronization with rotation of a photosensitive drum.

[0002]

2. Description of the Related Art Conventionally, as a sheet conveying device in an electrophotographic copying machine, as described in Japanese Patent Application Laid-Open No. 63-220176, sheets fed one by one from a sheet feeding section in which sheets are stacked. Is fed to the pair of registration rollers in the stopped state, the leading edge of the paper is thrust into the nip portion of the pair of registration rollers to form a loop at the leading edge of the paper, and the leading edge of the paper and the image forming area on the photosensitive drum are The rotation of the registration roller pair is turned on based on the synchronization signal so that the leading end and the transfer position coincide with each other.

[0003]

By the way, in this type of sheet conveying apparatus, the registration roller pair can convey the sheet at an accurate timing based on the synchronization signal, and has a function of correcting skew of the sheet. Required to have. However, in the conventional paper transporting device, since the registration roller pair is in a state in which the rotation is stopped between the time when the paper is rushed in and the transportation is restarted, and the registration roller pair is a roller having a high friction coefficient, the nip The movement of the leading edge of the paper that has rushed into the section is greatly restricted, the skew feeding function of the paper is insufficient, and the leading edge of the paper slips into the nip portion and the leading edge of the paper slips when the transport is restarted. However, there is a problem in that the synchronization shift occurs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a sheet transporting device which can resume the transport of the sheet at an accurate timing and has an excellent skew feeding correction function.

[0005]

In order to achieve the above object, the sheet conveying apparatus according to the present invention is a pair of registration rollers in which a first roller having a low friction coefficient and a second roller having a high friction coefficient are in contact with each other. Drive means for independently rotating and driving the first roller and the second roller, and control means having an operation mode for rotating the first roller in the paper rotation direction and stopping the rotation of the second roller. Is equipped with.

When the synchronizing signal is generated, the second roller is driven to rotate in the sheet conveying direction. The first roller continues to rotate during the paper transport mode, or is rotationally driven immediately before the paper rushes into the nip portion of the registration roller pair until it finishes rushing or immediately before the synchronization signal is generated. .

According to the present invention, when the leading edge of the sheet is in the nip portion of the pair of registration rollers, the first roller is rotationally activated in the sheet conveying direction. The first roller is a roller having a low coefficient of friction and has a good slippage with the leading edge of the sheet. The leading edge of the sheet fits in the nip portion formed by the first roller and the second roller having a high coefficient of friction to accurately enter abruptly. Therefore,
The skew of the paper is accurately corrected, and the paper is restarted at a correct timing without slipping due to the rotation of the second roller based on the generation of the synchronization signal.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a sheet conveying device according to the present invention will be described below with reference to the accompanying drawings. FIG.
FIG. 1 shows an electrophotographic copying machine equipped with a paper transporting device according to an embodiment of the present invention.

This copying apparatus comprises an upper copying machine body 10 and a lower paper feeding cabinet 50. A photoconductor drum 11 is rotatably installed in the direction of an arrow a at a substantially central portion of the copying machine main body 10, and a charging charger 12, an inter-image / image end eraser 13, a developing device 14, a transfer charger 15 are provided around the photoconductor drum 11. A sheet separation charger 16, a residual toner cleaner 17, and an residual charge eraser lamp 18 are provided. Note that the configurations and operations of these elements are well known, and description thereof will be omitted.

The scanning optical system 20 is composed of an exposure lamp 21, movable mirrors 22, 23 and 24, a variable magnification imaging lens 25, and fixed mirrors 26, 27 and 28. Lamp 21
And the mirror 22 move in the direction of arrow b at v / m (v is the peripheral speed of the photosensitive drum 11, m is the copy magnification), and the mirror 23,
24 moves in the direction of arrow b at a speed of v / 2m. Based on this movement, the optical system 20 scans and exposes the image of the original document set on the platen glass 29 onto the photosensitive drum 11.

Sheets are fed one by one from a manual paper feed section 30 provided on the left side of the paper feed cabinet 50 or the copying machine main body 10. The paper fed from the paper feed cabinet 50 reaches the registration roller pair 42 from the intermediate conveyance roller 41.
From the manual paper feed unit 30, the paper set on the table 31 reaches the registration roller pair 42 through the intermediate conveyance roller 33 based on the rotation of the paper feed roller 32.

The sheet stands by in a state where the leading end thereof has entered the nip portion of the registration roller pair 42, and is conveyed from the registration roller pair 42 to the transfer position T in synchronization with the toner image formed on the photosensitive drum 11. It will be restarted. Transfer position T
In, the paper is transferred with the toner image by the electric field applied from the transfer charger 15, and then the separation charger 16
Is removed by an AC electric field applied from the photoconductor drum 11 and separated from the photoconductor drum 11. Next, the paper is sent to the fixing device 47 by the air suction belt 46 to fix the toner, and is discharged from the discharge roller 48 to the tray 49.

The paper feed cabinet 50 incorporates four paper feed trays 51 and a vertical transport path 55. Each tray 51 includes a paper feed roller 52 and a paper separation roller pair 53. The vertical transport path 55 includes a vertical transport roller 56, a guide plate 57,
It consists of 58. The tray 51 for feeding the paper is automatically selected by the operator or from the document size and the copy magnification. The sheet fed from the selected tray 51 is sent to the copying machine main body 10 through the vertical transport path 55.

Here, the paper transport system will be described.
The transfer system in the copying machine main body 10 has a main motor M1 except for the lower roller 42b (see FIG. 2) of the registration roller pair 42.
Is driven to rotate. Various rollers are turned on and off at appropriate timings by a clutch. The upper registration roller 42a is connected to the main motor M1 via a pulley (not shown) and a timing belt, and is rotationally driven in the sheet conveyance direction c in synchronization with the driving of the main motor M1. As shown in FIG. 3, the lower registration roller 42b is rotationally driven by a registration motor M4 via a reduction gear mechanism 43. As the registration motor M4, a pulse motor having a stable starting characteristic is used, and its drive timing will be described in detail below.

By the way, the upper roller 42a constituting the registration roller pair 42 is made of a material having a low friction coefficient, and the lower roller 42b is made of a material having a high friction coefficient. For example, with respect to standard paper, the friction coefficient of the upper roller 42a is 0.2 or less, and the friction coefficient of the lower roller 42b is 1.2.
It is about 1.5.

On the other hand, in the paper feed cabinet 50,
The vertical transport rollers 56 are respectively coupled to the vertical transport motor M2 via clutches. Each paper feed roller 52 and pair of separation rollers 53 is connected to a paper feed motor M3 provided for each paper feed tray 51. Various sensors for detecting paper are installed on the paper passage. Sensor S
E1 detects the paper fed from each paper feed tray 51. The sensor SE2 detects the sheet immediately before the intermediate conveyance roller 41, and the sensor SE3 detects the sheet immediately before the registration roller pair 42. The sensor SE4 is a manual feed table 31.
It is detected that a sheet has been inserted, and the detection signal starts the copying operation in the manual feed mode. The sensor SE5 detects the sheet immediately after the intermediate conveyance roller 33. Sensor SE
6 detects a sheet discharged to the tray 49.

FIG. 5 shows the main part of the control circuit of the above-mentioned copying machine. The first CPU 70 is a microcomputer that controls the entire copying apparatus, and the second CPU 80 is a registration motor M.
Microcomputers controlling 4
M and RAM are provided, and control is performed according to a predetermined program stored in ROM. The third CPU (not shown) controls the optical system 20. From the output ports A ₁ and A _{2 of the first} CPU 70, control signals for the clutch of the vertical conveyance roller 56 and the clutch of the intermediate conveyance roller 41 are OR gate OR.
1 and OR2, and an ON / OFF control signal for the registration motor M4 is output from the output port A ₃ to the second CPU 8
It is output to 0 through the OR gate OR3. Sheet detection signal from the input port B _1, sensor SE3 to B ₃ are, SE1 is inputted. The sync signal transmitted from the third CPU is input to the input port B ₂ . This synchronization signal is also input to the OR gates OR1, OR2 and OR3.

Further, a pulse motor driver 71 for driving the sheet feeding motor M3 is connected to the output ports A ₄ , A ₅ and A ₆ . Two-phase excitation signals φ ₀ and φ ₁ are output from the output ports A ₄ and A _5, and an enable signal Ena for energization is output from the output port A ₆ .

The second CPU 80 exclusively controls the registration motor M4 that rotationally drives the registration roller 42b. The output ports D ₁ , D ₂ , D ₃ , and D ₄ are connected to the pulse motor driver 81, and the excitation signals φ ₀ , φ ₁ , φ ₂ , and φ ₃ are output. When the signal "High" from the OR gate OR3 is input to the input port C ₁ , the second CPU 80 activates the registration motor M4 according to a predetermined program. When the signal "Low" is input from the OR gate OR3, the registration motor M4 is stopped and locked by the brake.

FIG. 6 shows a paper feeding / conveying operation. Here, a case where a plurality of sheets are continuously fed from the paper feed cabinet 50 will be described. First, when a copy start switch on an operation panel (not shown) is turned on and a copy start signal is issued, the main motor M1 and the vertical conveyance motor M2 are turned on. Next, the paper feed motor M3 is turned on, and the vertical conveyance roller clutch and the intermediate conveyance roller clutch are turned on. Feed motor M3 is turned off from the leading end of the sheet is detected by the paper feeding sensor SE1 after a time t _2. On the other hand, the exposure lamp 21 of the optical system 20 is preliminarily turned on based on the copy start signal, and the photosensitive drum 1
1 also starts rotating. The sheet fed from the sheet feed tray 51 is conveyed from the vertical conveyance path 55 to the registration roller pair 42 via the intermediate conveyance roller 41.

The leading edge of the fed sheet is the registration sensor S.
When detected at E3, off the vertical conveyance roller clutch and intermediate conveyance roller clutch after a time t _1. At this time,
The leading edge of the sheet projects into the nip portion of the registration roller pair 42, forms a predetermined amount of loop immediately before the roller pair 42, and stands by. The lower registration roller 42b is a registration motor M.
4 is in the OFF state, the rotation is stopped, and the upper registration roller 42a is rotated by the main motor M1 at the peripheral speed v ₁
Spinning at. At this time, the second CPU is controlled so that the registration lower roller 42b does not follow the rotation of the upper roller 42a.
Reference numeral 80 fixes the excitation phase of the registration motor M4 to perform brake control.

In FIG. 4A, the paper P is the registration roller pair 4
Immediately before entering 2 FIG. 4B shows a state in which the leading edge of the paper P has entered the nip portion of the registration roller pair 42, and the upper roller 42 a also rotates and the lower roller 42 also at this time.
b is stopped. Since the friction coefficient of the upper roller 42a is smaller than that of the lower roller 42b, the upper roller 42a
Causes the tip of the paper P to be biased in the direction of arrow c to rotate in a slip manner. Since the upper roller 42a having a small friction coefficient is rotated and the lower roller 42b having a large friction coefficient is stopped, the leading edge of the sheet P is well fitted into the nip portion and the sheet P is skewed. Correctly corrected. Furthermore, the paper P
Regardless of the difference in the paper thickness and the humidity, and the difference in the degree of wear of the rollers 42a and 42b, the entry position is stable, and the paper P is registered at the correct position (see FIG. 4B). Intermediate transport roller 41
Is turned off after the time t ₁ from when the registration sensor SE3 is turned on, the sheet P forms a loop just before the registration roller pair 42 by an amount corresponding to the time t ₁ .

On the other hand, in the optical system 20, the exposure lamp 21 is switched from the preliminary lighting to the main lighting, and the image exposure on the photosensitive drum 11 is started. Then, a synchronization signal is output from a third CPU (not shown) that controls the optical system 20. When the synchronization signal is turned on, each OR gate OR1, OR2
The output signal of OR3 becomes "High", the intermediate conveyance roller 41 and the vertical conveyance roller 56 are rotationally driven, and the registration motor M4 is turned on to lower the registration roller 42b.
Starts to rotate. As a result, the paper P is restarted to be conveyed toward the transfer position T (see FIG. 4C). At this time, the upper roller 42a continues to rotate. As described above, since the leading edge of the sheet P surely protrudes into the nip portion of the registration roller pair 42, the conveyance is restarted at the same time when the registration motor M4 is turned on. In other words, the timing of turning on the synchronization signal coincides with the timing of sheet re-conveyance, and at the transfer position T, the leading edge of the image forming area on the photoconductor drum 11 and the leading edge of the sheet coincide exactly.

[0024] The 1CPU70 the synchronization signal after it has been turned off, and outputs a signal "High" from the output port _{A 1, A 2, A 3} . With this, OR gates OR1, OR2, OR
3 maintains "High", and the registration roller 42b, the intermediate conveyance roller 41, and the vertical conveyance roller 56 continue to be in the ON state. The trailing edge of the paper has passed the registration sensor SE3,
When the sensor SE3 is turned off, the registration motor M4 is turned off after the lapse of time t ₄ , and the next sheet is ready to stand by. The time t ₄ corresponds to the time until the trailing edge of the sheet has passed through the registration roller pair 42 from the sensor SE3.

By the way, in the present embodiment, the paper feed roller 5
When the leading edge of the paper fed by 2 turns on a paper feed sensor SE1, stops the paper feed motor M3 after a time t _2. At time t _2, the leading end of the fed paper is the vertical conveyance roller 5
It is the time required to reach 6. The feeding of the second sheet is similarly controlled. However, at the time of feeding the third and subsequent sheets, the control for holding the sheet by the registration roller pair 42 is performed in parallel, so the time t ₂ is changed to t ₃ . Time t ₂ , t ₃
Is set according to the following equation. t ₃ = t ₂ + paper standby time

7 to 10 show the registration roller pair 4
2 shows a control procedure of the sheet registration operation according to 2. Here, in step S10, the count value of the resist counter is checked, and the following processing is performed according to the count value.

[0027] When the state counter is "1" (the initial state), after confirming the on-edge of the registration sensor SE3 in step S11, sets the time t ₁ to the timer T ₁ in step S12, the resist counter in step S13 Set to "2".

When the registration counter is "2", when it is confirmed in step S14 that the count of the timer T ₁ is completed, the intermediate conveying roller clutch is turned off in step S15, and the synchronization signal is turned on in step S16. wait.
When the synchronization signal is turned on, the intermediate conveyance roller clutch is turned on in step S17, and the registration motor M4 is turned on in step S18. Next, in step S19, the resist counter is set to "3".

[0029] When the resist counter is "3", upon registration sensor SE3 is confirmed to be turned off in step S20, sets the time t ₄ the timer T ₄ in step S21. Then, when it is confirmed in step S22 that the timer T ₄ has finished counting, the registration motor M4 is turned off in step S23. Next, in step S24, the resist counter is set to "1".

The sheet conveying apparatus according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the gist thereof. In particular, the upper registration roller 4
The timing for rotating 2a in the paper transport direction is as follows.
In addition to continuing the rotation during the paper transport mode as in the above embodiment, the paper is rotated from immediately before entering the nip portion of the registration roller pair until the end of the entry, or immediately before the synchronization signal is generated. You may do it. Further, in the paper transport mode, first, the lower roller 42b is also rotated together with the upper roller 42a, the rotation of the lower roller 42b is stopped immediately before the leading edge of the paper enters the nip portion of the rollers 42a and 42b, and then the lower roller 42b.
May be rotated again in response to the generation of the synchronization signal.

As a drive system for the registration rollers 42a and 42b, the registration lower roller 42b may be connected to the main motor M1 via a clutch or the like, and the drive timing may be controlled by turning the clutch on or off. Alternatively, a dedicated drive motor may be provided on the upper registration roller 42a.

Further, in the above embodiment, the registration motor M is stopped while the lower roller 42b is stopped so that the registration lower roller 42b does not follow the rotation of the upper roller 42a.
However, if the detent torque of the registration motor M4 is sufficiently large, the braking operation for locking the excitation phase is not necessary.

The peripheral velocities v ₁ and v ₂ of the registration rollers 42a and 42b are usually set to the same velocity as the system velocity v of the copying machine (v = v ₁ = v ₂ ). However, the peripheral velocity v ₁ of the upper roller 42a may be set to satisfy the relationship of v ₁ > v ₂ = v depending on the friction coefficient of the rollers 42a and 42b and the pressure contact force of the nip portion. Rather, the roller 42 at the leading edge of the paper
It is preferable that the peripheral speed v ₁ of the upper roller 42a is high in terms of stability of the entry of the a and 42b into the nip portion.

Further, the present invention can be applied to a digital type laser printer in which image information is transferred from a host computer or the like. Alternatively, the present invention can be applied to a sheet conveying device for winding a sheet around a drum with a full color printer or the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a copying machine provided with a sheet conveying device according to an embodiment of the present invention.

FIG. 2 is an elevational view showing the sheet conveying device.

FIG. 3 is a perspective view showing a drive system of a lower registration roller.

FIG. 4 is an explanatory diagram showing a sheet conveyance state by a pair of registration rollers.

FIG. 5 is a block diagram showing a control circuit of the copying apparatus.

FIG. 6 is a timing chart showing a paper feeding / conveying operation.

FIG. 7 is a flowchart showing a control procedure of registration operation.

FIG. 8 is a flowchart showing a control procedure of registration operation.

FIG. 9 is a flowchart showing a control procedure of registration operation.

FIG. 10 is a flowchart showing a control procedure of registration operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Copier main body 11 ... Photosensitive drum 20 ... Scanning optical system 42 ... Registration roller pair 42a ... Registration upper roller (low friction coefficient) 42b ... Registration lower roller (high friction coefficient) M1 ... Main motor M4 ... Registration motor

Claims (6)

[Claims] 1. A paper transporting device for temporarily stopping a transported paper and restarting the transport of the paper based on the generation of a synchronization signal, wherein a first roller having a low friction coefficient and a second roller having a high friction coefficient are provided. A pair of registration rollers that are in contact with each other, a drive unit that independently rotationally drives the first roller and the second roller, and rotationally drive the first roller in the paper transport direction,
A control device having an operation mode for stopping the rotation of the second roller, and a sheet transporting device. 2. The control means continues the rotation of the first roller during the paper transport mode, and when the synchronization signal is generated, the second means
The sheet conveying device according to claim 1, wherein the roller is rotated in the sheet conveying direction. 3. The control means rotates the first roller in the sheet conveying direction from immediately before the sheet enters the nip portion of the registration roller pair until the end of the sheet, and at least the second roller rotates the sheet when the synchronization signal is generated. The sheet conveying device according to claim 1, wherein the sheet conveying device is rotated in a conveying direction. 4. The control means rotates the first roller in the paper transport direction immediately before the synchronization signal is generated, and rotates the second roller in the paper transport direction when the synchronization signal is generated. 1. The sheet conveying device according to 1. 5. The sheet conveying device according to claim 1, 2, 3, or 4, wherein the driving unit rotates the first roller and the second roller at the same peripheral speed. 6. The sheet conveying device according to claim 1, wherein the driving unit rotates the first roller at a peripheral speed higher than that of the second roller. .