JP3259625B2 - Paper transport device - Google Patents

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 synchronization with the rotation of a photosensitive drum in an image forming apparatus such as an electrophotographic copying machine or a laser printer.

[0002]

2. Description of the Related Art Conventionally, as a paper conveying device in an electrophotographic copying machine, as described in JP-A-64-13348 and JP-A-5-5109, a sheet feeding unit in which sheets are stacked is described. The paper fed one by one is fed to a registration roller in a stopped state, and the leading end of the paper is brought into contact with a nip portion of the registration roller to form a loop at the leading end of the paper. The rotation of the registration roller is turned on based on the synchronization signal so that the leading end of the image forming area on the drum coincides with the transfer position.

[0003]

By the way, in this type of paper conveying apparatus, in addition to the function of correcting the skew of the paper, it is necessary that the leading edge of the paper and the leading edge of the image forming area correctly match at the transfer position. (Improving resist accuracy)
is important. For this reason, the registration roller must restart the conveyance of the sheet at an accurate timing based on the synchronization signal. However, if the paper is a slippery material, the registration roller is worn, or the humidity is low, the registration roller slips at the start of rotation, and the registration accuracy is reduced.

Therefore, in the above publication, a paper detection sensor is provided downstream of the registration roller in the conveyance direction, and the registration roller is determined based on the paper detection timing by the sensor, the paper conveyance time up to that time, the conveyance distance to the transfer position, and the like. It has been proposed to adjust the rotational speed of the motor. However, this countermeasure requires a separate sheet transport sensor, and also requires a control mechanism for calculating the rotational speed of the registration roller. Moreover, the paper detection sensor has a limit in detection accuracy, and it is difficult to obtain high registration accuracy.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sheet conveying apparatus which can resume sheet conveyance at a precise timing by a registration roller with a simple mechanism and control, and thereby improve registration accuracy. Is to do.

[0006]

In order to achieve the above object, a paper transport apparatus according to the present invention comprises a registration roller, a rotation driving means thereof, and a control means, and the control means performs control based on generation of a synchronization signal. When rotating the registration roller, the driving means is selectively used in a first control mode in which the rising speed of rotation is set to a normal speed or in a second control mode in which the rising speed of rotation is set lower than in the first control mode. Can be controlled. Paper is slippery or slippery (for example, low humidity, abrasion of registration rollers)
When the operator demands particularly high registration accuracy, the control means operates the driving means in the second control mode. In the second control mode, the registration roller is started up at a relatively low speed, so that slippage does not occur and the leading edge of the sheet is reliably gripped and the conveyance is started.
Therefore, the conveyance of the sheet is resumed at an accurate timing, and the registration accuracy is improved.

Further, in the paper transporting apparatus according to the present invention, the control means may control the registration roller at a predetermined timing based on the generation of the synchronization signal or at a predetermined timing based on the generation of the synchronization signal. The registration roller driving means can be selectively controlled in the second control mode in which the registration roller is slightly rotated immediately before the registration roller is rotated to pinch the leading end of the sheet to the registration roller. In the second control mode, the registration roller grips the leading edge of the sheet in advance. Therefore, the conveyance of the sheet is resumed at an accurate timing, and the registration accuracy is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a paper transport device according to the present invention will be described below with reference to the accompanying drawings. FIG.
1 shows an analog electrophotographic copying machine provided with a sheet conveying device according to an embodiment of the present invention.

A photosensitive drum 1 rotatably driven in the direction of arrow a is disposed substantially at the center of the main body of the copying machine. Around the periphery of the photosensitive drum 1, a charging charger 2, a developing device 3, a transfer charger 4,
A paper separation charger 5, a residual toner cleaner 6, and a residual charge eraser 7 are provided. The configuration and operation of these elements are well known, and description thereof is omitted.

The document table 10 is located at the top of the copier main body with an arrow b.
The original moves while being placed on the original table 10. The optical system 15 includes an exposure lamp 16 and a self-lens array 17, and transfers an image of a document on the document table 10 moving in the direction of arrow b to the photosensitive drum 1.
The upper position E is exposed and scanned. An actuator 11 is fixed to the lower surface of the document table 10. The actuator 11 operates the sensors SE <b> 1 and SE <b> 2 as the document table 10 moves. The sensor SE1 outputs an exposure start signal, and the sensor SE2 outputs a synchronization signal for determining the timing of transporting the sheet to the transfer position T as described later.

The paper transport device feeds and discharges paper to a paper feed roller 21, a registration roller 22, an air suction belt 23, a toner fixing device 24, and a tray 26 for feeding paper one by one from a paper feed tray 20. It is constituted by a roller 25. The rollers for transporting the paper are connected to a main motor (not shown) via a clutch, and are each driven to rotate at a predetermined timing. However, the registration roller 22 is independently driven by the stepping motor M, and its on / off timing and control of the number of rotations will be described later in detail. Further, the sensor SE3 is provided in the paper transport path.
And various other paper detection sensors. Sensor SE
Reference numeral 3 is for detecting a sheet immediately before the registration roller 22.

FIG. 2 shows the registration roller 22, the transfer position T
And the relationship between the exposure position E and the exposure position E. From the registration rollers 22 and the distance L ₀ to the transfer position T photosensitive drum 1 and the distance L ₁ that rotates from the exposure position E to the transfer position T is, L ₀ <L ₁
The relationship is set. The registration roller 22 conveys the sheet at a timing and speed at which the leading end of the sheet coincides with the leading end of the image forming area on the photosensitive drum 1 at the transfer position T based on the synchronization signal generated from the sensor SE2.

Next, the control of the registration roller 22 will be described with reference to the timing chart of FIG. When the print switch is turned on and the copying operation starts,
The feed roller 21 is turned on, and the first sheet is fed. After the sheet is detected by the sensor SE3, the sheet comes into contact with the nip portion of the registration roller 22 in a stopped state, and waits in a state where a loop is formed at the leading end. Sensor SE3
T ₁ when the feed roller 21 is turned off from the on-edge of
Is set to the time during which a required amount of loop is formed at the leading edge of the sheet.

When a time t ₂ elapses from the on-edge of the sensor SE3, the original table 10 starts moving, and the photosensitive drum 1
An image is formed thereon. When the sensor SE2 is turned on with the movement of the document table 10, the registration roller 22 is driven to rotate when the correction time t ₃ (the correction time t ₃ is changed by the modes 1 and 2 described below) elapses, and at the same time, The paper feed roller 21 also restarts rotation. Thus, the sheet is conveyed from the registration roller 22 to the transfer position T. At this time, the sheet feeding roller 21 is turned off in a relatively short time, and after the turning off, the sheet feeding roller 21 rotates following the sheet conveyed by the registration roller 22.

A motor M for driving the registration roller 22
Is controlled by the motor drive clock signal shown in FIG. This control is performed in one of the mode 1 in which the rotation start-up speed is set to the normal speed and the mode 2 in which the rotation start-up speed is set to be lower than the mode 1. That is, if the paper has a normal thickness and the wear of the registration roller 22 has not progressed, the registration roller 22 is started up in the normal mode 1. However, when the registration roller 22 is in a state in which the registration roller 22 easily slips, for example, when the paper is thin paper, the wear of the registration roller 22 is large, or the humidity is low, the mode 2 is executed, and the registration roller 22 starts up at a low speed. By the control in the mode 2, the registration roller 22 reliably grips the leading edge of the sheet and restarts the conveyance.

FIG. 4 shows a change in the number of revolutions of the registration roller 22 at the time of startup in modes 1 and 2. Mode 2
In this case, if the registration motor M is turned on at the same timing as in Mode 1, the time required for the leading edge of the paper to reach the transfer position T is delayed because the rise speed of the registration roller 22 is low. Therefore, it is necessary to change the correction time t ₃ between mode 1 and mode 2. For example, if the mode 1, the correction time t ₃ to 20 ms, mode 2, the correction time t ₃
Is set to 10 ms, and control is performed such that the leading edge of the sheet reaches the transfer position T at the same timing in both modes 1 and 2.

On the other hand, the registration roller 22 is provided with a sensor SE3.
There are off when turned off (the paper trailing edge sensor SE3 is detected) to time t ₄ has elapsed since. At this time, the rear end of the sheet has completely passed through the registration roller 22. Further, when the time t ₅ from off sensor SE3 has elapsed, the on-paper feed roller 21, the second sheet is fed, the same control as described above is executed.

In this copying machine, mode 1 is normally selected. Mode 2 is selected in the following cases. (1) A switch for inputting that the paper is thin paper is provided on the operation panel, and mode 2 is selected based on the switch being turned on. Alternatively, a paper thickness detecting means is provided in the paper transport path,
Mode 2 is automatically selected when thin paper is detected.

(2) A resist stabilization selection switch is provided on the operation panel so that mode 2 can be selected at the discretion of the operator. Note that even in the case of (1), the thin paper input switch functions as a resist stable selection switch. (3) When the paper size and type are set on the operation panel, the control means determines whether or not the paper is slippery. If the paper is slippery, the mode 2 is automatically selected.

(4) A durability counter for counting the number of times the registration roller 22 has been used is provided. When a predetermined count value is reached, it is determined that the registration roller 22 has become worn and slippage has occurred, and mode 2 is automatically selected. I do. This counter can be replaced with a copy number counter. (5) A humidity sensor is provided in the copying machine, and if the humidity is low, the mode 2 is automatically set. Mode 2 may be selected by appropriately combining the above conditions.

FIG. 5 shows a control circuit of the copying machine.
PU, 51 is a switch matrix composed of numeric keys and the like on the operation panel, 52 is a drive circuit of the registration motor M, and 53 is a display for displaying the number of copies on the operation panel. SW1 is a thin paper input switch. When the switch SW1 is turned on, the mode 2 is selected / selected.
Be executed. Note that, instead of the switch SW1, the above-described paper thickness detecting means, a resist stability selection switch, a resist roller durability counter, or a humidity sensor may be provided.

Next, a first example of the control of the copying machine will be described with reference to the flowcharts of FIGS. 6 and 7 show a main routine of the CPU 50. When the power is turned on and the program starts, first, in step S1, C
The PU 50 is initialized and each device is set to an initial state. Next, the internal timer is set to a predetermined value in step S2, and the control timer is counted in step S3. In step S4, the count value of the main counter is checked, and the following process is executed based on the count value (counts "0" to "4" cyclically).

If the main counter is "0", blank display processing is performed in step S5, input processing from the switch matrix 51 is performed in step S6, and step S7 is performed.
Set the display data on the operation panel with. When the main counter is "1", display processing of the hundreds digit on the display 53 is performed in step S8, and mode-specific processing according to the operation mode of the copying machine is performed in step S9.

When the main counter is "2", the display process of the tens digit of the display 53 is performed in step S10,
At 11, a jam is detected, and at step S12, a trouble is detected. If the main counter is "3", step S
In step 13, the process of displaying the first digit of the display 53 is performed, in step S14, AIDC control, that is, automatic image density control is performed, and in step S15, toner empty determination control is performed.

When the main counter is "4", the process of turning on and off the various display LEDs on the operation panel is performed in step S16, the process of inputting from various keys on the operation panel is performed in step S17, and the process of the fixing unit 24 is performed in step S18. Adjust the temperature.

When the above-described subroutines are completed, SCP processing is performed in step S20, and registration processing by the registration roller 22 is performed in step S21. next,
In step S22, the main counter is incremented,
In step S23, the process returns to step S3 after the end of the internal timer.

FIG. 8 shows a subroutine of the input process executed in step S6. In step S31, it is determined whether the thin paper input switch SW1 is on or off. If it is on, mode 2 is set in step S32, and if it is off, mode 1 is set in step S33. Next, other processing is performed in step S34, and the process returns to the main routine.

FIGS. 9 and 10 show a subroutine of the registration process executed in step S21. here,
First, in step S41, the count value of the registration counter is checked, and the following processing is executed based on the count value.

[0029] When the resist counter is "0", is set based on the mode 1 or mode 2 the timer T ₃ has already been selected for counting the correction time t ₃ at step S42. Next, to confirm the on-edge of the sensor SE2 at step S43, a timer is started T ₃ in step S44. Further, when the end of the timer T ₃ at step S45 is confirmed, (set to "1" in this case) incrementing the resist counter step S52 to.

When the registration counter is "1", the registration roller drive signal is turned on in step S46, the start-up process is executed in step S47, and the registration counter is incremented (here, set to "2") in step S52. ). If the registration counter is "2", a constant speed frequency is output as a clock signal to the registration motor drive circuit 52 in step S48, and step S49 is performed.
In Check out on-edge sensor SE3, namely, the trailing edge of the sheet passes through the detection point of the sensor SE3, a timer is started T ₄ for counting time t ₄ at step S50. When the completion of the timer T ₄ is confirmed in step S51, the resist counter incremented in step S52 (in this case, set to "3") to.

When the registration counter is "3", the registration roller drive signal is turned off in step S53, and the frequency of the clock signal is set to "0" in step S54. Next, in step S55, the registration counter is set to "0".
Reset to.

FIG. 11 shows a subroutine for setting the correction time executed in step S42. Here, when confirming that the mode 1 in step S61 is set, the timer is set T ₃ to 20ms in step S62. Further, the mode 2 in step S63 to confirm that it is set, the timer T ₃ in step S64 1
Set to 0 ms. That is, in the mode 2, the delay of sheet conveyance due to the low-speed driving of the rise of the registration roller 22 is corrected by slightly advancing the drive-on timing.

FIG. 12 shows a subroutine of the start-up process executed in step S47. Here, if it is confirmed that the mode 1 is set in the step S71, the start-up data in the mode 1 is outputted in a step S72, and the rotation of the registration roller 22 is started at a normal speed. If it is confirmed in step S73 that the mode 2 is set, the start-up data in the mode 2 is output in step S74, and the rotation of the registration roller 22 is started up at a low speed.

Next, a second example of control will be described with reference to FIGS. Here, as shown in FIG. 13, the start-up of the registration roller 22 is processed in one of the mode 1 for driving at a normal speed and the modes 2, 3, and 4 for driving at a lower speed. The criteria for selecting the modes 1 to 4 are the thickness of the paper, the degree of wear of the registration roller 22 (substituted by the number of copies), and humidity.

Specifically, as shown in FIG. 14, when plain paper is used (NO in step S101), the number of copies is less than 100,000 (YES in step S102), and the humidity is less than 30%. When high (step S1
03; YES), mode 1 is set in step S104. Even when plain paper is used, if the number of copies is 100,000 or more (N in step S102)
O) When the humidity is higher than 30% (step S10)
6 is YES), mode 2 is set in step 107,
If the humidity is 30% or less (N in step S106)
O) In step S109, mode 3 is set.

On the other hand, when thin paper is used (step S1)
01, YES), if the number of copies is less than 100,000 (YES in step S105) and the humidity is higher than 30% (YES in step S106), mode 2 is set in step S107, and the humidity is 30%. If not (NO in step S106), the mode is set to mode 3 in step S109. Thin paper and 1 copy
If it is not less than 00,000 (N in step S105)
O) When the humidity is higher than 30% (step S10)
If YES in step S108, mode 3 is set in step S109, and if the humidity is 30% or less (N in step S108).
O), Mode 4 is set in step S110.

The start-up process of the registration roller 22 is shown in FIG.
5, the modes set in steps S121 to S124 are determined.
In steps S125 to S128, start-up data corresponding to each of the modes 1 to 4 is output.

Next, a third example of control will be described. This third
In the example, in addition to the mode 1, the control can be performed in the advance mode in which the registration roller 22 is slightly rotated just before the registration roller 22 is rotated for synchronization so that the leading end of the sheet is pinched by the registration roller. The rotation speed at the time of advance is preferably low as in the modes 2 to 4,
For the paper transport after the advance feeding, the same start-up processing as in mode 1 is executed. The advance mode is executed under the same conditions as those in the above modes 2 to 4, that is, when the registration roller 22 is in a state of being easily slipped.

However, in the advance mode, if the sheet conveyance by the registration rollers 22 is resumed at the same timing as in the mode 1 after the advance, the timing at which the leading edge of the sheet reaches the transfer position T is the same as the mode 1 in the advance length. Be faster. Therefore, in the advance mode, it is necessary to set the correction time t ₃ later by a time corresponding to the advance length.

FIG. 16 shows a subroutine for setting a correction time in the third example of the control. Here, step S1
Determining whether the first operating mode 51, when the normal mode 1 it is set, the timer is set T ₃ to 20ms in step S153. This is the same correction time as in step S62. On the other hand, if the first-out mode is set, the timer is set T ₃ to 30ms in step S152. The difference 10 ms is a correction value for the advance of the sheet.

The paper transporting apparatus according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention. For example, the present invention can be applied to a digital laser printer in which image information is transferred from a host computer or the like. Alternatively, the present invention can be applied to a paper transport device for winding a paper around a drum by 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 explanatory diagram showing a relationship between a registration roller, an exposure position, and a transfer position.

FIG. 3 is a timing chart showing a resist operation in a first control example.

FIG. 4 is a graph showing a change in the number of rotations of the roller when the registration operation is started in the first control example.

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

FIG. 6 is a flowchart showing a main routine in a first control example.

7 is a flowchart showing a main routine in a first control example, and is a continuation of FIG. 6;

FIG. 8 is a flowchart illustrating a subroutine of an input process in a first control example.

FIG. 9 is a flowchart illustrating a subroutine of a registration process in the first control example.

FIG. 10 is a flowchart showing a subroutine of a registration process in the first control example, and is a continuation of FIG. 9;

FIG. 11 is a flowchart illustrating a subroutine for setting a correction time in a first control example.

FIG. 12 is a flowchart showing a subroutine of a startup process in the first control example.

FIG. 13 is a graph illustrating a change in the number of rotations of the roller when the registration operation is started in the second control example.

FIG. 14 is a flowchart illustrating a subroutine of an input process in a second control example.

FIG. 15 is a flowchart illustrating a subroutine of a startup process in a second control example.

FIG. 16 is a flowchart showing a subroutine for setting a correction time in a third control example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum 22 ... Registration roller 50 ... CPU 52 ... Registration motor drive circuit SE2 ... Timing sensor SW1 ... Thin paper input switch M ... Registration motor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-116812 (JP, A) JP-A-6-336353 (JP, A) JP-A-62-131642 (JP, A) JP-A-4- 134358 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B65H 9/14

Claims (6)

(57) [Claims] A sheet transport device for temporarily stopping the transported sheet, forming a loop at the leading end of the sheet, and resuming the transport of the sheet based on the generation of a synchronization signal; A registration roller for resuming the conveyance of the sheet after stopping, a driving unit for rotationally driving the registration roller, and when the registration roller is rotated based on the generation of a synchronizing signal, the rising speed of the rotation is set to a normal speed. Control means for selectively controlling the driving means in a first control mode for setting the rotation speed or a second control mode for setting the rising speed of rotation to be lower than the first control mode. Paper transport device. 2. A sheet conveying device for temporarily stopping a conveyed sheet, forming a loop at the leading end of the sheet, and resuming the conveying of the sheet based on the generation of a synchronization signal. A registration roller for restarting the conveyance of the sheet after stopping, a driving unit for driving the registration roller to rotate, a first control mode or a synchronization signal for rotating the registration roller at a predetermined timing based on generation of a synchronization signal Control means capable of selectively controlling the drive means in a second control mode in which the registration roller is slightly rotated immediately before the registration roller is rotated at a predetermined timing based on the occurrence of the sheet, and the leading end of the sheet is held between the registration rollers. And a paper transport device comprising: And a means for inputting or detecting whether or not the sheet is slippery. When the input or detection is made that the sheet is slippery, the control means controls the driving means in a second control mode. The method according to claim 1 or 2, wherein
Paper transport device according to the above. 4. The apparatus according to claim 1, further comprising means for counting the number of times the timing roller has been used, wherein the control means controls the driving means in a second control mode after reaching a predetermined number of times. Alternatively, the sheet transport device according to claim 2. 5. The apparatus according to claim 1, further comprising humidity detecting means, wherein when the detected humidity is equal to or less than a predetermined value, said control means controls said driving means in a second control mode. Paper transport device according to the above. 6. The sheet transport device according to claim 1, further comprising the second control mode selection unit.