JP3666833B2 - Sheet separating apparatus and image forming apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet separating apparatus for separating and feeding sheets one by one in a sheet feeding device of an image forming apparatus such as a printer, a copier, or a fax machine.
[0002]
[Prior art]
FIG. 12 shows an example of a conventional sheet separating apparatus. In the figure, the pickup roller 1 moves downward in the vertical direction so as to contact the sheets 5 stacked in the tray 7 by turning on a pickup solenoid (not shown). One or more stacked sheets 5 are conveyed toward the nip portion of the feed roller 2 by the pickup roller 1 driven for a predetermined time. The pickup roller 1, the feed roller 2, the reverse roller 3, and the grip roller pair 4 are all driven by a common transport motor (not shown).
[0003]
The feed roller 2 is given a conveyance driving force via a feed roller clutch (not shown). The reverse roller 3 is driven via a torque limiter (not shown) so that the driving force is applied in the direction opposite to the rotation direction of the feed roller 2. For this reason, the uppermost sheet in contact with the feed roller 2 advances in the conveying direction, and at the same time, the second and subsequent sheets are pushed back toward the tray 7 by the returning action of the reverse roller 3. In a state where only one sheet is sandwiched in the nip portion, the reverse roller 3 is in a rotating state while applying a load torque set by the torque limiter to the sheet.
[0004]
The sheets 5 thus separated into one sheet are conveyed to the image forming unit by the grip roller pair 4. Further, after the conveyance by the grip roller pair 4 is performed, the feed roller clutch is turned off, and the feed roller 2 and the reverse roller 3 are rotated along with the conveyance of the sheet to avoid sheet tension and sagging. .
[0005]
Next, a schematic sheet separation condition at the nip portion will be described with reference to FIG. The conveying force for the sheet is determined by the friction coefficient μr between the roller and the sheet, the friction coefficient μp between the sheets, the pressing contact force PB, and the return torque TA shown in FIG. FIG. 4B is a graph showing sheet separation conditions based on these parameters. In this graph, if there are conditions of the pressing contact force PB and the return torque TA in the hatched area in the figure formed by two relational expressions PB = 1 / μp · TA and PB = 1 / μr · TA, the sheet It will be separated one by one. When the pressing contact force PB is low and the return torque TA is large, non-feeding of the sheet occurs, and when the pressing contact force PB is large and the return torque TA is small, double feeding occurs.
[0006]
[Problems to be solved by the invention]
On the other hand, the friction coefficients μp and μr vary depending on various conditions such as sheet type, temperature, humidity, and stacking condition. Further, the set values of the return torque TA and the pressing contact force PB also vary due to component variations and the like. For this reason, as shown in FIG. 14, the appropriate region for sheet separation formed by the above two relational expressions fluctuates. In the conventional sheet separating apparatus shown in FIG. There was a case where feed or double feed occurred.
[0007]
On the other hand, there has been proposed a detecting means for detecting that a sheet has been conveyed in the separation region, wherein the pressing contact force is reduced before the detection, and the pressing contact force is largely controlled after the detection (Japanese Patent Application Laid-Open (JP-A)). Sho 63-171736).
[0008]
However, in the above conventional technique, the pressing contact force only changes in a binary manner, and the pressing contact force during the separation operation does not change. Therefore, there has been a problem that it is impossible to cope with the poor separation caused by the change in the friction coefficient of the sheet.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet separating apparatus that can reliably perform separation without causing non-feed even when the condition of stacked sheets changes.
[0010]
An object of the present invention is to provide a sheet separating apparatus capable of reliably separating the above-described sheets and preventing the sheet double feed.
[0011]
An object of the present invention is to prevent a decrease in feeding rate when a large number of sheets are separated and fed continuously.
[0012]
An object of the present invention is to prevent a separation failure caused by a change in sheet characteristics over time without lowering a feeding rate.
[0013]
An object of the present invention is to prevent a separation failure caused by a change in sheet characteristics caused by a new sheet stacking without lowering the feeding rate.
[0014]
[Means for Solving the Problems]
The sheet separating apparatus according to the first aspect of the present invention includes a conveying roller that is driven in a sheet feeding direction, and a separating roller that is opposed to the conveying roller and is driven in a direction opposite to the feeding direction. A pressure contact force adjusting means for changing a pressure contact force between the transport roller and the separation roller, and detecting whether the sheet is properly fed by the transport roller. A sheet detecting unit, and when the predicted time elapses from the start of driving of the conveying roller and the separating roller until the sheet is correctly separated and the leading end of the sheet arrives at a position detected by the sheet detecting unit. depending on whether the detection means has detected the sheet, it controls the pressure contact force adjustment unit, the sheet is not properly fed by the sheet detecting means If it is the cross-sectional, characterized in that to increase the pressure contact force between the conveying roller and the separation roller.
[0015]
According to the second aspect of the present invention, the pressing contact force between the conveying roller and the separation roller is set to a value that is small enough to prevent the sheet from being fed properly at the start of sheet feeding, and the value is the sheet detecting means. The pressure contact force adjusting means is controlled so as to maintain the value at that time until it is gradually increased until it is determined that the sheet has been properly fed and then separation of the sheet is completed. To do.
[0016]
According to the third aspect of the present invention, when the sheet feeding is not performed for a predetermined time or more, the maintained pressing contact force is released, and the pressing contact force with respect to the sheet is reset. It is characterized by.
[0017]
According to the fourth aspect of the present invention, the apparatus includes an operation detection unit that detects that an operation necessary for the sheet stacking operation on the sheet stacking position has been performed, and the operation detection unit performs an operation necessary for the sheet stacking operation. When it is detected that the operation has been performed , the maintained pressing contact force is released, and the pressing contact force for the next sheet is reset.
[0018]
The image forming apparatus according to claim 5 is characterized by using the sheet separating apparatus according to any one of claims 1 to 4 .
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view of a sheet separation apparatus according to a first embodiment of the present invention. In this embodiment, the same components as those of the conventional sheet separating apparatus shown in FIG. In the figure, in addition to the conventional apparatus configuration shown in FIG. 12, the sheet separating apparatus of the present invention further includes a pressing contact force adjusting means including a pressing lever 12, a pressing spring 13, and a linear actuator 14. .
[0020]
The pressing contact force adjusting means is for adjusting the pressing contact force between the two rollers by moving the reverse roller 3 toward and away from the feed roller 2. The L-shaped pressure lever 12 has a reverse roller 3 pivotally supported at one end and the other end connected to a linear actuator 14 via a pressure spring 13. By the operation of the linear actuator 14, the pressure lever 12 rotates around the fulcrum 12 a to change the pressing contact force of the reverse roller 3 against the feed roller 2.
[0021]
In the figure, 6 is a paper sensor for detecting whether or not the sheet is properly fed by detecting the leading edge of the sheet 5. That is, when a predicted time Tb from when the pickup roller 1 is activated until the leading edge of the sheet 5 is detected by the paper sensor 6 is set, the sheet sensor 6 does not detect the sheet even if the predicted time Tb elapses. It is determined that the sheet is not fed properly.
[0022]
FIG. 2 shows a flowchart of the operation in the first embodiment. The operation of the sheet separating apparatus will be described below according to this flowchart. When a paper feed command is output from the control unit of the image forming apparatus (not shown), a conveyance motor that drives each roller is activated (step 1), the feed clutch and the pickup solenoid are turned on, and the sheet 5 is conveyed by the pickup roller 1. Is started (step 2). After the pickup solenoid is driven Ta for a predetermined time (step 3), the pickup solenoid is stopped, and the sheet feeding by the pickup roller 1 is finished (step 4). The leading edge of the sheet 5 is fed to the nip portion between the feed roller 2 and the reverse roller 3 by the pickup roller 1, and further fed by the feed roller 2 while being separated into one sheet by the reverse roller 3.
[0023]
Next, the control unit reads the output of the paper sensor 6 when the predicted time Tb until the leading edge of the sheet arrives at the paper sensor 6 when the sheet is correctly separated (steps 5 and 6). If the sheet sensor 6 does not detect the leading edge of the sheet at that time, it is determined that the sheet is not being fed properly, the linear actuator 14 is driven, and the pressure between the feed roller 2 and the reverse roller 3 is determined. The contact force is increased and separation conveyance is performed again (step 7). As a result, as shown in FIG. 3, the setting (point A in the figure) in the non-feed condition area shifts to the separation condition area (point B in the figure), and the sheet 5 is correctly separated into one sheet and fed. It will be.
[0024]
If the sheet sensor 6 detects the sheet when the estimated time Tb has elapsed, it is determined that the sheet has been properly conveyed, the feed roller clutch is turned off, and the feed roller 2 is stopped ( Step 8). After the feed roller clutch is turned off, the trailing edge of the sheet is detected by the sheet sensor 6 (step 9), and if it is detected, the linear actuator 14 is returned to the initial state (step 10). This operation is performed by continuously driving the linear actuator 14 in the reverse direction and forcibly returning it to the home position. When sheets are continuously fed, the above operation is repeated (step 11). Otherwise, the transport motor is stopped and the feeding operation is terminated (step 12).
[0025]
Next, a second embodiment of the sheet separating apparatus of the present invention will be described. FIG. 4 is a schematic side view of the sheet separating apparatus according to the second embodiment. In the figure, the same components as those of the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted. In the present embodiment, the sheet separating apparatus further includes two paper sensors 10 and 11. The paper sensors 10 and 11 are installed on a conveyance path between the feed roller 2 and the grip roller pair 4 and detect the leading edge of the sheet 5 after passing through the feed roller 2. These paper sensors 10 and 11 can detect the non-feeding of the sheet at a point earlier than the paper sensor 6.
[0026]
In this embodiment, the pressing contact force PB between the feed roller 2 and the reverse roller 3 is changed together with the position of the sheet detected by each of the paper sensors 10 and 11. FIG. 5A is a graph showing the relationship between the pressing contact force PB and the sheet conveying position. As shown in the figure, the linear actuator is driven from the time when the leading edge of the sheet arrives at the paper sensor 11 by the action of the pickup roller 1, and the pressing contact force PB is gradually increased. Assuming that the pressing contact force Pp before driving the linear actuator is at point P as shown in FIG. 4B, when the pressing contact force becomes Pq by driving the linear actuator, the operating point is separated from the non-feed area. Move to point Q on the boundary line of the region. As a result, the sheet 5 stopped in the non-feed state in the separation unit starts to be conveyed. When the sheet 5 is conveyed and the leading edge thereof is detected by the paper sensor 10, the linear actuator is stopped after a lapse of a predetermined time Δt, and the pressing contact force Pr at the point R capable of stable feeding is maintained.
[0027]
As described above, the pressing contact force PB is initially set so as to be in the non-feeding region in advance, and the pressing contact force is gradually increased, so that the separation can be reliably performed even when the sheet separation characteristic changes to the double feeding side. It becomes possible to automatically adjust and select a low pressing contact force that is a possible condition.
[0028]
FIG. 6 shows a flowchart of the operation in the second embodiment. The operation of the sheet separating apparatus will be described below according to this flowchart. When a paper feed command is output from the control unit of the image forming apparatus (not shown), a conveyance motor that drives each roller is activated (step 1), the feed clutch and the pickup solenoid are turned on, and the sheet 5 is conveyed by the pickup roller 1. Is started (step 2). When the paper sensor 11 detects the leading edge of the sheet 5 (step 3), the pickup solenoid is stopped and the sheet feeding by the pickup roller 1 is finished (step 4). At this time, the linear actuator 14 is simultaneously operated to gradually pressurize the reverse roller 3 (step 4). When the pressure contact force between the feed roller 2 and the reverse roller 3 is gradually increased by driving the linear actuator 14, the sheet 5 starts to be conveyed at a certain point. When the sheet 5 is conveyed and detected by the paper sensor 10 (step 5), after waiting for a predetermined time Δt (step 6), the linear actuator 14 is stopped and the pressing contact force at the stop point is maintained (step 7).
[0029]
Next, when the leading edge of the sheet is detected by the paper sensor 6 (step 8), the feed roller clutch is turned off and the drive of the feed roller 2 is stopped (step 9). When the trailing edge of the sheet is detected by the paper sensor 11 (step 10), the linear actuator 14 is reset (step 11). Further, when the trailing edge of the sheet is detected by the sheet sensor 6 (step 12), it is determined whether or not the sheet is continuously fed (step 13). The operation is repeated, otherwise the transport motor is stopped and the feeding operation is terminated (step 14).
[0030]
Next, a third embodiment of the sheet separating apparatus of the present invention will be described. In the second embodiment, the pressing contact force is automatically adjusted for each sheet separation operation. For this reason, the continuous feeding rate is lowered only for the time required for the automatic adjustment. By the way, the separation condition of the sheet material varies little for each sheet of the same kind and the same pack loaded in the same environment. In view of this point, in the present invention, when the sheet is continuously conveyed, the separation conveyance is performed without performing the subsequent automatic adjustment while maintaining the initially adjusted pressing contact force. The configuration of the sheet separating apparatus in the present embodiment is the same as that of the second embodiment shown in FIG.
[0031]
Hereinafter, the separating and conveying operation in the present embodiment will be described with reference to the flowchart shown in FIG. In the present embodiment, the separation and conveyance of the first sheet is the same as the operation in the second embodiment (steps 1 to 11). When the conveyance of the first sheet is completed, it is determined whether or not the next sheet feeding is continuously performed (step 12). If continuous sheet feeding is performed, the process is not returned to the first process. Execute along steps 13-18. That is, the feed clutch and the pickup solenoid are turned on to start feeding the next sheet (step 13). Here, the pressing contact force is not adjusted by the linear actuator. Next, when the leading edge of the sheet is detected by the paper sensor 6 (step 14), the feed roller clutch is turned off and the drive of the feed roller 2 is stopped (step 15). When the trailing edge of the sheet is detected by the paper sensor 11 (step 16) and the trailing edge of the sheet is further detected by the paper sensor 6 (step 17), it is determined whether or not to continuously feed sheets. (Step 18). When continuous paper feeding is performed, the operations in steps 13 to 17 are repeated. Otherwise, the transport motor is stopped (step 19), the linear actuator is also reset, and the feeding operation is finished ( Step 20).
[0032]
In this embodiment, an example of omitting readjustment of the pressing contact force when continuously conveying sheets without stopping the conveyance motor has been described. Further, for example, pressing is performed only at the first sheet conveyance immediately after power-on. You may comprise so that contact force may be adjusted automatically, and you may provide the automatic adjustment mode which can be started by manual operation.
[0033]
Next, a fourth embodiment of the sheet separating apparatus of the present invention will be described. It is known that the separation characteristics of the sheets stacked on the tray gradually change depending on the room temperature, humidity, weight, and the like. In the present invention, prior to the start of the sheet separating operation, the standby time Tc is measured, and it is determined whether or not to automatically adjust the pressing contact force according to the standby time Tc. Thereby, it is possible to prevent the occurrence of non-feed and multi-feed with the passage of time without lowering the continuous transport rate.
[0034]
Hereinafter, the operation in the present embodiment will be described with reference to the flowchart shown in FIG. In this embodiment, after the conveyance motor that drives each roller based on a paper feed command is turned on (step 1), when the sheet is placed in the tray for a predetermined waiting time Tc or longer, the pressing contact In order to reset the force, the processing from step 3 to step 14 is executed. The processing performed in steps 3 to 14 is the same as the processing shown in FIG.
[0035]
If the sheet is placed in the tray for the waiting time Tc or less, the pressing contact force set in the previous process is maintained, and steps 15 to 20 are executed without resetting. The That is, the feed clutch and the pickup solenoid are turned on to start feeding the next sheet (step 15). Here, the pressing contact force is not adjusted by the linear actuator. Next, when the leading edge of the sheet is detected by the paper sensor 6 (step 16), the feed roller clutch is turned off and the driving of the feed roller 2 is stopped (step 17). When the trailing edge of the sheet is detected by the paper sensor 11 (step 18) and the trailing edge of the sheet is further detected by the paper sensor 6 (step 19), it is determined whether or not to continuously feed sheets. (Step 20). When continuous paper feeding is performed, the operations of steps 15 to 19 are repeated. Otherwise, the transport motor is stopped (step 21), and the feeding operation is ended.
[0036]
Next, a fifth embodiment of the sheet separating apparatus of the present invention will be described. The change in the separation characteristics of the stacked sheets becomes prominent when a sheet of another type or another storage state is newly stacked. In the present invention, the opening / closing of the cover that covers the stacked sheets is detected, and when the opening / closing is performed, it is determined that the sheet has been replaced, and the pressing contact force is reset when the next sheet is conveyed. That is, as shown in FIG. 9, the switch 23 is arranged at the sheet insertion opening of the copying machine main body 22 so that when the cover 21 is closed, the convex portion 24 provided on the cover side presses the switch 23. .
[0037]
FIG. 10 is a flowchart of the operation in this embodiment. In the figure, it is determined whether or not the switch 23 has been pressed (step 2) after the transport motor that drives each roller is turned on based on a paper feed command (step 1). If the switch 23 is pressed, it is determined that the sheet has been exchanged, and the processing from step 3 to step 14 is executed in order to reset the pressing contact force. The processing performed in steps 3 to 14 is the same as the processing shown in FIG. If the switch 23 is not pressed, it is determined that the sheet is not exchanged, the pressing contact force set in the previous process is maintained, and steps 15 to 20 are performed without resetting. Executed. The processing performed in steps 15 to 20 is the same as the processing in steps 15 to 20 in FIG. Thereby, it is possible to prevent the occurrence of non-feed and multi-feed with the passage of time without lowering the continuous transport rate.
[0038]
In each of the above embodiments, each control of the paper sensors 6, 10, 11, switch 23, the conveyance motor that drives each roller, the pickup solenoid, the feed roller clutch, and the linear actuator 14 is controlled by a one-chip microcomputer as shown in FIG. Can be realized.
That is, when the sheet separating apparatus according to the present invention determines that the sheet is not fed properly, it performs control to increase the pressing contact force, and does not cause non-feed even if the sheet condition changes. Ensure separation. In addition, by gradually increasing the pressing contact force from the non-feeding state, once the sheet is separated and transported, control to maintain the pressing contact force and continue the separation operation is performed. Also prevents the occurrence of. Further, the maintained pressing contact force is used as a pressing contact force for subsequent continuous sheet separation, so that the time required for the control for obtaining the pressing contact force is reduced and the feeding rate is improved. In addition, if the sheet is not fed properly, the pressing contact force that has been maintained is released and reset, resulting in changes in sheet characteristics such as temperature and humidity over time. The separation failure is prevented without lowering the feeding rate. Furthermore, when a new sheet stacking is performed, control is performed again to obtain a pressing contact force, and separation defects caused by changes in the sheet material characteristics accompanying the new sheet stacking are reduced. Prevents without lowering.
[0039]
【The invention's effect】
As described above, since the present invention controls to increase the pressing contact force when it is determined that the sheet is not properly fed, the condition of the stacked sheets changes. However, there is an effect that separation can be surely performed without causing non-feed.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a sheet separating apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing an operation in the first embodiment.
FIG. 3 is a graph showing a relationship between a pressing contact force and a return torque in the first embodiment.
FIG. 4 is a schematic side view of a sheet separating apparatus according to a second embodiment.
5A is a graph showing the relationship between the pressing contact force and the sheet conveying position, and FIG. 5B is a graph showing the relationship between the pressing contact force and the return torque in the second embodiment.
FIG. 6 is a flowchart showing an operation in the second embodiment of the sheet separating apparatus of the present invention.
FIG. 7 is a flowchart showing the operation of the third embodiment of the sheet separating apparatus of the present invention.
FIG. 8 is a flowchart showing an operation in the fourth embodiment of the sheet separating apparatus of the present invention.
FIG. 9 is a perspective view of a sheet insertion port of a copying machine according to a fifth embodiment of the sheet separating apparatus of the present invention.
FIG. 10 is a flowchart showing an operation in the fifth embodiment.
FIG. 11 is a diagram showing a one-chip microcomputer used for the control of the present invention.
FIG. 12 is a schematic side view of a conventional sheet separating apparatus.
13A is a diagram for explaining a force acting on a nip portion, and FIG. 13B is a graph showing a relationship between a pressing contact force and a return torque in the nip portion.
FIG. 14 is a correspondence diagram of FIG. 13B for explaining a change in the separation region due to a change in condition.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pickup roller 2 Feed roller 3 Reverse roller 4 Grip roller pair 5 Sheet 6 Paper sensor 7 Tray 10 Paper sensor 11 Paper sensor 12 Pressure lever 13 Pressure spring 14 Linear actuator 21 Cover 22 Copying machine main body 23 Switch 24 Convex part

Claims (5)

A sheet separating apparatus comprising: a conveying roller that is driven in a sheet feeding direction; and a separation roller that is opposed to the conveying roller and is driven in a direction opposite to the feeding direction. A pressing contact force adjusting means for changing the pressing contact force between the sheet and a sheet detecting means for detecting whether or not the sheet is properly fed by the conveying roller, and starting driving of the conveying roller and the separation roller. The pressing contact force depends on whether or not the sheet detecting means detects the sheet when a predicted time elapses until the sheet is correctly separated and the leading end of the sheet arrives at a position detected by the sheet detecting means. controls adjustment means, when the sheet is determined not to be properly fed by the sheet detecting means, between the conveying roller and the separation roller Sheet separating apparatus characterized by increasing the pressure contact force.   The pressing contact force between the conveying roller and the separation roller is set to a value that is small enough that the sheet is not fed properly at the start of sheet feeding, and the value is set by the sheet detecting unit. 2. The sheet separating apparatus according to claim 1, wherein the pressure contact force adjusting means is controlled so as to be gradually increased to a time point at which the determination is made and thereafter to maintain the value at the time point until the separation of the sheet is completed. 3. The sheet according to claim 2 , wherein when the sheet is not fed for a predetermined time or more, the maintained pressing contact force is released, and the pressing contact force is reset on the sheet. Separation device. When an operation detecting means for detecting that an operation necessary for the sheet stacking operation on the sheet stacking position has been performed is detected, and the operation detecting means detects that an operation necessary for the sheet stacking operation has been performed. 4. The sheet separating apparatus according to claim 3, wherein the maintained pressing contact force is released and the pressing contact force is reset for the next sheet. An image forming apparatus using the sheet separating apparatus according to claim 1 .

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