JP7019361B2 - Seat feeder - Google Patents

Description

The present invention relates to a sheet feeding device that feeds sheets.

An image forming apparatus such as a copying machine, a printer, and a facsimile uses a sheet feeding device that feeds sheets loaded on a sheet loading unit one by one. In many cases, the frictional force generated between the mounting surface of the sheet loading part and the sheet is smaller than the frictional force generated between the sheets, and the sheet in contact with the mounting surface (final sheet) is the same. It is known that it is easy to be transported together with the sheet that overlaps on top.

Patent Document 1 describes a feeding device in which a friction member is arranged at a position facing the feeding roller on the upper surface of a bottom plate on which paper is loaded. The friction member is configured to apply a frictional force larger than the frictional force generated between the papers to the final paper so as to prevent the final paper from being fed together with the paper overlapping on the final paper.

Japanese Unexamined Patent Publication No. 2010-70281

However, in the configuration described in Patent Document 1, the stick-slip phenomenon occurs due to the frictional force generated between the final sheet and the friction member when the sheet is fed, or the frictional force generated between the sheets. There was a case that abnormal noise was generated due to.

Therefore, an object of the present invention is to provide a sheet feeding device capable of reducing the generation of abnormal noise when feeding a sheet.

The sheet feeding device according to one aspect of the present invention includes a sheet loading means on which a sheet is loaded, a feeding means that abuts on the sheet loaded on the sheet loading means and feeds the sheet, and the sheet loading means. A friction member arranged to face the feeding means, a driving means for driving the feeding means, a detecting means for detecting vibration of the device, and a control means for controlling the driving means. When the control means detects the occurrence of the stick-slip phenomenon based on the magnitude of the vibration detected by the detection means after the driving means starts driving the feeding means at the first speed. It is characterized in that the driving means is driven by the feeding means at a second speed higher than the first speed.

According to the configuration according to the present invention, it is possible to reduce the generation of abnormal noise when feeding the sheet.

The schematic diagram of the image forming apparatus which concerns on this disclosure. The schematic diagram of the sheet feeding apparatus which concerns on Example 1. FIG. The graph which shows the result of having verified the vibration of the apparatus when the sheet was fed at a different feeding speed (a, b). The block diagram which shows the control composition of the sheet feeding apparatus which concerns on Example 1. FIG. A diagram showing the transfer of a sheet by the sheet feeding operation according to the first embodiment. A chart showing the relationship between the sheet transfer speed and the stick-slip phenomenon. The flowchart which shows the control method of the sheet feeding operation which concerns on Example 1. A diagram showing a modified example (a, b) of a method of controlling a transport speed in a sheet feeding operation. The flowchart which shows the modification of the control method of a sheet feeding operation. The schematic diagram of the sheet feeding apparatus which concerns on Example 2. The block diagram which shows the control composition of the sheet feeding apparatus which concerns on Example 2. The flowchart which shows the control method of the sheet feeding operation which concerns on Example 2.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an image forming apparatus 201 according to the present disclosure. An image forming unit 201B that forms an image on a sheet is mounted on an image forming apparatus main body (hereinafter referred to as an apparatus main body) 201A, and an image reading device 202 is installed substantially horizontally above the apparatus main body 201A. A discharge space S for discharging a sheet is formed between the image reading device 202 and the device main body 201A.

At the lower part of the apparatus main body 201A, a plurality of seat feeding devices 230 including a feeding cassette 1 for storing the seat P and a feeding unit 13 for feeding the seat P from the feeding cassette 1 are arranged. There is. The sheet P used as a recording medium includes paper such as plain paper and thick paper, special paper such as coated paper, plastic film for overhead projectors, cloth, envelopes, and the like. Each feeding unit 13 includes a pickup roller 8 that feeds the sheet P from the feeding cassette 1, a feed roller 9 and a retard roller 10 that separate and convey the sheet P fed from the pickup roller 8.

The image forming unit 201B as an image forming means is a 4-drum full-color electrophotographic unit. That is, the image forming unit 201B includes a laser scanner 210 and four process cartridges PY, PM, which form four color toner images of yellow (Y), magenta (M), cyan (C), and black (K). Equipped with PC and PK. Each process cartridge PY to PK includes a photosensitive drum 212 which is a photoconductor, a charger 213 which is a charging means, and a developing device 214 which is a developing means. Further, the image forming unit 201B includes an intermediate transfer unit 201C arranged above the process cartridges PY to PK, and a fixing unit 220. A toner cartridge 215 for supplying toner to the developer 214 is mounted above the intermediate transfer unit 201C.

The intermediate transfer unit 201C includes an intermediate transfer belt 216 wound around a drive roller 216a and a tension roller 216b. Inside the intermediate transfer belt 216, a primary transfer roller 219 is provided that abuts on the intermediate transfer belt 216 at a position facing each photosensitive drum 212. The intermediate transfer belt 216 is rotated counterclockwise in the figure by a drive roller 216a driven by a drive unit (not shown), and the negative electrode toner image carried on the photosensitive drum 212 is sequentially transferred by the primary transfer roller 219. Multiple transfer is performed on the belt 216.

At a position facing the drive roller 216a of the intermediate transfer unit 201C, a secondary transfer roller 217 for transferring the color image supported on the intermediate transfer belt 216 to the sheet P is provided. The fixing portion 220 is arranged above the secondary transfer roller 217, and the first discharge roller pair 225a, the second discharge roller pair 225b, and the double-sided reversing portion 201D are arranged above the fixing portion 220. The double-sided reversing section 201D is provided with a reversing roller pair 222 capable of forward / reversing and a re-conveying passage R or the like for transporting a sheet having an image formed on one surface to the image forming section 201B again. Further, the image forming apparatus 201 is equipped with a control unit 260 as a control means for controlling an image forming operation, a sheet feeding operation, and the like.

Next, the image forming operation of the image forming apparatus 201 will be described. The image information of the original is read by the image reading device 202, processed by the control unit 260, converted into an electric signal, and transmitted to the laser scanner 210 of the image forming unit 201B. In the image forming unit 201B, the laser beam from the laser scanner 210 is irradiated to the photosensitive drum 212 whose surface is uniformly charged to a predetermined polarity and potential by the charger 213, and the drum surface is exposed as the drum rotates. Will be done. As a result, electrostatic latent images corresponding to monochromatic images of yellow, magenta, cyan, and black are formed on the surface of the photosensitive drum 212 of each process cartridge PY to PK. These electrostatic latent images are developed and visualized by each color toner supplied from the developer 214, and then superposed on each other from the photosensitive drum 212 to the intermediate transfer belt 216 by the primary transfer bias applied to the primary transfer roller 219. It is also primary transferred.

In parallel with such a toner image forming operation, the sheets P are fed one by one from any of the sheet feeding devices 230 and 250 toward the registration roller pair 240. After correcting the skew of the sheet P, the registration roller pair 240 sends the sheet P toward the secondary transfer roller 217 in accordance with the progress of toner image formation by the image forming unit 201B. In the transfer section (secondary transfer section) formed between the secondary transfer roller 217 and the intermediate transfer belt 216, full-color toner is applied to the sheet P due to the secondary transfer bias applied to the secondary transfer roller 217. The images are collectively secondarily transferred. The sheet P on which the toner image is transferred is conveyed to the fixing unit 220, and the toner of each color is melt-mixed by the heat and pressure applied in the fixing unit 220, so that the toner image is fixed on the sheet P as a color image.

After that, the sheet P is discharged to the discharge space S by the first discharge roller pair 225a or the second discharge roller pair 225b provided downstream of the fixing portion 220, and is discharged to the loading portion 223 arranged at the bottom of the discharge space S. It will be loaded. When an image is formed on both sides of the sheet P, the sheet P on which the image is formed on the first surface is conveyed to the retransport passage R in a state of being inverted by the reversing roller pair 222, and is conveyed to the image forming unit 201B again. To. Then, the sheet P whose image is formed on the second surface by the image forming unit 201B is discharged to the loading unit 223 by the first discharge roller pair 225a or the second discharge roller pair 225b.

The above image forming unit 201B is an example of an image forming means, and an electrophotographic unit of a direct transfer method that directly transfers a toner image formed on a photoconductor to a sheet may be used, and an inkjet method or an offset printing method may be used. Image forming means may be used.

Next, the sheet feeding device according to the first embodiment (Embodiment 1) will be described. As shown in FIG. 1, the sheet feeding device 230 according to this embodiment is assembled to the device main body 201A of the image forming device 201. That is, the feeding unit 13 is supported by the frame body of the apparatus main body 201A, and the feeding cassette 1 is inserted into the apparatus main body 201A so as to be retractable.

As shown in FIG. 2, the feed cassette 1 as a sheet loading means on which the sheet P is loaded is a sheet that can rotate in the vertical direction (vertical direction) about the rotation axis 3 with respect to the cassette body 1a. It is provided with a loading unit 2. An arm plate 4 rotatably supported by the cassette body 1a is arranged below the seat loading portion 2, and the arm plate 4 is driven by the lifter motor M1 (see FIG. 3) to rotate around the rotation shaft 5. By moving, the seat loading unit 2 moves up and down. The seat feeding device 230 is provided with a height detection sensor capable of detecting the height of the uppermost seat of the seat P loaded on the seat loading unit 2. When the sheet P is fed, the top sheet is at a predetermined height based on the detection signal of the height detection sensor (the height at which the feeding unit 13 comes into contact with the top sheet and the feeding operation can be executed. ), The lifter motor M1 is driven.

A friction member 6 is provided on the upper surface 2a, which is the mounting surface of the seat loading portion 2, at a position facing the pickup roller 8. That is, the friction member 6 is arranged at a position where the sheet P is sandwiched between the pickup roller 8 and the pickup roller 8 in a state where the pickup roller 8 is in contact with the uppermost sheet.

As described above, the feeding unit 13 includes a pickup roller 8, a feed roller 9, and a retard roller 10. The pickup roller 8 and the feed roller 9 rotate along the sheet transport direction D1 by transmitting a driving force from a driving means such as the feed motor M2 (see FIG. 3). The retard roller 10 is attached to the non-rotating shaft via a torque limiter in a state of being pressed against the feed roller 9. The portion where the feed roller 9 and the retard roller 10 are in pressure contact with each other constitutes a separation nip portion for conveying the sheets P while separating them one by one.

The pickup roller 8 is rotatably held by a roller holder 18 which is a holding member. The roller holder 18 is supported by a feeding frame 19 fixed to a frame body of the apparatus main body in a state in which the roller holder 18 can swing about the axis of the feed roller 9. The pickup roller 8 is a top-level sheet that has risen to a predetermined height due to the weight of the roller holder 18 and the pickup roller 8 or the like, or the weight of these and the urging force of a spring or the like (not shown) that urges the roller holder 18 downward. Press contact with the upper surface.

When feeding the seat P, the pickup roller 8 and the feed roller 9 are rotated by the driving force supplied from the feed motor M2 in a state where the seat P is in contact with the pickup roller 8 due to the rise of the seat loading portion 2. Driven. As a result, the uppermost sheet is sent out to the separation nip portion by the pickup roller 8 and conveyed to the image forming portion 201B in a state of being separated from the other sheets by the feed roller 9 and the retard roller 10.

The mechanism by which the sheet is separated at the separation nip portion will be described. The drive of the feed motor M2 is transmitted to the feed roller 9 by a drive transmission mechanism such as a gear train, and rotates in the rotation direction along the seat transfer direction D1. Here, the torque input to the retard roller 10 by the frictional force between the feed roller 9 and the retard roller 10 is set to Ta in a state where the sheet P is not inserted in the separation nip portion. Further, with only one sheet P entering the separation nip portion, the torque input from the feed roller 9 to the retard roller 10 via the sheet P due to friction between the sheet P and each roller is referred to as Tb. do. At this time, the allowable torque Ttl of the torque limiter of the retard roller 10 is set so as to satisfy the following conditions (1) and (2).
Ta> TTL ... (1)
Tb> TTL ... (2)

When these conditions are satisfied, the torque limiter idles due to an overload, and the retard roller 10 rotates along with the feed roller 9 in the rotational direction along the sheet transport direction D1. Therefore, when only one sheet P enters the separation nip portion, the sheet P is conveyed in the sheet conveying direction D1.

On the other hand, assuming that the torque input from the feed roller 9 to the torque limiter via the plurality of sheets P in a state where two or more sheets P have entered the separation nip portion is Tc, the size of Tc is usually large. Limited by the frictional force between the sheets. The frictional force between the sheets is affected by the material of the sheets (for example, with or without surface treatment) and the atmosphere (for example, humidity), but the allowable torque of the torque limiter should satisfy the following condition (3) under normal conditions. Is set to.
Tc <Ttl ... (3)

When this condition is satisfied, the torque limiter does not slip, and the retard roller 10 does not rotate with the feed roller 9 and remains stopped. Then, while the uppermost sheet is conveyed in the sheet conveying direction D1 by the feed roller 9, the sheet overlapping under the uppermost sheet is stopped by the retard roller 10 and slides with respect to the uppermost sheet, so that the weight of the sheet P is increased. Feeding is prevented.

Next, the friction member 6 attached to the seat loading portion 2 will be described. The friction member 6 has a sheet transport direction D1 with respect to a sheet that is finally fed from the feed cassette 1, that is, a sheet that is in contact with the upper surface 2a of the sheet loading unit 2 (hereinafter referred to as a final sheet). Gives frictional force in the opposite direction. The friction member 6 is configured so that the following condition (4) is satisfied in a state where a plurality of seats P are loaded on the seat loading portion 2 and the pickup roller 8 is in contact with the uppermost seat.
Fa> Fb ・ ・ ・ (4)
However, Fa is the frictional force (maximum static frictional force) received by the final sheet from the friction member 6, and Fb is the frictional force (maximum static frictional force) received by the final sheet from the sheet on which the final sheet is superimposed.

When this condition is satisfied, the final sheet is stationary with respect to the friction member 6, and the sheet overlapping the final sheet slides with respect to the final sheet by receiving a tangential force larger than Fb from the pickup roller 8. .. That is, the friction member 6 prevents the final sheet from being fed by the pickup roller 8 together with the sheet loaded on the final sheet, and improves the double feeding performance of the seat feeding device, that is, the ability to prevent double feeding of the sheet. be able to.

The pickup roller 8 and the friction member 6 are both made of an elastic material (soft material) capable of surface contact with the surface of the sheet P. The pickup roller 8 is made of a material such as EPDM (ethylene propylene diene rubber) or polyurethane, and the friction member 6 is made of a material such as polyurethane resin or cork.

(Stick slip)
Here, a stick-slip phenomenon that may occur at the contact surface between the friction member 6 and the final sheet or the contact surface between the sheets when feeding the sheets will be described. When the stick-slip phenomenon occurs, the seat and the pickup roller 8 vibrate, and the vibration is amplified by the frame or the like of the seat feeder 230, which may cause an abnormal noise.

The stick-slip phenomenon is generally more likely to occur as the coefficient of static friction between sliding objects is larger. Further, it is known that the slower the relative movement speed between objects (the sheet transport speed in the case of this embodiment), the longer the stick state becomes and the larger the static friction force becomes, so that the stick-slip phenomenon is likely to occur. .. For example, see Masayoshi Muraki (2007) "Illustrated Tribology: The Science of Friction and Lubrication Technology", Nikkan Kogyo Shimbun.

Therefore, setting the sheet transport speed (feeding speed) at the time of feeding the sheet to a high speed is effective in preventing the occurrence of the stick-slip phenomenon. However, when increasing the feeding speed, it is necessary to pay attention to the deterioration of the heavy feeding resistance. The reason for this is as follows. The sheets that reach the separation nip portion in a state where a plurality of sheets are overlapped (double feed state) are separated by the action of the feed roller 9 and the retard roller 10. Here, the higher the feeding speed, the higher the rotation speed of the feed roller 9 and the rotation speed of the retard roller 10 that is taken to the feed roller 9 in a state where the sheet does not exist in the separation nip portion. Therefore, when the sheet in the double feed state reaches the separation nip portion, the retard roller 10 cannot immediately stop the rotation due to the inertial force acting on the retard roller 10, and the sheet is passed in the double feed state. It may end up. Then, when the sheet in the double-fed state reaches the transfer member on the downstream side of the separation nip portion (for example, the transfer roller pair 14 in FIG. 1), or when the sheet position at the start of the next sheet feeding operation shifts, It may cause transport abnormalities such as jams (paper jams).

Here, when the vibration of the device when the stick-slip phenomenon occurs on the contact surface between the friction member 6 and the sheet or the contact surface between the sheets is measured, it is known that the component of a specific frequency is increased. .. It is known that the same result can be obtained regardless of whether the measurement target portion is the pickup roller 8, the feeding unit 13, or the apparatus main body 201A. FIG. 3A is an example of an experimental result of analyzing the vibration of the device for each frequency when stick slip does not occur, and FIG. 3B is an example of an experimental result when stick slip occurs. In FIG. 3B, the vibration of the frequency Fn is increasing, and it can be determined that the vibration of the frequency Fn is caused by the stick slip.

Therefore, it is conceivable to switch between a state in which the feeding speed is set to a relatively low speed and a state in which the feeding speed is set to a relatively high speed according to the magnitude of vibration at a specific frequency of the device. Then, by setting the feed rate to a high speed only when the vibration of a specific frequency is large, it is possible to prevent the stick-slip phenomenon and reduce the generation of abnormal noise while minimizing the deterioration of the heavy feed resistance. can. Hereinafter, the control method of the seat feeding operation in this embodiment will be described.

As shown in FIG. 2, the seat feeding device 230 is provided with an acceleration sensor 11 as a detecting means capable of detecting the physical vibration of the device. The acceleration sensor 11 is attached to a feeding frame 19 fixed to a frame body of the apparatus main body 201A. As shown in FIG. 4, the acceleration sensor 11 is connected to the control unit 260 mounted on the image forming apparatus 201, and the control unit 260 drives the lifter motor M1 and the feed motor M2 based on the detection result of the acceleration sensor 11. Control the state. The control unit 260 is an example of a control means for controlling the sheet feeding device, and is a memory 262 as a storage unit for storing information such as a control program and sheet attributes, and a CPU (CPU) that reads and executes a program from the memory 262. Central processing unit) 261 and is included.

The control unit 260 acquires acceleration information in the vicinity of the frequency Fn of vibration caused by the stick-slip phenomenon, that is, in a preset frequency band from the acceleration sensor 11, and sticks when the acceleration within this range exceeds the threshold value. Judge that slip has occurred. It has been found by experiments and the like that when an abnormal noise is generated by the stick-slip phenomenon, a difference of at least 10 times or more is generated in the peak value of acceleration as compared with the case where the abnormal noise is not generated. Therefore, in this embodiment, first, the peak value of the acceleration in the vicinity of the frequency Fn when no abnormal noise is generated is acquired. Compared with this value, when the peak value in the vicinity of the frequency Fn becomes 10 times or more, it is determined that abnormal noise is generated due to stick slip.

The control unit 260 receives the detection signal from the acceleration sensor 11 after starting the feeding of the seat at a low speed (first speed), and determines whether or not the stick-slip phenomenon has occurred based on the detection signal. do. Then, when it is determined that the stick-slip phenomenon has occurred, the feeding speed of the sheet is switched to a high speed (second speed). The high-speed feeding speed is a speed set so as not to cause a stick-slip phenomenon between the seat and the friction member 6, and this will be described in detail later.

Here, a method of maintaining an appropriate distance between the preceding sheet and the succeeding sheet when the feeding speed of a certain sheet (successor sheet) is switched from low speed to high speed will be described. In FIG. 5, the vertical axis shows the positions of the front end and the rear end of the sheet, that is, the positions of the downstream end and the upstream end in the sheet transport direction, and the horizontal axis shows the time. It is assumed that the feeding speed of the preceding sheet and the succeeding sheet at the start of feeding is V1, and the feeding speed when the feeding speed of the succeeding sheet is switched to a high speed is V2. Further, it is assumed that the feeding interval of the preceding sheet and the succeeding sheet is Δt0. However, the feeding interval is that the leading sheet starts feeding by the pickup roller 8, the tip of the leading sheet starts moving from the tip setting position of the feeding cassette 1, and then the tip of the succeeding sheet starts moving from the tip setting position. Time interval until. V1 and V2 are V1 <V2 ... (5)
When the sheet is conveyed at the feeding speed V2, the stick-slip phenomenon does not occur on the contact surface between the final sheet and the friction member 6 or the contact surface between the preceding sheet and the succeeding sheet.

Here, regardless of whether or not the feeding speed of the succeeding sheet (second sheet) is switched, from the time when the preceding sheet (first sheet) enters the transfer section to the time when the succeeding sheet enters the transfer section. It is preferable that the time interval is constant (Δt0). Further, the sheet transfer speed in the transfer unit is preferably constant (V1) regardless of whether or not the feed rate is switched. This is to prevent the influence of image density unevenness and the like from appearing between the sheets by forming the image under the uniform conditions as much as possible.

After the feeding of the preceding sheet is started at the speed V1 at the time t0, the feeding of the succeeding sheet is started at the speed V1 at the time t1 when the time (first time) from the time t0 to Δt0 has elapsed. When the control unit 260 does not detect the occurrence of stick slip from the detection signal of the acceleration sensor 11, the feeding speed is not switched for the succeeding seat, and the feeding is continued at a constant speed V1 (see the broken line). In this case, by continuing the sheet transfer at the speed V1, the time interval (Δt0) between the sheets and the sheet transfer speed (V1) in the transfer unit are kept constant.

On the other hand, when the control unit 260 detects the occurrence of stick slip, the transfer of the succeeding sheet is temporarily stopped at the same time as the detection (time t3). After that, at the time t4 when the time of Δt2 has elapsed from the temporary stop, the feeding speed is switched to V2 and the feeding of the succeeding sheet is restarted. Further, at the time t5 when the tip of the succeeding sheet enters the transfer unit, the control of switching the speed to V1 is performed again. The length of the waiting time (Δt2) until the sheet transfer is restarted is set so that the sheet reaches the transfer unit at the same time as the sheet is fed from the time t1 to the transfer unit at the speed V1 (time t5). Will be done. That is, when the feeding start time such that the sheet arrives at the transfer section at time t5 when the sheet is fed to the transfer section at the speed V2 from the beginning is set to t2, the time t4 for restarting the sheet transfer is as follows. It can be obtained by the equation (6) of.
t4 = (V1 / V2) × Δt1 + t2… (6)
By such control, even when the feeding speed of the succeeding sheet is switched, the succeeding sheet can be moved to the preceding sheet at a time interval of Δt0 and at the same sheet transport speed (V1) as the preceding sheet. It can be sent to the transfer unit.

Next, a method for determining the speed V2 at which the stick slip does not occur will be described. From the examination of experiments and the like, it is found that the factors that influence the presence or absence of the stick-slip phenomenon in the seat feeding device are mainly the rigidity of the feeding frame 19 and the damping coefficient of the roller holder 18 that holds the pickup roller 8. Do you get it. The rigidity of the feeding frame 19 is calculated by, for example, using structural analysis software and calculating from the amount of deformation of the frame when a force assuming feeding is applied. Here, the damping coefficient is defined as a logarithmic ratio of the amplitudes of adjacent peaks of vibration when an object is freely vibrated. In other words, the damping coefficient is a coefficient that indicates how easily the vibration of an object is attenuated. The damping coefficient of the roller holder 18 can be calculated by, for example, performing a hammering test or the like.

FIG. 6 shows a graph showing the damping coefficient of the roller holder 18 on the vertical axis and the rigidity of the feeding frame 19 on the horizontal axis. The rigidity K of the feeding frame 19 of a certain sheet feeding device and the damping coefficient C of the roller holder 18 are graphed. The one plotted above is the star mark. As mentioned above, the feeding speed of the seat affects the susceptibility to the stick-slip phenomenon. Therefore, for any feeding speed Va, Vb, Vc, the boundary line that separates the region where stick slip occurs and the region where stick slip does not occur is information on the mass, rigidity, damping coefficient of the sheet feeder, and the friction coefficient of the friction member. Calculated from, the curve shown in FIG. 6 is drawn. However, Va <Vb <Vc.

In FIG. 6, the plot (star mark) of the rigidity K and the damping coefficient C for a certain sheet feeder is located in the region on the upper right of the Vb boundary line and on the lower left of the Va boundary line. That is, when the sheet is fed by this sheet feeding device, it can be seen that stick slip may occur if the feeding speed is Va, and stick slip does not occur if the feeding speed is Vb or higher. .. Therefore, even if stick slip occurs when the seat feeding speeds V1 and V2 are uniformly set to Va, the occurrence of stick slip is suppressed by setting the seat feeding speed V2 to the speed Vb. be able to. With respect to the speeds V1 and V2, the productivity is set to 45 sheets per minute, for example, V1 = 200 [mm / s] and V2 = 300 [mm / s]. As a matter of course, the values of V1 and V2 are appropriately changed depending on the configuration of the sheet feeder (plot position on the graph) and the required productivity.

(Control of delivery task)
Next, the control method of the feeding task in this embodiment will be described with reference to the flowchart shown in FIG. When a signal requesting image output (image forming job) is input to the image forming apparatus, the control unit 260 starts a sheet feeding task to feed the sheets necessary for executing the image forming job. .. First, the control unit 260 determines whether or not stick slip has occurred based on the detection signal from the acceleration sensor 11 after starting the feeding of the seat at the speed V1 (S10). The control unit 260 continuously executes such a determination process until the rear end of the seat passes through the pickup roller 8.

When the stick slip has not occurred (NO in S11), the control unit 260 continues feeding the seat at the speed V1 (S12). After that, it is determined whether or not the feeding task is completed (S13), if it is completed, the operation is stopped (YES in S13), and if it is not completed, the processing for the next sheet is started (NO in S13).

On the other hand, when it is determined that the stick slip has occurred (YES in S11), the control unit 260 suspends the feed motor M2 at that time (S14), and calculates the time t4 for resuming the transfer described above. Then, after waiting until the time t4 (NO in S15), when the time t4 (YES in S15), the feeding speed is changed to V2 and the sheet feeding is restarted (S16). After that, it is determined whether or not the feeding task is completed (S13), if it is completed, the operation is stopped (YES in S13), and if it is not completed, the processing for the next sheet is started (NO in S13).

As described above, in this embodiment, after the seat feeding is started at the first speed (V1), the feeding speed is determined when it is determined that the stick slip has occurred based on the detection result of the acceleration sensor 11. To a second speed (V2) higher than the first speed. As a result, it is possible to reduce the generation of abnormal noise due to the stick-slip phenomenon when feeding the sheet. Further, when the stick slip does not occur, the sheet is fed at the first speed, so that the deterioration of the heavy feed resistance performance can be minimized.

Further, in the present embodiment, when the feeding speed is switched, the feeding motor M2 is controlled to be temporarily stopped and then restarted at the speed V2 after the switching. (See FIG. 5). As a result, the difference between the feeding speeds V1 and V2 is offset by the pause operation, and the sheet spacing in the transfer section is set to a substantially constant spacing suitable for the image forming section 201B to stably form a high-quality image. It can be kept at Δt0).

[Modification example]
In the first embodiment, the feeding speed of the sheet is controlled according to the chart shown in FIG. 5, but it is also possible to control the feeding speed by a different method. An example thereof is shown in FIGS. 8 (a) and 8 (b). In the example shown in FIG. 8A, when the acceleration sensor 11 detects the occurrence of stick slip at time t3 after starting the feeding of the succeeding sheet at time t1, the speed is switched to V2 and the feeding is continued. .. After that, the sheet transfer is temporarily stopped at the time t6 when the time of Δt6 has elapsed from the start of feeding, that is, the time when the succeeding sheet reaches the speed switching point (the position after passing through the section where stick slip is likely to occur). The sheet transfer is restarted at the speed V1. At this time, the time Δt6 for continuing the feeding of the sheet at the speed V2 is calculated by the following equation (7) when the distance from the tip set position to the speed switching point is L1.
Δt6 = (L1-V1 × Δt1) / V2 ・ ・ ・ (7)

Further, in the example of FIG. 8B, when the acceleration sensor 11 detects the occurrence of stick slip at time t3 after starting the feeding of the succeeding sheet at time t1, the speed is switched to V2 and the feeding is continued. do. Then, after decelerating the sheet transfer speed to V3 at the time t6 when the time of Δt6 has elapsed from the start of feeding, the transfer speed is switched to V1 at the time t3 when the tip of the sheet reaches the transfer unit. However, it is assumed that the velocities V1, V2 and V3 satisfy the following equation (6).
V2>V1> V3 ... (6)

In both the examples of FIGS. 8A and 8B, the sheet transport speed is switched until the tip of the sheet reaches a predetermined position (here, the transfer portion), and the speed is smaller than the speed V1 (in this case, the transfer speed is smaller than V1). There is a period (including the case where the speed is zero). In this way, instead of the method of temporarily stopping the feeding of the seat and then switching the feeding speed to V2 as in the first embodiment, the method of decelerating the feeding speed of the seat in the middle is also used at the predetermined position. It is possible to keep the sheet spacing and the transport speed constant. In this embodiment, the spacing between the sheets in the transfer unit (secondary transfer unit) is controlled to be constant, but in the case of a sheet feeding device that feeds the sheets to other parts of the image forming apparatus. , The target position (predetermined position) that keeps the sheet spacing constant is replaced. For example, in the case of a sheet feeding device that feeds a sheet to be a document in the image reading device 202 (see FIG. 1), the sheet spacing and the transport speed at the reading position where the sheet is scanned by the reading unit may be constant. preferable.

Further, in the first embodiment, the occurrence of the stick-slip phenomenon is suppressed by increasing the sheet transport speed, but reducing the load generated on the contact surfaces between the objects is also effective in suppressing the stick-slip phenomenon. It is known. Therefore, as shown in FIG. 9, a method of reducing the contact pressure between the pickup roller 8 and the seat when the drive load of the feed motor M2 becomes a predetermined value or more may be used (S12b, S14b). In FIG. 9, the contact pressure P2 (second contact pressure) when the drive load of the feed motor M2 exceeds a predetermined value is the contact pressure P1 (second contact pressure) when the drive load does not exceed the predetermined value. It is set smaller than the contact pressure of 1. In this case, the contact pressure between the pickup roller 8 and the seat can be adjusted by controlling the angle of the arm plate 4 (see FIG. 2) by, for example, the lifter motor M1. The arm plate 4 is an example of an adjusting means capable of adjusting the contact pressure, and a cam mechanism or a solenoid for swinging the roller holder 18 may be arranged.

By setting the contact pressure P2 of the pickup roller 8 with respect to the seat to be small, the frictional force generated between the seat and the friction member 6 or between the seat and the seat underneath the seat is reduced, and the stick-slip phenomenon occurs. Occurrence is suppressed. On the other hand, the contact pressure P1 when the drive load of the feed motor M2 does not exceed a predetermined value is set to a value larger than P2 so that the pickup roller 8 can reliably feed the seat. In the example shown in FIG. 9, the contact pressure P2 is kept constant when the drive load of the feed motor M2 exceeds a predetermined value, but the contact pressure is set to zero as a form of reducing the contact pressure. May be acceptable. In that case, for example, a method of separating the pickup roller 8 from the seat after the seat reaches the separation nip portion can be considered.

The pickup roller 8 in the first embodiment is an example of a feeding means for feeding a sheet from the seat loading means. For example, the pickup roller 8 is omitted and the feed roller 9 is mounted on the seat loaded portion 2. It may be configured to directly contact and feed. Even in such a case, the feeding speed can be switched according to the drive load of the driving means for driving the feed roller 9, and the feeding speed can be appropriately set according to the configuration of the seat feeding device. The same effect as in Example 1 can be obtained. Further, in the first embodiment, the driving force is not transmitted to the retard roller 10, but the retard roller 10 is used as a driving source so that the driving force in the direction of returning the seat P (the direction opposite to the seat transport direction D1) is input. May be connected to (see Figure 2). Further, a pad member may be used as a separating member instead of the roller member to separate the sheet conveyed by the feed roller 9 from other sheets.

Next, a second embodiment (Example 2) will be described. In the first embodiment, the feeding speed is switched in order to reduce the generation of abnormal noise due to the stick-slip phenomenon, but in this embodiment, the driving force input to the pickup roller 8 is weakened to reduce the abnormal noise. Reduce the occurrence. Hereinafter, the elements common to the first embodiment are designated by the same reference numerals as those of the first embodiment, and the description thereof will be omitted.

FIG. 10 is a schematic diagram for explaining the configuration of the sheet feeding device 230 according to the present embodiment. The seat feeding device 230 includes a feeding cassette 1 as a seat loading means and a feeding unit 13 including a pickup roller 8 as a feeding means. A friction member 6 is arranged at a position facing the pickup roller 8 in the seat loading portion 2 of the feeding cassette 1.

Here, in this embodiment, the sheet detection sensor 15 is arranged as a sheet detecting means for detecting that the sheet has reached the transport roller pair 14 arranged downstream of the feed roller 9 and the retard roller 10. As shown in FIG. 11, the seat detection sensor 15 is connected to the control unit 260 together with the acceleration sensor 11 attached to the feeding frame 19. The control unit 260 controls the drive state of the lifter motor M1, the feed motor M2, and the transfer motor M3 that drives the transfer roller pair 14 based on the detection signals from these sensors.

As described above, when the sheet is conveyed, a stick-slip phenomenon may occur on the contact surface between the final sheet and the friction member 6 or the contact surface between the sheets, and the vibration is amplified by the frame of the sheet feeder 230 or the like. Abnormal noise is generated by being done. Here, it is known that when vibration caused by a stick-slip phenomenon occurs in or near a certain roller, the vibration can be suppressed by weakening the driving force input to the roller. This is because by weakening the drive, the influence of play between the members in the transmission path of the drive force from the drive source to the roller increases, and the apparent rigidity of the configuration that holds the roller changes. be. In other words, even if a periodic external force is applied to the roller, the displacement of the roller is absorbed by the backlash, so that it is possible to suppress the propagation of vibration to the extent that it is not perceived as an abnormal noise.

In the case of this embodiment, as shown in FIG. 10, the driving force of the feed motor M2 is input to the drive shaft 9A of the feed roller 9 via the drive transmission unit 17 such as a gear train or a belt transmission mechanism. Further, the rotation of the drive shaft 9A is transmitted to the pickup roller 8 via a transmission member such as an idler gear held by the roller holder 18. Therefore, by reducing the torque output by the feed motor M2, the vibration applied to the pickup roller 8 is transmitted from the feed motor M2 to the pickup roller 8 via the drive transmission unit 17 and the drive shaft 9A. It becomes easy to absorb.

By the way, if the driving force of a roller for transporting a sheet such as the pickup roller 8 is weakened, there is a concern that the sheet transporting capacity is lowered and the sheet is not fed. Therefore, the control unit 260 controls to weaken the driving force of the pickup roller 8 when the occurrence of stick slip is detected based on the detection signal from the acceleration sensor 11.

Hereinafter, the control method of the feeding task in this embodiment will be described with reference to the flowchart of FIG. When the seat feeding task is started, the control unit 260 starts driving the feeding motor M2 (S20), and determines whether or not vibration due to stick slip is generated (S21). When vibration is not generated (NO in S21), the feed motor M2 and the transport motor M3 are driven by normal control to transport the seat P (S22 to S24). In this case, even if the seat detection sensor 15 detects (S22) that the seat has reached the transport roller pair 14, the pickup roller 8 is continued to be driven by the feed motor M2. Then, the feed motor M2 is stopped at an appropriate timing before the rear end of the sheet passes through the pickup roller 8 so as not to feed the next sheet (S23, S24). The stop timing of the feed motor M2 is calculated from, for example, the size information of the sheet loaded on the feed cassette 1 and the feed speed of the sheet. After that, it is determined whether or not the feeding task is completed, and if it is completed, the operation is terminated (YES in S25), and if it is not completed, the processing for the next sheet is started (NO in S25).

On the other hand, when it is detected from the detection signal of the acceleration sensor 11 that vibration due to stick slip is generated (YES in S21), the control unit 260 performs a process of turning off the drive of the pickup roller 8 by the feed motor M2. That is, the control unit 260 waits until the seat reaches the transport roller pair 14 based on the detection signal from the seat detection sensor 15 (NO in S26). When it is determined that the seat has reached the transport roller pair 14 (YES in S26), the drive of the feed motor M2 is stopped (S27). At this time, the drive of the transfer roller pair 14 by the transfer motor M3 is continued, and the sheet is continuously conveyed toward the image forming portion by the transfer roller pair 14. After that, it is determined whether or not the feeding task is completed, and if it is completed, the operation is terminated (YES in S25), and if it is not completed, the processing for the next sheet is started (NO in S25).

As described above, in this embodiment, after the seat feeding is started, the driving force transmitted from the feeding motor M2 to the pickup roller 8 when vibration due to stick slip occurs based on the detection result of the acceleration sensor 11. It is controlled to weaken. As a result, it is possible to reduce the generation of abnormal noise due to the stick-slip phenomenon when feeding the sheet. Further, when the stick slip does not occur, the feeding of the seat is continued with a constant driving force (first driving force), so that the possibility of non-feeding of the seat can be minimized.

Further, in this embodiment, the drive of the pickup roller 8 is stopped when the seat reaches the transport roller pair 14 downstream of the pickup roller 8. In other words, in the second feeding mode, the driving force transmitted to the feeding means is weakened until the driving force transmitted to the feeding means becomes zero in a state where the sheet reaches the transport means downstream from the feeding means. As a result, even if vibration due to the stick-slip phenomenon occurs, it can be sufficiently damped before it is transmitted to the feeding frame 19 or the like of the seat feeding device 230, and the generation of abnormal noise can be suppressed more effectively. can.

[Modification example]
In the second embodiment, control is performed to turn off the drive of the pickup roller 8 (make the drive force zero) when the vibration of the device is detected. However, the output torque (second driving force) of the feeding motor M2 when the vibration of the device is detected is set to a value smaller than the output torque (first driving force) at the start of feeding, and the feeding is performed. The driving of the motor M2 may be continued. For example, if a DC motor is used as the feed motor M2 and the maximum value of the current flowing through the windings of the motor when the vibration of the device is detected is limited to be smaller than that when the vibration of the device is not detected. good. Further, in this embodiment, whether or not the sheet has arrived at the transport roller pair 14 is determined by using the sheet detection sensor 15. For example, the elapsed time from the start of driving of the feeding unit 13 by the feeding motor M2. May determine the arrival of the sheet on the transport rollers vs. 14.

[Other embodiments]
In each of the above embodiments, the sheet feeding device 230 (see FIG. 1) having a feeding cassette that can be attached to and detached from the device main body 201A of the image forming apparatus 201 has been described. May be applied. The manual feed feeding device 250 provided on the side surface of the image forming apparatus 201 is an example of such a sheet feeding device. The manual feed feeding device 250 has a manual feed tray 20 (seat loading means) provided on the side surface of the device main body 201A so as to be openable and closable, and the sheets set by the user in the manual feed tray 20 are separated one by one by the feed unit 130. And send it. Further, the document feeding device for feeding the sheet as the document in the image reading device 202 is another example of the sheet feeding device.

By the way, in the first and second embodiments, the acceleration sensor 11 attached to the feeding frame 19 is used as a detecting means for detecting the vibration of the device caused by the stick-slip phenomenon. However, other sensors capable of detecting the physical displacement of the device, such as an optical displacement sensor and a rotary encoder, may be used as the detection means. Further, the acceleration sensor 11 or another sensor may be attached to a portion other than the feeding frame 19, for example, to the roller holder 18. However, in order to reduce the influence of vibration that causes noise, it is preferable to mount the sensor at a position close to the vibration source when stick slip occurs. Therefore, as in the first and second embodiments, it is preferable to arrange the detecting means in the unit (feeding unit 13) which is provided with the feeding means (pickup roller 8) and which can be attached to and detached from the apparatus main body 201A.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

1,20 ... Sheet loading means (feeding cassette, manual feed tray) / 4 ... Adjusting means (arm plate) / 6 ... Friction member / 8 ... Feeding means (pickup roller) / 11 ... Detection means (accelerometer) / 14 ... Conveying means (conveying roller pair) / 15 ... Sheet detecting means (seat detection sensor) / 17 ... Transmission unit (drive transmission unit) / 18 ... Holding member (roller holder) / 201,230,250 ... Sheet feeding device ( Image forming device, manual feeding device) / 201B ... Image forming means (image forming unit) / 260 ... Control means (control unit) / M2 ... Driving means (feeding motor)

Claims (9)

The sheet loading means on which the sheet is loaded and the sheet loading means
A feeding means that abuts on the sheet loaded on the sheet loading means and feeds the sheet, and a feeding means.
A friction member arranged on the sheet loading means so as to face the feeding means, and
The driving means for driving the feeding means and
Detection means to detect the vibration of the device and
A control means for controlling the drive means is provided.
When the control means detects the occurrence of the stick-slip phenomenon based on the magnitude of the vibration detected by the detection means after the driving means starts driving the feeding means at the first speed, the control means said. The driving means is driven by the feeding means at a second speed higher than the first speed.
A sheet feeding device characterized by that. When the control means detects the occurrence of the stick-slip phenomenon based on the magnitude of the vibration detected by the detection means after the driving means starts driving the feeding means at the first speed, the control means said. After stopping the driving of the feeding means by the driving means, the driving means is made to start driving the feeding means at the second speed.
The sheet feeding device according to claim 1, wherein the sheet feeding device is characterized in that. When the control means detects the occurrence of the stick-slip phenomenon based on the magnitude of the vibration detected by the detection means after the driving means starts driving the feeding means at the first speed.
From the time when the driving means starts driving the feeding means at the second speed to the time when the sheet reaches a predetermined position downstream of the feeding means in the sheet transporting direction, the sheet transport speed is adjusted. A period for keeping the speed smaller than the first speed is provided.
The sheet feeding device according to claim 1 or 2, wherein the sheet feeding device is characterized in that. When the control means does not detect the occurrence of the stick-slip phenomenon based on the magnitude of the vibration detected by the detection means after the driving means starts driving the feeding means at the first speed. , The driving of the feeding means by the driving means is continued at the first speed.
The sheet feeding device according to any one of claims 1 to 3, wherein the sheet feeding device is characterized by the above. The detection means is an acceleration sensor.
The sheet feeding device according to any one of claims 1 to 4, wherein the sheet feeding device is characterized by the above. The control means determines whether or not a stick-slip phenomenon has occurred based on a peak value in a preset frequency band among the components of each frequency of vibration detected by the detection means.
The sheet feeding device according to any one of claims 1 to 5, wherein the sheet feeding device is characterized in that. The feeding means is provided in a unit that is detachably attached to the main body of the apparatus.
The detecting means is attached to the unit.
The sheet feeding device according to any one of claims 1 to 6, wherein the sheet feeding device is characterized in that. The friction member is made of an elastic material having a larger coefficient of static friction with respect to the sheet than the surface on which the sheet of the sheet loading means is loaded.
The sheet feeding device according to any one of claims 1 to 7, wherein the sheet feeding device is characterized by the above. An image forming means for forming an image on a sheet fed from the sheet loading means is provided.
The sheet feeding device according to any one of claims 1 to 8, wherein the sheet feeding device is characterized in that.

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