JP2008007284A - Sheet feeder, method of controlling it, and image forming device with the sheet feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem with conventional lift-up control wherein the control is complicated since a time required for feeding sheets is long and a processing for storing the rise time counted by a timer is required. <P>SOLUTION: When a sheet loading part is moved from a sheet supplementing position to a sheet feed position where sheets can be fed by a feed means, a sheet feeder is continuously driven until it is detected (On in S2) that the sheet loading part reaches a predetermined position other than the feeding position. The sheet feeder is intermittently driven until it is detected (Off in S5) that the sheet loading part is moved to the feeding position after the detection (S4, S6). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet feeding apparatus that supplies a sheet such as a document or recording paper to an image forming apparatus such as a printer, a facsimile machine, and a copying machine, a control method therefor, and an image forming apparatus having the sheet feeding apparatus. It is.

  2. Description of the Related Art Image forming apparatuses such as printers, copiers, and facsimile machines are provided with a sheet feeding device that feeds sheets to an image forming unit (recording unit). In this sheet feeding apparatus, a plurality of sheets are stacked and stored on a sheet stacking member that can be raised and lowered provided in a sheet storage unit that can store sheets, and the sheet stacking member is placed at a position where the sheet can be fed. After moving (raising), the sheet is fed by the sheet feeding means. In such a feeding device, the sheet storage unit can be pulled out from the sheet feeding device so that sheets can be easily stacked on the sheet storage unit. In the pulling operation, the sheet stacking member is automatically lowered to a predetermined sheet stacking position. In particular, in a sheet feeding apparatus connected to a printer, a paper surface sensor that detects the height of the uppermost sheet stacked on the sheet stacking member is provided. The position of the sheet stacking member is controlled based on the information from the paper surface sensor so that the position of the uppermost sheet is always at a substantially constant height.

  Further, when a sheet feeding signal is sent from the image forming apparatus main body, the sheet feeding means rotates in contact with the uppermost sheet. In this way, the uppermost sheet is fed to the next pair of separation rollers. The pair of separation rollers separates the sheets fed by the rotation of the feeding roller one by one, and feeds the separated sheets into the image forming apparatus main body. Further, at this time, when the feeding roller feeds the sheet to the pair of separation rollers, the pair of separation rollers is retracted above the sheet so as not to contact the sheet so as not to interfere with the separation of the sheet. In this way, the sheet feeding device repeats such an operation every time a sheet feeding signal is sent, and feeds the sheets one by one to the image forming apparatus main body.

  In such a feeding mechanism, the uppermost sheet position on the sheet stacking member is such that the feeding roller contacts the uppermost sheet with an appropriate feeding pressure in order to prevent non-feeding and double feeding of the sheet, and It is desirable that the feeding roller be held at a position where it can be reliably fed to the nip of the separation roller pair. However, when a drive motor is used as a drive source for raising the sheet stacking member, the rotation cannot be stopped immediately by inertia force (overrun) even if the rotation of the drive motor is stopped. Therefore, the position of the uppermost sheet on the sheet stacking member varies. In particular, when the sheet stacking member is moved in a state where a small number of sheets are stacked on the sheet stacking member, the driving force of the drive motor increases with respect to the weight of the sheet on the sheet stacking table. For this reason, the inertial force also increases and the position of the uppermost sheet varies greatly.

  As a method of solving such a problem, after raising the sheet stacking member to the feedable position, the sheet stacking member is once lowered, and then the input applied voltage to the drive motor is lowered and then raised again. Proposed. As a result, the overrun of the drive motor can be reduced, and variations in the position of the uppermost sheet on the sheet stacking member can be reduced (see Patent Document 1).

In addition, if the micro switch that detects the position of the form at a predetermined time does not detect the form, the rotation of the motor that moves up and down is stopped. Thereafter, it has been proposed to intermittently drive the motor. As a result, when the number of stacked paper sheets is large and the overrun is small, the time required for driving the motor is shortened by moving the motor up and down without intermittent driving. Further, when the number of stacked paper sheets is small and overrun is likely to occur, the paper is quickly moved up and down without intermittent driving until a predetermined time. After that, it has also been proposed that the motor is intermittently driven so that it can be moved up and down in a shorter time and the overrun is reduced (see Patent Document 2).
JP-A-9-086680 JP-A-4-159932

  According to the configuration of Patent Document 1, the sheet stacking member is once lowered, and then the input applied voltage to the drive motor is lowered and raised again. For this reason, there is a problem that not only the movement control is complicated, but also a circuit for making the motor rotatable in both directions and reducing the voltage applied to the motor is required, leading to an increase in cost. In addition, since it is necessary to raise the sheet stacking member twice, there is a problem that it takes a long time until the sheet can be fed.

  Further, in Patent Document 2, if the power is turned off while the hopper is being lifted, it is impossible to measure the time required for the lift, and thus it is not possible to reliably prevent hopper overrun. Although it is conceivable to store the rising time measured by the timer in a storage medium (for example, EEPROM) that can retain data even when the power is turned off, it leads to a cost increase that requires a new storage medium. In addition, there is a problem that the control becomes complicated because processing for constantly storing time in the storage medium is required.

  An object of the present invention is to solve the above-mentioned conventional problems.

  The feature of the present invention is that the sheet stacking section can be raised to a position where the sheet can be fed in a relatively short time with simple control, and the overrun of the sheet stacking section can be reduced.

In order to achieve the above object, a sheet feeding apparatus according to an aspect of the present invention has the following configuration. That is,
A sheet stacking means capable of stacking and storing sheets;
A feeding means for feeding the sheet in contact with the uppermost sheet stacked on the sheet stacking means;
Drive means for moving the sheet stacking portion of the sheet stacking means from a sheet replenishment position to a feeding position capable of being fed by the feeding means;
First detection means for detecting that the sheet stacking unit has moved to the feeding position;
Second detection means for detecting that the sheet stacking unit has reached a predetermined position other than the feeding position;
The driving unit is continuously driven until the second detection unit detects that the sheet stacking unit has reached the predetermined position, and after the detection by the second detection unit, the sheet stacking unit is moved by the first detection unit. Control means for controlling the driving means to be intermittently driven until it is detected that has moved to the feeding position.

In order to achieve the above object, a sheet feeding apparatus according to an aspect of the present invention has the following configuration. That is,
A sheet stacking means capable of stacking and storing sheets;
A feeding means for feeding the sheet in contact with the uppermost sheet stacked on the sheet stacking means;
Drive means for moving the sheet stacking portion of the sheet stacking means from a sheet replenishment position to a feeding position capable of being fed by the feeding means;
A sheet presence / absence detecting means for detecting the presence / absence of a sheet on the sheet stacking unit according to the movement of the sheet stacking means;
Control means for continuously driving the drive means when the sheet presence / absence detection means does not detect the sheet, and controlling the drive means to be intermittently driven when the sheet presence / absence detection means detects the sheet; It is characterized by having.

In order to achieve the above object, an image forming apparatus according to an aspect of the present invention has the following configuration. That is,
A sheet feeding device according to any one of claims 1 to 3,
Image forming means for forming an image on a sheet conveyed from the sheet feeding device;
It is characterized by having.

In order to achieve the above object, a sheet feeding control method according to an aspect of the present invention includes the following steps. That is,
A driving step of moving a sheet stacking unit of a sheet stacking unit capable of stacking and storing sheets from a sheet replenishment position to a feeding position capable of feeding by a feeding roller;
A first detection step of detecting that the sheet stacking unit has moved to the feeding position;
A second detection step of detecting that the sheet stacking unit has reached a predetermined position other than the feeding position;
In the driving process, continuous driving is performed in the driving process until it is detected in the second detecting process that the sheet stacking unit has reached the predetermined position, and the feeding position is detected in the first detecting process from the predetermined position. A control step of controlling the sheet stacking unit to move intermittently in the driving step until it is detected that the sheet stacking unit has been moved,
It is characterized by having.

In order to achieve the above object, a sheet feeding control method according to an aspect of the present invention includes the following steps. That is,
A driving step of moving a sheet stacking unit of a sheet stacking unit capable of stacking and storing sheets from a sheet supply position to a feeding position capable of being fed by the feeding unit;
A sheet presence / absence detection step for detecting the presence / absence of a sheet on the sheet stacking unit according to the movement of the sheet stacking unit;
When the sheet is not detected in the sheet presence detection step, the sheet is continuously driven in the driving step, and when the sheet is detected in the sheet presence detection step, the sheet stacking unit is moved intermittently in the driving step to move the sheet stacking unit. A control process for controlling
It is characterized by having.

  The means for solving this problem does not enumerate all the features of the present invention, and other claims described in the claims and combinations of these feature groups can also be the invention. .

  According to the present invention, it is possible to reduce the influence due to the overrun of the sheet stacking unit accompanying the movement of the sheet stacking unit. In addition, the sheet stacking unit can be moved from the sheet feeding position to a feedable position while suppressing an increase in the time required to move the sheet stacking unit.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the present invention according to the claims, and all combinations of features described in the present embodiments are essential to the solution means of the present invention. Not exclusively.

  As an embodiment of the present invention, a sheet storage device connected to a laser beam printer (hereinafter referred to as LBP) will be described as an example.

  FIG. 1 is an external perspective view of an LBP according to an embodiment of the present invention.

  Reference numeral 1 denotes an LBP as an image forming apparatus. Reference numeral 2 denotes a cassette in which the sheets S are stacked and stored, and only one level is provided inside the LBP 1. The three-stage cassette deck 51 serving as a sheet storage device also serves as a mounting table for the LBP 1 and is disposed at the lower part of the LBP 1. The deck 51 is provided with sheet feeding cassettes 52a, 52b, and 52c, each of which stores a plurality of sheets of various sizes and basis weights. Furthermore, casters are attached to the sheet storage device 51 at four locations on the lower surface of the sheet storage device 51 in consideration of movement in a state where the LBP 1 is placed. A discharge tray 12 stacks and stores the discharged printed sheets with the printing surface (image surface) facing down.

  FIG. 2 is an external perspective view showing a state in which the paper feed cassette 52a is pulled out from the state of FIG.

  Each paper feed cassette is provided in the cassette 52a so as to be movable up and down, and has a sheet storage portion provided with a middle plate 101, which is a sheet stacking portion for stacking sheet bundles, and regulation plates 57, 58, 59, and the like.

  FIG. 3 is a schematic cross-sectional view showing the entire configuration of the LBP 1 equipped with the sheet storage device according to the present embodiment, and the same parts as those in the above-mentioned drawings are indicated by the same symbols.

  Reference numeral 3 denotes a pickup roller (feed roller), which feeds the sheets S stacked on the cassette 2 from the uppermost side by rotation thereof. Reference numeral 4 denotes a retard roller pair, which separates and conveys the sheets S sent out by the rotation of the pickup roller 3 one by one. Reference numerals 5 and 6 denote conveying rollers for conveying the sheets S thus separated one by one in the main body.

  Reference numeral 7 denotes a process cartridge containing a known process means for image formation, which is detachably provided from the apparatus main body. The process cartridge 7 contains a photosensitive drum 7a as an image carrier. A charger 7b uniformly charges the surface of the photosensitive drum 7a. By irradiating the surface of the photosensitive drum 7a charged by the charger 7b with laser light corresponding to the image information from the laser exposure device 8, an electrostatic latent image is formed on the surface. The developing device 7c makes the electrostatic latent image a toner image by attaching toner to the surface of the drum 7a on which the electrostatic latent image is formed. The transfer roller 9 is pressed against the photosensitive drum 7a, and when the sheet S conveyed by the conveyance roller 6 passes between the photosensitive drum 7a and the transfer roller 9, the toner on the surface of the drum is transferred. The image is transferred to the sheet S. Reference numeral 10 denotes a fixing device, which applies heat and pressure to the sheet S after the image has been transferred in this way to fix the transferred image. Then, the sheet S after the image is fixed is conveyed and discharged by the discharge roller pair 11 onto the discharge tray 12 formed on the upper surface of the apparatus with the image surface facing down. A cleaning device 7d collects toner remaining on the surface of the drum 7a without being transferred, and cleans the drum surface.

  Next, the feeding means and cassette provided in the deck 51 will be described. Since the three feeding units and the cassette have the same configuration, the feeding unit and the cassette 52a arranged in the upper stage will be described here as an example.

  As shown in FIGS. 2 and 3, each sheet feeding cassette is capable of moving up and down in the cassette, and is provided with a middle plate 101 that is a sheet stacking member for stacking the sheet bundle Sa, and regulation plates 57, 58, 59, and the like. It has a storage part. Further, the sheet feeding roller 53a is a sheet feeding unit that feeds the uppermost sheet S1 of the sheet bundle Sa stacked on the intermediate plate 101. Further, a separation roller pair constituted by a feed roller 54a and a retard roller 55a for separating the sheet S fed by the rotation of the feeding roller 53a is provided. Further, a transport roller 56a for transporting the sheet S separated and fed one by one by the pair of separation rollers to the image forming apparatus main body is provided. The feed rollers 53b and 53c, the feed rollers 54b and 54c, the retard rollers 55b and 55c, and the transport rollers 56b and 56c in the other paper feed cassettes 52b and 52c also play the same role.

  2 and 4, the intermediate plate 101 is provided so as to be connectable to a lifter driving device 103 provided in the sheet storage device 51 via a lift arm 102. As shown in FIG. 5, the lifter driving device 103 includes gears 111, 112, 113 and a lift motor 114. When the lift motor 114 is driven to rotate, it is decelerated by the gears 111, 112, and 113, and the gear 110 provided in the cassette 52 and the half-moon gear 109 connected to the lift arm 102 are driven to rotate. Thereby, the middle plate 101 is moved (lifted up) in the upward (arrow A) direction.

  FIG. 4 is a mechanism diagram showing details of the sheet feeding unit of the sheet feeding cassette 52 (a general term for 52a to 52c). Here, the middle plate 101 is shown in a lifted state. In FIG. 4, reference numerals 53 to 56 respectively correspond to the feed rollers 53a to 53c, the feed rollers 54a to 54c, the retard rollers 55a to 55c, and the transport rollers 56a to 56c.

  The paper surface detection unit 104 is arranged on the upper part of the sheet bundle stacked on the intermediate plate 101, and can be turned on / off by a flag 107 that can rotate by contacting the uppermost sheet of the sheet bundle Sa. A photosensor 115 is provided. Further, the paper presence / absence detection unit 105 detects whether or not a sheet is stacked on the intermediate plate 101, and sets a photo sensor 106 and a paper presence / absence detection flag 107 capable of turning on / off infrared rays to the photo sensor 106. Have. When one end of the paper presence / absence detection flag 107 is pressed against the uppermost surface of the sheet, the paper presence / absence detection flag 107 rotates about the axis. As a result, the flag 107 that has shielded the infrared rays from the photosensor 106 moves, and the photosensor 106 enters a translucent state (this state (paper detection) is set to sensor-on). This paper presence / absence detection flag 107 stands by at a position lowered by its own weight unless an external force is applied (FIG. 8A). At this time, the infrared rays to the photosensor 106 are shielded by the flag 107 (this state is sensor-off (no paper)). Further, as shown in FIG. 4, the intermediate plate 101 is provided with a through hole portion 108. As a result, when the middle plate 101 is raised in a state where no sheets are stacked on the middle plate 101, the paper presence / absence detection flag 107 does not come into contact with the middle plate 101 and remains in a state of waiting due to its own weight. Become. As a result, the photosensor 106 remains in the light-shielded state (sensor off) as described above.

  Here, the paper presence / absence detection signal 1051 (FIG. 10) from the paper presence / absence detection unit 105 is changed from an off state to an on state (paper) when a sheet is mounted on the middle plate 101 at a predetermined position during lift-up of the middle plate 101. The presence / absence detection flag 107 is switched to contact with the sheet. Also, the paper surface detection signal 1041 (FIG. 10) from the paper surface detection unit 104 is turned off (can be fed) when the uppermost sheet of the intermediate plate 101 is raised to a position where it can be fed by the feeding roller 53. .

  FIG. 5 is a diagram for explaining a lift-up mechanism for the middle plate 101 of the sheet feeding cassette 52.

  FIG. 6 is an external view of the mechanism portion showing a state where the intermediate plate 101 is lowered from the state of FIG.

  As shown in FIG. 2 described above, when the sheet feeding cassette 52a is pulled out from the sheet storage device (deck) 51, the connection with the lifter driving device 103 (FIG. 4) provided in the sheet storage device 51 is released. As a result, the intermediate plate 101 is lowered to the lowest part of the paper feed cassette 52a by its own weight.

  On the other hand, the stacking of the sheet bundle Sa on the intermediate plate 101 is completed, and the sheet feeding cassette 52a is set in the sheet storage device 51 as shown in FIG. The lifter driving device 103 is rotationally driven by the control unit (1001 in FIG. 10) that detects this, and the connected intermediate plates 101 are raised. At this time, on the upper side of the sheet bundle Sa stacked on the intermediate plate 101, as described above, the paper presence / absence detection flag 107 that can rotate by contacting the uppermost sheet of the sheet bundle Sa and the paper presence / absence detection are provided. A paper surface detection unit 104 including photosensors 106 and 115 that are turned on / off by a flag 107 is provided.

  In this paper surface detection unit 104, when the uppermost sheet on the middle plate 101 is at a position lower than a certain predetermined position, the paper presence / absence detection flag 107 deviates from the position where the light of the photosensor 115 is blocked by its own weight, and the photo is detected. The output of the sensor 115 is turned on. Thereafter, when the intermediate plate 101 is raised by the lifter driving device 103 described above and the uppermost sheet on the intermediate plate 101 is raised to a predetermined position, the paper presence / absence detection flag 107 comes into contact with the uppermost sheet. Then, the paper presence / absence detection flag 107 is rotated to a position where the light of the photosensor 115 is blocked, and the output of the photosensor 115 is turned off. Here, the position where the output of the photo sensor 115 is turned off is a position where the uppermost sheet on the intermediate plate 101 is fed by the rotation of the sheet feeding roller 53 and can smoothly enter the nip of the separation roller pair 54 and 55. It is comprised so that it may become (feed position). The lifter driving device 103 is controlled to stop rotating when the paper surface detection signal 1041 from the paper surface detection unit 104 is in an off state (up to the position where the uppermost sheet on the intermediate plate 101 can be fed). As a result, the uppermost sheet on the intermediate plate 101 is always placed at a position where it can be fed.

  FIG. 7 is a diagram for explaining a state in which the uppermost sheet of the paper feeding cassette is fed. Portions common to the above-described drawings are indicated by the same symbols.

  When a sheet feeding signal is sent from the main body of the image forming apparatus, the feeding roller 53 rotates in contact with the uppermost sheet S1, as indicated by 53-1. As a result, the uppermost sheet is fed to the pair of separation rollers 54 and 55. A pair of separation rollers 54 and 55 separates and feeds the sheets fed by the rotation of the feeding roller 53 one by one, and feeds them into the image forming apparatus. At this time, when the feeding roller 53 feeds the sheet to the pair of separation rollers 54 and 55, as shown in the drawing, the feeding roller 53 retracts above the sheet S1 so as not to interfere with the separation of the separation roller pair 54 and 55. Thus, the sheet S1 is not contacted. In this way, every time a sheet feeding signal is sent from the image forming apparatus, the above-described operation is repeated to convey the sheets one by one to the image forming apparatus main body.

  8A and 8B are views for explaining the lift-up of the intermediate plate 101 in the paper feed cassette according to this embodiment.

  FIG. 8A shows a state where the middle plate 101 is lowered to the lowest position. In this state, the paper presence / absence detection flag 107 stands by at the position shown in FIG. At this time, the infrared rays of the photosensor 106 are shielded by the flag 107 (off state). On the other hand, the photosensor 115 is in an ON state because light is not blocked by the flag 107 in this state.

  FIG. 8A illustrates a lift-up period in which the middle plate 101 is lifted up from the lowest position by a normal lift-up process. On the other hand, FIG. 8B shows a lift-up control for controlling the lift-up operation in a predetermined section until the middle plate 101 is lifted up from the lowest position to the uppermost position (feeding position). Indicates the period. This lift-up control period will be described in detail later. Here, as shown in FIG. 8B, when the paper presence / absence detection unit 105 switches from the sensor-off state to the sensor-on state during lift-up, the lift-up operation is temporarily stopped and lift-up control described later is executed.

  9A and 9B are diagrams for explaining a state in which the middle plate 101 is raised and paper can be fed, and FIG. 9A shows a state in which a sheet exists on the middle plate 101 and there is a sheet. FIG. 9B shows a state without a sheet.

  With the sheets stacked on the intermediate plate 101, the intermediate plate 101 is raised to the paper feed position by the lifter driving device 103 described above. As a result, one end of the paper presence / absence detection flag 107 comes into contact with the uppermost surface of the sheet S1 and is pushed upward. As a result, the paper presence / absence detection flag 107 rotates in the clockwise direction around the shaft 107a. As a result, as shown in FIG. 9A, the infrared rays of the photosensor 115 are shielded, and the photosensor 115 is shielded (off state).

  Further, as shown in FIG. 9B, when the intermediate plate 101 is raised in a state where no sheets are stacked on the intermediate plate 101, the paper presence / absence detection flag 107 is set to the through-hole portion 108 (FIG. 4). ) As a result, as in the case of FIG. 8 (A), the vehicle waits by its own weight without coming into contact with the intermediate plate 101. As a result, the light to the photosensor 106 remains in a light-shielded state, and the infrared rays of the photosensor 115 remain unshielded.

  Therefore, if the signal of the photo sensor 106 remains off after the middle plate 101 is raised to the feeding position, it can be determined that no sheets are stacked on the middle plate 101. In this case, the sheet feeding operation is prohibited and the operation unit 1004 (FIG. 10) on the image forming apparatus displays that there is no paper, and can prompt the operator or the like to replenish sheets.

  FIG. 10 is a block diagram showing a schematic configuration of the LBP 1 according to the present embodiment.

  The control unit 1001 controls the overall operation of the LBP1. The control unit 1001 includes a CPU 1010 such as a microprocessor, a ROM 1011 for storing programs executed by the CPU 1010 and data, a RAM 1012 for temporarily storing various data, and the like. The printer engine 1002 includes the laser exposure device 8 shown in FIG. 3, various motors for mounting the process cartridge 7 to form an image, the fixing device 10, and the like. The motor driver 1003 controls the lift up of the intermediate plate 101 by rotating the lift motor 114 based on an instruction from the control unit 1001. As described above, the paper surface detection unit 104 has the paper presence / absence detection flag 107 and the photo sensor 115, and when the uppermost sheet on the intermediate plate 101 is raised to a position where it can be fed by the rotation of the feeding roller 53. The paper surface detection signal 1051 is set to low level (off). As described above, the paper presence / absence detection unit 105 has the paper presence / absence detection flag 107 and the photo sensor 106. When the sheet is mounted on the intermediate plate 101 at a predetermined position during the lift-up of the intermediate plate 101, the presence / absence detection of the paper is detected. The signal 1041 is switched from the off state to the on state. The operation unit 1004 includes a display unit that displays a message to the user, an operation panel operated by the user, and the like. In FIG. 10, other sensors, mechanisms, and the like that are not referred to in the description of the present embodiment are omitted.

  FIG. 11 is a flowchart for explaining the control when the intermediate plate 101 as the sheet stacking table is raised in the LBP 1 according to the present embodiment. A program for executing this processing is stored in the ROM 1011 and is executed under the control of the CPU 1010.

  The processing shown in FIG. 8 is started when the sheet feeding cassette 52 is inserted into the sheet storage device 51, for example. Here, a sheet cassette detection means (not shown) detects the insertion of the cassette. At that time, normally, as shown in FIG. 8A, the paper surface detection unit 104 is in the sensor-on state, and the paper presence / absence detection unit 105 is in the sensor-off state. Therefore, in step S1, it is determined whether or not the paper surface detection signal 1041 is on. Since the paper surface detection signal 1041 is on, the process proceeds to step S2, and it is determined whether or not the paper presence / absence detection signal 1051 is on (paper present). Here, since the paper presence / absence detection signal 1051 is OFF, the process proceeds to step S3, and the lift motor 114 is rotationally driven via the motor driver 1003 to perform a normal lift-up operation.

  Then, as shown in FIG. 8B, when the paper presence / absence detection signal 1051 from the paper presence / absence detection unit 105 is switched from the sensor-off state to the sensor-on state during the lift-up, the process proceeds from step S2 to step S4. In step S4, the rotation of the lift motor 114 is stopped, and the lift-up operation is stopped for an arbitrary time. Here, for example, it stops for 100 ms. In step S5, it is determined whether the paper surface detection signal 1041 from the paper surface detection unit 104 has been turned off (has reached the paper feed position). If the paper surface detection signal 1041 is still in the ON state, the process proceeds to step S6, and the lift motor 114 is driven to rotate for 30 ms, for example, for 30 ms. Then, the process proceeds to step S4, the rotation of the lift motor 114 is again stopped for a predetermined time, the process proceeds to step S5, and the above-described processing is repeated. In this way, when the paper surface detection signal 1041 is turned off in step S5 and it is determined that the uppermost sheet of the intermediate plate 101 has reached the paper feed position, the process proceeds to step S7, and the paper feed standby as shown in FIG. It becomes a state.

  On the other hand, if the paper surface detection signal 1041 is off (the topmost sheet reaches the paper feed position) in step S1, the process proceeds to step S8, and it is determined whether or not the paper presence / absence detection signal 1051 at that time is on (paper present). If it is off here, it means that there is no sheet in the cassette, so the process proceeds to step S8, and a display indicating no sheet is displayed on the operation unit 1004 to warn the user. If the paper presence / absence detection signal 1051 is on (paper present) in step S8, the process proceeds to step S7, and a paper feed standby state as shown in FIG.

  FIG. 12 is a diagram comparing the lift-up operation control according to the present embodiment and the normal lift-up operation based on the number of sheets stacked in the cassette and the overrun amount.

  Reference numeral 1200 indicates lift-up operation control according to the present embodiment, and reference numeral 1201 indicates conventionally known lift-up operation control. According to this, it can be seen that the amount of overrun caused by the lift-up operation is reduced even when the number of cassettes loaded is small by the control of the present embodiment.

  FIG. 13 is a timing chart for explaining lift-up operation control in the LBP according to the present embodiment.

  Here, the rotation drive of the lift motor 114 is started with the paper surface detection signal 1041 being on and the paper presence / absence detection signal 1051 being off (timing T1). At timing T2, the paper presence / absence detection signal 1051 changes from the off state to the on state, so that the process proceeds from step S2 to step S4 in FIG. 11 to temporarily stop the rotation of the lift motor 114. In the lift-up control section 1300, for example, in the above-described example, the lift motor 114 is intermittently rotated every 30 ms to repeatedly perform lift-up driving (S6). At timing T3, when the paper surface detection signal 1041 is turned off and the uppermost sheet on the intermediate plate 101 can be fed, the rotational drive of the lift motor 114 is stopped, and the lift of the intermediate plate 101 is performed. Has finished up.

  By performing such control, as shown in FIG. 12, the overrun amount of the intermediate plate 101, such as the intermediate plate 101 being raised too much by the inertial force of the lifter motor 114, is reduced as compared with the normal lift-up control. it can. As a result, the sheet feeding position during sheet feeding is stabilized, and problems such as sheet non-feeding and double feeding can be prevented.

  Further, by using the control according to the present embodiment, the time required for lift-up becomes longer than that during normal lift-up. However, in the present embodiment, the interval for intermittent driving is limited using the detection result of the paper presence / absence detection unit 105, so that the time required for lift-up can be made relatively short.

  Even when the power is turned off while the middle plate 101 is being lifted, the state of the middle plate 101 as the sheet stacking table is detected by the paper presence / absence detection unit 105 when the power is turned on next time. Can be confirmed. This eliminates the need to memorize the situation during the lift-up, and even if the power is turned off during the lift-up, the raising operation of the intermediate plate 101 can be properly controlled.

  In the present embodiment, the existing paper presence / absence detection unit is used as a trigger for starting the control. For example, a sheet remaining amount detection unit that detects the remaining amount of sheets on the intermediate plate 101 is used. Detect remaining sheet capacity. The lift-up control may be executed when the predetermined sheet remaining amount is reached.

  In the present embodiment, the photo sensor 106, the photo sensor 115, and the flag 107 are used to perform the paper surface detection and the paper presence / absence detection. However, the present invention is not limited to this. For example, the paper surface detection and the paper presence / absence detection can be performed by changing the shape of the flag 107 and using one photosensor. In this case, the flag 107 may have a shape such as providing a slit at a portion that obliquely illuminates the photosensor.

1 is an external perspective view of an LBP according to an embodiment of the present invention. FIG. 2 is an external perspective view showing a state in which a paper feed cassette is pulled out from the state of FIG. 1. It is a schematic cross section which shows the whole structure of LBP which mounted | wore with the sheet storage apparatus based on this Embodiment. FIG. 4 is a mechanism diagram illustrating details of a sheet feeding unit of a sheet feeding cassette. It is a figure explaining the lift-up mechanism of the middle plate of a paper feed cassette. It is an external view of the mechanism part which shows the state which the intermediate plate fell from the state of FIG. FIG. 6 is a diagram illustrating a state in which the uppermost sheet of a paper feed cassette is fed. It is a figure explaining the lift up of the middle board in the paper feed cassette concerning this embodiment. FIGS. 9A and 9B are diagrams illustrating a state in which the middle plate is raised and paper can be fed. FIG. 9A illustrates a state with a sheet, and FIG. 9B illustrates a state without a sheet. It is a block diagram which shows schematic structure of LBP which concerns on this Embodiment. 6 is a flowchart for explaining control at the time of rising of a middle plate that is a sheet stacking base in the LBP according to the present embodiment. It is a figure which compares the lift-up operation control which concerns on this Embodiment, and normal lift-up operation by the sheet | seat stack | stacked number of sheets and overrun amount. It is a timing diagram explaining the lift-up operation control in LBP which concerns on this Embodiment.

Claims (7)

A sheet stacking means capable of stacking and storing sheets;
A feeding means for feeding the sheet in contact with the uppermost sheet stacked on the sheet stacking means;
Drive means for moving the sheet stacking portion of the sheet stacking means from a sheet replenishment position to a feeding position capable of being fed by the feeding means;
First detection means for detecting that the sheet stacking unit has moved to the feeding position;
Second detection means for detecting that the sheet stacking unit has reached a predetermined position other than the feeding position;
The driving unit is continuously driven until the second detection unit detects that the sheet stacking unit has reached the predetermined position, and after the detection by the second detection unit, the sheet stacking unit is moved by the first detection unit. Control means for controlling the drive means to be intermittently driven until it is detected that has moved to the feeding position;
A sheet feeding apparatus comprising: A sheet stacking means capable of stacking and storing sheets;
A feeding means for feeding the sheet in contact with the uppermost sheet stacked on the sheet stacking means;
Drive means for moving the sheet stacking portion of the sheet stacking means from a sheet replenishment position to a feeding position capable of being fed by the feeding means;
A sheet presence / absence detecting means for detecting the presence / absence of a sheet on the sheet stacking unit according to the movement of the sheet stacking means;
Control means for continuously driving the drive means when the sheet presence / absence detection means does not detect the sheet, and controlling the drive means to be intermittently driven when the sheet presence / absence detection means detects the sheet; ,
A sheet feeding apparatus comprising:   A sheet remaining amount detecting unit configured to detect a remaining amount of the sheet on the sheet stacking unit; and the control unit detects the remaining amount of the sheet detected by the sheet remaining amount detecting unit when the remaining amount of the sheet is a predetermined amount or less. The sheet feeding apparatus according to claim 1, wherein the driving unit is controlled. A sheet feeding device according to any one of claims 1 to 3,
Image forming means for forming an image on a sheet conveyed from the sheet feeding device;
An image forming apparatus comprising: A driving step of moving a sheet stacking unit of a sheet stacking unit capable of stacking and storing sheets from a sheet replenishment position to a feeding position capable of feeding by a feeding roller;
A first detection step of detecting that the sheet stacking unit has moved to the feeding position;
A second detection step of detecting that the sheet stacking unit has reached a predetermined position other than the feeding position;
In the driving process, the sheet is continuously driven in the driving process until it is detected in the second detection process that the sheet stacking unit has reached the predetermined position, and the feeding position is detected in the first detection process from the predetermined position. A control step of controlling the sheet stacking unit to move intermittently in the driving step until it is detected that the sheet stacking unit has been moved,
A sheet feeding control method comprising: A driving step of moving a sheet stacking unit of a sheet stacking unit capable of stacking and storing sheets from a sheet supply position to a feeding position capable of being fed by the feeding unit;
A sheet presence / absence detection step for detecting the presence / absence of a sheet on the sheet stacking unit according to the movement of the sheet stacking unit;
When the sheet is not detected in the sheet presence detection step, the sheet is continuously driven in the driving step, and when the sheet is detected in the sheet presence detection step, the sheet stacking unit is moved intermittently in the driving step to move the sheet stacking unit. A control process for controlling
A sheet feeding control method comprising:   A sheet remaining amount detecting step for detecting a remaining amount of sheets on the sheet stacking unit; and in the control step, the remaining amount of sheets detected in the sheet remaining amount detecting step is less than a predetermined amount. The sheet feeding control method according to claim 5, wherein the driving process is controlled.

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