JP2007197196A - Sheet supply device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet carrying device and an image forming device capable of quickly starting the movement of a lifting plate when moving the lifting plate to a proper carrying position from a document set position. <P>SOLUTION: In the document set position, when detecting a document bundle on a document tray by a set switch 603, when an upper limit switch 311 detecting that the lifting plate exists in the carrying proper position is in an off-state, a preliminary operation control part 602 drives a lift motor 503 so as to be liftable by a backlash quantity of a driving system gear of the lifting plate. Thus, since the lifting plate starts lifting driving without a delay after inputting a document supply starting indication, a first copy time can be shortened. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet supply apparatus and an image forming apparatus for supplying a sheet such as a document or a sheet onto which an image of the document is transferred, and in particular, a sheet supply apparatus having an elevating plate attached to a sheet placement surface to be movable And an image forming apparatus.

  An image forming apparatus such as a copying machine, a facsimile machine, a scanner, or a multifunction machine may be equipped with a document feeding device (sheet feeding device). By automatically conveying a plurality of documents one by one to the image reading position using the document feeder, the image forming apparatus can continuously read each document.

  The document feeder brings a bundle of documents into contact with a pickup roller in order to separate a plurality of documents stacked on a document tray one by one. Since the thickness of the original bundle varies depending on the number of originals stacked on the original tray, the distance between the original placement surface and the pickup roller should be set to the thickness of the original bundle in order for the original bundle to always contact properly. It is necessary to adjust accordingly. For this adjustment, an elevating plate attached to the document placement surface so as to be movable up and down can be used. The elevating plate is driven to push up the bundle of documents on the elevating plate and contact the pickup roller. For example, a lifting plate is pivotally supported upstream of the pickup roller in the document conveying direction, and the lifting plate is swung with respect to the shaft by a motor. As a result, the leading edge of the uppermost sheet of the original comes into contact with the pickup roller, and the pickup roller sends out the original.

  The stop position (proper conveyance position) of the lifting plate when the document is fed is detected by an upper limit position sensor (hereinafter referred to as an upper limit switch). The upper limit switch detects whether the upper surface of the document bundle is in contact with the pickup roller. For example, in the document feeder having a configuration in which the position of the pickup roller is fixed, the stop position is detected by the upper limit switch detecting the position of the upper surface of the document bundle. Further, in a document feeder having a mechanism in which the pickup roller comes into contact with the upper surface of the document bundle and then moves up with the lifting plate, the upper limit switch sets the position of the pickup roller or a member that moves in conjunction with the pickup roller. By detecting, the stop position is detected.

On the other hand, when the document is placed on the lifting plate, the lifting plate is at the document setting position (sheet setting position). The document setting position is usually the lower limit of the lifting range of the lifting plate. The lifting plate is moved to the document setting position when the previous document conveyance is completed. That is, when the sensor for detecting the presence / absence of a document on the document tray enters a non-detection state (no document), the elevating plate is driven downward. The elevating plate is lowered until the elevating plate is detected by a lower limit position sensor (hereinafter referred to as a lower limit switch) provided at a position facing the lower surface of the elevating plate (for example, Patent Documents 1 to 3). reference.).
JP 2000-53255 A JP 2000-95358 A JP 2005-187145 A

  The document feeder described above has a method of raising the lifting plate to a proper conveyance position when a document supply start instruction is input. In the document feeder employing this method, the elevating plate does not rise until the supply start instruction is input. Therefore, when the user misplaces the document bundle, the document is rearranged, or the document placed on the document tray. Documents can be added to the bundle.

  In this type of document feeder, when the document supply start instruction is input, a phenomenon that the lifting plate does not start to rise quickly occurs. As a result of analyzing this phenomenon, the inventors of the present application have come to the conclusion that the phenomenon is caused by backlash (backlash) of the gear that drives the lifting plate. When the elevating plate is raised to the proper conveyance position, the immediately preceding elevating plate is driven to move down to the original setting position. That is, when the elevating plate is raised to the proper conveyance position, the driving direction of the elevating plate is reversed from the previous driving direction. In such an operation in which the driving direction is reversed, even when the lift motor is driven, the driving force is not transmitted to the lifting plate until the gear backlash is eliminated. For this reason, the above phenomenon occurs.

  The present invention has been made in view of such a problem in the conventional technology, and when moving the lifting plate from the document setting position to the proper conveyance position, the sheet that can start the movement of the lifting plate without delay. An object of the present invention is to provide a transport device and an image forming apparatus.

  In order to achieve the above object, the present invention employs the following means. That is, in the sheet supply apparatus of the present invention, the elevating plate is attached to the sheet placement surface so as to be movable up and down. The sheet placed on the lift plate is sent out by a pickup roller. The driving means drives the lifting plate via a gear over a sheet setting position where the sheet is loaded and an appropriate conveyance position where the upper surface of the loaded sheet and the pickup roller are in contact with each other. The upper limit position sensor detects whether the upper surface of the sheet is in contact with the pickup roller. Then, when the upper limit position sensor detects that the upper surface of the sheet and the pickup roller are not in contact with each other when the sheet is mounted on the lifting plate, the preliminary operation control unit only drives the driving amount corresponding to the gear backlash. The drive means is operated in the upward direction. Here, the sheet supply apparatus is an apparatus that sends out sheet-like members such as a sheet on which a document or a document image is transferred one by one.

  In this sheet supply apparatus, the drive amount corresponding to the backlash of the gear that drives the lifting plate is driven in advance before being driven from the sheet setting position to the proper conveyance position. Accordingly, the movement of the lifting plate is started without delay. The above configuration is particularly suitable when the lifting plate is driven to an appropriate conveyance position when a sheet supply start instruction is input.

  In another aspect, the present invention can provide an image forming apparatus including the above-described sheet supply device. By supplying the original to the image reading position using the sheet supply apparatus or supplying the paper on which the image is formed to the image forming position, it is possible to appropriately form the image of the original.

  By adopting the above configuration, in the present invention, the backlash of the drive system gear is eliminated before driving of the lifting plate is started. For this reason, when the elevating plate is moved from the sheet setting position to the proper conveyance position, the elevating plate can be quickly moved. In addition, since there is no period during which the driving force is not transmitted to the elevating plate after the sheet supply start instruction is input, the first copy time can be shortened as compared with the prior art.

  Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings. In the following, the present invention is embodied as a digital copying machine equipped with a document feeder.

  FIG. 1 is a schematic diagram showing the overall configuration of the copying machine. As shown in FIG. 1, the copying machine 101 includes an image reading unit 102 and an image forming unit 103. The image reading unit 102 reads an image of a document and generates digital data of the image. The image reading unit 102 has a document table 104 made of a transparent plate such as contact glass on the upper surface of the casing. The document can be placed on the document table 104. A scanning optical system 105 is disposed below the document table 104. The scanning optical system 105 includes a first carriage 106, a second carriage 107, and a condenser lens 108. The first carriage 106 is provided with a linear light source 109 and a mirror 110, and the second carriage 107 is provided with mirrors 111 and 112. A light source 109 illuminates the document. The mirrors 110, 111, and 112 guide reflected light from the original to the lens 108, and the lens 108 forms an optical image on the light receiving surface of the line image sensor 113. In the scanning optical system 105, the first carriage 106 and the second carriage 107 are provided so as to be able to reciprocate in the sub-scanning direction 114. By moving the first carriage 106 and the second carriage 107 in the sub-scanning direction 114, the image of the document placed on the document table 104 can be read by the image sensor 113. The image sensor 113 generates document image data from the light image incident on the light receiving surface.

  The image forming unit 103 prints image data obtained by the image reading unit 102 or image data received from another device through a network via a network adapter (not shown) on paper. The image forming unit 103 is provided with a photosensitive drum 115. The photosensitive drum 115 rotates in the arrow direction 116 at a constant speed. Around the photosensitive drum 115, a charger 117, an exposure device 118, a developing device 119, a transfer device 120, and a cleaning unit 121 are arranged in this order from the upstream side in the rotation direction. The charger 117 uniformly charges the surface of the photosensitive drum 115. The exposure device 118 irradiates the uniformly charged surface of the photosensitive drum 115 with light according to the image data to form an electrostatic latent image on the photosensitive drum 115. The developing device 119 forms a toner image on the photosensitive drum 115 by attaching toner to the electrostatic latent image. The transfer device 120 transfers the toner image on the photosensitive drum 115 to a sheet. The cleaning unit 121 cleans the surface of the photosensitive drum 115 by removing waste toner remaining on the surface of the photosensitive drum 115 from the photosensitive drum 115 after the transfer. These processes are performed in a series as the photosensitive drum 115 rotates.

  The image forming unit 103 feeds paper from the manual feed tray 131, the paper feed cassettes 122 and 123, and the like to the transfer unit between the photosensitive drum 115 and the transfer device 120. Various sizes of paper can be placed or stored in the manual feed tray 131 and the paper feed cassettes 122 and 123. The image forming unit 103 selects a sheet specified by the user or a sheet corresponding to the automatically detected document size, and pulls out the selected sheet from the manual feed tray 131 or the cassettes 122 and 123 by the feeding roller 124. The drawn paper is sent to the transfer section by the transport roller 125 and the registration roller 126. The sheet on which the toner image is transferred is conveyed to the fixing device 127. The fixing device 127 includes a fixing roller 128 and a pressure roller 129, and fixes the toner image on the paper by heat and pressing force. The image forming unit 103 discharges the sheet that has passed through the fixing device 127 to the discharge tray 130.

  In such a copying machine 101, a document feeder 135 (sheet supply device) is attached to the upper side of the image reading unit 102 so as to be openable and closable. The document feeder 135 includes a document tray 136, a conveyance path 137, and a paper discharge tray 138. The user places a document on the document table 104 or sets a document (sheet) on the document feeder 135. The document feeder 135 sends the documents set on the document tray 136 one by one to the conveyance path 137. There is an image reading position 139 on the conveyance path 137. On the upper surface of the casing of the image reading unit 102, not only the document table 104 but also a reading glass 140 for the image reading position 139 is provided. When reading an image of a document set on the document feeder 135, the image reading unit 102 temporarily fixes the first carriage 106 and the second carriage 107 to the image reading position 139. When the document passes through the image reading position 139, the document is illuminated through the reading glass 140 to read the image of the document. The document that has passed the image reading position 139 is discharged to a discharge tray 138.

  FIG. 2 is a perspective view showing the appearance of the document feeder. In this document feeder 135, a lifting plate 203 having a document cursor 202 is attached to the document tray 136 downstream of the document transport direction 201 so as to be movable up and down. The document cursor 202 is provided so as to reciprocate in the document width direction 204. By using this document cursor 202 to align the document placed on the document tray 136, the center of the document in the width direction can be aligned with the machine. The elevating plate 203 forms a document placement surface together with the document tray 136, and pushes up the leading edge of the document in order to feed the documents one by one from the bundle of documents set on the placement surface to the conveyance path 137.

  FIG. 3 is a sectional view showing the entire configuration of the document feeder in more detail. The document feeder 135 includes a pickup roller 301, a feeding belt 302, and a separation roller 303 for separating documents one by one from a bundle of documents placed on a document tray 136. When the elevating plate 203 is raised, the leading edge of the uppermost sheet of the document bundle is pressed against the pickup roller 301.

  The pickup roller 301 is supported by the support case 310 so as to be rotatable in the document transport direction. The support case 310 is supported by the upper surface cover 320 so as to be swingable, for example, so that the pickup roller 301 can move upward. The upper cover 320 is provided with an upper limit switch 311 for detecting that the elevating plate 203 is in an appropriate position. The upper limit switch 311 is configured by a transmissive photo interrupter, for example. The support case 310 is provided with a protrusion 310a that reaches the photo interrupter and blocks light when the uppermost sheet of the document bundle is at an appropriate position for document conveyance. With this configuration, when the bundle of documents placed on the lifting plate 203 comes into contact with the pickup roller 301, the pickup roller 301 moves upward as the lifting plate 203 moves up. When the protrusion 310a reaches the upper limit switch 311, the lifting of the lifting plate 203 is stopped. Hereinafter, this position is referred to as an appropriate conveyance position.

  By driving the pickup roller 301 in this state, the original is pulled out from the original bundle. Even if there are two or more drawn documents, the first document is separated from the documents by the feeding belt 302 and the separation roller 303 and conveyed to the downstream side of the conveying path 137. A registration roller 304 and a conveyance roller 305 are provided downstream thereof. The timing at which the registration roller 304 conveys the image to the image reading position 139 is adjusted, and the conveying roller 305 conveys the document to the image reading position 139. An image on one side of the document is read at the image reading position 139. In the document feeder 135, a document reading unit 306 that employs a close contact optical system is disposed downstream of the image reading position 139. When reading images on both sides of the original, the original reading unit 306 reads the images on the remaining side. The document that has passed through the document reading unit 306 is transported to the discharge roller 308 by the intermediate transport roller 307, and is discharged to the discharge tray 138 by the discharge roller 308.

  A feed switch 321 made of a reflective photo interrupter or the like is disposed on the wall surface of the conveyance path 137 near the downstream side of the separation roller 303. A registration switch 322 made of a reflective photo interrupter or the like is disposed on the wall surface of the conveyance path 137 near the downstream side of the registration roller 304. Further, a timing switch 323 made of a reflective photo interrupter or the like is disposed on the wall surface of the conveyance path 137 between the registration switch 322 and the image reading position 139. By monitoring the timing at which these feed switch 321, registration switch 322, and timing switch 323 detect the presence or absence of a document, it is detected whether or not the document is normally conveyed on the conveyance path 137.

  When the last document on the document tray 136 is sent out, the elevating plate 203 is lowered. A rectangular frame 403 (see FIG. 4) on which the elevating plate 203 is installed is provided with a lower limit switch 312 made of a transmissive photo interrupter at a position facing the back surface of the elevating plate 203. On the back surface of the lifting plate 203 corresponding to the lower limit switch 312, a projection (not shown) is provided. When the protrusion on the rear surface of the lifting plate 203 reaches the lower limit switch 312 due to the lowering, the lowering of the lifting plate 203 stops. Hereinafter, this position is referred to as a document setting position (sheet setting position).

  FIG. 4 is a view showing a state in which the top cover 320 of the document feeder is opened. The document feeder 135 includes an upper surface cover 320 attached so as to be openable and closable. The conveyance path 137 is exposed by opening the upper surface cover 320. When a document is jammed on the conveyance path 137, the top cover 320 is opened and removed. The inner surface plate 402 of the upper surface cover 320 constitutes the upper surface of the transport path 137. A pickup roller 301 and a feeding belt 302 are disposed on the inner surface plate 402. Further, one of the pair of registration rollers 304 and the pair of transport rollers 305 is also disposed. The other of the registration roller 304 and the conveyance roller 305 and the separation roller 303 are provided on the main body side. When the top cover 320 is closed, the pickup roller 301 faces the lifting plate 203 on the downstream side of the lifting plate 203 in the document conveying direction 201. The elevating plate 203 is fitted in a rectangular frame 403 provided on the document tray 136. In the document feeder 135, the lift plate 203 swings in the vertical direction about an axis provided upstream of the lift plate 203 in the document transport direction 201.

  FIG. 5 is a perspective view showing a driving mechanism of the lifting plate. The elevating plate 203 has an insertion hole 501 for inserting the swing shaft on the upstream side of the document conveying direction 201 on the side surface. A drive mechanism 502 for swinging the lift plate 203 is disposed below the lift plate 203. The drive mechanism 502 includes a lift motor 503 formed of a stepping motor. A rotation shaft 504 of the lift motor 503 is connected to a drive shaft 506 via a gear group 505. A support plate 507 for supporting the elevating plate 203 is integrally attached to the drive shaft 506. When the drive shaft 506 rotates, the downstream side in the document transport direction of the lifting plate 203 supported by the support plate 507 moves up and down.

  FIG. 6 is a schematic functional block diagram showing a control unit of the document feeder 135 having the above-described configuration. FIG. 7 is a flowchart showing processing when a document bundle is placed on the document feeder 135. As shown in FIG. 6, the control unit 600 includes a transport control unit 601 and a preliminary operation control unit 602. The control unit 600 is configured as, for example, hardware including a dedicated arithmetic circuit, a processor and a memory such as a RAM and a ROM, and software stored in the memory and operating on the processor.

  The transport control unit 601 is connected to a lift motor 503, a paper feed motor 611, a registration motor 612, a transport motor 613, and a paper discharge motor 614, and controls each motor independently. Here, the sheet feeding motor 611 rotates the pickup roller 301 and also rotates the separation roller 303 via the feeding belt 302. The registration motor 612 rotates the registration roller 304. The carry motor 613 drives the carry roller 305 to rotate. A paper discharge motor 614 drives the intermediate conveyance roller 307 and the paper discharge roller 308 to rotate. The paper feed motor 611, the registration motor 612, the transport motor 613, and the paper discharge motor 614 are configured by stepping motors similarly to the lift motor 503.

  Further, output signals of the above-described upper limit switch 311, lower limit switch 312, feed switch 321, registration switch 322, timing switch 323, and set switch 603 are input to the conveyance control unit 601. The set switch 603 is a sensor that detects the presence or absence of a document on the document tray 316. The transport controller 601 outputs drive signals to the lift motor 503, the paper feed motor 611, the registration motor 612, the transport motor 613, and the paper discharge motor 614 based on these output signals.

  Output signals from the set switch 603 and the upper limit switch 311 are also input to the preliminary operation control unit 602. The preliminary operation control unit 602 is connected to the lift motor 503, and based on these output signals, the lift motor 503 outputs a control signal for driving a drive amount corresponding to backlash (backlash) of the gear group 505 (see FIG. 5). Output to. The driving amount corresponding to the backlash is obtained in advance by experiments and set in the preliminary operation control unit 602. When the lift motor 503 is a stepping motor, the drive amount can be set as the number of drive pulses of the lift motor 503, for example.

  Now, as shown in FIG. 7, when a document bundle is set on the document tray 136, the set switch 603 is switched from an OFF state to an ON state, for example, and the document bundle is detected (S701 in FIG. 7). In response to the change in the state of the set switch 603, the preliminary operation control unit 602 determines whether or not the upper limit switch 311 detects the rise of the pickup roller 301 (S702 in FIG. 7). In the present embodiment, the upper limit switch 311 is turned on when the pickup roller 301 is raised, and is turned off when the pickup roller 301 is not raised. For example, when a document bundle close to the upper limit capacity of the document tray 316 is placed, the upper limit switch 311 is turned on. When a small amount of document bundles are placed on the document tray 316, the upper limit switch 311 is turned off.

  When the upper limit switch 311 is in the OFF state, the preliminary operation control unit 602 performs a preliminary operation that drives the lift motor 503 in the upward direction by the amount of backlash (FIG. 7, S702 No → S709). When the lift plate 203 is at the document setting position, the drive direction of the previous lift plate 203 is the downward direction. Therefore, in the ascending driving of the lifting plate 203 that is executed for the first time after the document bundle is placed, the driving direction is reversed from the previous driving, so that the lift motor 503 is driven until the backlash of the gear group 505 is resolved. Force is not transmitted to the lift plate 203. However, in the present embodiment, since the backlash of the gear group 505 is eliminated by the preliminary operation, the subsequent lifting operation of the lifting plate 203 is executed without delay. When the preliminary operation is completed, the document feeder 135 enters a conveyance standby state until a document supply instruction is input (No in S703 in FIG. 7). On the other hand, when the upper limit switch 311 is in the ON state, the preliminary operation control unit 602 does not execute the preliminary operation, and the document feeder 135 enters the conveyance standby state until the document supply instruction is input (S702 Yes → S703 in FIG. 7). ).

  When the start button of the copying machine 101 is pressed in the above-described conveyance standby state, a document supply instruction (sheet supply start instruction) is input to the conveyance control unit 601. In response to the document supply instruction, the conveyance control unit 601 checks whether the upper limit switch 311 is on or off (S704 in FIG. 7).

  When the upper limit switch 311 is in the OFF state, the transport control unit 601 outputs a control signal that instructs the lift motor 503 to drive up. Thereby, the raising / lowering board 203 raises (FIG. 7 S704No-> S710). In the present embodiment, since the above-described preliminary operation is performed, the lifting plate 203 starts to rise without delay. When the pickup roller 301 is pushed up while abutting the upper surface of the document bundle while the elevating plate 203 is raised, the upper limit switch 311 is switched from the off state to the on state. In response to the state change of the upper limit switch 311, the conveyance control unit 601 instructs the lift motor 503 to stop the ascending drive. As a result, the lifting plate 203 stops at the proper transport position of the document (S704 Yes → S705 in FIG. 7). Further, when the protrusion on the rear surface of the lifting plate 203 escapes from the lower limit switch 312 while the lifting plate 203 is raised, the lower limit switch 312 is switched from an on state to an off state, for example. If the upper limit switch 311 is on when the document supply instruction is input, the conveyance control unit 601 does not drive the lift motor 503 (S704 No → S705 in FIG. 7).

  When it is confirmed that the upper limit switch 311 is in the ON state, the conveyance control unit 601 executes document conveyance (S706 in FIG. 7). First, the transport control unit 601 inputs a drive signal to the paper feed motor 611 and rotates it in the transport direction. When the feed switch 321 detects a document within a predetermined number of drive pulses (set time) from the start of driving of the paper feed motor 611, the transport control unit 601 further increases the constant drive pulse number from the time when the feed switch 321 detects the document. Only the paper feed motor 611 is rotated in the transport direction and stopped. By this operation, the document is pressed against the registration roller 304 in a state where the deflection is formed. At this time, the excitation of the paper feed motor 611 is maintained.

  Next, the conveyance control unit 601 rotationally drives the registration motor 612, the conveyance motor 613, and the paper discharge motor 614 in the conveyance direction. When the registration switch 322 detects a document within a predetermined set time (number of drive pulses) from the start of driving of the registration motor 612, the conveyance control unit 601 waits until the timing switch 323 detects the document. When a document detection signal is input from the timing switch 323, the conveyance control unit 601 registers the registration switch 322 within a predetermined number of drive pulses (conveyance amount) set according to the document size from the time when the document is detected. The registration motor 612 is stopped when it is confirmed that the document has passed. At this time, the excitation of the registration motor 612 is maintained.

  If the set switch 603 is on (original is present) when the registration motor 612 is stopped, the conveyance control unit 601 determines the state of the upper limit switch 311 (S707 Yes → S704 in FIG. 7). At this time, if the upper limit switch 311 is in the ON state, the conveyance control unit 601 conveys the next original document in the stopped state without driving the lift motor 503 (FIG. 7, S704 Yes → S705 → S706). If the upper limit switch 311 is off, the conveyance control unit 601 drives the lift motor 503 to raise the lift plate 203 until the upper limit switch 311 is turned on (S704 No → S710 in FIG. 7). When the upper limit switch 311 is turned on, the conveyance control unit 601 stops the lifting of the elevating plate 203 and executes the conveyance of the next original (FIG. 7, S704 Yes → S705 → S706).

  On the other hand, if the registration switch 322 confirms that the document has passed, and the set switch 603 is off (no document), the conveyance control unit 601 sets the conveyance motor 613 and the discharge motor 614 according to the document size. After driving the predetermined number of drive pulses and conveying the final document, the excitation of the motors 611, 612, 613, and 614 is turned off. At the same time, the conveyance control unit 601 drives the lift motor 503 downward until the lower limit switch 312 detects a protrusion on the back surface of the lift plate 203 (S706 No. → S707 in FIG. 7). When the lower limit switch 312 detects the lifting plate 203, the transport control unit 601 turns off the excitation of the lift motor 503.

  Although not shown in FIG. 7, when the document detection states of the feed switch 321, the registration switch 322, and the timing switch 323 are different from the above-described states, the conveyance control unit 601 performs a retry process according to the states. Do. If normal document conveyance is not performed even by the retry process, the conveyance control unit 601 determines conveyance failure (jam) and stops the document conveyance operation.

  As described above, in the document feeding device (sheet conveying device) of the copying machine according to the present embodiment, the backlash of the drive system gear is eliminated before the driving of the lifting plate is started. For this reason, when the elevating plate is moved from the sheet setting position to the proper conveyance position, the elevating plate can be quickly moved. In addition, since there is no period during which the driving force is not transmitted to the elevating plate after the sheet supply start instruction is input, the first copy time can be shortened as compared with the prior art. Further, in the present embodiment, the preliminary operation is performed only when the upper limit switch 311 is in the off state when the document bundle is placed on the document tray 316. This is because when the upper limit switch 311 is in the ON state, the document is conveyed without being raised, so that there is no difference from the conventional one in terms of the first copy time. Of course, the preliminary operation may be performed when the upper limit switch 311 is in the ON state.

  The above-described embodiments do not limit the technical scope of the present invention, and various modifications and applications other than those already described are possible within the scope of the present invention. For example, in the above-described embodiment, the document is moved up and down by swinging one end of the lifting plate, but the present invention is not limited to this. The present invention can also be applied to a document feeder that moves a document up and down by moving a lift plate up and down.

  In the above-described embodiment, the present invention is embodied as an original feeding device of a digital copying machine. However, the present invention is applied to a paper supply device such as a cassette type paper tray or a manual feed tray as shown in FIG. It is also possible. In addition, the present invention can be applied not only to a digital copying machine but also to an apparatus having a sheet supply function, such as a facsimile, a scanner, and a multifunction machine.

  The sheet supply apparatus and the image forming apparatus according to the present invention can reliably supply originals and papers in a short time, and are useful for various devices such as copiers, facsimiles, scanners, and multifunction machines.

1 is a schematic configuration diagram showing the overall configuration of a copying machine to which the present invention is applied. 1 is a perspective view showing an external appearance of a document feeder in one embodiment of the present invention. Sectional drawing which shows the structure of the document feeder in one Embodiment of this invention. The perspective view which shows the state which opened the upper surface cover of the original feeding apparatus in one Embodiment of this invention. The perspective view which shows the drive mechanism of the raising / lowering board in one Embodiment of this invention. 1 is a block diagram showing a control unit of a document feeder in one embodiment of the present invention. The flowchart which shows the process of the document feeder in one Embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Copier 102 Image reading part 103 Image forming part 135 Document feeder (sheet supply apparatus)
136 Document tray 203 Lift plate 301 Pickup roller 311 Upper limit switch (upper limit position sensor)
502 Drive Mechanism 503 Lift Motor 505 Gear Group 601 Conveyance Control Unit 602 Preliminary Operation Control Unit 603 Set Switch

Claims (3)

An elevating plate attached to the seating surface so as to be movable up and down;
A pick-up roller for feeding out the sheet placed on the lifting plate;
Means for driving the elevating plate through a gear over a sheet setting position where the sheet is mounted and an appropriate conveyance position where the upper surface of the mounted sheet and the pickup roller abut;
An upper limit position sensor for detecting whether or not the upper surface of the sheet and the pickup roller are in contact with each other;
When the sheet is mounted on the lift plate, when the upper limit position sensor detects that the upper surface of the sheet and the pickup roller are not in contact with each other, the drive means is driven by a drive amount corresponding to the backlash of the gear. Means for performing a preparatory movement to move in the upward direction;
A sheet supply apparatus comprising:   The sheet feeding apparatus according to claim 1, wherein when the sheet feeding start instruction is input, the lifting plate is driven to the proper conveyance position. An image forming apparatus comprising the sheet supply device according to claim 1.

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