JP2012035969A - Document feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid upsizing of a motor, an increase in power consumption and an increase in cost of a document feeding device, and also, to detect whether a pickup roller is located in a retreat position in the document feeding device.SOLUTION: In the document feeding device 100, a sensor 260 is configured to detect the presence or the absence of the document on a paper feed tray 14. Besides, when a prescribed omission pattern is detected in the detection output of the sensor 260 during the non-feed period of the document feeding device 100 (in the state in which the pickup roller 104 should be located in the retreat position), it is determined that the pickup roller 104 is shifted from the retreat position, and then, a process (step S16) to locate the pickup roller 104 in the retreat position again is performed.

Description

  The present invention relates to an original conveying apparatus, and more particularly, to an original conveying apparatus that conveys an original by rotating a roller.

  Conventionally, in a document conveying device applied to a facsimile machine, a copying machine, a scanner device, etc., after separating a document placed on a document tray one by one and conveying it to an image reading unit along a document conveying path, A mechanism is employed that discharges an original whose image has been read to a discharge tray. In such a document conveying device, the document placed on the document tray is fed out to the document conveying path by a pickup roller.

  In such a document transport device, the pickup roller is held at the retracted position so as not to interfere with the next document placed on the document tray when the document is not fed out. Various mechanisms for holding the pickup roller at the retracted position have been disclosed. For example, Japanese Patent Laid-Open No. 2002-249246 discloses a configuration in which a pickup roller is held by a torque limiter. Specifically, the pickup roller (feeding roller) is pivotally supported by a bracket, is rotationally driven in conjunction with the paper feed roller, and moves to a standby position by rotating the bracket. The bracket is rotatably supported by the drive shaft. The pickup roller that has moved to the standby position is held at the standby position by the torque limiter holding torque applied to the drive shaft until the next paper feeding operation is performed.

JP 2002-249246 A

  In the mechanism disclosed in Patent Document 1, the pickup roller is held at the standby position by the torque limiter. Therefore, when the pickup roller moves from the paper feeding position to the retracted position or from the retracted position to the paper feeding position. During the paper feeding operation, torque of the torque limiter is applied to the motor as a driving load, which increases the size of the motor, hinders downsizing of the device, increases power consumption, etc. There was a problem.

  On the other hand, when the holding at the retracted position by the torque limiter is not performed, it is necessary to detect that the pickup roller is held at the retracted position. If a dedicated sensor is mounted for the detection, the cost of the apparatus is reduced. There is a new challenge of raising it.

  The present invention has been conceived in view of the actual situation, and an object of the present invention is to provide a pickup roller in a document conveying device while avoiding an increase in motor size and power consumption, and an increase in cost of the device. It is to detect whether or not it is held at the retracted position.

  The document conveying device of the present invention is a document conveying device that includes a tray and conveys a document stacked on the tray, and includes a pickup roller that picks up the document from the tray by contacting the document on the tray, and a pickup roller. Switching for switching between a driving means for driving, a driving shaft for transmitting power of the driving means to the pickup roller, and a state in which the driving shaft is connected to the driving means and a state in which the connection with the driving means is released Means, a holding means for holding the pickup roller at a retracted position with respect to the document on the tray when the drive shaft is disconnected from the drive means, and a detection means for detecting the presence or absence of the document on the tray And the detection means is in a first state when a document is present on the tray and is in a second state when a document is not present on the tray. The lever member temporarily takes the second state during the period in which the pickup roller is displaced from the retracted position to the paper feed position where the pickup roller contacts the document on the tray, and the detection means is driven by the switching means and the drive shaft. When the connection with the means is released, it is detected that the pickup roller is out of the retracted position on condition that the lever has been in the second state for a certain period or longer.

  The document conveying device of the present invention further includes moving means for moving the pickup roller to the retracted position, and the moving means moves the pickup roller when the detecting means detects that the pickup roller has moved out of the retracted position. It is preferable to move to the retracted position.

  The document conveying device of the present invention further includes a case that covers the outer periphery of the document conveying device so as to be openable and closable, and a detection unit that detects whether the case is open or closed. On this condition, it is preferable to move the pickup roller to the retracted position.

  In the document conveying device of the present invention, when the moving unit moves the pickup roller to the retracted position more than a predetermined number of times within a predetermined time, the moving means moves to the retracted position of the pickup roller further during the predetermined period. It is preferable not to move.

  According to the present invention, it is possible to detect that the pickup roller is out of the retracted position by using the detection unit that detects the presence or absence of the document on the tray.

  As a result, it is possible to detect that the pickup roller is out of the retracted position without holding the pickup roller by the torque limiter and without adding a dedicated sensor.

(A) is a schematic diagram illustrating copying machine 1 according to the embodiment of the present invention, and (B) is a cross-sectional view of document conveying apparatus 100 according to the embodiment of the present invention. FIG. 2 is an enlarged view for explaining a configuration of a paper feed roller and a drive unit thereof in FIG. 1. It is an enlarged view for demonstrating the structure of the supporting member vicinity of FIG. FIG. 2 is a diagram for explaining a mechanism for detecting the presence / absence of an original on the paper feed tray of FIG. 1. FIG. 2 is a diagram for explaining a mechanism for detecting the presence / absence of an original on the paper feed tray of FIG. 1. FIG. 2 is a diagram for explaining a mechanism for detecting the presence / absence of an original on the paper feed tray of FIG. 1. FIG. 2 is a control block diagram of the document conveying device in FIG. 1. 3 is a flowchart of processing executed by the CPU of the document conveying device in FIG. 1 to detect that the pickup roller has moved out of the retracted position. 10 is a flowchart of processing executed in Modification 1 of the document feeder. 10 is a timing chart showing the operation timing of each element in Modification 1 of the document feeder. 10 is a flowchart of processing executed in Modification 2 of the document feeder.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same.

FIG. 1A is a schematic diagram illustrating a copying machine 1 according to an embodiment of the present invention.
Referring to FIG. 1A, copying machine 1 according to the embodiment of the present invention includes a document conveying device 100 and an image forming apparatus 200 connected thereto. The image forming apparatus 200 reads an image on a document surface, temporarily stores it in a memory, performs various image editing processes as necessary, forms an image on a recording sheet by a known electrophotographic method, and copies it from a discharge unit. This is called a so-called digital copying machine that discharges the used sheets one by one.

  In the copying machine 1, the document conveying device 100 is mounted on the upper part of the image forming apparatus 200. The document conveying apparatus 100 conveys one or more documents set on the sheet feeding tray 14 one by one, causes the image reader unit 20 of the image forming apparatus 200 to read an image, and after the image reading is completed. The original is discharged onto the paper discharge tray 16 and stacked. In the case of a double-sided document, the document conveying device 100 conveys both the front and back images so as to pass through the image reader unit 20 and then discharges them onto the sheet discharge tray 16. These document conveyance controls are performed by the document conveyance control unit 15.

  The image forming apparatus 200 includes a control unit 22 and an image forming unit 24. A document set on a platen glass (not shown) by the document conveying apparatus 100 or hand placement is read by the image reader unit 20, converted into digital data, and stored in the memory of the control unit 22. The image forming unit 24 reads the image data from the memory of the control unit 22, executes an image printing process on the recording paper P supplied from the paper feeding unit 18, and prints the recording paper after the printing process. Discharge.

FIG. 1B is a cross-sectional view of document conveying apparatus 100 according to the embodiment of the present invention.
Referring to FIG. 1B, document conveying apparatus 100 is covered with a cover 102, and various members including a plurality of conveying rollers are provided inside. Note that the cover 102 includes a door 102 </ b> A so as to cover the outline of the document conveying apparatus 100 so as to be opened and closed. The door 102A is configured to be rotatable in the direction of the double arrow A10 about the shaft 102X.

  The document conveying device 100 is in contact with the uppermost document 122 of the bundle of documents 122 to be conveyed, and a pickup roller 104 that conveys the document to the inside of the document conveying device 100, a separation roller 106 that separates the documents 122 one by one, and A sheet feeding roller 105, a document 122 separated into one sheet, a registration roller 110 that corrects skew of the document, and a document 122 sent by the registration roller 110 are transported to a reading position 212 on the platen glass 210. The reading pressure roller 116 that makes a pair with the pre-reading roller 115 and the pre-reading roller 115 that performs, and the conveyance pressure that makes a pair with the post-reading roller 120 and the post-reading roller 120 that convey the original 122 after passing through the reading position to the discharge tray. And a roller 121. It is assumed that the pressure with which the reading pressure roller 116 and the pre-reading roller 115 sandwich the document 122 is generated by the pressure spring 114.

  The document feeder 100 includes a sensor 160 that detects the presence or absence of a document on the paper feed tray 14. Sensor 160 includes a lever 162. In the present embodiment, the sensor 160 detects whether or not the pickup roller 104 that should be in the retracted position is not out of the retracted position, in addition to the presence or absence of the document on the paper feed tray 14. Details of these detections will be described later.

  In the document conveying apparatus 100 according to the present embodiment, the pickup roller 104 is positioned on the placement indicated by the solid line in FIG. 1B when the document 122 on the sheet feeding tray 14 is fed out to the conveying path. On the other hand, the pickup roller 104 is located at the retracted position as indicated by a broken line 104A in FIG. A mechanism for holding the pickup roller 104 at the retracted position will be described later.

FIG. 2 is an enlarged view for explaining the configuration of the paper feed roller 105 and its drive unit.
Referring to FIG. 2, paper feed roller 105 is provided on drive shaft 131. A pair of support members 142 and 143 are provided on both sides of the paper feed roller 105. The support members 142 and 143 are rotatably supported on the drive shaft 131.

  The pickup roller 104 has its shaft portion (pickup roller shaft 137) held by a pair of holding members 132 and 133 in a rotatable manner. A pulley 134 on the drive shaft 131 and a pulley 138 on the pickup roller shaft 137 are connected by a timing belt 135. The pickup roller 104 is configured to rotate in conjunction with the rotation of the drive shaft 131 by the timing belt 135.

  A paper feed motor 203 is provided as a drive source of each roller shown in FIG. By the pulley 136, the timing belt 139, and the gear train 140, the driving force of the paper feed motor 203 is transmitted to the drive shaft 131 while being decelerated.

  One gear in the gear train 140 is provided with an electromagnetic clutch 205 (see FIG. 7). When the electromagnetic clutch 205 is turned on, the driving force of the paper feed motor 203 is transmitted to the drive shaft 131. When the electromagnetic clutch 205 is turned off, the transmission of the driving force of the paper feed motor 203 to the drive shaft 131 is released.

  The electromagnetic clutch 205 is turned on when the paper feeding roller 105 and the pickup roller 104 are rotated to feed a document. In all other cases, the electromagnetic clutch 205 is normally turned off. When the electromagnetic clutch 205 is turned off, the rotation of the drive shaft 131 is also free. When the rotation of the drive shaft 131 is in a free state, if there is nothing to hold the pickup roller 104, the pickup roller 104 is lowered to the paper feeding position by its own weight. When the pickup roller 104 is lowered to the sheet feeding position, the pickup roller 104 becomes an obstacle when setting a document on the sheet feeding tray 14.

  In document conveying apparatus 100 of the present embodiment, protrusions 142A and 143A are provided on the side surfaces of support members 142 and 143. The protrusions 142A and 143A are held by the holding members 132 and 133 configured by leaf springs, whereby the pickup roller 104 and the support members 142 and 143 can be retracted at the retracted position.

FIG. 3 is an enlarged view for explaining the configuration in the vicinity of the support members 142 and 143.
Referring to FIG. 3, torque limiters 152 and 153 are provided at portions where support members 142 and 143 are pivotally supported on drive shaft 131. The torque limiters 152 and 153 and the drive shaft 131 are engaged by a balance pin (not shown).

  When the drive shaft 131 rotates in the direction of feeding the document, a constant moment is applied to the pickup roller 104 in the direction of pressing the document by the torque limiters 152 and 153. As a result, the document is fed to the transport path.

  When the pickup roller 104 and the support members 142 and 143 move to the retracted position, the drive shaft 131 rotates in the direction of arrow A1 in FIG. As the drive shaft 131 rotates in this way, the pickup roller 104 moves to the retracted position held by the holding members 132 and 133. As a result, the pickup roller 104 is held at the retracted position.

  When the pickup roller 104 and the support members 142 and 143 move from the retracted position to the paper feeding position, the drive shaft 131 rotates in the direction of arrow A2 in FIG. As the drive shaft 131 rotates in the arrow A2 direction, the pickup roller 104 moves to the paper feed position. The pickup roller 104 can feed a sheet by applying a constant pressing force by the torque limiters 152 and 153.

  4 to 6 are views for explaining a mechanism for detecting the presence or absence of a document on the paper feed tray 14.

  In the document conveying device 100, a lever 162 is provided in the vicinity of the pickup roller shaft 137 and between the two pickup rollers 104. The tip of the lever 162 is located between the light projecting unit 161A and the light receiving unit 161B of the detection sensor 161. FIG. 5 shows a state where the pickup roller 104 is located at the retracted position.

  When the pickup roller 104 is displaced from the retracted position as shown in FIG. 5 to the paper feeding position, the pickup roller shaft 137 contacts the portion of the arrow A3 lever 162 surrounded by the circle R1. When the pickup roller shaft 137 contacts the portion surrounded by the circle R1, the lever 162 rotates in the direction indicated by the arrow A4 about the shaft 160A. Thereby, the light emitted from the light projecting unit 161A is temporarily received by the light receiving unit 161B.

  When the pickup roller 104 moves from the state shown in FIG. 5 to the paper feeding position, the lever 162 rotates about the shaft 160A in the direction opposite to the arrow A4 and returns to the state shown in FIG. Accordingly, the tip of the lever 162 is again positioned between the light projecting unit 161A and the light receiving unit 161B. Thereby, the light emitted from the light projecting unit 161A is blocked by the tip of the lever 162 and does not reach the light receiving unit 161B.

  The flow of displacement of the pickup roller shaft 137 and the lever 162 when the pickup roller 104 moves from the retracted position to the paper feeding position will be described with reference to FIGS.

  6A shows the positions of the pickup roller shaft 137 and the lever 162 when the pickup roller 104 is located at the retracted position. When the pickup roller 104 moves out of the retracted position and moves to the paper feeding position, the pickup roller shaft 137 contacts the lever 162 as shown in (B) to rotate the lever 162. Note that the state shown in (B) of the lever 162 corresponds to the state when the document 122 is present on the paper feed tray 14.

  A state in which the pickup roller shaft 137 moves downward as the pickup roller 104 further approaches the paper feeding position is shown in FIG.

  (D) shows the position of the pickup roller shaft 137 when the pickup roller 104 moves to the paper feed position. In this state, the lever 162 is returned to the state shown in (A) when the contact with the pickup roller shaft 137 is released. Accordingly, the tip of the lever 162 is positioned between the light projecting unit 161A and the light receiving unit 161B.

FIG. 7 is a control block diagram of the document conveying device 100.
Referring to FIG. 7, document conveying apparatus 100 includes a CPU (Central Processing Unit) that controls the operation of document conveying apparatus 100 as a whole. The CPU 201 executes the program stored in the memory 201A to operate the document conveying apparatus 100 in the manner described in this specification.

The detection output of the sensor 260 is input to the CPU 201.
Document conveying apparatus 100 further includes a motor 207 for rotating the registration roller 110 and a registration clutch 209 that switches between fixing and releasing the registration roller 110 at the registration position. Further, the document conveying apparatus 100 includes a motor driving circuit 202, a clutch driving circuit 204, a motor driving circuit 206, and a clutch driving circuit 208 for driving each of the paper feeding motor 203, the electromagnetic clutch 205, the conveying motor 207, and the registration clutch 209. including.

  The document feeder 100 further includes sensors 500, 501 and 502 for detecting the length of the document on the paper feed tray 14. These detection outputs are input to the CPU 201.

  Further, the document conveying apparatus 100 includes sensors 210, 211, 212, and 213 for detecting the position of the document on the conveying path. These detection outputs are input to the CPU 201.

  The document feeder 100 also includes a sensor 214 that detects opening and closing of the door 102A.

  The CPU 201 of the document conveying apparatus 100 is configured to be able to communicate with the image reader unit 20.

  The image reader unit 20 drives the CPU 221 that controls the image reader unit 20 as a whole, a motor 223 for moving a light receiving element such as a CCD (Charge Coupled Devices) that reads an image of a document, and a motor 223. A motor driving circuit 222, an image reading unit 225 including the light receiving element, and an image processing unit 224 that appropriately processes an image read by the image reading unit 225.

  The CPU 201 of the document feeder 100 is configured to be able to communicate with the CPU 221 of the image reader unit 20.

  In the document conveying apparatus 100 of the present embodiment described above, as described mainly with reference to FIGS. 6A to 6D, the sensor 160 that detects the presence or absence of the document on the sheet feeding tray 14. It is possible to detect that the pickup roller 104 is out of the retracted position using the detection output.

  Specifically, the drive shaft 131 is rotated in the direction of arrow A1 in FIG. 3 so that the pickup roller 104 is held in the retracted position, and before the drive shaft 131 is rotated in the direction of arrow A2 in FIG. When the light receiving unit 161B receives light in the sensor 160, it is determined that the pickup roller 104 has deviated from the retracted position on the assumption that the pickup roller shaft 137 is displaced as shown in FIGS. .

  As shown in FIGS. 6A to 6D, when the pickup roller shaft 137 is displaced from the retracted position to the paper feeding position, the light receiving unit 161B is shown in FIG. As shown, light is received for a certain period TA. In FIG. 6E, the state where the light receiving unit 161B does not receive light is indicated by “OFF”, and the state where light is received is indicated by “ON”. 6 (B) and 6 (C), the period when the tip of the lever 162 is not positioned between the light projecting unit 161A and the light receiving unit 161B is rotated by contact with the pickup roller shaft 137. Opposite the period TA.

  FIG. 8 is a flowchart of processing executed by the CPU 201 of the document conveying apparatus 100 to detect that the pickup roller 104 is out of the retracted position.

  Referring to FIG. 8, when a certain condition is satisfied, CPU 201 sets document conveying apparatus 10 to the standby mode in step S10, and advances the process to step S12. Note that the certain conditions include, for example, that the copying machine 1 does not input an instruction for image formation for a specific period. In step S10, the CPU 201 performs processing for holding the pickup roller 104 in the retracted position (controls the motor drive circuit 202 so as to rotate the drive shaft 131 in the direction of arrow A1 in FIG. 3).

  In step S12, the CPU 201 starts checking the detection output of the sensor 260 and advances the process to step S14.

  In step S14, the CPU 201 determines whether or not a predetermined dropout pattern has been detected in the output of the sensor 260. If it is determined that the detection has been detected, the process proceeds to step S16.

  Here, the dropout pattern is a pattern as indicated by a line L1 in FIG. Specifically, this is a pattern in which a corresponding signal is detected only when a document is present on the sheet feed tray 14 for a predetermined period. In step S14, the period in which the signal corresponding to the document existing on the paper feed tray 14 is detected has a width from a certain short period to a certain long period with respect to the period TA in FIG. If it is included, it may be determined that an output corresponding to the dropout pattern described above has been detected.

  In step S16, the CPU 201 executes a process for holding the pickup roller 104 in the retracted position, and returns the process to step S12. The process for holding the pickup roller 104 in the retracted position includes, for example, controlling the motor drive circuit 202 so as to rotate the drive shaft 131 in the direction of arrow A1 in FIG.

  The process shown in FIG. 8 is continued until the condition for canceling the standby mode in the document conveying apparatus 100 is satisfied.

  Note that the CPU 201 may control the rotation of the drive shaft 131 in the direction of arrow A2 in FIG. 3 to return the pickup roller 104 to the paper feed position when the standby mode of the document conveying apparatus 100 is released.

(Modification 1)
In the document conveying apparatus 100 of the present embodiment described above, the presence / absence of a document on the paper feed tray 14 is detected during a period in which the document is not conveyed (when the pickup roller 104 should be in the retracted position). If a predetermined dropout pattern is detected in the detection output of the sensor 260, the process for relocating the pickup roller 104 to the retracted position (step S16) is executed again assuming that the pickup roller 104 has moved out of the retracted position. Is done.

  The determination as to whether or not the detection output of the sensor 260 has become a drop pattern does not have to be executed when the cover 102 (door 102A) is in the open state.

  In such a modification, the process described with reference to FIG. 8 is changed as shown in the flowchart of FIG.

  Referring to FIG. 9, in this modification, CPU 201 determines whether or not the door is open in step S <b> 11 after placing document feeder 100 in standby mode in step S <b> 10. And if it is judged that it is an open state, a process will be returned to step S10. On the other hand, if it is determined that the door 102A is closed, the process proceeds to step S12.

  Whether door 102A is open or closed is determined based on the detection output of sensor 214.

  FIG. 10 is a timing chart showing the operation timing of each element of the document conveying apparatus according to this modification.

  In FIG. 10, a line L11 indicating the presence / absence of a document conveying operation in the document conveying apparatus 100, a line L12 indicating the presence / absence of light reception in the light receiving unit 161B of the sensor 260, and a line L13 indicating the open / closed state of the door 102A (cover 102). A line L14 indicating the ON / OFF state of the control for raising the pickup roller 104 to the retracted position is shown.

  In FIG. 10, first, it is shown that the document conveying operation is being executed from time T10 to T12 (line L11). As a result, line L12 indicates that a document was present on paper feed tray 14 until time T11 (line L12).

  When the document conveying apparatus 100 shifts to the standby mode at time T12 (“standby” on the line L11), a check is started as to whether or not the above-described dropping pattern is detected in the output of the sensor 260.

  In the example of FIG. 10, a signal received by the light receiving unit 161B is output from time T13 to T14. This is assumed to match the dropout pattern described above. In response, the pick-up roller lifting control is started from time T14 (line L14).

  In FIG. 10, as indicated by an ellipse R, a signal corresponding to the output of the sensor 260 when a document is present on the paper feed tray 14 is output. This is caused by the pickup roller 104 coming into contact with the lever 162 when the pickup roller 104 is moved to the retracted position. When the pickup roller 104 moves to the retracted position, as shown in FIGS. 6D to 6A, that is, in a mode opposite to the displacement from the retracted position to the sheet feeding position. The pickup roller shaft 137 and the lever 162 are displaced.

  In the example of FIG. 10, it is detected from time T17 to T20 that the cover 102 (door 102A) is opened (line L13). From this, during this period, from time T18 to T19, a signal matching the drop pattern described above is output from the sensor 260 (line L12), but since the door 102A is in the open state, the step The processes after S12 are not performed (when YES is determined in step S11 of FIG. 9).

(Modification 2)
In the document conveying apparatus 100 of the present embodiment, when the pickup roller ascent control is executed more than a predetermined number of times within a predetermined time, an error is displayed and the pickup roller 104 is not ascended further. It can also comprise.

In such a modification, the flowchart of FIG. 8 is changed as shown in FIG.
FIG. 11 is a flowchart of processing executed in Modification 2 of the document conveying device.

  Referring to FIG. 11, in the present modification, after the process of moving pickup roller 104 to the retracted position is executed in step S16, the process proceeds to step S17.

  In step S17, the CPU 201 increments the count value n of the counter for the number of times the above-described increase control has been performed, increments the count value of the timer T by 1, and advances the process to step S18.

  In step S18, the CPU 201 starts counting the timer T and advances the process to step S19.

  In step S19, the CPU 201 determines whether or not the count value of the timer has reached y. If it is determined that the timer has not yet reached, the process proceeds to step S20.

  In step S20, the CPU 201 determines whether or not the count value n of the number of increases has reached y, and if it has not yet reached, returns the process to step S14.

  On the other hand, when determining in step S20 that the number of times of increase n has reached X, the CPU 201 advances the process to step S21.

  In step S <b> 21, the CPU 201 notifies the operation failure of the pickup roller 104 and ends the process. The malfunction notification is realized, for example, by providing a lamp or the like on the document feeder and turning on the lamp.

  If it is determined in step S19 that the count value of timer T has not yet reached y, the process returns to step S10.

  In this modification, the count value of the timer T is reset every time the standby mode is set in step S10. Note that the count operation of the timer T is continued until the reset is performed in this manner.

  In the present modification described above, the timer T starts counting when the pickup roller lift control is executed. Then, when the pickup roller ascent control is executed X times or more from the start of the counting operation of the timer T until the time y elapses, the ascent control of the pickup roller 104 is executed (step S16). The malfunction of the pickup roller 104 is notified without executing the process (steps S12 to S14).

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 Document transport device, 14 Paper feed tray, 104 Pickup roller, 105 Paper feed roller, 131 Drive shaft.

Claims (4)

A document conveying device that includes a tray and conveys documents stacked on the tray,
A pickup roller for feeding out the original from the tray by contacting the original on the tray;
Driving means for driving the pickup roller;
A drive shaft for transmitting the power of the drive means to the pickup roller;
Switching means for switching the drive shaft between a state connected to the drive means and a state of releasing the connection with the drive means;
Holding means for holding the pickup roller at a retracted position with respect to the document on the tray when the drive shaft is disconnected from the drive means;
Detecting means for detecting the presence or absence of a document on the tray;
The detection means includes a lever member that is in a first state when a document is present on the tray and is in a second state when a document is not present on the tray;
The lever member temporarily takes the second state during a period in which the pickup roller is displaced from the retracted position to a paper feeding position where the pickup roller contacts the document on the tray,
The detection means is provided on the condition that when the switching means is in a state of releasing the connection between the drive shaft and the drive means, it is detected that the lever has been in the second state for a certain period or more. A document conveying device that detects that the pickup roller is out of the retracted position. A moving means for moving the pickup roller to the retracted position;
The document conveying apparatus according to claim 1, wherein the moving unit moves the pickup roller to the retracted position when the detecting unit detects that the pickup roller has deviated from the retracted position. A case that covers the outline of the document feeder so as to be openable and closable;
And further comprising detecting means for opening and closing the case,
The document conveying apparatus according to claim 2, wherein the moving unit moves the pickup roller to the retracted position on condition that the detecting unit detects that the case is in a closed state.   The moving means does not move the pickup roller to the retracted position any more within the certain period when the pickup roller is moved to the retracted position a predetermined number of times or more within a certain time. The document conveying device according to claim 2.

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