Document transport device and image forming device equipped therewith

Abstract

To provide a document transport device and an image forming device that can suppress foreign matter from being caught in the gap between a discharge section, which can move in the vertical direction, and a paper feeding tray, which is located above the discharge section.SOLUTION: The document transport device is equipped with a paper feeding tray, a paper feeding section, a transport section, a discharge tray, a discharge section, a lift motor and a control section. The control section drives the lift motor to raise the discharge section to execute an adjustment process to adjust the document discharge distance, which is the vertical distance from the top-most document being discharged in the discharge tray to a discharge port, to a pre-determined proper distance. When executing the adjustment process, the control section moves the discharge section to a predetermined detection position to determine the possibility of foreign matter being caught in the gap between the paper feeding tray and the discharge section, and if it is determined that there is a possibility of foreign matter being caught, the control section lowers the discharge section to the lower discharge limit position.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a document transport device and an image forming apparatus equipped with the document transport device. [Background technology]

[0002] A conventional document transport device feeds documents set in a paper feed tray to a transport path, transports the documents, and discharges the documents to a discharge tray. For example, the paper feed tray and the discharge tray are arranged to face each other in the vertical direction. The paper feed tray is arranged on the upper side, and the discharge tray is arranged on the lower side. Such a document transport device is disclosed in, for example, Patent Document 1.

[0003] In Patent Document 1, the paper feed tray is movable in the vertical direction. In this configuration, for example, when a document is to be removed from the discharge tray, the paper feed tray can be raised. This makes it easier to remove the document from the discharge tray. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-41695 Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration of Patent Document 1, a discharge section (discharge roller) that discharges documents onto a discharge tray can move up and down. The discharge section moves up and down together with the paper feed tray. Therefore, when the number of documents loaded is small, the paper feed tray rises to a high position, and the discharge section integrated with the paper feed tray also rises to a high position. In this state, there is a problem in that it becomes difficult to align the documents being discharged.

[0006] In addition, in the configuration of Patent Document 1, the gap between the discharge unit and another member (e.g., a paper feed tray) becomes larger or smaller as the discharge unit moves. Therefore, if a foreign object (e.g., a user's finger) enters the gap when the gap between the discharge unit and another member becomes smaller, there is a risk of the foreign object being caught.

[0007] In consideration of the above problems, the present invention aims to provide a document transport device and an image forming device that can prevent foreign objects from becoming caught in the gap between the discharge section that discharges documents to a discharge tray and a paper feed tray located above the discharge section, in a configuration in which the discharge section can move in the vertical direction. [Means for solving the problem]

[0008] In order to achieve the above object, a first configuration of the present invention is a document transport device including a paper feed tray, a paper feed section, a transport section, a discharge tray, a discharge section, a lift motor, and a control section. Documents are set in the paper feed tray. The paper feed section feeds the documents set in the paper feed tray to a transport path. The transport section transports the documents along the transport path. The discharge tray is disposed below the paper feed tray. The discharge section is disposed between the paper feed tray and the discharge tray, is independently movable in the vertical direction, and has a discharge outlet for discharging documents on the transport path to the discharge tray. The lift motor moves the discharge section up and down between a lower discharge limit position and an upper discharge limit position. The control section controls the driving of the lift motor. The control section drives the lift motor to raise the discharge section, thereby executing an adjustment process for adjusting a document discharge distance, which is a vertical distance from the topmost document discharged to the discharge tray to the discharge outlet, to a predetermined appropriate distance. When performing the adjustment process, the control unit moves the discharge unit to a predetermined detection position to determine the possibility of a foreign object being caught in the gap between the paper feed tray and the discharge unit, and if it determines that there is a possibility of a foreign object being caught, it lowers the discharge unit to the lower discharge limit position. Effect of the Invention

[0009] According to the first configuration of the present invention, by performing the document discharge distance adjustment process, it is possible to prevent a new document from being discharged from a position that is far away in the vertical direction from documents already discharged to the discharge tray, and the stacking positions of multiple documents on the discharge tray are less likely to become uneven. Also, while the discharge section is rising in the document discharge distance adjustment process, it is determined whether or not there is a possibility of a foreign object being caught in the gap at the detection position, and if it is determined that there is a possibility of a foreign object being caught, the discharge section is lowered to the discharge lower limit position. This makes it possible to prevent a user's fingers or foreign objects from being caught in the gap between the paper feed tray and the discharge section. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a side cross-sectional view showing a schematic configuration of a document transport device 100 according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a side cross-sectional view of the document transport device 100 of the present embodiment, showing a state in which the discharge unit 5 is raised. [Diagram 3] FIG. 1 is a diagram showing the positional relationship between the paper feed tray 2, the discharge tray 4, and the discharge section 5 of the document transport device 100 of the present embodiment, and shows a state in which the discharged document sensor 52 is off. [Figure 4] FIG. 1 is a diagram showing the positional relationship between the paper feed tray 2, the discharge tray 4, and the discharge section 5 of the document transport device 100 of the present embodiment, and shows a state in which the discharged document sensor 52 is on. [Diagram 5] FIG. 1 is a block diagram showing a control path of a document transport device 100 according to an embodiment of the present invention. [Figure 6] A flowchart showing an example of adjustment control of the document discharge distance in the document transport device 100 of the present embodiment. [Figure 7] FIG. 2 is a plan view showing the positions of the gap sensor 21 and the foreign object sensor 60 of the document transport device 100 of the present embodiment. [Figure 8] FIG. 1 is a diagram showing the positional relationship between the paper feed tray 2, the discharge tray 4, and the discharge unit 5 of the document transport device 100 of the present embodiment, and showing a state in which a foreign object is present in the gap G. [Figure 9]FIG. 1 is a diagram showing the positional relationship between the paper feed tray 2, the discharge tray 4, and the discharge section 5 of the document transport device 100 of the present embodiment, and showing a state in which the discharge section 5 has been lowered to a lower discharge limit position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The document transport device 100 of the present invention will be described below with reference to the drawings. In the following description, the direction perpendicular to the installation surface on which the document transport device 100 is installed is defined as the up-down direction of the document transport device 100. Also, the direction perpendicular to the document transport direction is referred to as the width direction. The width direction corresponds to the front-rear direction of the document transport device 100. In the following description, the right side is one side in the left-right direction when the document transport device 100 is viewed from the front, and the left side is the other side in the left-right direction when the document transport device 100 is viewed from the front.

[0012] The document transport device 100 transports the document D. The document transport device 100 has a scanning function (reading unit 7 described later) and reads the document D while it is being transported. However, the document transport device 100 does not necessarily have to be equipped with a scanning function. In this case, although not shown, the document transport device 100 is installed on an image reading device. The image reading device reads the document D at a predetermined reading position (contact glass). The document transport device 100 transports the document D so that it passes through the reading position of the image reading device.

[0013] Moreover, the document transport device 100 and the printing device 200 may constitute an image forming device 1000 (see FIG. 5). In other words, the document transport device 100 may be installed in the image forming device 1000. The printing device 200 performs printing by an electrophotographic method or an inkjet method. The printing device 200 prints an image based on image data of the document D obtained by reading the document D by the document transport device 100 onto a sheet.

[0014] <Overall configuration of the document transport device> FIG. 1 is a side cross-sectional view showing a schematic configuration of a document transport device 100 according to an embodiment of the present invention. FIG. 2 is a side cross-sectional view of the document transport device 100, showing a state in which the discharge unit 5 is raised. As shown in FIG. 1, the document transport device 100 includes a main body part MB having a transport path 10 along which a document D is transported. The main body part MB is a left part of the document transport device 100. The transport path 10 is curved in a substantially U-shape. Specifically, the transport path 10 extends from the right side of the main body part MB to the left side, turns back midway, and extends to the right side. The document D is transported along the transport path 10. In other words, the transport path 10 guides the transport of the document D.

[0015] For example, the main body MB further includes a horizontal conveying path 110. The horizontal conveying path 110 may be omitted. The horizontal conveying path 110 extends in a substantially straight line from the right side to the left side of the main body MB. The horizontal conveying path 110 shares a part with the conveying path 10, and branches off from the conveying path 10 midway from the most upstream side to the downstream side in the document conveying direction. The branching point between the conveying path 10 and the horizontal conveying path 110 is denoted by the symbol BP. In FIG. 1, the conveying path 10 is indicated by a thick arrow, and the portion of the horizontal conveying path 110 after branching off from the conveying path 10 is indicated by a thin arrow.

[0016] The document transport device 100 includes a transport unit 1. The transport units 1 are installed at multiple locations on the transport path 10. The transport units 1 are also installed on the horizontal transport path 110. The locations and number of the transport units 1 are not particularly limited, and may be changed as appropriate depending on the shape of the transport path 10, etc.

[0017] The transport unit 1 includes a transport roller pair. The transport roller pair is rotatably supported and is composed of a pair of transport rollers that are in pressure contact with each other. One of the pair of transport rollers rotates by a driving force transmitted from a transport motor (not shown), and the other transport roller rotates following the one transport roller. The transport roller pair forms a transport nip between the transport rollers. The transport unit 1 holds the original D in the transport nip and rotates the transport roller pair in this state. As a result, the transport unit 1 transports the original D along the transport path 10 or the horizontal transport path 110.

[0018] The document transport device 100 includes a paper feed tray 2. The paper feed tray 2 is disposed on the right side of the main body part MB. The paper feed tray 2 has a setting surface (reference number omitted) on which the document D is set. The setting surface of the paper feed tray 2 is inclined diagonally downward and left toward the main body part MB when viewed from the front of the device. This makes it easy for the document D on the paper feed tray 2 to move diagonally downward and left toward the main body part MB when viewed from the front of the device.

[0019] The user sets the original D before transport on the paper feed tray 2. The original D on the paper feed tray 2 is fed to the transport path 10 and transported along the transport path 10. On the set surface of the paper feed tray 2, the original transport direction is the direction diagonally downward to the left (i.e., the direction along the set surface). Here, the paper feed tray 2 is movable in the up and down directions. Details will be described later.

[0020] The document transport device 100 includes a paper feed unit 3. The paper feed unit 3 feeds the document D from the paper feed tray 2 to the transport path 10. The paper feed unit 3 is disposed above the end of the paper feed tray 2 that is downstream in the document transport direction. In other words, the paper feed unit 3 is disposed at the feed port of the document D from the paper feed tray 2 to the transport path 10. In further other words, the paper feed unit 3 is disposed at a position that faces the document D on the paper feed tray 2 in the up-down direction. Thereby, when the paper feed tray 2 is raised, the document D on the paper feed tray 2 comes into contact with the paper feed unit 3.

[0021] The paper feed unit 3 is composed of a paper feed rotating body that is rotatably supported. The paper feed rotating body contacts the documents D on the paper feed tray 2 from above and rotates in that state. This causes the documents D on the paper feed tray 2 to be fed to the transport path 10. When multiple documents D are set in the paper feed tray 2, the documents D are fed to the transport path 10 in order starting from the topmost document D. The paper feed rotating body may be a paper feed roller that is rotatably supported and whose outer circumferential surface contacts the documents D. The paper feed rotating body may also be a paper feed belt that is rotatably stretched by rollers and whose outer circumferential surface contacts the documents D.

[0022] The document transport device 100 includes a discharge tray 4. The discharge tray 4 is disposed on the right side of the main body MB. The discharge tray 4 is disposed below the paper feed tray 2. The paper feed tray 2 is vertically movable, but there is always a vertical gap between the paper feed tray 2 and the discharge tray 4. The vertical position of the discharge tray 4 is fixed.

[0023] The discharge tray 4 has a discharge surface (reference number omitted) on which the document D is discharged and stacked. The discharge surface of the discharge tray 4 is inclined diagonally downward to the left toward the main body part MB (upstream side in the discharge direction) when viewed from the front of the device. This makes it easy for the document D on the discharge tray 4 to move diagonally downward to the left toward the main body part MB when viewed from the front of the device.

[0024] The discharge tray 4 has a discharged paper detection sensor 30. The discharged paper detection sensor 30 changes its output depending on the presence or absence of a document D discharged onto the discharge tray 4. The discharged paper detection sensor 30 is composed of, for example, a reflective optical sensor that irradiates light onto the document D discharged onto the discharge tray 4 and receives the reflected light.

[0025] The document transport device 100 includes a discharge unit 5. The discharge unit 5 discharges the document D from the transport path 10 to the discharge tray 4. In other words, the discharge unit 5 transports the document D toward the discharge tray 4. The document D is discharged from the transport path 10 to the discharge tray 4, whereby the document D is loaded on the discharge tray 4.

[0026] The discharge section 5 has a discharge port 510. The discharge section 5 discharges the document D from the conveying path 10 to the discharge tray 4 from the discharge port 510. Specifically, the discharge section 5 includes a discharge roller pair 51. The discharge roller pair 51 is rotatably supported and is composed of a pair of discharge rollers that are in pressure contact with each other. Of the pair of discharge rollers, one discharge roller is rotated by a driving force transmitted from a discharge motor (not shown), and the other discharge roller is rotated following the one discharge roller. The discharge roller pair 51 forms a discharge nip between the discharge rollers. This discharge nip becomes the discharge port 510. The discharge section 5 pinches the document D in the discharge nip and rotates the discharge roller pair 51 in this state. As a result, the document D is discharged from the discharge nip as the discharge port 510 to the discharge tray 4.

[0027] Here, the discharge section 5 is disposed on the right side of the main body section MB and between the paper feed tray 2 and the discharge tray 4 in the vertical direction. The discharge section 5 is capable of moving independently in the vertical direction between the paper feed tray 2 and the discharge tray 4. As the discharge section 5 moves in the vertical direction, the discharge opening 510 moves in the vertical direction.

[0028] The discharge section 5 is connected to a transport guide 101 that constitutes a part of the transport path 10 on the downstream side in the document transport direction. As the discharge section 5 moves up and down, the vertical position of the end of the transport guide 101 on the downstream side in the document transport direction is displaced. For example, when the discharge section 5 rises, the position of the end of the transport guide 101 on the downstream side in the document transport direction is displaced upward, as shown in FIG.

[0029] The configuration of the transport guide 101 is not particularly limited. For example, the upstream end of the transport guide 101 in the document transport direction is connected to a fixed transport guide (reference number omitted). The fixed transport guide does not change its position. When the discharge section 5 moves in the vertical direction, the transport guide 101 slides its upstream end in the document transport direction relative to the fixed transport guide, while displacing the position of its downstream end in the document transport direction in accordance with the movement of the discharge section 5.

[0030] The discharge section 5 has a discharged document sensor 52. The discharged document sensor 52 changes its output according to a document discharge distance L (see FIG. 3). In other words, the discharged document sensor 52 changes its output according to the amount of documents D discharged to the discharge tray 4. The document discharge distance L is the vertical distance from the top document D discharged to the discharge tray 4 to the discharge outlet 510. More specifically, the document discharge distance L is the vertical distance from the end of the top document D downstream in the transport direction to the discharge outlet 510. The configuration of the discharged document sensor 52 is not particularly limited. An example of the discharged document sensor 52 will be described below.

[0031] The discharged document sensor 52 may be configured as a reflective optical sensor that irradiates light onto the document D discharged on the discharge tray 4 and receives the reflected light. In this configuration, the threshold amount is set so that the amount of reflected light received when the document D is loaded until the document discharge distance L becomes the distance requiring adjustment becomes greater than the threshold amount, and it is detected whether the document discharge distance L has become the distance requiring adjustment based on the amount of reflected light received and the threshold amount.

[0032] The discharged document sensor 52 may be configured as a transmissive optical sensor having a light emitting section and a light receiving section that face each other and sandwich the document D on the discharge tray 4 in the width direction. In this configuration, when the document D is loaded to the extent that the document discharge distance L reaches the distance requiring adjustment, the amount of received light decreases, making it possible to detect that the document discharge distance L has reached the distance requiring adjustment.

[0033] Alternatively, the discharged document sensor 52 may be composed of a transmissive optical sensor and an actuator. In this configuration, the actuator has a detection piece that is the detection target of the optical sensor. The actuator is supported so as to be rotatable. The actuator displaces the position of the detection piece according to the document discharge distance L. When the document D is discharged to the discharge tray 4, the actuator is pushed in the direction in which the document D rotates, thereby displacing the position of the detection piece. The optical path between the light-emitting section and the light-receiving section of the optical sensor (herein referred to as the detection area) is disposed on the movement path of the detection piece. The optical sensor changes its output according to whether the detection area is light-shielded by the detection piece. The movement path of the detection piece is set so that the detection area switches to a light-shielded state (or a light-unshielded state) when the document discharge distance L becomes the distance requiring adjustment.

[0034] For example, when the document discharge distance L is a predetermined appropriate distance, the discharged document sensor 52 is in an OFF state (in other words, it outputs a signal of one of H level and L level). The appropriate distance is set to a distance at which the discharge of the document D from the discharge port 510 is not hindered by the document D already discharged onto the discharge tray 4.

[0035] Furthermore, the discharged document sensor 52 maintains the OFF state until the document discharge distance L becomes a distance requiring adjustment that is smaller than the appropriate distance. When the document discharge distance L becomes a distance requiring adjustment, the discharged document sensor 52 switches from the OFF state to the ON state (in other words, outputs a signal of the other level of the H level or the L level). The adjustment required distance is the distance to which the document discharge distance L should be adjusted.

[0036] 3 is a diagram showing the positional relationship between the paper feed tray 2, the discharge tray 4, and the discharge section 5 of the document transport device 100, and shows a state in which the discharged document sensor 52 is off. In the state shown in FIG. 3, the document discharge distance L is the appropriate distance.

[0037] Fig. 4 is a diagram showing a state in which the discharged document sensor 52 is on. Let us assume that, from the state shown in Fig. 3, the document D continues to be discharged to the discharge tray 4 without being removed from the discharge tray 4. In this case, the document discharge distance L eventually becomes the distance requiring adjustment as shown in Fig. 4. If the document discharge distance L becomes smaller than the distance requiring adjustment, there is a high possibility that the discharge of the document D from the discharge port 510 will be obstructed by the document D already discharged to the discharge tray 4. Therefore, when the document discharge distance L becomes the distance requiring adjustment, it is preferable to adjust the document discharge distance L to return it to the appropriate distance.

[0038] Fig. 5 is a block diagram showing a control path of the document transport device 100 of this embodiment. As shown in Fig. 5, the document transport device 100 includes a control unit 6. The control unit 6 has a CPU 61 that performs various processes. The control unit 6 has a memory 62 such as a ROM and a RAM. The control unit 6 controls the transport of the document D. That is, the control unit 6 controls the transport unit 1, the paper feed unit 3, and the discharge unit 5.

[0039] The control unit 6 has a current detection circuit 63. The current detection circuit 63 is a circuit for detecting a current value of the lift motor LM described later, and is connected to the lift motor LM. The current detection circuit 63 includes a shunt resistor and detects a potential difference generated by the shunt resistor. An output of the current detection circuit 63 is connected to an analog port of the CPU 61. The control unit 6 calculates a current value of the lift motor LM.

[0040] The document transport device 100 includes a paper feed movement mechanism 20. The paper feed movement mechanism 20 moves the paper feed tray 2 in the vertical direction. The paper feed movement mechanism 20 includes a tray motor TM. The tray motor TM is a DC brush motor. The tray motor TM is connected to the paper feed tray 2. When the tray motor TM is driven, the driving force of the tray motor TM is transmitted to the paper feed tray 2 via a transmission member (not shown) such as a gear, and the paper feed tray 2 moves in the vertical direction. The control unit 6 controls the paper feed movement mechanism 20. That is, the control unit 6 controls the driving of the tray motor TM to appropriately move the paper feed tray 2 in the vertical direction.

[0041] The document transport device 100 includes a discharge movement mechanism 50. The discharge movement mechanism 50 moves the discharge section 5 in the vertical direction. That is, the discharge movement mechanism 50 moves the discharge port 510 in the vertical direction. The discharge movement mechanism 50 includes a lift motor LM. The lift motor LM is a DC brush motor. The lift motor LM is connected to the discharge section 5. When the lift motor LM is driven, the driving force of the lift motor LM is transmitted to the discharge section 5 via a transmission member (not shown) such as a gear, and the discharge section 5 moves in the vertical direction.

[0042] The lift motor LM is driven in the forward direction to raise the discharge section 5. On the other hand, the lift motor LM is driven in the reverse direction to lower the discharge section 5. The control unit 6 controls the discharge movement mechanism 50. That is, the control unit 6 controls the driving of the lift motor LM. The control unit 6 controls the driving of the lift motor LM to move the discharge section 5 to an appropriate position in the vertical direction. The control unit 6 controls the vertical movement of the discharge section 5 to perform an adjustment process of the document discharge distance L.

[0043] The document transport device 100 includes a reading unit 7. The reading unit 7 is a CIS (Contact Image Sensor). The reading unit 7 reads the document D being transported along the transport path 10, and generates image data of the read document D. For example, the reading unit 7 reads the document D upstream of the branch point BP in the document transport direction. Alternatively, the reading unit 7 reads the document D downstream of the branch point BP in the document transport direction. In this case, a reading unit 7 that reads the document D on the transport path 10 and a reading unit 7 that reads the document D on the horizontal transport path 110 may be provided.

[0044] The document transport device 100 includes an operation unit 8. The operation unit 8 is, for example, an operation panel installed in the document transport device 100, and accepts various operations such as a start operation of a job involving transport of a document D (hereinafter simply referred to as a document transport job). The control unit 6 detects an operation accepted by the operation unit 8 from a user. When a start operation on the operation unit 8 is detected, the control unit 6 starts a document transport job. The control unit 6 can also cause the operation unit 8 to display notification information such as a message. The operation unit 8 may be an operation panel of a printing device 200 connected to the document transport device 100, or a personal computer connected to the document transport device 100 so as to be communicable therewith.

[0045] <Feed tray lift control> Although not shown, the document transport device 100 includes a document set sensor. The document set sensor changes its output depending on the presence or absence of a document D on the set surface of the paper feed tray 2. The control unit 6 detects whether or not a document D is set in the paper feed tray 2 based on the output of the document set sensor.

[0046] Furthermore, the document transport device 100 includes a tray position sensor 22 (see FIG. 5). The tray position sensor 22 has an upper limit sensor, an intermediate sensor, and a lower limit sensor (none of which are shown). The control unit 6 detects the vertical position of the paper feed tray 2 based on the outputs of the upper limit sensor, the intermediate sensor, and the lower limit sensor.

[0047] When the vertical position of the setting surface of the paper feed tray 2 or the vertical position of the topmost document D set in the paper feed tray 2 is at a predetermined tray upper limit position, the upper limit sensor is turned on. The upper limit sensor is turned on by raising the paper feed tray 2 until the setting surface of the paper feed tray 2 or the topmost document D set in the paper feed tray 2 comes into contact with the paper feed section 3. The vertical position of the paper feed tray 2 when the upper limit sensor is turned on is the paper feed position. In a document transport job, the document D is fed from the paper feed tray 2 to the transport path 10 at the paper feed position.

[0048] When the vertical position of the paper feed tray 2 is at a predetermined tray lower limit position, the lower limit sensor is turned on. When the paper feed tray 2 is at an intermediate position between the vertical position of the tray upper limit position and the tray lower limit position, the intermediate sensor is turned on.

[0049] The control unit 6 controls the elevation of the paper feed tray 2 based on the outputs of the document set sensor and the tray position sensor 22 (upper limit sensor, intermediate sensor, and lower limit sensor).

[0050] The home position of the paper feed tray 2 is a position that is a predetermined set amount below the tray upper limit position (this position is above the intermediate position). When the control unit 6 detects that the document D has been set in the paper feed tray 2, it raises the paper feed tray 2 until the upper limit sensor turns on. Next, the control unit 6 lowers the paper feed tray 2 by a predetermined set amount and keeps the paper feed tray 2 waiting at that position (i.e., the home position). After that, when the control unit 6 detects a start operation on the operation unit 8, it raises the paper feed tray 2 to the paper feed position (i.e., the tray upper limit position) to start the document transport job.

[0051] After the document transport job is started, the number of documents D on the paper feed tray 2 decreases. That is, the vertical position of the topmost document D set on the paper feed tray 2 is displaced below the paper feed position. Therefore, during the execution of the document transport job, the control unit 6 performs a process of raising the paper feed tray 2 and holding it at the paper feed position.

[0052] For example, when no document D is set in the paper feed tray 2, that is, when the document D is to be set in the paper feed tray 2, the paper feed tray 2 may be lowered to the tray lower limit position. This makes it easier to set the document D in the paper feed tray 2. However, if the paper feed tray 2 is held at the tray lower limit position, it is difficult to remove the document D from the discharge tray 4. For this reason, when the document D remains in the discharge tray 4, it is preferable that the control unit 6 hold the paper feed tray 2 in an intermediate position without lowering it to the tray lower limit position.

[0053] <Lifting control of discharge section> The document transport device 100 includes a gap sensor 21. The gap sensor 21 is disposed on the lower surface of the paper feed tray 2 at a position facing the discharge unit 5 in the up-down direction. The gap sensor 21 measures the vertical distance to the discharge unit 5. By providing the gap sensor 21 on the lower surface of the paper feed tray 2, the vertical distance between the paper feed tray 2 and the discharge unit 5 can be measured. In other words, it can be detected that the vertical distance between the paper feed tray 2 and the discharge unit 5 has become smaller.

[0054] The gap sensor 21 changes its output depending on whether the vertical distance between the paper feed tray 2 and the discharge unit 5 has become small enough to reach a predetermined threshold distance. That is, when the vertical distance between the paper feed tray 2 and the discharge unit 5 is larger than the threshold distance, the gap sensor 21 becomes one of the ON state and the OFF state (in other words, it outputs a signal of one of the H level and the L level). When the vertical distance between the paper feed tray 2 and the discharge unit 5 becomes equal to or smaller than the threshold distance, the gap sensor 21 becomes the other of the ON state and the OFF state (in other words, it outputs a signal of the other of the H level and the L level).

[0055] For example, when the vertical distance between the paper feed tray 2 and the discharge unit 5 is greater than the threshold distance, the gap sensor 21 is in the OFF state. On the other hand, when the vertical distance between the paper feed tray 2 and the discharge unit 5 is equal to or less than the threshold distance, the gap sensor 21 is in the ON state. In other words, when the gap sensor 21 switches from the OFF state to the ON state, it means that the vertical distance between the paper feed tray 2 and the discharge unit 5 has reached (become smaller than) the threshold distance.

[0056] The document transport device 100 also includes an upper discharge limit sensor and a lower discharge limit sensor, not shown. When the vertical position of the discharge section 5 is at a predetermined upper discharge limit position, the upper discharge limit sensor is turned on. When the vertical position of the discharge section 5 is at a predetermined lower discharge limit position, the lower discharge limit sensor is turned on. The control section 6 detects whether the discharge section 5 is at the upper discharge limit position or the lower discharge limit position based on the output of the upper discharge limit sensor and the lower discharge limit sensor. The control section 6 does not move the discharge section 5 above the upper discharge limit position, nor does it move it below the lower discharge limit position.

[0057] When the state transitions from a ready state (standby state) to a state where a document transport job can be executed and the document transport job is started, the control unit 6 performs a process to lower the discharge unit 5. In addition, the control unit 6 detects whether or not there is a document D on the discharge tray 4 (i.e., whether or not the discharged document D remains on the discharge tray 4) based on the output of the discharged paper detection sensor 30.

[0058] When no document D remains on the discharge tray 4, the control unit 6 holds the discharge unit 5 at the lowest discharge position. On the other hand, when a document D remains on the discharge tray 4, the discharge unit 5 is lowered, and the discharged document sensor 52 turns on. When the discharged document sensor 52 turns on, the control unit 6 performs an adjustment process to adjust the document discharge distance L to an appropriate distance. At this time, the control unit 6 raises the discharge unit 5 while stopping the vertical movement of the paper feed tray 2.

[0059] Furthermore, after the document transport job is started (i.e., while the document transport job is being executed), the control unit 6 performs an adjustment process to adjust the document discharge distance L to an appropriate distance. During the execution of the document transport job, when the discharged document sensor 52 is switched from an off state to an on state, the control unit 6 performs an adjustment process of the document discharge distance L. At this time, the control unit 6 raises the discharge unit 5 while stopping the vertical movement of the paper feed tray 2. Note that, if the document D continues to be discharged to the discharge tray 4 without being removed from the discharge tray 4, the discharged document sensor 52 is switched from an off state to an on state.

[0060] When the gap sensor 21 is turned on during the adjustment process of the document discharge distance L (during the upward movement of the discharge unit 5), that is, when the distance between the paper feed tray 2 and the discharge unit 5 in the vertical direction becomes equal to or smaller than the threshold distance, the control unit 6 stops the document transport job. In addition, the control unit 6 stops the forward rotation of the lift motor LM to stop the upward movement of the discharge unit 5. This makes it possible to prevent the discharge unit 5 from colliding with the paper feed tray 2.

[0061] Then, the control unit 6 causes the operation unit 8 to display a message urging the user to check the state of the discharge tray 4. A message urging the user to remove the document D on the discharge tray 4 may be displayed on the operation unit 8. This removes the document D from the discharge tray 4, making it possible to execute the document transport job. Thereafter, when the control unit 6 detects that there is no document D left on the discharge tray 4, it causes the discharge unit 5 to lower to the lower discharge limit position and resumes the document transport job.

[0062] <Detection of foreign objects between the paper feed tray and the ejection section in the vertical direction> As shown in FIG. 3, a gap G is generated between the feed tray 2 and the discharge section 5 in the vertical direction. As the discharge section 5 rises, the gap G between the feed tray 2 and the discharge section 5 in the vertical direction becomes smaller. Therefore, if a foreign object is caught between the feed tray 2 and the discharge section 5 in the vertical direction, the foreign object will be pinched between the feed tray 2 and the discharge section 5. For example, a user's finger as a foreign object may be pinched between the feed tray 2 and the discharge section 5, causing pain or injury. Furthermore, if the discharge section 5 continues to rise with a foreign object caught between the feed tray 2 and the discharge section 5 in the vertical direction, it may cause a malfunction.

[0063] Therefore, in the document transport device 100 of this embodiment, the discharge unit 5 is stopped at the detection position to detect whether or not a foreign object is present in the gap G between the paper feed tray 2 and the discharge unit 5 in the vertical direction. If a foreign object is present in the gap G, the discharge unit 5 is lowered to the lowest position and then started to rise again.

[0064] Fig. 6 is a flowchart showing an example of adjustment control of the document discharge distance in the document transport device 100 of this embodiment. The procedure for adjusting the document discharge distance will be described following the steps in Fig. 6, with reference to Figs. 1 to 4 and Figs. 7 to 9, which will be described later, as necessary.

[0065] When a document transport command is input from the printing device 200 or a higher-level device such as a personal computer and a document transport job is started (step S1), the control unit 6 determines whether the discharged document sensor 52 has switched from an off state to an on state (step S2). That is, the control unit 6 determines whether the document discharge distance L has become a distance requiring adjustment. If it is determined that the discharged document sensor 52 has not switched from an off state to an on state (No in step S2), the process of step S1 is repeated.

[0066] If originals D remain on the discharge tray 4 when the document transport job is started, the discharge section 5 is lowered, and the discharged document sensor 52 is switched from the off state to the on state. However, if the amount of originals D remaining on the discharge tray 4 is small, the discharge section 5 is lowered to the lowest discharge position. In this case, there is no need to perform the adjustment process for the document discharge distance L. Also, after the document transport job is started (during the document transport job), if a certain number of originals D continue to be discharged without raising the discharge section 5, the discharged document sensor 52 is switched from the off state to the on state.

[0067] If it is determined that the discharged document sensor 52 has switched from an OFF state to an ON state (Yes in step S2), the control unit 6 drives the lift motor LM in the forward direction to lift the discharge unit 5 (step S3). Then, the control unit 6 determines whether the discharged document sensor 52 has switched from an ON state to an OFF state (step S4). That is, the control unit 6 determines whether the document discharge distance L has become an appropriate distance.

[0068] If it is determined that the discharged document sensor 52 has not switched from the on state to the off state (No in step S4), the control unit 6 determines whether the discharge unit 5 has moved to the detection position (step S5).

[0069] The determination as to whether the discharge unit 5 has moved to the detection position is based on the movement time of the discharge unit 5. Specifically, when the document transport device 100 is manufactured, the movement time Tm of the discharge unit 5 from the discharge lower limit position to the discharge upper limit position is stored in the memory 62. The control unit 6 calculates the movement time Td from the discharge lower limit position to the detection position based on the movement time Tm stored in the memory 62 and the distance from the discharge lower limit position to the detection position. Then, when the drive time of the lift motor LM reaches the movement time Td, it is determined that the discharge unit 5 has moved to the detection position.

[0070] The movement time Tm varies depending on the characteristics of the lift motor LM for each document transport device 100. As described above, by measuring the movement time Tm during the manufacture of the document transport device 100 and storing it in the memory 62, it is possible to move the discharge section 5 to a constant detection position regardless of variations in the characteristics of the lift motor LM.

[0071] If it is determined that the discharge unit 5 has not moved to the detection position (No in step S5), the processes in steps S3 to S5 are repeated. If it is determined that the discharge unit 5 has moved to the detection position (Yes in step S5), the control unit 6 stops the forward rotation of the lift motor LM to stop the discharge unit 5, and determines whether or not there is a possibility of a foreign object being caught in the gap G (step S6).

[0072] 7 is a plan view showing the positions of the gap sensor 21 and the foreign object sensor 60 of the document transport device 100 of the present embodiment. In FIG. 7, the user's finger that may be caught in the gap G between the paper feed tray 2 and the discharge unit 5 in the vertical direction is denoted by the symbol F.

[0073] A first method for determining the possibility of a foreign object being caught is to use the gap sensor 21. For example, the possibility of a foreign object being caught can be determined by detecting whether or not a foreign object is present within the detection range of the gap sensor 21 in the gap G (see FIG. 3) between the paper feed tray 2 and the discharge unit 5 in the vertical direction. However, the method using the gap sensor 21 cannot detect a foreign object present in a position outside the detection range of the gap sensor 21 in the gap G between the paper feed tray 2 and the discharge unit 5. For example, as shown in FIG. 7, if a user's finger F enters a position outside the detection range of the gap sensor 21, the gap sensor 21 cannot detect the finger F.

[0074] Therefore, it is preferable to arrange multiple gap sensors 21 in the width direction in consideration of the detection range of gap sensor 21 so that foreign objects can be detected over the entire width direction. Alternatively, since it is the front side of document transport device 100 (for example, the front side of the paper in FIG. 1, the left side in FIG. 7) where fingers or foreign objects are likely to get caught, the arrangement and number of gap sensors 21 may be determined so that the detection range is from the center in the width direction to the front side.

[0075] A second method for determining the possibility of a foreign object being trapped is to use a dedicated foreign object sensor 60. The foreign object sensor 60 changes its output depending on the presence or absence of a foreign object in the gap G between the paper feed tray 2 and the discharge unit 5 in the vertical direction. The foreign object sensor 60 is a transmissive optical sensor that includes a light-emitting unit 61 and a light-receiving unit 62.

[0076] 7, the light-emitting unit 61 and the light-receiving unit 62 are disposed to face each other in the width direction across the gap G between the top-bottom direction of the paper feed tray 2 and the discharge unit 5. The light-emitting unit 61 is disposed on one side of one end of the gap G in the width direction. The light-receiving unit 62 is disposed on the other side of the end of the gap G in the width direction.

[0077] The foreign object sensor 60 changes its output depending on whether or not a foreign object is present in the gap G between the vertical direction of the paper feed tray 2 and the discharge section 5. When no foreign object is present in the gap G, the detection area of ​​the foreign object sensor 60 (i.e., the light path between the light emitter 61 and the light receiver 62 in the width direction) is not blocked, and when a foreign object is present in the gap G, the detection area of ​​the foreign object sensor 60 is blocked, and the output of the foreign object sensor 60 changes depending on the presence or absence of a foreign object in the gap G. In the example shown in Fig. 7, even if the user's finger F enters a position that cannot be detected by the gap sensor 21, the foreign object sensor 60 detects the user's finger F.

[0078] The foreign object sensor 60 is attached to the frame of the document transport device 100. Although not shown, the foreign object sensor 60 may be attached to a sensor holder (not shown) that protrudes to the right from the frame of the main body section MB. The foreign object sensor 60 may be attached to a sensor holder that protrudes downward from the paper feed tray 2. The foreign object sensor 60 may be attached to a sensor holder that protrudes upward from the discharge section 5.

[0079] While the discharge unit 5 is rising in the process of adjusting the discharge document distance L, the control unit 6 monitors the output of the foreign object sensor 60. Based on the output of the foreign object sensor 60, the control unit 6 determines whether or not a foreign object is present in the gap G between the paper feed tray 2 and the discharge unit 5 in the vertical direction.

[0080] Fig. 8 is a diagram showing a state in which a foreign object (e.g., a user's finger F) is present in the gap G. As shown in Fig. 8, when it is determined that there is a possibility of a foreign object being caught in the gap G (Yes in step S6), the control unit 6 drives the lift motor LM in the reverse direction to lower the discharge unit 5 (step S7). Then, the control unit 6 determines whether the discharge unit 5 has been lowered to the lower discharge limit position (step S8).

[0081] Fig. 9 is a diagram showing a state in which the discharge unit 5 has been lowered to the lower discharge limit position. As shown in Fig. 9, when the discharge unit 5 has been lowered to the lower discharge limit position (Yes in step S8), the control unit 6 stops the reverse driving of the lift motor LM (step S9). That is, the control unit 6 stops the descent of the discharge unit 5. Then, the control unit 6 performs a process to notify an error. For example, the control unit 6 causes the operation unit 8 to display an error message indicating that a foreign object is present in the gap G between the paper feed tray 2 and the discharge unit 5.

[0082] If it is determined in step S6 that there is no possibility of a foreign object being caught in the gap G (No in step S6), the control unit 6 drives the lift motor LM in the normal direction to raise the discharge unit 5 (step S10). Then, the control unit 6 determines whether the discharged original sensor 52 has switched from an ON state to an OFF state (step S11). That is, the control unit 6 determines whether the original discharge distance L has become an appropriate distance.

[0083] If it is determined that the discharged document sensor 52 has switched from the on state to the off state (Yes in step S11), the control unit 6 stops the forward rotation of the lift motor LM (step S9). That is, the control unit 6 determines that the document discharge distance L has become the appropriate distance, stops the discharge unit 5, and ends the adjustment process of the document discharge distance.

[0084] If it is determined that the discharged document sensor 52 has not switched from the on state to the off state (No in step S11), the control unit 6 determines whether the discharge unit 5 has moved to the upper discharge limit position (step S12). If it is determined that the discharge unit 5 has not moved to the upper discharge limit position (No in step S12), the processes in steps S10 to S11 are repeated.

[0085] If it is determined that the discharge unit 5 has moved to the upper discharge limit position (Yes in step S12), the control unit 6 stops the forward driving of the lift motor LM (step S9). That is, the control unit 6 determines that the discharge unit 5 has moved to the upper discharge limit position when the document discharge distance L is not the appropriate distance, and stops the discharge unit 5. Then, the control unit 6 causes the operation unit 8 to display a message urging the user to check the state of the discharge tray 4. Alternatively, the control unit 6 may cause the operation unit 8 to display a message urging the user to remove the document D on the discharge tray 4.

[0086] According to the control example shown in Fig. 6, the adjustment process of the document discharge distance L is performed, thereby making it possible to prevent a new document D from being discharged from a position that is significantly separated in the vertical direction from the document D already discharged to the discharge tray 4. If a new document D is discharged from a position that is significantly separated in the vertical direction from the document D already discharged to the discharge tray 4, the large drop causes an inconvenience in that the loading position of the newly discharged document D on the discharge tray 4 is shifted. That is, an inconvenience occurs in that the loading positions of the multiple documents D on the discharge tray 4 become uneven. On the other hand, if it is possible to prevent a new document D from being discharged from a position that is significantly separated in the vertical direction from the document D already discharged to the discharge tray 4, it is less likely that the loading positions of the multiple documents D on the discharge tray 4 become uneven.

[0087] Furthermore, by executing the adjustment process of the document discharge distance L, the discharge unit 5 rises, and the gap G becomes smaller in the vertical direction. Therefore, while the discharge unit 5 is rising in the adjustment process of the document discharge distance L, the control unit 6 determines whether or not there is a possibility that a foreign object may be caught in the gap G at the detection position. This makes it possible to prevent a user's fingers or a foreign object from being caught in the gap G between the paper feed tray 2 and the discharge unit 5.

[0088] Here, the movement time Tm for determining that the discharge section 5 has moved to the detection position changes due to deterioration of the lift motor LM over time. Therefore, in the document transport device 100 of this embodiment, a calibration is performed in which the movement time Tm is remeasured at a certain frequency (for example, every time 1000 documents D are transported) and the movement time Tm stored in the memory 62 is overwritten (updated).

[0089] This allows the discharge portion 5 to be constantly moved to a fixed detection position regardless of aging of the lift motor LM, and therefore allows the possibility of a foreign object being caught to be determined with greater accuracy.

[0090] In this embodiment, as described above, the reading unit 7 is provided in the document transport device 100. This allows the document transport device 100 to function as an image reading device.

[0091] Furthermore, as the printing device 200 connected to the document transport device 100, various printing devices 200 such as electrophotographic or inkjet type monochrome or color copying machines, digital multifunction machines, etc. can be used.

[0092] In addition, the present invention is not limited to the above-mentioned embodiment, and various modifications are possible within the scope of the present invention. In other words, the embodiments disclosed herein are illustrative in all respects and should be considered as not limiting. The scope of the present invention is indicated by the claims, not the description of the above-mentioned embodiment, and further includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0093] 1. Conveyor section 2 Paper feed tray 3 Paper feed section 4 Output Tray 5 Discharge section 6. Control Unit 7 Reading section 10 Transport path 21 Gap Sensor 52 Document ejection sensor 60 Foreign object sensor 100 Document transport device 200 Printing device (image forming section) 510 Outlet 1000 Image forming device D Manuscript G Gap LM Lift Motor TM Tray Motor

Claims

1. A paper feed tray on which documents are placed; a paper feed unit that feeds the document set in the paper feed tray to a transport path; a transport unit that transports the document along the transport path; an ejection tray disposed below the paper feed tray; a discharge unit disposed between the paper feed tray and the discharge tray, movable independently in a vertical direction, and having a discharge port for discharging the document on the transport path to the discharge tray; a lift motor that moves the discharge unit up and down between a lower discharge limit position and an upper discharge limit position; A control unit that controls the driving of the lift motor; In a document transport device comprising: the control unit executes an adjustment process for adjusting a document discharge distance, which is a vertical distance from the top document discharged to the discharge tray to the discharge outlet, to a predetermined appropriate distance by driving the lift motor to raise the discharge unit; The control unit, when executing the adjustment process, moves the discharge unit to a predetermined detection position to determine the possibility of a foreign object being caught in the gap between the paper feed tray and the discharge unit, and if it determines that there is a possibility of a foreign object being caught, lowers the discharge unit to the lower discharge limit position.

2. a storage unit that stores a movement time of the discharge unit from the lower discharge limit position to the upper discharge limit position, The document transport device according to claim 1 , wherein the control unit detects that the discharge unit has moved to the detection position based on the movement time stored in the storage unit.

3. 3. The document transport device according to claim 2, wherein the control unit executes a calibration for re-measuring the movement time at a certain frequency and overwriting the movement time stored in the storage unit.

4. a gap sensor that changes an output depending on whether the gap reaches a predetermined threshold distance; 2. The document transport device according to claim 1, wherein the control unit determines the possibility of the foreign object being trapped by detecting whether the foreign object is present within a detection range of the gap sensor.

5. a foreign object sensor that changes its output depending on the presence or absence of the foreign object in the gap, 2. The document transport device according to claim 1, wherein the control unit determines the possibility of the foreign object being trapped by detecting whether the foreign object is present within a detection range of the foreign object sensor.

6. The document transport device according to claim 1, characterized in that when the document discharge distance is adjusted to the appropriate distance before the discharge section moves to the detection position, the control unit terminates the adjustment process without determining the possibility of a foreign object being trapped in the gap.

7. 2. The document transport device according to claim 1, wherein the control unit, when it is not determined that there is a possibility of the foreign object being trapped, raises the discharge unit until the document discharge distance becomes the appropriate distance.

8. The document transport device according to claim 7 , wherein the control unit stops driving the lift motor when the discharge unit reaches the upper discharge limit position before the document discharge distance becomes the appropriate distance.

9. a display unit that displays notification information regarding a state of the document transport device, The document transport device according to claim 8, characterized in that, if the discharge section reaches the upper discharge limit position before the document discharge distance becomes the appropriate distance, the control section uses the display section to display a message encouraging the removal of the document discharged onto the discharge tray.

10. A tray motor is provided to move the paper feed tray vertically, 2. The document transport device according to claim 1, wherein the control unit raises the paper feed tray by a predetermined distance in association with the transport of the document set in the paper feed tray.

11. A document transport device according to any one of claims 1 to 10, an image reading unit that reads the document conveyed by the document conveying device and generates image data of the document; an image forming unit that forms an image on a recording medium based on the image data generated by the image reading unit; An image forming apparatus comprising:

Images