JP4488217B2 - Paper conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus including the sheet conveying apparatus, and more particularly to a sheet conveying apparatus and an image forming apparatus that easily acquire a reference position of a switching claw.

A sheet conveying device is used in a conventional double-sided image forming apparatus such as a copying machine or a printer, a post-processing apparatus after image formation, or the like. The paper transport device is used for reversing and discharging after forming an image on the paper, or for reversing the paper when forming images on both sides of the paper. In a conventional sheet conveying apparatus, a means for driving a switching claw with a solenoid is used as means for switching a sheet delivery destination to a plurality of sheet conveying paths. However, as the productivity of image forming devices has improved, the paper conveyance speed has been increased and the paper interval has been shortened during continuous printing. It is coming. For this reason, it is conceivable that the switching claw is driven by a motor in order to switch the conveyance path at a higher speed. Conventionally, several techniques related to paper conveyance and reversal have been proposed (see Patent Documents 1, 2, and 3).
JP-A-5-323730 JP 2004-51345 A JP 2004-75305 A

  As described above, when the switching claw for switching the conveyance path is driven by the motor, the position of the switching claw is controlled by the driving amount of the motor, but in order to control to an appropriate position, the reference of the switching claw is used. A position is needed. In addition, when the switching claw is driven by a motor, the position of the switching claw stops at an arbitrary position if the machine suddenly stops due to a jam or for some reason (such as opening the cover or turning off the power). . In this case, when trying to process the paper remaining in the machine, the switching claw in an indefinite position prevents the paper from being processed, and the paper may be caught or torn.

  The present invention has been made in view of the above problems, and it is an object of the present invention to easily obtain a reference position for the position control of the switching claw in the paper transport device and to improve maintainability such as processing of paper left in the machine. And

  The invention according to claim 1 further includes a conveyance path switching unit that switches a conveyance path of a sheet, and a driving unit that drives the conveyance path switching unit. In the sheet conveyance apparatus, the driving unit includes the conveyance path switching unit. Can be moved and stopped at an arbitrary position within a predetermined movable range, and when the driving means releases the driving of the conveying path switching means, the conveying path switching means is moved to a predetermined position. A moving means for stopping is provided.

According to a second aspect of the present invention, in the apparatus according to the first aspect, the moving means is an urging means for urging the transport path switching means in the predetermined position direction.
According to a third aspect of the present invention, there is provided the apparatus according to the first or second aspect, further comprising position detecting means for detecting a position of the transport path switching means.
According to a fourth aspect of the present invention, in the apparatus according to the third aspect, the position detecting means moves the transport path switching means moved to the predetermined position by the moving means in one direction by the driving means. The predetermined position is detected.

According to a fifth aspect of the present invention, in the apparatus according to the fourth aspect, the moving unit is a biasing unit that biases the transport path switching unit in the predetermined position direction, and the transport path switching unit is driven. The predetermined position is detected by moving the biasing means in a direction opposite to the biasing direction of the biasing means.
According to a sixth aspect of the present invention, in the apparatus according to any one of the first to fifth aspects, the drive means is a stepping motor.

  According to a seventh aspect of the invention, there is provided a paper transport device having a transport path switching means for switching the transport path of the paper and a driving means for driving the transport path switching means, and the driving means sets the transport path switching means to a predetermined value. Can be moved and stopped at any position within the movable range, and when the driving means releases the driving of the transport path switching means, the transport path switching means is moved to a predetermined position and stopped. A moving means is provided.

The invention according to claim 8 is the apparatus according to claim 7, wherein the moving means is an urging means for urging the transport path switching means in the predetermined position direction.
According to a ninth aspect of the present invention, in the apparatus according to the seventh or eighth aspect, a position detecting means for detecting a position of the transport path switching means is provided.
According to a tenth aspect of the present invention, in the apparatus according to the ninth aspect, the position detecting means moves the transport path switching means moved to the predetermined position by the moving means in one direction by the driving means. However, the position is detected.

According to an eleventh aspect of the present invention, in the apparatus according to the tenth aspect, the moving means is an urging means for urging the conveying path switching means in the predetermined position direction, and the driving path switching means is driven. The predetermined position is detected by moving the biasing means in a direction opposite to the biasing direction of the biasing means.
According to a twelfth aspect of the present invention, in the apparatus according to any one of the seventh to eleventh aspects, the driving means is a stepping motor.

  According to the first, second, seventh, or eighth aspect of the invention, the driving means can move and stop the conveyance path switching means to an arbitrary position within the movable range. Since the path switching unit moves to a predetermined position, it is possible to easily process the paper remaining in the apparatus and to obtain a reference position for driving control of the transport path switching unit at the start of driving. . In particular, in image forming apparatuses, it is possible to reliably perform switching of the paper transport path with easy control even for high speed and high production, and it is possible to easily perform paper processing such as when a paper jam occurs. Can be improved.

According to the invention of claim 3 or 9, since the driving means releases the driving of the transport path switching means and detects that the transport path switching means has moved to a predetermined position, the driving means is immediately activated to drive it. The reference position for control can be obtained with high accuracy.
According to the invention of claim 4, 5, 10 or 11, when the driving is released, the transport path switching means moves to a predetermined position, activates the drive means and drives in one direction, so that the transport path switching means The reference position can be obtained with high accuracy, and the position of the transport path switching means can be controlled easily and quickly.

  According to the sixth or twelfth aspect of the invention, since the stepping motor is used as the means for driving the conveyance path switching means, it corresponds to a high-productivity and high-speed paper conveyance apparatus, and the position control of the conveyance path switching means is performed. It can be started easily and quickly, and the operability of the paper transport device can be improved.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram schematically showing an image forming apparatus provided with a sheet conveying apparatus according to an embodiment of the present invention.
In the image forming apparatus, when performing double-sided printing in which an image is formed on one side of a sheet and then an image is formed on the other side, the sheet needs to be reversed and conveyed again to the image forming unit. In such an image forming apparatus, as shown in FIG. 1, a paper discharge path 21 that conveys and discharges paper on which an image is formed to a paper discharge tray 20, and refeed that reverses the paper and conveys it again to the image forming unit 10. A switching claw 30 is provided to switch the transport destination to the paper path (including the carry-in path 41, the switchback transport path 42, and the carry-out path 43).

  In the paper reversing device 40 that reverses and conveys the paper through the refeed path, the paper that has been conveyed from the image forming unit 10 (including the four photosensitive drums 11 and the intermediate transfer belt 12) via the carry-in path 41 is switched. The paper is pulled into the back conveyance path 42, detected by the sensor 44 in the switchback conveyance path, temporarily stopped at a predetermined position, and then conveyed in the reverse direction to send the paper to the carry-out path 43. To the image forming unit 10. At this time, in order to send the reversely conveyed paper to the carry-out path 43 without returning it to the carry-in path 41, a switching claw 45 for switching the conveyance path is provided.

  When images are continuously formed on both sides of a sheet, it is necessary to switch between the paper discharge path 21 and the transport destination of the refeed path and to reverse the sheet within a short sheet interval. As the productivity of the image forming apparatus is improved, the paper conveyance speed is higher and the paper interval is shorter. For this reason, a switching claw 30 for switching the transport destination of the paper discharge path 21 and the re-feeding path and a switching claw for guiding the paper that is reversely transported after the paper is carried into the switchback conveyance path 42 to the carry-out path 43. It is necessary to move 45 in a short time, and for this reason, a stepping motor with good responsiveness is used for driving these switching claws 30 and 45. The switching claws 30 and 45 are urged in one direction by a spring.

  FIG. 2 shows a configuration example of the switching claws 30 and 45 (only the switching claw 30 is shown), and shows the stepping motor 32 and the spring 33. As shown in the figure, the switching claws 30 and 45 are provided with a plurality of claws on the rotating shaft 31, and the rotating shaft 31 is rotationally driven by a stepping motor 32. There is also a stopper (not shown) for stopping the switching claws 30 and 45 biased by the spring 33 so that the posture of the switching claws 30 and 45 becomes a predetermined position. For example, in the case of the switching claw 30 for switching the transport destination between the paper discharge path 21 and the refeed path, the predetermined position is an initial stage for guiding the paper to the paper discharge path 21 to the paper discharge tray 20 which is a standard transport destination. In the case of the switching claw 45 of the sheet reversing device, it is a retreat position when the sheet is carried from the carry-in path 41 to the switchback conveyance path 42. In a state where the stepping motor 32 is not excited, the switching claws 30 and 45 are biased by the spring 33 and are in the predetermined position by the stopper. When the image forming apparatus is operated, the stepping motor 32 that drives the switching claws 30 and 45 is excited, and a predetermined position of each switching claw at this time is set as a reference position for switching claw control.

  In FIG. 3, the switching claw 30 discharges paper to the paper discharge tray 21 as shown in FIG. 3A, or conveys it to the carry-in path 41 of the refeed path for duplex printing as shown in FIG. 3B. In response to an instruction from the transport destination, the posture of the switching claw 30 is moved at a predetermined timing.

  In FIG. 4, the switching claw 45 of the sheet reversing device is fixed at the retracted position in the default state, and a conveyance path for guiding the sheet from the carry-in path 41 to the switchback conveyance path 42 is secured. Since the sheet reversing device 40 reverses the sheet within a short sheet interval, after the image formation on the sheet is completed, the conveyance speed of the carry-in path 41 is increased and the sheet is fed into the switchback conveyance path 42 (FIG. 4 ( a)). In the switchback conveying path 42, the sensor 44 detects the leading edge of the paper, and from the information on the length of the paper, after the trailing edge of the paper has passed through the switching claw 45, the switching claw 45 is guided from the retracted position to the carry-out path 43. The sheet is moved to the position, and the sheet is stopped after a predetermined time (FIG. 4B). The switchback conveyance path 42 conveys the paper in the reverse direction and sends it to the carry-out path 43 (FIG. 4C). The sensor 44 detects the rear edge of the paper, and the rear edge of the paper is switched by the paper length information. The switching claw 45 is again moved to the retracted position at the timing when it has exited 45.

  The amount of movement of the switching claws 30 and 45 is controlled by the number of driving steps of the stepping motor 32 from that position, with each initial position as a reference position. If a paper jam or abnormality occurs during image formation or paper conveyance, the apparatus stops and the stepping motor 32 that drives the switching claws 30 and 45 is also de-energized. At this time, the position of the switching claws 30 and 45 is not known, but when the stepping motor 32 is de-energized, the switching claws 30 and 45 are moved to their predetermined positions by the urging force of the spring 33. Stop by the stopper. In this way, even when the apparatus stops unexpectedly, the switching claws 30 and 45 return to the predetermined retracted position, so that when the paper remaining in the apparatus is processed, the switching claws become an obstacle and difficult to operate. Never become.

The urging force of the spring 33 is a weak force that is necessary and sufficient to move the unloaded switching claws 30 and 45. Therefore, the stepping motor 32 is excited even when the switching claw is stopped with a sheet of paper. By trying to move the switching claws 30 and 45 by the cutting spring force, the paper is not damaged.
The image forming device recovers after the paper jam has been cleared or when the device recovers from the abnormality, and the stepping motor is energized again. At this time, the position of the switching claw is set to a predetermined initial position (reference position). Yes, switching claw control can be resumed simply by resetting the reference position information.

  In the present embodiment, the switching pawls 30 and 45 are controlled with the initial position biased by the spring 33 as a reference position, but the switching pawl is detected in the vicinity of the initial position biased by the spring 33. By arranging the sensor 44, a more accurate reference position can be obtained. FIG. 5 shows an example in which a transmissive photo interrupter 34 is used to detect the reference position of the switching claw 30 (45). When the stepping motor 32 is not excited, the switching claw 30 (45) is biased by the spring 33, and the switching claw 30 (45) is stopped at the initial position by a stopper (not shown). In this state, the transmissive photo interrupter 34 is arranged so as to be shielded from light by the light shielding plate of the switching claw. After being excited, the stepping motor 32 drives the switching claw 30 (45) in the direction opposite to the biasing direction of the spring 33, and the position at which the photo interrupter 34 is switched from the light shielding state to the transmission state is set as a reference position. In this case, the initial position by the urging of the spring 33 is set to be outside the range of the control position used when transporting the paper.

  By disposing the sensor 44 that detects the attitude of the switching claws 30 and 45 as described above, the stepping motor 32 is excited when the image forming apparatus is operated or when the apparatus is restarted after being stopped due to a paper jam or the like. In this case, the reference position can be obtained immediately by slightly driving the switching claws 30 and 45 in one direction, and the control of the switching claws 30 and 45 can be started easily and quickly.

  In this embodiment, the image forming apparatus having the double-sided printing function has been described. However, when the image forming apparatus has a face-up discharge tray and a face-down discharge tray, or a paper discharge apparatus having a plurality of bins, image formation is performed. The same applies to the switching claw that selects and switches the paper discharge destination of the subsequent paper. The paper reversing device 40 is used not only for double-sided printing, but also when discharging the paper on which the image is formed upside down to the paper discharge tray, when reversing the paper and discharging it to the post-processing device. The present invention can also be applied to a sheet reversing device.

1 is a configuration diagram schematically illustrating an image forming apparatus according to an embodiment of the present invention. It is a lineblock diagram of a change claw concerning one embodiment of the present invention. It is a lineblock diagram of switching claw 30 concerning one embodiment of the present invention. It is a lineblock diagram of switching claw 45 concerning one embodiment of the present invention. It is a block diagram of the switching claw provided with the sensor which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming part 11 Photoconductor drum 12 Intermediate transfer belt 20 Paper discharge tray 21 Paper discharge path 30, 45 Switching claw 31 Rotating shaft 32 Stepping motor 33 Spring 34 Transmission type photo interrupter 40 Paper reversing device 41 Carry-in path 42 Switchback transport path 43 Conveyance path 44 Sensor

Claims (12)

A transport path switching means for switching the transport path of the paper;
Drive means for driving the transport path switching means,
The drive means can move and stop the transport path switching means to an arbitrary position within a predetermined movable range;
A sheet conveying apparatus comprising: a moving unit that moves and stops the conveying path switching unit to a predetermined position when the driving unit releases the driving of the conveying path switching unit.   2. The paper conveying apparatus according to claim 1, wherein the moving means is an urging means for urging the conveying path switching means in the predetermined position direction.   3. A sheet conveying apparatus according to claim 1, further comprising position detecting means for detecting a position of the conveying path switching means.   4. The position detecting unit detects the predetermined position while moving the transport path switching unit moved to the predetermined position by the moving unit in one direction by the driving unit. The paper conveying apparatus as described.   The moving means is an urging means for urging the transport path switching means in the predetermined position direction, and the transport path switching means is moved in a direction opposite to the urging direction of the urging means by the driving means. 5. The paper conveying apparatus according to claim 4, wherein the predetermined position is detected.   6. The paper conveying apparatus according to claim 1, wherein the driving unit is a stepping motor. A transport path switching means for switching the transport path of the paper;
A sheet conveying device having a driving means for driving the conveying path switching means,
The drive means can move and stop the transport path switching means to an arbitrary position within a predetermined movable range;
An image forming apparatus comprising: a moving unit configured to move the conveyance path switching unit to a predetermined position and stop when the driving unit releases the driving of the conveyance path switching unit.   8. The image forming apparatus according to claim 7, wherein the moving unit is a biasing unit that biases the transport path switching unit in the predetermined position direction.   9. The image forming apparatus according to claim 7, further comprising a position detection unit that detects a position of the conveyance path switching unit.   10. The position detecting unit detects the predetermined position while moving the transport path switching unit moved to the predetermined position by the moving unit in one direction by the driving unit. The image forming apparatus described.   The moving means is an urging means for urging the transport path switching means in the predetermined position direction, and the transport path switching means is moved in a direction opposite to the urging direction of the urging means by the driving means. The image forming apparatus according to claim 10, wherein the predetermined position is detected.   The image forming apparatus according to claim 7, wherein the driving unit is a stepping motor.

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