JP4349201B2 - Paper transport device - Google Patents

Description

  The present invention relates to a sheet conveying device used for a copying machine, a printer device, and the like.

In general, a copying machine, a printer device, and the like are equipped with a paper transport device for transporting paper stored in a paper feed tray to an image forming unit that transfers a toner image onto the paper.
As a sheet conveying device, for example, one configured as shown in FIG. 6 is widely known. In the illustrated sheet conveying apparatus, a pickup roll 23 that feeds out the sheet 22 from the sheet feeding tray 21, and a feed roll 24 a and a retard roll 24 b for conveying the sheet 22 fed out to the pickup roll 23 on each leaf are conveyed. A pair of feed rolls 24, a takeaway roll pair 25 disposed on the rear side of the sheet conveying direction with respect to the feed roll pair 24, and a registration roll pair 26 disposed on the rear side of the takeaway roll pair 25. ing. When the paper 22 is fed out from the feed roll pair 24 one by one, the take-away roll pair 25 nips and conveys the paper 22 toward the rear side, and abuts against the registration roll pair 26 that has stopped rotating. 22 is caused to bend and thereby the skew (inclination) of the sheet 22 is corrected. Then, the registration roll pair 26 starts rotating in accordance with the operation timing of the image forming unit (not shown). The paper is nipped and conveyed toward the image forming unit on the rear side (see, for example, Patent Document 1).

  By the way, in recent years, there has been a strong demand for miniaturization and cost reduction for copying machines, printer devices, and the like. Along with this, in the paper transport device, the distance from the feed roll pair 24 to the registration roll pair 26 tends to be short. In addition, some paper transport apparatuses eliminate the takeaway roll pair in order to cope with further miniaturization and the like, and the feed roll pair and the registration roll pair are arranged side by side on the paper transport path. (For example, refer to Patent Document 2).

JP-A-10-316256 JP 2002-255403 A

However, in the paper transport device provided with the takeaway roll pair 25, when the distance from the feed roll pair 24 to the registration roll pair 26 is shortened, the distance between the takeaway roll pair 25 and the registration roll pair 26 is also shortened accordingly. For this reason, even if the paper 22 is abutted against the registration roll pair 26, an appropriate bending loop cannot be generated in the paper 22 due to the presence of the takeaway roll pair 25. As a result, the skew correction of the paper 22 is uncertain. There is a risk of becoming.
On the other hand, with a paper transport device that eliminates the takeaway roll pair, skew correction for the paper can be ensured even if the distance from the feed roll pair to the registration roll pair is shortened, but there is a takeaway roll pair. In comparison with this, the paper conveyance load on the pair of feed rolls becomes large. This pair of feed rolls is originally intended to spread the fed paper every leaf. Therefore, unlike the case where the wear of the feed roll pair becomes noticeable or the take away roll pair exists, the paper transport speed of the registration roll pair is adjusted to the same time when the load on the paper of the feed roll pair is released. There may be fluctuations.
Any of these can be a cause of image formation failure in the image forming unit. That is, both when the skew correction is uncertain and when the conveyance failure of the sheet due to the registration roll pair occurs, it may cause a smear on the formed image, an image magnification defect, and the like.

  Therefore, the present invention ensures skew correction for the paper and further optimizes paper conveyance even when the distance from the feed roll pair to the registration roll pair tends to be short in order to cope with downsizing and the like. Accordingly, an object of the present invention is to provide a paper transport device that does not cause image formation defects in the image forming unit.

The present invention is a paper transport device devised to achieve the above object, and is a paper transport device that is mounted and used in an image forming apparatus that outputs an image on paper. A pair of feed rolls that convey the paper fed out from the paper tray every leaf, and correct the skew of the paper by abutting the paper and operate at a predetermined timing to form the image on the image forming apparatus. A pair of registration rolls that are nipped and conveyed to a section , a takeaway roll pair that is disposed between the pair of feed rolls and the registration roll pair on the conveyance path of the sheet, and the pair of takeaway rolls can nipping and conveying the sheet and a switching means for switching between non-clamping condition to be state of each roll leaves constituting the holding state and the take-away roll pair, the take away Russia When the pair of rollers is in the non-clamping state, the pair of feed rolls abuts against the registration roll pair that conveys the sheet and stops the rotation of the sheet, and the pair of feed rolls conveys the sheet even after the abutment. The sheet is bent, the skew of the sheet is corrected, and after the operation of the registration roll pair is started, the switching means switches the take away roll pair to the clamping state, and the feed roll pair, the take roll The sheet is sandwiched and conveyed by each of the away roll pair and the registration roll pair .

  According to the paper transport device having the above-described configuration, the takeaway roll pair can be switched between the nipping state and the non-nipping state. Therefore, for example, when skew correction is performed on a sheet, by setting the takeaway roll pair to the non-clamping state, the takeaway roll pair does not interfere with the bending loop generated on the sheet, and the skew correction can be ensured. Further, for example, when the paper is transported to the rear side of the registration roll pair, the paper is sandwiched and transported between the takeaway roll pair by placing the takeaway roll pair in a sandwiched state. Can be reduced, and paper conveyance to the subsequent stage can be made appropriate.

  The paper transport device of the present invention ensures skew correction for paper by switching the take-away roll pair between the sandwiching state and the non-nipping state even when the distance from the feed roll pair to the registration roll pair tends to be short. In addition, it is possible to make the paper transport more appropriate, so that it is possible to reduce the size and price of a copying machine or printer that is equipped with the paper transport device, while at the same time forming a defective image at the image forming unit. The image formation can be improved and the image formation can be improved.

  Hereinafter, a sheet conveying apparatus according to the present invention will be described with reference to the drawings. The paper conveying apparatus described here is used by being mounted on a copying machine, a printer apparatus, or the like. Since the copying machine, the printer apparatus, or the like is realized by a publicly known technique, the description thereof will be given here. Is omitted.

  FIG. 1 is a schematic diagram illustrating a schematic configuration example of a paper conveying apparatus according to the present invention. In the illustrated sheet conveying apparatus, a pickup roll 3 that feeds out the sheet 2 from the sheet feeding tray 1, and a feed roll 4 a and a retard roll 4 b for conveying the sheet 2 that has been fed out to the pickup roll 3 on every leaf. A feed roll pair 4, a take-away roll (TA Roll) pair 5 arranged on the rear side of the paper transport direction with respect to the feed roll pair 4, and a rear side of the take-away roll pair 5. And a registered Reg Roll pair 6. A curved paper guide (not shown) is provided between the roll pairs 4 to 6 along the conveyance path 7 of the paper 2, and the paper guide guides the paper 2. Yes.

  Among these, the takeaway roll pair 5 can be switched between a holding state in which the sheet 2 can be held and conveyed and a non-nipping state in which the rolls constituting the takeaway roll pair 5 are separated as described later. It is configured. Switching between the pinching state and the non-pinching state is performed by switching means 10 provided accompanying the takeaway roll pair 5.

  Here, the switching means 10 for switching the take-away roll pair 5 between the pinching state and the non-pinching state will be described. FIG. 2 is a schematic diagram illustrating a configuration example of a main part of the paper transport device according to the present invention.

  As the switching means 10, as shown in FIG. 2A, one of the rolls 5 a and 5 b constituting the takeaway roll pair 5, for example, a roll 5 a positioned on the outer peripheral side with respect to the curved portion of the paper guide. It can be considered that the switch is arranged at one end of the swingable link 11 and the electromagnetic solenoid 12 is connected to the other end of the link 11. In the switching means 10 having such a configuration, the take-away roll pair 5 can be switched between the holding state and the non-holding state by the operation of the electromagnetic solenoid 12, and the take-away roll pair 5 is held in the holding state through the operation state of the electromagnetic solenoid 12. It is possible to recognize whether it is in a non-clamping state. Further, as shown in FIG. 2 (b), the switching means 10 has a roll 5a disposed at one end of a swingable link 11, and an eccentric cam 13 is brought into contact with the other end of the link 11, and the eccentricity. A configuration in which the cam 13 can be rotationally driven by the electric motor 14 is also conceivable. In the switching means 10 having such a configuration, the operation of the electric motor 14 can switch between the sandwiched state and the non-clamped state of the takeaway roll pair 5 through the rotation of the eccentric cam 13. If the notch of the plate mounted on the driven shaft of the eccentric cam 13 or the drive shaft of the electric motor 14 is detected by the sensor, the takeaway roll pair 5 is in either the clamping state or the non-clamping state through the detection result. It will also be able to recognize what is in. These switching means 10 are merely examples, and other known techniques can be used as long as the takeaway roll pair 5 can be switched between the pinching state and the non-pinching state and the state can be recognized. It may be realized. However, in any case, the switching unit 10 has a control function including a CPU (Central Processing Unit) that executes a predetermined program in order to perform state recognition, drive instruction, and the like. .

  Next, an example of processing operation in the case of carrying the paper 2 fed from the paper feed tray 1 in the paper carrying device configured as described above will be described.

First, an initialization process that is performed prior to the conveyance of the sheet 2 will be described. FIG. 3 is a flowchart illustrating an example of the procedure of the initialization process.
In copying machines and printers, for example, initialization of the device is performed at a predetermined timing such as when the power to the device is turned on or when the so-called sleep mode is restored. Also in the apparatus, initialization processing described below is performed at the predetermined timing. That is, at a predetermined timing, the takeaway roll pair 5 is in a sandwiched state (hereinafter, the sandwiched state is simply referred to as “nip”) and in a non-clamped state (hereinafter, the unpinched state is simply referred to as “release”). The switching means 10 recognizes which state is present (step 101, hereinafter “step” will be abbreviated as “S”), and in the case of the nip, the drive source such as the electromagnetic solenoid 12 or the electric motor 14 is driven to start the release operation. (S102), and this is performed until the release is completed and nipping is performed (S103). As a result of the recognition, if it has already been released, the release operation is unnecessary. That is, in the initialization process, the take away roll pair 5 is released.

  Thereafter, when there is an instruction to start printing from a control unit such as a copier or printer equipped with a paper transport device, a paper transport process as described below is performed. FIG. 4 is a flowchart illustrating an example of the procedure of the paper transport process.

  When an instruction to start printing is given from the control unit, in the paper transport device, the pick-up roll 3 feeds the paper 2 from the paper feed tray 1, and the feed roll pair 4 rolls the paper 2 every leaf, and the takeaway roll pair 5 and It is conveyed toward the registration roll pair 6 side. At this time, the takeaway roll pair 5 is in a released state by the initialization process described above. Accordingly, the sheet 2 fed out from the sheet feeding tray 1 is conveyed by the pair of feed rolls 4 until the leading end of the sheet abuts against the registration roll pair 6 whose rotation is stopped, thereby generating a bending loop and correcting the skew. . After the skew correction, the registration roll pair 6 starts rotating operation in accordance with the operation timing of the image forming unit in the copying machine, the printer device, etc., and nipping and conveying the sheet 2 toward the image forming unit on the rear side.

  In parallel with the conveyance of the sheet 2, in the sheet conveyance apparatus, when there is an instruction to start printing, the switching unit 10 causes the information relating to the nip timing of the takeaway roll pair 5 (hereinafter simply “nip timing information”). (S201). “Nip timing information” refers to information for specifying the timing for switching the takeaway roll pair 5 from release to nip. Specifically, from the start of conveyance by the feed roll pair 4 for specifying the switching timing. Information on the elapsed time. The nip timing information may be set in advance based on, for example, the conveyance speed of the paper 2 or the distance between each pair of rolls 4 to 6. A RAM (Random Access Memory) or ROM that can be accessed by the switching means 10. What is necessary is just to store in the information storage means implement | achieved by memory | storage devices, such as (Read Only Memory), for example in a table format.

  When the nip timing information is obtained, the switching means 10 monitors the elapsed time from the start of conveyance using, for example, a timer function (S202), and when it is time to nip the takeaway roll pair 5, the electromagnetic solenoid 12 or A driving source such as the electric motor 14 is driven to start a nip operation (S203), and this is performed until the nip is completed (S204). As will be described later, the nip timing of the takeaway roll pair 5 is from when the registration roll pair 6 starts conveying the paper 2 to when the trailing edge of the paper 2 passes the feed roll pair 4. It shall be in

  Thereafter, the switching unit 10 obtains information related to the release timing of the takeaway roll pair 5 (hereinafter simply referred to as “release timing information”) (S205). “Release timing information” refers to information for specifying the timing for switching the takeaway roll pair 5 from the nip to the release, and specifically relates to the elapsed time after completion of the nip for specifying the switching timing. Information. Similarly to the nip timing information, the release timing information may be set in advance based on, for example, the conveyance speed of the sheet 2 or the distance between each pair of rolls 4 to 6 and can be accessed by the switching unit 10. The information storage means may be stored in a table format, for example.

  When the release timing information is obtained, the switching means 10 monitors the elapsed time after completion of the nip using, for example, a timer function (S206), and when it is time to release the takeaway roll pair 5, the electromagnetic solenoid 12 Alternatively, the drive source such as the electric motor 14 is driven to start the release operation (S207), and this is performed until the release is completed (S208). As will be described later, the take-away roll pair 5 is released after the rear end of the sheet 2 passes through the take-away roll pair 5 and then the feed roll pair 4 conveys the next sheet 2. It shall be between.

  Thereafter, if there is a next sheet 2 in the sheet feed tray 1, that is, if there is a subsequent sheet to be conveyed next by the feed roll pair 4, the switching means 10 repeats the above steps again (S201 to S201). This is repeated until there is no subsequent sheet (S209).

  The sheet conveyance process of the above procedure will be described in more detail together with the flow of the sheet 2 and the operations of the roll pairs 4 to 6. FIG. 5 is an explanatory diagram showing an outline of the flow of paper and the operation of each roll pair during the paper transport process.

  As described above, when there is a print start instruction from the control unit, the feed roll pair 4 starts conveying the first sheet 2 in the sheet conveying apparatus. As a result, the sheet 2 is conveyed toward the takeaway roll pair 5 and the registration roll pair 6 as shown in FIG.

  Thereafter, the sheet 2 conveyed to the feed roll pair 4 abuts against the registration roll pair 6 whose leading end is stopped from rotating, but since the feed roll pair 4 continues to convey the sheet thereafter, as shown in FIG. Therefore, a bending loop is generated. However, at this time, the takeaway roll pair 5 is in a released state. Accordingly, the sheet 2 is not affected by the presence of the takeaway roll pair 5, that is, the takeaway roll pair 5 does not get in the way, and an appropriate bending loop is generated.

  When an appropriate bending loop occurs in the paper 2, the paper transport device stops driving the feed roll pair 4 as shown in FIG. 5C, thereby ending skew correction for the paper 2. In addition, the drive stop of the feed roll pair 4 may be performed, for example, after a predetermined time has elapsed since the start of driving of the feed roll pair 4. The predetermined time is set in advance based on the conveyance speed of the sheet by the feed roll pair 4, the distance from the feed roll pair 4 to the registration roll pair 6, and the like. Even when the skew correction is thus completed, the takeaway roll pair 5 does not interfere with the bending loop generated in the paper 2, so that the skew correction can be reliably performed.

  After that, as shown in FIG. 5D, the registration roll pair 6 starts rotating operation in accordance with the operation timing of the image forming section (not shown) on the subsequent stage side, and sandwiches and conveys the sheet 2. Also, the drive of the feed roll pair 4 is resumed in accordance with the start of the rotation operation of the registration roll pair 6, and the drive of the takeaway roll pair 5 is also started. However, at this time, the feed roll pair 4 is driven so that the conveyance speed of the paper 2 by the feed roll pair 4 is slower than the conveyance speed of the paper 2 by the registration roll pair 6. As a result, the bending loop generated in the paper 2 gradually decreases as the paper 2 is conveyed. Then, as shown in FIG. 5E, when the flexion loop is eliminated, the paper 2 of the takeaway roll pair 5 is a roll 5b positioned on the inner peripheral side of the curved portion of the paper transport path and a paper (not shown). It will be guided by the guide.

  When the bending loop is eliminated in this way, the nip timing specified by the nip timing information is reached, so that the switching means 10 starts the nip operation as shown in FIG. Nips the paper 2. As a result, the sheet 2 is nipped and conveyed by each of the feed roll pair 4, the takeaway roll pair 5 and the registration roll pair 6. In addition, the conveyance speed of the paper 2 by each roll pair 4-6 at this time shall be the same.

  Thereafter, the feed roll pair 4 stops its rotating operation before the rear end of the sheet 2 passes through the feed roll pair 4 as shown in FIG. This is to prevent the second sheet in the sheet feeding tray 1 from following the conveyance of the first sheet 2, that is, to prevent double feeding of the sheet 2. Accordingly, the sheet 2 held between the feed roll pair 4 is moved by the nipping conveyance by the takeaway roll pair 5 and the registration roll pair 6 and the action of the one-way clutch or torque limiter attached to the feed roll pair 4 and the like. The end is pulled out from the feed roll pair 4.

  At this time, as the rear end of the sheet 2 passes through the feed roll pair 4, the load due to the feed roll pair is released. However, the takeaway roll pair 5 is in a state where the paper 2 is nipped, and the paper 2 is nipped and conveyed by the takeaway roll pair 5, so that even if the load of the feed roll pair is removed, the paper 2 There is no fluctuation in the conveyance speed. That is, since the sheet 2 is nipped and conveyed while the takeaway roll pair 5 is nipped, the conveyance load of the sheet 2 on the feed roll pair 4 or the registration roll pair 6 does not become excessive. For this reason, it is possible to stably carry the paper 2 while effectively preventing double feeding.

  When the trailing edge of the sheet 2 passes through the feed roll pair 4, the takeaway roll pair 5 and the registration roll pair 6 thereafter sandwich and convey the sheet 2 toward the image forming unit. When the trailing edge of the sheet 2 passes the takeaway roll pair 5, the release timing specified by the release timing information is reached, so that the switching unit 10 starts the release operation as shown in FIG. 5 (h). . As a result, the takeaway roll pair 5 is released again, and the feed roll pair 4 is ready to start transporting the second sheet.

  As described above, according to the sheet conveying apparatus described in the present embodiment, the switching unit 10 switches the takeaway roll pair 5 between the nip state and the release state. For this reason, when the skew correction is performed on the paper 2, the takeaway roll pair 5 is released to prevent the takeaway roll pair 5 from interfering with the bending loop generated on the paper 2, thereby ensuring the skew correction. Can be planned. Further, when the paper is transported to the image forming unit on the rear side of the registration roll pair 6, the take-away roll pair 5 is nipped so that the paper 2 is nipped and transported by the take-away roll pair 5. Thus, it is possible to reduce the paper transport load on the feed roll pair 4 and to optimize the paper transport.

  Therefore, according to the paper transport device of the present embodiment, the nip / release of the takeaway roll pair 5 can be performed even if the distance from the feed roll pair 4 to the registration roll pair 6 tends to be short in order to cope with downsizing and the like. By switching, the skew correction for the paper 2 can be assured and the paper conveyance can be made appropriate, so that the copying machine and printer device equipped with the paper conveyance device can be reduced in size and price can be reduced. In addition, it is possible to prevent image formation defects in the image forming unit and improve the image formation.

  In the above-described embodiment, the preferred specific example of the present invention has been described. However, the present invention is not limited to the content, and can be appropriately changed without departing from the gist of the present invention. It is.

  For example, in the present embodiment, the case where the takeaway roll pair 5 is released in the initialization process has been described as an example. However, the present invention is not necessarily limited thereto, and the skew correction of the paper 2 is performed. If the takeaway roll pair 5 is in the released state, the skew correction can be ensured.

  Further, for example, when switching from the released state to the nipped state, if the skew of the sheet 2 is corrected and the rear end of the sheet 2 passes through the feed roll pair 4, the sheet conveyance is made appropriate. Can be planned. However, as described in the present embodiment, if the switching from the release to the nip is performed after the bending loop generated in the paper 2 is eliminated, the skew correction is not affected by the nip. This is suitable for ensuring the correction. Further, as described in the present embodiment, if the feed roll pair 4 stops rotating before the trailing edge of the paper 2 passes through the feed roll pair 4, the timing until the stop, that is, the paper If switching from the release to the nip is performed at a timing earlier than the time when the rear end of the feed roll pair 4 passes, the effect of stopping the rotation of the feed roll pair 4 (for example, the load and impact associated with the stop) ) Can be suppressed from reaching the paper 2, which is very suitable for appropriate paper conveyance.

FIG. 3 is a schematic diagram illustrating a schematic configuration example of a paper conveying apparatus according to the present invention. FIG. 3 is a schematic diagram illustrating a configuration example of a main part of a paper transport device according to the present invention. 6 is a flowchart illustrating an example of a procedure of an initialization process in the paper conveying apparatus of the present invention. 6 is a flowchart illustrating an example of a procedure of a paper transport process in the paper transport device of the present invention. FIG. 6 is an explanatory diagram showing an outline of a sheet flow and an operation of each roll pair during a paper conveyance process in the paper conveyance device of the present invention. FIG. 10 is a schematic diagram illustrating a schematic configuration example of a conventional paper conveyance device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Paper feed tray, 2 ... Paper, 3 ... Pickup roll, 4 ... Feed roll pair, 5 ... Take away roll pair, 5a, 5b ... Roll, 6 ... Registration roll pair, 7 ... Conveyance path, 10 ... Switching means

Claims (5)

A paper transport device that is mounted and used in an image forming apparatus that outputs an image on paper,
A pair of feed rolls that conveys the paper fed from the paper feed tray of the image forming apparatus through each leaf;
A pair of registration rolls that operate at a predetermined timing after the skew of the paper is corrected by abutment of the paper, and sandwich and convey the paper to the image forming unit of the image forming apparatus ;
A takeaway roll pair disposed between the feed roll pair and the registration roll pair on the paper conveyance path;
Switching means for switching between a holding state in which the takeaway roll pair can hold and convey the paper and a non-holding state in which the rolls constituting the takeaway roll pair are separated from each other ; and
When the takeaway roll pair is in a non-clamping state, the feed roll pair abuts against the registration roll pair that transports the paper and stops the rotation of the paper, and after the abutment, the feed roll pair Continues the paper transport to cause a flexion loop in the paper, correct the skew of the paper,
After the operation of the registration roll pair is started, the switching unit switches the takeaway roll pair to a nipping state, and nipping and conveying the sheet by each of the feed roll pair, the takeaway roll pair, and the registration roll pair. Paper transport device. The switching means switches the takeaway roll pair from the non-clamping state to the clamping state until the trailing edge of the paper passes through the feed roll pair after skew correction of the paper. Item 2. A sheet conveying apparatus according to Item 1 . The switching means switches the takeaway roll pair from the non-clamping state to the clamping state after the registration roll pair starts operating and the bending loop generated in the sheet due to abutment against the registration roll pair is eliminated. The sheet conveying apparatus according to claim 2 . After nipping and transporting the paper by each of the feed roll pair, the takeaway roll pair, and the registration roll pair, the rotation operation of the feed roll pair is stopped before the rear end of the paper passes through the feed roll pair. Do
4. A paper conveying apparatus according to claim 1, 2, or 3. The sheet conveying apparatus according to claim 4 , wherein the switching unit switches the takeaway roll pair from the non-clamping state to the clamping state until the rotation of the feed roll pair is stopped .

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