JP4586586B2 - Sheet feeding device - Google Patents

Description

  The present invention relates to a sheet feeding apparatus that feeds a plurality of sheets stored in a sheet storage unit that stores sheets one by one to an image forming unit that forms an image on the surface of the sheet with a time interval.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a print is provided with a sheet feeding device that feeds a sheet of a sheet storage unit that stores a sheet to an image forming unit that forms an image on the surface of the sheet.

  Such a sheet feeding apparatus includes a pair of rolls provided on the image forming unit side and whose peripheral surfaces are in contact with each other. The sheet is sandwiched between the pair of rolls and fed to the image forming unit. The pair of rolls rotates while adjusting the timing, and includes a registration roll that feeds the sheet to the image forming unit and a pair of rolls provided on the sheet storage unit side and whose peripheral surfaces are in contact with each other. The sheet is sandwiched in the nip region formed between the two and the pair of rolls rotates to feed the sheet with a conveying force toward the registration roll, and the feed roll and the registration roll are connected and fed. A transport path that is shorter than the length in the transport direction of the sheet and does not include a member that applies the transport force to the sheet; Deployed between Le, and take away rolls to give a conveying force to the sheet, there is what is composed of a passage detection sensor for detecting passage of the sheet leading edge to be conveyed along the conveying path.

  In the sheet feeding apparatus having such a configuration, after the sheet feeding instruction is received, the passage of the leading edge of the conveyed sheet is detected by the passage detection sensor and is fed until it is determined that the leading edge of the sheet has reached the registration roll. After the roll and the takeaway roll are rotated and it is determined that the leading edge of the sheet has reached the registration roll, the sheet conveyance is left to the takeaway roll and the registration roll to stop the rotation of the feed roll.

  Incidentally, in recent years, there has been an increasing demand for downsizing and cost reduction of devices.

  Accordingly, it has been proposed to answer these requirements by omitting the take-away roll that assists the conveyance in the middle of the conveyance path between the feed roll and the registration roll, and shortening the conveyance path (see Patent Document 1).

In this proposal, after it is determined that the leading edge of the sheet has reached the registration roll, the rotational torque of the feed roll is reduced to the extent that it cannot rotate in order to prevent double feeding of the sheet.
Japanese Patent No. 3488018

  However, if the take-away roll is omitted and the conveyance path is shortened, for example, the sheet is still in the nip portion of the feed roll where the rotational torque has been reduced to the extent that it cannot rotate due to the fact that the leading edge of the sheet has reached the registration roll. There may be a state where the rear end is sandwiched. In this state, when the sheet is conveyed by the registration roll, the registration roll conveys the sheet to the image forming unit while pulling out the sheet sandwiched between the nip portions of the feed roll, and as a result, the rotational torque of the registration roll changes. May adversely affect the transfer.

  In view of the above circumstances, an object of the present invention is to provide a sheet feeding apparatus that contributes to suppression of deterioration in image quality while preventing double feeding.

In order to achieve the above object, a sheet feeding apparatus according to the present invention comprises:
In a sheet feeding apparatus that feeds a plurality of sheets stored in a sheet storing unit that stores sheets one by one to an image forming unit that forms an image on the surface of the sheet with a time interval,
The pair of rolls provided on the image forming unit side includes a pair of rolls whose peripheral surfaces are in contact with each other, and adjusting the timing at which the sheet is sandwiched between the pair of rolls and the sheet is fed to the image forming unit. , The registration roll that feeds this sheet into the image forming unit,
This sheet comprises a pair of rolls provided on the sheet accommodating means side and whose peripheral surfaces are in contact with each other. The sheet is sandwiched in a nip region formed between the pair of rolls, and the pair of rolls rotates to rotate the sheet. In addition, a feed roll that gives a conveying force toward the register roll,
A transport path that connects the feed roll and the registration roll and is shorter than the length in the transport direction of the sheet to be fed, and in which a member that provides the transport force to the sheet is not provided,
A detection unit that is disposed in the conveyance path and detects that sheets to be fed overlap each other;
The rotation of the pair of rolls forming the nip region is continued until the detection unit detects that the sheets overlap each other, and when the detection unit detects that the sheets overlap each other, this rotation is performed. And a control unit for stopping the operation.

  In the sheet feeding apparatus of the present invention, the rotation of the feed roll is continued until the detection unit detects that the sheets overlap each other, that is, until the double feeding is detected. Therefore, according to the sheet feeding apparatus of the present invention, the rotation of the feed roll is not stopped uniformly after it is determined that the leading edge of the sheet has reached the registration roll in preparation for double feeding that does not occur. For example, until the trailing edge of the sheet has passed through the nip area of the feed roll, in principle, the feed roll is rotated so that the rotational torque of the registration roll is not affected, but if double feed is detected in the meantime Stop the rotation of the feed roll. Thereby, it can contribute to suppression of the fall of image quality, preventing double feeding.

  Here, the detection unit is preferably a sensor provided in the vicinity of the feed roll.

  In this way, since the overlap between the sheets can be detected as early as possible, the sheet that is sandwiched between the nip regions of the feed roll that has stopped rotating after the detection of the overlap between the sheets is transferred from the sheet storage unit to the conveyance path side. Thus, it is possible to avoid a situation in which the sheet pulled out greatly and the sheet pulled out greatly when the sheet storage means is pulled out from the apparatus.

  Further, the detection unit may detect that the sheets to be fed overlap with each other using sound waves, or a pair of rolls forming the nip region include sheets in the nip region. It may be one that detects that the sheets to be fed overlap each other based on the magnitude of the force received by sandwiching the sheet, or has a sensor that detects that the trailing edge of the sheet has passed. The time from when the sensor detects that the trailing edge of the sheet has passed to the time when the sensor detects that the trailing edge of the next sheet to be fed has passed is calculated, and based on the calculated time. Alternatively, it may be detected that the sheets to be fed overlap each other.

  According to the sheet feeding apparatus of the present invention, it is possible to contribute to suppression of deterioration in image quality while preventing double feeding.

  Hereinafter, embodiments of the sheet feeding apparatus of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of a printer provided with a first embodiment of a sheet feeding apparatus of the present invention.

  FIG. 1 shows an image forming unit 100 and a sheet feeding unit 200 which is a first embodiment of the sheet feeding apparatus of the present invention, which constitutes the printer 1.

  The image forming unit 100 shown in FIG. 1 includes four toner image forming units 10Y, 10M, 10C, and 10K. Each toner image forming unit includes a photoreceptor roll 11Y, 11M, 11C, and 11K, respectively. , Chargers 12Y, 12M, 12C, 12K, exposure devices 13Y, 13M, 13C, 13K, developing rolls 14Y, 14M, 14C, 14K, and primary transfer rolls 15Y, 15M, 15C, 15K. The printer 1 is capable of full-color printing, and the symbols Y, M, C, and K attached to the end of each of the above-described constituent elements are yellow, magenta, cyan, and black, respectively. Indicates an element.

  The image forming unit 100 also includes an intermediate transfer belt 120, a secondary transfer roll 140, and an image control unit 110 that controls the operation of each toner image forming unit.

  A basic image forming operation in the printer 1 will be described.

  First, toner image formation by the yellow toner image forming unit 10Y is started, and a predetermined charge is applied to the surface of the photoreceptor roll 11Y rotating in the arrow A direction by the contact-type charger 12Y. Next, the exposure device 13Y irradiates the surface of the photoreceptor roll 11Y with exposure light corresponding to a yellow image to form a latent image. The latent image is developed with yellow toner by the developing roll 14Y, and a yellow toner image is formed on the photoreceptor roll 11Y. The toner image is transferred to the intermediate transfer belt 120 by the primary transfer roll 15Y.

  The intermediate transfer belt 120 circulates in the direction of arrow B, and is synchronized with the timing at which the yellow toner image transferred onto the intermediate transfer belt 120 reaches the primary transfer roll 15M of the next color toner image forming unit 10M. Then, the magenta toner image forming unit 10M forms a toner image so that the next color magenta toner image reaches the primary transfer roll 15M. The magenta toner image formed in this way is transferred onto the yellow toner image on the intermediate transfer belt 120 while being superimposed on the primary transfer roll 15M.

  Subsequently, toner image formation by the cyan and black toner image forming units 10C and 10K is performed at the same timing as described above, and sequentially on the yellow and magenta toner images of the intermediate transfer belt 120 in the primary transfer rolls 15C and 15K. It is transcribed again.

  Thus, the multicolor toner image transferred onto the intermediate transfer belt 120 is secondarily transferred onto the sheet 400 by the secondary transfer roll 140. The multicolor toner image is transported together with the sheet 400 in the direction of arrow C, which is the sheet transport direction, sent to a fixing device (not shown), and fixed on the sheet 400 by being heated and pressed.

  Here, a sheet feeding unit 200 that feeds sheets to the image forming unit 100, which is a component of the printer 1, will be described.

  The sheet feeding unit 200 shown in FIG. 1 includes a sheet tray 270 in which a plurality of sheets 400 are stacked and stored, a nudger roll 290 that sequentially draws the uppermost sheet from the sheet tray 270, and a nudger roll 290. A feed roll 220 that applies a conveyance force to the sheet 400 fed to the conveyance path 300 indicated by a dotted line, and a feed roll 220 are provided opposite to the feed roll 220, and a nip portion 225 is formed between the feed roll 220 and the double feed. The resist roll 240 is arranged on the downstream side of the transport path with respect to the retard roll 230 and the feed roll 220 for prevention, and on the upstream side of the secondary transfer roll 140 with respect to the transport path.

  Also, the sheet feeding unit 200 shown in FIG. 1 is provided on the upstream side of the conveyance path in the vicinity of the registration roll 240, and is provided in the vicinity of the registration sensor 250 and the retard roll 230 that detect passage of the leading edge of the conveyed sheet 400. A position displacement sensor 260 for detecting the displacement of the retard roll 230 caused by the passage of the nip portion 225 of the feed roll 220 and the sheet tray 270 are accommodated in the lap portion generated when the sheets are multi-fed. The size sensor 280 detects the size of the sheet 400 in the conveyance direction. FIG. 1 shows a state where the sheet 400 is being conveyed along the conveyance path 300. Further, the sheet 400 conveyed in the printer 1 is longer in the conveyance direction than the conveyance path 300 that connects the registration roll 240 and the feed roll 220.

  Here, FIG. 2 is an external perspective view of the sheet tray shown in FIG.

  A sheet tray 270 shown in FIG. 2 is of a type capable of accommodating a plurality of types of sheets, and has a side guard 271 and an end guide 272 slidable on the inner bottom surface according to the size of the sheets to be accommodated. Is shown being deployed. The arrangement of the side guide 271 and the end guide 272 is detected by the size sensor 280 shown in FIG. 1, and the size sensor 280 transmits a detection signal to the conveyance control unit 210 described later. Based on this detection signal, the conveyance control unit 210 acquires the size of the sheet 400 currently stored in the sheet tray 270 in the conveyance direction. 2 is a direction in which the sheet 400 stored in the sheet tray 270 is conveyed.

  FIG. 3 is a diagram illustrating the conveyance control unit.

  FIG. 3 shows a conveyance control unit 210 that controls the rotation of the feed roll 220, the retard roll 230, the registration roll 240, and the nudger roll 290 based on the signals transmitted from the sensors shown in FIG. ing.

  In this printer 1, an instruction to start image formation is issued from the central control unit 2 to each unit in response to a print instruction from the operator. In FIG. 3, a sheet is sent from the central control unit 2 to the conveyance control unit 210. A state in which the conveyance instruction can be transmitted is shown.

  Upon receiving the sheet conveyance instruction, the conveyance control unit 210 instructs the feed roll 220 to start rotation, and then instructs the nudger roll 290 to start rotation. When the feed roll 220 rotates, the retard roll 230 that is in contact with the feed roll 220 is driven to rotate. The conveyance control unit 210 includes a feed timer 211, a registration timer 212, and a memory 213, which will be described in detail later.

  The nudger roll 290 feeds the uppermost sheet among the sheets 400 accommodated in the sheet tray 270 to the nip portion 225 formed between the feed roll 220 and the retard roll 230 and then to the nip portion 225. The sheet 400 is conveyed along the conveyance path 300 by the rotation of the feed roll 220. Thereafter, after receiving that the registration sensor 250 detects the passage of the leading edge of the sheet 400 being conveyed along the conveyance path 300, the conveyance control unit 210 synchronizes the transfer from the image formation control unit 110. The registration roll 240 is instructed to start rotation after waiting for the timing synchronization signal to arrive.

  In addition, the conveyance control unit 210 starts time measurement by the feed timer 211 in response to the passage of the leading edge of the sheet 400 being conveyed along the conveyance path 300 being detected by the registration sensor 250, and the size sensor 280. Referring to the reference table stored in the memory 213 on the basis of the sheet size of the conveyed sheet recognized by step S2 and the rotation speed of the feed roll 220, the trailing edge of the sheet is detected after the passage of the sheet front end is detected by the registration sensor 250. Standard time A is acquired as an estimated time until the nip portion 225 of the feed roll 220 passes through.

  Further, normally, the conveyance control unit 210 stops the rotation of the feed roll 200 when the standard time A elapses from the timing when the leading edge of the sheet 400 is detected by the registration sensor 250. However, when the position displacement sensor 260 detects double feeding before the standard time elapses, the transport control unit 210 stops the rotation of the feed roll 220 even before the standard time elapses.

  As described above, in the sheet control unit 200 of the printer 1, when the multi-feed is detected by the position displacement sensor 260 from the detection timing of passage of the sheet leading edge by the registration sensor 250 to the lapse of the standard time A, at that time. The feed roll 220 is instructed to stop rotation.

  Therefore, according to the sheet feeding apparatus 200 of the present embodiment provided in the printer 1, the feed roll 220 is uniformly obtained after it is determined that the leading edge of the sheet has reached the registration roll in preparation for double feeding that is not determined whether or not it occurs. The rotation of the registration roll 240 is not affected by the rotation of the feed roll 220 until the trailing edge of the sheet completely passes through the nip portion 225 of the feed roll 220. Instead, when the double feed is detected, the rotation of the feed roll 220 is immediately stopped. Therefore, according to the sheet feeding unit 200 of the printer 1, it is possible to contribute to the suppression of the deterioration of the image quality while preventing the double feeding.

  FIG. 4 is a flowchart of a routine that is activated in the conveyance control unit when the printer is turned on.

  In step S <b> 1 shown in FIG. 4, the size of the sheets stored in the sheet tray 270 is detected from the detection signal from the sheet size sensor 280. In step S2, the standard time B from the start of rotation of the registration roll 240 to the stop of rotation is acquired from the sheet size detected in step S1 and the rotation speed of the registration roll 240 determined in advance. In step S3, a standard time A from when the registration sensor 250 detects the passage of the leading edge of the conveyed sheet until the feed roll 220 is stopped is acquired from the sheet size detected in step S1 and the rotation speed of the feed roll 220. . The conveyance control unit 210 has a memory 202 in which a reference table is stored, and the acquisition of the standard time A and the standard time B is performed with reference to the reference table stored in the memory 202. In step S4, the rotation of the registration roll 240 is stopped. In step S5, it is determined whether or not a sheet conveyance instruction is issued from the central control unit 2. If it is determined in step S5 that a conveyance instruction is not issued, step S5 is repeated, and the conveyance instruction is issued. If it is determined that there is, the process proceeds to step S6. In step S6, the feed roll 220 is instructed to start rotation. In step S7, the nudger roll 290 is instructed to feed the sheet, and in step S8, it is determined whether or not the registration sensor 250 detects passage of the leading edge of the sheet being conveyed. If it is determined in step S8 that the passage has already been detected, the process proceeds to step S9, and the feed timer 211 is started. In step S10, it is determined whether or not the value of the feed timer 211 is equal to or greater than the standard time A. If it is determined that the value is less than the standard time A, the process proceeds to step S12. On the other hand, if it determines with having become above, it will progress to step S11, will instruct | indicate rotation stop to the feed roll 220, and will progress to step S12. In step S <b> 12, it is determined whether or not a timing synchronization signal for taking a transfer timing is transmitted from the image control unit 110. If it is determined in step S12 that the timing synchronization signal has not been transmitted, the process proceeds to step S13, where it is determined whether the position displacement sensor 260 has detected a lap between sheets. If it is determined in step S13 that no lap has been detected, the process returns to step S10. If it is determined in step S13 that a lap has been detected, the process proceeds to step S14, where the rotation of the feed roll 220 is stopped. In step S15, it is determined whether or not a timing synchronization signal is transmitted from the image control unit 110. If it is not transmitted, the process waits in step S15 until it is transmitted. If it is determined that it has been transmitted, the process proceeds to step S19.

  On the other hand, if it is determined in step S8 that the passage of the leading edge of the sheet has not been detected yet, the process proceeds to step S16, and it is determined whether or not double feeding has been detected. If it is determined in step S16 that double feed is not detected, the process returns to step S8. If it is determined in step S16 that double feed is detected, the process proceeds to step S17 to instruct rotation stop of the feed roll 220. In step S18, it is determined whether or not a timing synchronization signal is transmitted from the image control unit 110. If it is not transmitted, the process waits in step S18 until it is transmitted, and if it is determined that it has been transmitted, the process proceeds to step S19. Since the timing synchronization signal has been transmitted, in step S19, the registration roll 240 is instructed to start rotation at a predetermined speed. In step S20, the start of the registration timer 212 is instructed. In step S21, it is determined whether or not the value of the feed timer 211 is equal to or greater than the standard time A. If it is determined that the value is less than the standard time A, the process proceeds to step S22 to determine whether or not there is a double feed, and a double feed is detected. If not, the process proceeds to step S21. If it is determined in step S22 that double feed has been detected, the process proceeds to step S23 to instruct to stop the rotation of the feed roll 220. In step S24, it is determined whether or not the value of the registration timer 212 is equal to or greater than the standard time B. If it is determined in step S24 that the value is not equal to or greater than the standard time B, the registration roll rotation waits in step S24. If it is determined in step S24 that the time is equal to or greater than the standard time B, the process proceeds to step S25 to instruct resetting of the feed timer 211 and the registration timer 212, and then returns to step S4.

  Next, another embodiment of the sheet feeding apparatus of the present invention will be described. In the following description, the description which overlaps with 1st Embodiment is abbreviate | omitted, and only a different point from 1st Embodiment is demonstrated.

  FIG. 5 is a view showing a second embodiment of the sheet feeding apparatus of the present invention.

  The difference between the sheet feeding unit 201 of the present embodiment shown in FIG. 5 and the first embodiment shown in FIG. 1 is that, in the first embodiment, the detection of double feeding is a nip portion 225 by double feeding. In the present embodiment, the change in the position of the retard roll 230 that occurs when the sheet passes through the sheet tray 270 is detected. Is measured by the sensor 260 until the passage of the trailing edge of the lower sheet is detected by the sensor 260, and the measured time is determined in advance based on the sheet size. Whether or not double feeding has occurred is determined based on whether or not it is shorter than the time.

  FIG. 6 is a view showing a third embodiment of the sheet feeding apparatus of the present invention.

  The difference between the sheet feeding unit 202 of the present embodiment shown in FIG. 6 and the first embodiment shown in FIG. 1 is that in the first embodiment, the detection of double feeding is performed by lap 225 by double feeding. In contrast, the present embodiment detects a change in the position of the retard roll 230 that passes through the sheet, and in the present embodiment, the ultrasonic sensor 260 disposed in the vicinity of the feed roll 220 reflects the emitted ultrasonic wave on the sheet. The lap is detected by the difference in the return time.

  FIG. 7 is a diagram showing another aspect of the first embodiment of the sheet feeding apparatus of the present invention.

  FIG. 7 does not directly detect a change in the position of the retard roll 230 that is caused when a lap caused by double feeding passes through the nip portion 225, but an arm 261 whose tip position changes as the position of the retard roll 230 changes. It is shown that the occurrence of double feed is indirectly detected by the sensor 260 disposed away from the retard roll by engaging the shaft with the shaft 262.

1 is a schematic configuration diagram of a printer provided with a first embodiment of a sheet feeding apparatus of the present invention. It is an external appearance perspective view of the sheet tray shown in FIG. It is a figure which shows a conveyance control part. 6 is a flowchart of a routine that is activated in a conveyance control unit when the printer is powered on. It is a figure which shows 2nd Embodiment of the sheet feeding apparatus of this invention. It is a figure which shows 3rd Embodiment of the sheet feeding apparatus of this invention. It is a figure which shows another aspect of 1st Embodiment of the sheet feeding apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 100 Image forming part 200 Sheet feeding part 210 Conveyance control part 211 Feed timer 212 Registration timer 213 Memory 220 Feed roll 230 Retard roll 240 Registration roll 250 Registration sensor 260 Position displacement sensor 280 Size sensor

Claims (5)

In a sheet feeding apparatus that recognizes the size of each of a plurality of sheets stored in a sheet storing unit that stores sheets , and feeds the images one by one to an image forming unit that forms an image on the surface of the sheet. ,
The pair of rolls provided on the image forming unit side are formed of a pair of rolls whose peripheral surfaces are in contact with each other, and the sheet is sandwiched between the pair of rolls while adjusting the timing of feeding the sheet to the image forming unit. A registration roll that feeds the sheet into the image forming unit by rotating,
A rotation speed that is provided on the sheet storage means side and includes a pair of rolls whose peripheral surfaces are in contact with each other, and the pair of rolls is set in advance by sandwiching the sheet in a nip region formed between the pair of rolls. A feed roll that gives the sheet a conveying force toward the registration roll by rotating at
A conveyance path in which a member that applies the conveyance force to the sheet is shorter than a length in the conveyance direction of the sheet to be fed and connected to the registration roll,
A detection sensor for detecting that the leading edge of the sheet being fed has reached the registration roll;
A timer for measuring an elapsed time from the detection for each detection of the arrival of the leading edge of the sheet by the detection sensor;
Based on the size information of the sheet being fed and the rotation speed information of the feed roll, the time from when the leading edge of the sheet reaches the registration roll until the trailing edge of the sheet passes through the nip portion of the feed roll is calculated. A time acquisition unit to acquire;
An overlap detection unit that is disposed in the conveyance path and detects that sheets to be fed overlap each other;
When the overlap detecting unit does not detect that the overlapping sheets to each other, the stops the rotation of the feed roll when the time acquired has passed by the time obtaining means, the time obtained by the time obtaining means A control unit that stops rotation of the feed roll when the overlap detection unit detects that the sheets overlap each other before passing . A sheet feeding apparatus characterized by that. The sheet feeding apparatus according to claim 1, wherein the overlap detection unit is a sensor disposed in the vicinity of the feed roll. 2. The sheet feeding apparatus according to claim 1, wherein the overlap detection unit detects, using sound waves, that sheets to be fed overlap each other. The overlap detection unit detects that the sheets to be fed overlap each other based on the magnitude of the force received by the feed roll sandwiching the sheet in the nip region. The sheet feeding apparatus according to claim 1. The overlap detection unit includes a sensor that detects that the trailing edge of the sheet has passed, and the trailing edge of the sheet that is next fed from the sensor when the sensor detects that the trailing edge of the sheet has passed. 2. The sheet feeding according to claim 1, wherein a time until the point of time when it is detected that the sheet has passed is calculated, and based on the calculated time, it is detected that the sheets to be fed overlap each other. Feeding device.

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