JPH0780634B2 - Double-sided image forming device - Google Patents

Description

The present invention relates to a double-sided image forming apparatus such as a double-sided printing apparatus,
More specifically, the present invention relates to a sheet conveying mechanism that holds and conveys a sheet on the intermediate tray by an auxiliary roller and a sheet guide that can move in a substantially vertical direction in the sheet conveying direction.

(B) Conventional Technology Conventionally, as shown in FIG. 5, a sheet conveying mechanism in a double-sided image forming apparatus conveys a sheet 2 to an intermediate tray 1 and a sheet 2 from the intermediate tray 1 again in the image forming apparatus. The sheet re-feeding roller 5 and the separation roller 5'which are means for feeding to the sheet, and the auxiliary roller 6 which is movable up and down with respect to the conveying direction of the sheet 2 and assists the sheet re-feeding means 5, 5 '. A sheet retainer 9 rotatably supported around the central shaft 7 and a sheet guide 10 for guiding the sheet 2 on the intermediate tray 1 are provided. Then, in order to re-feed the sheet 2 temporarily stored in the intermediate tray 1,
First, the sheet retainer 9 is rotated downward as shown by the arrow to contact the sheet 2 as indicated by the solid line (state of reference numeral 9 '), and then the sheet re-feed roller 5, which is the sheet re-feed means, is separated. The roller 5'is operated, and the auxiliary roller 6 is rotated in synchronization therewith, and at the same time, the auxiliary roller 6 is moved upward with respect to the sheet conveying direction, and the sheet 2 is conveyed while being pinched by the sheet retainer 9'and the auxiliary roller 6. It was sent to the sheet re-feeding means, which is the transport system of.

(C) Problems to be Solved by the Invention However, in the above-mentioned conventional apparatus, in order to guide the sheet from the intermediate tray to the re-feeding means, the sheet is held and conveyed by the sheet retainer and the auxiliary roller. However, there is a problem in that the structure, driving method, sequence, etc. of each of the sheet retainer and the auxiliary roller are complicated and a failure is likely to occur.

(D) Means for Solving the Problem The present invention is intended to solve the above-mentioned problems, and is arranged so that the seat is inclined so that it is guided downward by its own weight. An intermediate tray for storing, a sheet re-feeding unit arranged at a lower end portion of the inclination of the intermediate tray for re-feeding a sheet from the intermediate tray, and a sheet guided in a curved reversing passage are provided for inclining the intermediate tray. The transport means for transporting the sheet in the direction opposite to the moving direction of the sheet onto the intermediate tray, the sheet guide disposed above the intermediate tray, and the stacking surface of the intermediate tray so as to be retractable and retractable vertically. And an auxiliary roller that conveys the sheet in the same direction as the sheet conveying direction by the sheet re-feeding means, in the conveying direction of the conveying means and the sheet re-feeding means. Assuming that the distance is A and the distance between the auxiliary roller and the sheet re-feeding unit in the transport direction is B, the distance relationship is A> B, and the sheet guide is the sheet re-feeding unit and the transporting unit. Is fixed and arranged between the conveying means and the conveying means, the upper side of the inclination of the intermediate tray of the conveying means is opened, and the auxiliary roller conveys a sheet to the intermediate tray by the conveying means. When the sheet is not protruded upward from the stacking surface of the intermediate tray and the sheet is re-fed by the sheet re-feeding unit, the sheet stacked on the tray is sandwiched between the sheet guide and conveyed. The double-sided image forming apparatus is characterized in that

(E) Operation Based on the above configuration, the sheets sent into the intermediate tray by the conveying means are stacked on the intermediate tray and temporarily stored. At this time, the auxiliary roller is located at a position where it does not project upward from the stacking surface of the intermediate tray, and does not prevent the sheet from moving along the inclination of the intermediate tray and being stacked on the intermediate tray. When the stacking of sheets is completed, the sheet re-feeding means and the auxiliary roller start rotating in the clockwise direction, and at the same time, the auxiliary roller also starts moving upward in the sheet conveying direction. Here, if the distance between the conveying means and the sheet refeeding means is A, and the distance between the auxiliary roller and the sheet refeeding means is B, there is a distance relationship of A> B, The auxiliary roller moves upward while lifting the sheet, and the auxiliary roller and the sheet guide press the sheet while sandwiching the sheet. Since the auxiliary roller is rotating in the clockwise direction, the lowermost sheet of the stacked sheets receives the conveying force from the auxiliary roller to the front and surely conveys it to the sheet re-feeding means which is the next conveying system. To be done.

(F) Example Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIG. 2, the double-sided printing device includes an image processing unit 12,
The image forming unit 11 includes an image forming unit 11 that prints an image signal sent from the image processing unit 12, a duplex unit 17, and a vertical conveying unit 19 that sorts sheets sent from the image forming unit 11. Image forming unit
The sheet feeding upper and lower cassettes 13 and 15 are arranged at 11, and the large-capacity sheet feeding deck (hereinafter referred to as a deck) 16 is arranged at the duplex unit 17, and the sheet feeding upper and lower cassettes 13 and 15 and Seats 13 ', 1 loaded on deck 16
One of 5'and 16 'is selected by a control signal from the image processing unit 12, and the pickup roller 2 corresponding thereto is selected.
The sheets 0, 21, 22 are rotated so that the sheet is fed into the image forming unit 11. The fed sheet reaches the registration roller 23, and is temporarily stopped there to correct the skew, and then conveyed again by the timing signal, and at the same time, the image signal transmitted from the image processing unit 12 is laser and laser. A latent image is formed on the photosensitive drum 25 by the scanning optical system and is visualized by a developing device (not shown) to be a toner image, which is transferred to a sheet. A fixing roller 27 is provided downstream of the photosensitive drum 25 via a first belt transport unit 26, and downstream of the fixing roller 27 via a transport roller 29.
30 are provided. The deflector 30 sorts the sheet to the discharge tray 51 or the double-sided unit 17 via the vertical transport unit 19. For example, when the deflector 30 moves upward, the sheet is conveyed to the duplex unit 17. The conveying roller 31 and the first sensor are provided downstream of the deflector 30 on the side of the duplex unit 17.
32 is provided, and when the first sensor 32 detects the leading edge of the sheet, the sheet is sent to the intermediate tray 33 at a timing based on the detected edge. The sheet is transported by the second transport unit 34 until it is sent to the intermediate tray 33,
The sensor 35 detects the leading edge of the sheet. Then, the sheet delay according to the timing based on the sensor 35,
Confirmation of retention is performed. The sheet that has passed through the second sensor 35 is sent to the intermediate tray 33 by the conveying means (conveying roller) 36. By the way, the intermediate tray 33 is for temporarily storing the sheet printed on the first surface (front surface), and the regulation guides 37 for regulating the width direction of the sheet are formed on both side surfaces in a vertical shape. As will be described later in detail, an auxiliary roller 39 is disposed downstream of the intermediate tray 33, and further downstream is provided with a sheet re-feeding unit including a sheet re-feeding roller 40 and a separation roller 40 '. . The auxiliary roller
39 is attached to an arm 41 supported rotatably around the axis of the sheet re-feed roller 40
It can rotate in synchronization with. On the other hand, on the intermediate tray 33, a sheet guide 42 is attached between the transport roller 36 and the separation roller 40 '. And
When the auxiliary roller 39 starts to rotate in the clockwise direction, an electromagnetic solenoid to be described later is driven, and accordingly, the arm 41 rotates clockwise about the axis of the sheet refeed roller 40. The sheet is moved up substantially at right angles to the conveying direction to come into contact with the sheet on the intermediate tray 33 and pushed up until the sheet comes into contact with the sheet guide 42. That is, since the auxiliary roller 39 rotates clockwise while holding the sheet in cooperation with the sheet guide 42, the sheet re-feeding roller 40 and the separation roller 4 are obtained by obtaining the conveying force forward of the lower sheet.
It is designed to be transported between 0 '. The sheet re-feed roller 40 rotates in the same direction as the sheet conveying direction, that is, in the clockwise direction, while the separation roller 40 'rotates counterclockwise, so that between the sheet re-feed roller 40 and the separation roller 40'. The sheets in the intermediate tray 33 are separated one by one and re-fed. A third sensor 44 is arranged downstream of the sheet re-feeding means via the conveying roller 43. When the third sensor 44 detects the leading edge of the sheet, the sheet is conveyed by the conveying roller 45, 4th sensor 4 through 46
Reach 7 The sheet that has passed the fourth sensor 47 passes through the conveyance roller 48 and the fifth sensor 50 and reaches the registration roller 23 in the same manner as the sheet 16 ′ in the deck 16. After passing through the registration roller 23, the toner image is transferred to the second surface (back surface) of the sheet in the same manner as at the beginning. Then, the sheet passing through the fixing roller 27 is sorted by the deflector 30 to the vertical transport unit 19 and is transported upward. Deflector 30
Conveying rollers 52 and 53 for discharging the sheet to the face-up discharging tray 51 are arranged downstream of the vertical conveying unit 19 side.

Next, the sheet conveying mechanism will be described in detail. As shown in FIGS. 1, 3, and 4, the sheet transport mechanism includes a transport roller 36 and a sheet refeed roller 4 which is a sheet refeed unit.
When the distance between the separation roller 40 'and the separation roller 40' is 0, and the distance between the auxiliary roller 39 and the sheet re-feeding means is B, the distance relations are A> B. On the other hand, the sheet guide 42 is fixedly arranged between the conveying roller 36, the sheet re-feeding roller 40 which is the sheet re-feeding means, and the separation roller 40 ', and is attached to the intermediate tray 33 with a distance C. . It should be noted that the upper part of the inclined upper part of the conveying roller 36 in the intermediate tray 33 is an open space for feeding the sheet from the roller 36 to the intermediate tray 33. Further, the distance D indicates an arbitrary stacking height equal to or less than the maximum number of sheets that can be stored in the intermediate tray 33. Since the relationship with the distances C and D is C> D, the sheet sent to the intermediate tray 33 from the transport roller 36 passes through the gap (CD), is guided by the sheet guide 42, and is re-sheeted. It reaches to just before the feeding sheet 40. Next, the auxiliary roller 39 will be described (see FIG. 3).
Drive pulley fixed coaxially with sheet refeed roller 40
A drive-side timing belt 57 is stretched between 54 and an idler pulley 56 rotatably supported by a pin 55 crimped on the arm 41, and a pulley 58 fixed to the shaft of the auxiliary roller 39. A timing belt 59 is stretched between the idler pulley 56 and the idler pulley 56. Therefore, the rotational force of the sheet re-feed roller 40 that rotates in the clockwise direction is
4, the driving side timing belt 57, the idler pulley 56, and the timing belt 59 are transmitted to the auxiliary roller 39. On the other hand, the electromagnetic solenoid 60 has a solenoid iron core 61 that moves forward and backward in the electromagnetic solenoid 60.
The tip of 61 is connected to one end of arm 41 via caulking pin 62. In addition, the angle attached to the intermediate tray 33
The reference numeral 33 'contacts the protrusion e provided on the side surface of the arm 41 on the auxiliary roller 39 side, and holds the auxiliary roller 39 on the same surface as the sheet stacking portion of the intermediate tray 33. Also,
As described above, the arm 41 is rotatably pivoted on the shaft of the sheet re-feed roller 40, and the other end supports the shaft of the auxiliary roller 39. When the electromagnetic solenoid 60 is energized, the solenoid iron core 61 is retracted, and the arm 41 is rotated clockwise around the axis of the sheet re-feed roller 40 accordingly, so that the auxiliary roller 39 moves upward while rotating. To do. The relationship of the distances A and B between the auxiliary roller 39, the conveyance roller 36, the sheet re-feed roller 40, and the separation roller 40 'is A> B. No sheet guide 42 and auxiliary roller 39
As shown in FIG. 4, while the sheet is sandwiched, the sheet is pressed and a conveying force is applied to the lowermost sheet.

Since the present embodiment is configured as described above, the image processing unit
When any one of the sheets 13 ', 15' and 16 ', for example the sheet 13', is selected by the control signal from the sheet 12, the pickup roller 20 rotates and the sheet 13 'is fed into the image processing section. . The fed sheet 13 ′ reaches the registration roller 23, and is temporarily stopped there to correct the skew, and then conveyed again by the timing signal, and at the same time, the image signal transmitted from the image processing unit 12 is laser and A latent image is formed on the photosensitive drum 25 by the laser scanning optical system and visualized by a developing device (not shown) to form a toner image, which is transferred to the sheet 13 '. The transferred sheet 13 'is the first belt transport unit.
It is fixed by the fixing roller 27 via 26 and sent to the deflector 30 by the conveying roller 29. Here, the deflector 30 moves upward and sorts the sheet 13 ′ to the duplex unit 17 side, and the sheet 13 ′ reaches the first sensor 32 via the transport roller 31. When the leading edge of the sheet 13 'is detected by the first sensor 32, the sheet 13' is fed into the intermediate tray 33 at a timing based on the detected edge. The sheet is conveyed by the section 34, and the leading edge of the sheet is detected by the second sensor 35. Then, according to the timing based on the second sensor 35, the sheet is confirmed to be delayed or accumulated. After that, the sheet 13 ′ that has passed the second sensor 35 is fed into the intermediate tray 33 by the transport roller 36. In this state, since the sheet re-feeding means has stopped driving, the auxiliary roller 39 is also not driven, and the electromagnetic solenoid 60 is not energized. Therefore, the protrusion e of the arm 41 forms the angle 33 'of the intermediate tray 33. Therefore, the auxiliary roller 39 is held on the same surface as the sheet stacking portion of the intermediate tray 33. A sheet guide 42 is disposed above the intermediate tray 33 between the transport roller 36 and the sheet refeed roller 40 and the separation roller 40 ', which are sheet refeed means, at a distance C from the intermediate tray 33. The sheets sent from the transport roller 36 to the intermediate tray 33 are stacked by a height distance D and temporarily stored. And
Since the relationship between the distances C and D is C> D,
The sheet guide 42 is provided on the intermediate tray 33 where the sheets are stacked.
The sheet always keeps a gap (C-D), and the sheet moves downward along the inclination of the intermediate tray 33 due to its own weight. At this time, the auxiliary roller 39 does not project above the stacking surface of the tray, and does not hinder the movement of the sheet. Next, when the stacking of the sheets is completed, the sheet re-feeding roller 40 starts driving in the clockwise direction, and at the same time, the electromagnetic solenoid 60 is energized. Then, the rotation of the sheet re-feed roller 40 is driven by the drive pulley 54 and the drive side timing belt 5.
7, idler pulley 56, timing belt 59, pulley 58
After being transmitted to the auxiliary roller 39, the auxiliary roller 39 also starts to rotate in the clockwise direction. On the other hand, in the electromagnetic solenoid 60 that has been energized, the solenoid iron core 61 is attracted and retracts, so that one end of the arm 41 is also attracted. Therefore,
Since the arm 41 rotates clockwise about the axis of the sheet re-feed roller 40, the auxiliary roller 39 pivotally supported on the other end of the arm 41 rotates and moves upward at a substantially right angle to the sheet conveying direction. Moving. Moreover, as described above, the transport roller
There is a relation A> B between the distance A between the sheet re-feeding means 36 and the sheet B and the distance B between the auxiliary roller 39 and the sheet re-feeding means. Since there is a distance (C-D) from the guide 42,
The auxiliary roller 39 moves upward while lifting the sheet, and as shown in FIG. 4, the auxiliary roller 39 and the sheet guide 42 press the sheet while sandwiching the sheet. Further, since the auxiliary roller 39 is rotating in the clockwise direction, the lowermost sheet among the stacked sheets obtains a conveying force in the forward direction from the auxiliary roller 39, and the sheet re-feeding means that is the next conveying system. Be transported to. Next, since the sheet re-feed roller 40 rotates in the clockwise direction and the separation roller 40 'rotates in the counter-clockwise direction, the sheets conveyed to the sheet re-feeding unit are completely separated one by one and re-fed. Be delivered. The re-fed sheet reaches the third sensor 44 via the conveyance roller 43. When the leading edge of the sheet is detected by the third sensor 44, the sheet reaches the fourth sensor 47 via the transport rollers 45 and 46 with reference to it. The sheet that has passed the fourth sensor 47 further reaches the registration roller 23 via the conveyance roller 48 and the fifth sensor 50. After passing through the registration rollers 23, the toner image is transferred to the second surface (back surface) of the sheet in the same manner as the first time. Then, the sheet that has passed the fixing roller 27 is sorted by the deflector 30 to the vertical transport unit 19 side, and is discharged to the face-up tray 51 via the transport rollers 52 and 53.

(G) Effect of the Invention As described above, according to the present invention, it is possible to apply a forward conveying force to a sheet on the intermediate tray in a state of being held by the sheet guide and the auxiliary roller, The sheet can be surely guided to the sheet re-feeding means without the conventional sheet pressing, and the sheet conveying structure and sequence can be simplified.

Further, while the sheet is carried into the intermediate tray by the conveying means, the auxiliary roller is in a position not protruding above the stacking surface of the intermediate tray, and the sheet from the conveying means moves along the inclination of the intermediate tray. On the other hand, the auxiliary rollers do not hinder the operation, and the sheets can be reliably and accurately stacked on the intermediate tray.

[Brief description of drawings]

FIG. 1 is a side view showing a sheet conveying portion according to the present invention, FIG. 2 is a vertical sectional view showing a double-sided image forming apparatus to which the present invention is applied, and FIG. 3 is a perspective view showing an embodiment of an auxiliary roller, Fourth
FIG. 5 is an explanatory view showing an operating state of a sheet conveying portion, and FIG. 5 is a side view showing a conventional sheet conveying portion. 33 ... Intermediate tray, 36 ... Conveying means (conveying rollers), 39
...... Auxiliary roller, 40 ...... Sheet refeed roller, 40 '...... Separation roller (40,40' are integrated as sheet refeed means), 41 ...... Arm, 42 ...... Sheet guide, A ... ... distance between the conveying means 36 and the refeeding means, B ... distance between the auxiliary roller and the sheet refeeding means, C ... distance between the intermediate tray 38 and the sheet guide 42, D ... loading on the intermediate tray 33 The distance to the top surface of the seat.

Claims (1)

[Claims] 1. An intermediate tray in which a sheet is inclined so as to be guided downward by its own weight and temporarily stores a sheet, and an inclined lower end portion of the intermediate tray, and the sheet is discharged from the intermediate tray. Sheet re-feeding means for re-feeding, sheet feeding means for guiding the sheet guided in the curved inversion path in the direction opposite to the sheet moving direction due to the inclination of the intermediate tray, and guiding the sheet onto the intermediate tray, A sheet guide disposed above the intermediate tray and a stacking surface of the intermediate tray are arranged so as to be retractable, move vertically, and move the sheet in the same direction as the sheet conveying direction by the sheet refeeding means. And an auxiliary roller for carrying, the distance between the carrying means and the sheet refeeding means in the carrying direction is A, and the auxiliary roller and the sheet refeeding means are provided with a distance in the carrying direction. Assuming that the distance is B, the distance relationship is A> B, the sheet guide is fixed and arranged between the sheet refeeding means and the conveying means, and the inclination of the intermediate tray of the conveying means is increased. The upper side is open, the auxiliary roller is in a position where it does not project upward from the stacking surface of the intermediate tray while the sheet is being carried into the intermediate tray by the conveying means, and The double-sided image forming apparatus is characterized in that, when the sheet is re-fed by the feeding means, the sheet stacked on the tray is sandwiched between the sheet guide and conveyed.