JP2001151376A - Sheet conveying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveying device having a simple structured driven roll capable of always providing a smooth and stable rotation independently of length of a roll width, in which the driven roll of a pair of conveying rolls mainly can be installed and mounted even when its installing space and a mounting-work space are difficult to be secured. SOLUTION: The driven roll 2 of the pair of conveying rolls 3 comprises a roll body 70 including a through hole 52 in the center, a hollow cylindrical shaft 75 that is engaged and penetrated through a through hole of the roll body 70 and rotatably supports the roll body, and an energizing elastic member 77 which is inserted through the hollow part of this cylindrical shaft 75, includes both ends 78 locked and fixed at respective positions projecting from both ends of the cylindrical shaft 75, and elastically energizes the roll body 70 via the cylindrical shaft 75 in the pressure contact direction with a driving roll 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus for conveying a sheet to a desired position by a conveying roll pair comprising a combination of a driving roll and a driven roll, and to a copying machine, a printer and the like using the conveying apparatus. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, a sheet-like material such as a recording sheet for forming an image made of toner is conveyed from a paper feeding unit to a paper discharging unit via an image forming unit. Various sheet conveying paths are provided inside the apparatus. As illustrated in FIG. 9, this type of sheet conveyance path is formed by combining a drive roll 110 that is rotationally driven by a rotational force of an electric motor or the like and a driven roll 120 that is pressed against the drive roll 110 and is driven to rotate. A plurality of transport roll pairs 130 and their respective transport roll pairs 130
The main part thereof is constituted by a conveyance guide member 140 and the like which are arranged with a gap up and down so as to sandwich the sheet conveyance path therebetween.

[0003] In the sheet conveying path constituted by such a sheet conveying apparatus, the sheet-like material 100 is
The pair of transport rolls 130 are sequentially transported while passing between the drive roll 110 and the driven roll 120, and are appropriately guided by the transport guide member 140 along the transport direction.

[0004]

By the way, the driven roll 12 of the pair of transport rolls 130 in this sheet transport apparatus is used.
In the case of No. 0, for example, when the installation space for disposing the driven roll 120 or the installation work space cannot be sufficiently secured, for example, a bearing type configuration as shown in FIG. 10 was used.

That is, a driven roll 120 of a bearing system shown in FIG. 10 is configured such that a rotating shaft 122 fixedly provided at a central portion of a roll main body 121 has a holding portion provided upright on a support frame 150 for the driven roll. After being inserted into the shaft mounting hole 151, it is inserted into the shaft mounting hole from the outside of the holding portion 151 and is rotatably supported by a bearing member 123 fitted into the outer periphery of the rotating shaft 122 at the same time. And finally, the driven roll 120 is driven by the coil spring 124 which extends over the outer periphery of the bearing member 123 and locks and fixes both ends to the support frame 150.
30 is configured to be urged so as to be elastically pressed against 30.

However, the driven roll 120 of this bearing type is used.
Requires a large number of man-hours for the mounting operation, and furthermore, in the mounting operation, it is necessary to insert the bearing member 123 into the shaft mounting hole and the rotating shaft 122 at the same time, or to suspend and lock the coil spring 124 so as not to rely on human hands. Since there is a complicated and delicate work that cannot be obtained, it is necessary to secure a certain mounting work space. For this reason, there is a drawback that the use of the driven roll 120 is not suitable especially when the arrangement space of the driven roll 120 is narrow or there is a structure around the arrangement space that hinders the mounting operation.

Conventionally, there has been proposed a paper transport apparatus using a coil spring shaft type driven roll for the purpose of keeping the pressure contact force when pressing the driven roll against the drive roll constant and simplifying the pressing structure. (JP-A-11-124246). As shown in FIG. 11, the driven roll 120 in the paper transport device according to this proposal has a through-hole (bearing hole) 125 at the center of the roll main body 121, and the through-hole 125 has only a coil-shaped spring. (Coil spring shaft) 126
And the both ends of the spring shaft 126 are locked to the locking portions 158 of the transport guide 155. Thus, the driven roll 120 is rotatably supported through a shaft 126 formed of only a coil spring, and is elastically pressed against the drive roll 130 by the coil spring shaft 126. It is a structure that is energized.

[0008] However, the driven roll 120 of the coil spring shaft type has the following problems.

First, the bearing hole 12 of the roll body 121 is
5 rotates in a state of being directly supported around the outer periphery of the spring shaft 126 which is wound by a coil, and thus may not rotate smoothly. Further, since the spring is used as a shaft as it is, when the roll width W is large, the number of coil turns of the spring must be increased, and when the roll width W is small, the spring draws an arc. In such a form, it does not function as a shaft. In particular, when the roll width W is narrow, a measure to greatly increase the width (length) of the spring as compared with the roll width in order to secure the function as an axis can be considered. A large mounting space for mounting is required.

On the other hand, in image forming apparatuses such as copying machines in recent years, the number of components in the apparatus has increased due to the increase in functions due to diversification of functions and reduction in the size of the entire apparatus. With an increase in the number of parts and an increase in the size of the apparatus, the installation space for each component is becoming narrower or more difficult to secure. Such a situation is the same in the above-described sheet conveying apparatus. Under the influence, for example, as described above, the installation space of the transport roll pair has become narrower and the mounting work space has been reduced, and the installation space of the driven roll of the transport roll pair has also become noticeable. In some cases, it is necessary to take measures and improvements to be able to adapt to the narrowing of the size and the reduction of the mounting work space.

[0011] Therefore, an object of the present invention is to enable the installation and installation of the driven roll of the pair of transport rolls as described above even when it is difficult to secure the installation space and the installation work space. It is another object of the present invention to provide a sheet conveying apparatus having a driven roll having a simple structure capable of always obtaining a smooth and stable rotation regardless of the size of the roll width.

Another object of the present invention is to secure an installation space and a mounting work space for a sheet conveying device (particularly, a driven roll in a conveying roll pair) constituting a sheet conveying path for conveying a sheet-shaped recording medium. An object of the present invention is to provide an image forming apparatus which can be installed and attached even in such a case, and can smoothly and stably convey the recording medium.

[0013]

According to the present invention, there is provided a sheet conveying apparatus comprising: a driving roll which is driven by rotation; and a driven roll which is pressed against the driving roll and driven to rotate. In a sheet transport device that transports a sheet-like material in a state of passing between a drive roll and a driven roll of the transport roll pair,
A driven roll of the transport roll pair, a roll main body having a through-hole formed in the center thereof, and a hollow cylindrical shaft which is fitted so as to penetrate through the through-hole of the roll main body and rotatably supports the roll main body. And, both ends are locked and fixed at positions protruding from both ends of the cylindrical shaft while being inserted so as to penetrate into the hollow portion of the cylindrical shaft, and the roll main body is fixed through the cylindrical shaft. And a biasing elastic member that resiliently biases in a direction to be brought into pressure contact with the drive roll.

According to the sheet conveying apparatus, the driven roll of the pair of conveying rolls has the above-described configuration, and the roll main body rotates around the hollow cylindrical shaft urged by the urging elastic member. Rotate. Accordingly, the driven roll always rotates while being rotatably supported by the cylindrical shaft regardless of the size of the roll width, thereby enabling smooth rotation. Incidentally, the cylindrical shaft is usually of a cylindrical shape, but the form is not particularly limited as long as the roll body can be stably rotatably supported. However, it is necessary that the cylindrical shaft has at least rigidity that is not easily deformed.

In addition, the driven roll is formed by inserting a cylindrical shaft into the through hole of the roll body and inserting the biasing elastic member into the cylindrical shaft. The assembly and installation are completed only by locking and fixing the. Thereby, even when it is difficult to secure the installation space and the installation space for the driven roll and the like, the installation and the installation can be performed, and it is possible to sufficiently cope with the problem.

Further, in the above-described sheet conveying apparatus of the present invention, a spring having at least both ends formed in a coil shape may be used as the biasing elastic member of the driven roll. In this case, if the urging force of the urging elastic member can be reliably applied to the cylindrical shaft, the other parts of the urging elastic member other than the coil-shaped part may have a shape other than the coil shape. Of any shape.

With this configuration, the biasing force of the biasing elastic member is exerted at least by the coil-shaped portion. Further, for example, when the roll width is widened, the number of windings of the coil can be reduced as compared with a case where the entire elastic member for biasing is a coil-shaped spring.

In the case of an elastic member for biasing a spring having coil ends at both ends, a portion of the elastic member to be inserted into the hollow portion of the cylindrical shaft is moved in the longitudinal direction of the cylindrical shaft. The shape may be such that it can match and contact the lower inner wall surface along. For example, the simplest shape of the portion may be a linear shape.

With this configuration, the urging force (urging force exerted mainly in the coil-shaped portion) by the urging elastic member is reliably and stably applied to the cylindrical shaft. As a result, the pressed state of the driven roll against the drive roll becomes stable. Further, the biasing elastic member itself can have a simple structure, and in particular, the coil portion can be pressed to the minimum necessary.

Further, in the sheet conveying apparatus according to the present invention, holding members which are opposed to each other in the vicinity of both sides of the roll main body of the driven roll at intervals with the cylindrical shaft fitted therein are provided, and the cylindrical shaft is provided with the holding members. It is preferable to provide a slit groove into which a part of the holding member is inserted when the cylindrical shaft is fitted between the holding members to position the cylindrical shaft.

In the case of such a configuration, the positioning of the cylindrical shaft is performed between the slit groove and the holding member. This prevents the cylindrical shaft from inadvertently moving during rotation of the driven roll, and ensures stable rotation without making the rotation of the driven roll unstable.

On the other hand, the image forming apparatus of the present invention, which can achieve the above object, is an apparatus for forming an image made of toner on a sheet-like recording medium, and has a sheet conveying path for conveying the recording medium. In the image forming apparatus provided, each of the above-described sheet conveying devices is used as a sheet conveying device constituting the sheet conveying path.

[0023]

[First Embodiment] FIG. 1 shows an intermediate transfer type color printer to which the present invention is applied. This color printer basically has four image forming units (image forming units) for forming toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively, by an electrophotographic method. Equipment) 10Y, 10
M, 10C, and 10K, an intermediate transfer belt (intermediate transfer body) 20 to which the toner images formed by the four image forming units 10 are transferred, and recording on which the toner image on the intermediate transfer belt 20 is transferred A fixing device 40 to which a sheet (recording medium) P is fed and the toner image is fixed;
It is provided with various paper (sheet) transport paths for transporting the recording paper P in the image forming apparatus. In addition, this color print is capable of single-sided and double-sided printing of a single-color image in addition to single-sided and double-sided printing of a full-color image.

The paper transport path mainly has a basic transport path and a duplex transport path. Among these, the basic transport path includes a paper feed transport path 51 that transports the recording paper P sent out from the paper storage tray 50 in which the recording paper P is stored by the feed roll 50a to the secondary transfer portion of the intermediate transfer belt 20,
The recording paper P after transfer from the secondary transfer section is fixed to the fixing device 40.
The transfer path 52 is configured to include a transfer path 52 that transfers the recording sheet P to the outside of the apparatus. On the other hand, the two-sided conveyance path is a delivery conveyance path 5 for sending the recording paper P on which single-sided image formation (single-sided printing) is completed to the two-sided conveyance side after fixing.
5, a reversing path 56 for once pulling out the fed recording paper P and then pulling it out in the opposite direction to reverse the front and back surfaces of the recording paper P; And a retransmission path 57 for retransmission.

In each of these transport paths, a paper feed transport path 51, a discharge transport path 53, and a two-sided transport transport path 5 are provided.
5. Regarding the reversing conveyance path 56 and the retransmission conveyance path 57, a plurality of conveyance roll pairs (combination of a driving roll and a driven roll) and upper and lower or It is composed of a plurality of transport guide members that are disposed to face each other at an interval on the left and right. The transfer conveyance path 52 is composed of two suction-type conveyance belt devices 52a and 52b that convey the recording paper P after the secondary transfer by suction and adsorption on the surface of the conveyance belt. In the drawing, reference numeral 51a denotes a pair of registration rolls arranged in the paper feed conveyance path 51 for feeding the recording paper P to the secondary transfer portion at a predetermined timing, and reference numeral 54 denotes a discharge conveyance path 53 and a delivery conveyance path. A transfer path switching gate (claw) for switching the transfer path of the recording paper P, which is disposed at the branch position 55.

The one-sided printing of a full-color image by the color printer is performed as follows.

First, the four image forming units 10Y, 10M, 10M
The four color toner images are respectively formed by C and 10K. That is, in each of the image forming units 10, the surface of each rotating photosensitive drum 12 is uniformly charged by the scorotron 13 as a charging device, and the charged surface of each photosensitive drum 12 is used as an image writing device. ROS
(Raster Output Scanner) 14 exposes and scans a laser beam based on the image information to form an electrostatic latent image, and each electrostatic latent image is developed by each developing unit 15 to a developer (toner) of a predetermined color. Is developed. This allows
Four color toner images are individually formed on each photosensitive drum 12.

Next, the four color toner images are transferred to a plurality of rolls 2 so as to pass through a primary transfer portion of each photosensitive drum 12.
Intermediate transfer belt 2 that rotates while being wrapped around 1 to 24
After the primary transfer so that they are sequentially superimposed on 0,
It is transported to the secondary transfer section. At this time, the primary transfer is performed by applying a primary transfer bias voltage having a polarity opposite to the charging polarity of the toner to a primary transfer roll 27 rotating so as to bring the belt 20 into contact with the drum 12 side. The transfer is performed electrostatically by the applied transfer electric field. After the primary transfer, the surface of the photosensitive drum 12 is cleaned by the drum cleaning device 16.

The toner image primarily transferred on the intermediate transfer belt 20 in this manner is secondarily transferred to the recording paper P at the secondary transfer portion. In the secondary transfer at this time, the recording paper P is transported from the paper feed transport path 51 to the secondary transfer roll 30 pressed against the backup roll 24 supporting the intermediate transfer belt 20, and the backup roll 24 A secondary transfer via voltage having the same polarity as the charge polarity of the toner transferred onto the intermediate transfer belt 20 is applied to the side via the power supply roll 31, and electrostatically performed by a transfer electric field formed by the bias voltage. . After the secondary transfer, the surface of the intermediate transfer belt 20 is cleaned by the belt cleaning device 26.

Next, the recording paper P after the secondary transfer is
After being separated from the intermediate transfer belt 20, it is fed to a fixing device 40 disposed downstream of the secondary transfer unit, and is heated and pressurized by passing between a heating roll 41 and a nip belt 42. The toner image is fixed. In the case of the single-sided print mode, the recording paper P after the fixing is sent out from the fixing device 40 and then discharged out of the device via a discharge paper conveyance path. As described above, a full-color image (for the front surface) is formed on (the front surface of) the recording paper P, and the one-sided printing is completed.

The two-sided printing of a full-color image by the printer is performed as follows.

First, the recording paper P on which single-sided printing has been completed
After the fixing, the sheet is sent to the side of the two-sided conveying path 55 by the switching operation of the conveying path switching gate 54, and the reversing conveying path 57 is turned over.
And is re-sent to the paper supply conveyance path 58 via. Next, the re-transmitted recording paper P is sent to the secondary transfer unit at the secondary transfer timing, and after the back surface toner image formed by the image forming unit 10 is transferred from the intermediate transfer belt 20, As in the case of the single-sided printing, the fixing device 4
0 and finally discharged through the discharge conveying path 53. As a result, a full-color image for the back surface is formed on the back surface of the recording paper P, and the duplex printing is completed.

The branch portion of the discharge conveyance path 53 and the double-sided conveyance path 55 in this printer is configured as follows.

That is, as shown in FIG. 2, the upper and lower transport guide members (paper chute) 60, which constitute the discharge transport path 53, form a branch between the discharge transport path 53 and the delivery transport path 55. The upper and lower transport guide members 62, 63 constituting the delivery transport path 55 are disposed in a lower right direction from the discharge transport path 53. It is arranged so as to form a conveying path space curved toward the vehicle.
The transfer path switching gate 54, which pivots up and down around a support shaft 54a, is provided at a branch portion between the discharge transfer path 53 and the delivery transfer path 55.

Reference numeral 53a in the figure denotes a pair of transport rolls disposed on the discharge transport path 53.
According to a, the recording paper P after fixing is discharged from the fixing device 40 and transported. Reference numeral 58 denotes a reverse discharge transport path for discharging the recording paper P on which one-side printing has been performed with its print surface facing downward (face down). The transport guide members 64 and 65 are arranged in such a manner that a transport path space is formed so that the transport guide members 64 and 65 merge with the unload transport path 53 after branching from the discharge transport path 53.

In this embodiment, in particular, as shown in FIG. 2, in a delivery transport path 55A corresponding to a portion sandwiched between the discharge transport path 53 and the reverse discharge transport path 58 (a kind of triangular zone). In addition, a sheet transport device 4 using a transport roll pair 3 in which a drive roll 1 and a driven roll 2 are combined is disposed.

As shown in FIGS. 2 and 3, the sheet conveying device 4 uses a plurality of conveying roll pairs 3 and
They are arranged at predetermined intervals in the width direction of the transport path. The transport roll pair 3 has the drive roll 1 disposed on the lower transport guide member 63 side of the transport path 55 for delivery,
The driven roll 2 is arranged on the upper transport guide member 62 side of the transport path 55 for delivery. In this embodiment, a part 61a of the lower transport guide member of the discharge transport path 53 and an upper transport guide member 64 of the reverse transport path 58 are integrated with the upper transport guide member 62 to which the driven roll 2 is attached. The structure has been made.

Further, as shown in FIGS. 4 to 7, each of the driven rolls 2 in the transport roll pair 3 has a main part including a roll body 70, a hollow cylindrical shaft 75, and a biasing spring 77. Is configured.

The roll body 70 has a through hole 7 at the center.
The roll base 72 is made up of a cylindrical roll support part 72 made of a synthetic resin or the like on which the base material 1 is formed, and a roll part 73 made of a rubber material or the like mounted on the outer periphery of the roll base 72. The diameter of the through hole 71 is slightly larger than the outer diameter of the cylindrical shaft 75. In addition, this roll body 70
If it can slide and rotate with respect to the cylindrical shaft 75, the roll portion 7
3 and a through hole 71 may be provided at the center thereof.

The hollow cylindrical shaft 74 is connected to the roll body 70.
The roll main body 70 is rotatably supported by being fitted into the through hole 72 of the roll base 72 (in this example) so as to rotatably support the roll main body 70. The roll main body 70 is formed of a cylindrical pipe made of a metal material or the like. 70 has a length such that it protrudes by a predetermined amount from both ends. Further, a slit groove 76 for positioning and locking is formed in a predetermined portion of the cylindrical shaft 75 as shown in FIG. Further, when the cylindrical shaft 74 has a large thickness, both ends of the hollow portion are preferably tapered so that the coil portion of the biasing spring 77 may be caught at the end of the hollow portion. Can be prevented.

The urging spring 77 is inserted into the hollow portion of the cylindrical shaft 75 so as to penetrate therethrough, and presses the roll main body 70 against the driving roll 1 via the cylindrical shaft 75 (see FIG. 5). In order to resiliently urge the coil spring in the direction indicated by the arrow X), both ends 78 have a coil winding shape and a central portion 79 has a single linear shape. It is configured. In particular, the linear portion of the central portion 79 has a spring portion which is
And is brought into contact with the lower inner wall surface along the longitudinal direction. In addition, biasing springs 77 are provided at both ends 78 thereof.
And a ring-shaped locking portion 78a used when locking and fixing is formed.

The driven roll 2 is mounted on a mounting plate 80 on which an upright shaft holding portion 81 is formed, as shown in FIGS.

Mounting plate 80 in this embodiment
Consists of a pair of components disposed opposite to each other with a gap so that the shaft holding portion 81 is located near both sides of the roll body 70 for each driven roll 2. The structure is fixed to the portion 62a. The drive roll 1 in the transport roll pair 3
Are arranged so that the upper surface of the roll is positioned within the notch 62a of the transport guide member 62. The reference numeral 1a in each figure is a rotation shaft for rotating each drive roll 1. The shaft holding portion 81 of the mounting plate 80 is
Basically, it is composed of two plate-like members 81a and 81b opposed to each other with an interval S such that the cylindrical shaft 75 is fitted. However, the shaft holding portion 81c for locking, which is located on the side where the slit groove 76 side of the cylindrical shaft 75 is fitted, is formed so as to be slightly closer to the shaft holding portion 81b opposed thereto, and the gap S is slightly narrower. Has become. Further, a locking projection 82 for hooking and locking the ring-shaped locking portion 78a of the urging spring 77 is provided on a flat portion of the mounting plate 80, and this locking projection 82 is one of the flat portions. It is formed by bending the notched portion until it is in a state facing obliquely upward.

The assembly of the driven roll 2 is performed as follows. That is, as shown in FIG.
After the cylindrical shaft 75 is fitted into the through-hole 71 of the roll body 70 (roll base 72) so as to penetrate the same, the cylindrical shaft 7
5 was inserted into the hollow portion of the cylindrical shaft 75 so as to penetrate the urging spring 77, or was inserted into the hollow portion of the cylindrical shaft 75 so as to penetrate the urging spring 77, and then the spring 77 was inserted. This is performed by fitting the cylindrical shaft 75 so as to penetrate the through hole 71 of the roll body 70.

Further, as shown in FIG. 8, the driven roll 2 is mounted by mounting the driven roll 2 in an assembled state to the mounting plates 80a and 80b.

That is, the mounting plate 8 is mounted so that the roll body 70 is held between the shaft holding portions 81 facing each other.
0, and the cylindrical shafts 75 protruding from both ends of the roll body 70 are fitted into the gaps of the holding portion 81. At this time, the cylindrical shaft 75 is fitted so that the side of the retaining portion 81c is inserted into the slit groove 76 formed in the cylindrical shaft 75. Thereby, the cylindrical shaft 75 is maintained in the positioned state without moving in either the cylindrical circumferential direction or the axial direction. Next, a locking portion 78a formed on an end portion 78 of a biasing spring 77 protruding from both ends of the cylindrical shaft 75.
Is hooked on the locking projection 82 of the mounting plate 80.

As a result, the driven roll 2 is mounted on the mounting plate 80 as shown in FIGS. As described above, the driven roll 2 can be mounted very easily, and the work operation range during the mounting operation can be sufficiently accommodated in the space of the mounting plate 80, so that the mounting space can be sufficiently small. Accordingly, the portion where the driven roll 2 is attached in this embodiment has a narrow and complicated structure in which a plurality of transport guide members 62, 54a and 64 are integrated as shown in FIGS. The attachment to the attachment plate 80 can be performed without any trouble.

The driven roll 2 thus attached is cylindrically shaped by an urging spring 77 whose both ends 78 are locked and fixed to the locking projections 82 and slightly bent downward. The roll body 70 is connected to the drive roll 1 via the shaft 75.
Is elastically urged in the direction X in which the member is pressed. Further, since the roll body 70 is rotatably supported by the cylindrical shaft 75 in such a biased state, the driving roll 1 is driven to rotate by being driven to rotate.

In addition, since the driven roll 2 has a cylindrical shaft 75 made of a rigid metal pipe, it does not deform so as to draw an arc, so that it can reliably function as a shaft (the roll body 70). It rotates smoothly. This is the same and does not change even if the roll width W increases, because the roll body 70 is rotatably supported by the cylindrical shaft 75. Moreover, the cylindrical shaft 75 has its slit groove 76
Since the cylindrical shaft 75 is displaced and locked, the cylindrical shaft 75 is not displaced to make the rotation of the roll body 70 unstable, thereby also ensuring the smooth rotation of the driven roll 2.

Further, the driven roll 2 is elastically urged in the pressing direction X by an urging spring 77, and has a shaft S opposed to the shaft with a gap S parallel to the direction along the pressing direction X. Since the recording paper P is movably fitted into the holding portion 81, for example, even if the thick recording paper P enters between the driven roll 2 and the driving roll 1 during conveyance, the driven roll 2 is opposite to the pressing direction X. The recording paper P can be displaced in the direction to absorb the thickness of the recording paper P.

The sheet conveying device 4 provided with the pair of conveying rolls 3 having the driven rolls 2 having the above-described configuration is similar to that shown in FIG.
The transport path 53 for discharge and the transport path 55 for delivery as shown in FIG.
It is used by being attached to the branch part. That is, the sheet conveying device 4 conveys the recording paper P that is conveyed and sent to the sending conveying path 55 instead of the discharging conveying path 53 by the conveying path switching gate 54 as in the case of double-sided printing. I have. At this time, the recording paper P
Is smoothly transported by the transport roll pair 3.

Reference numeral 66 in FIG. 2 denotes a transfer guide film for a branch portion, one end of which is fixed to the upper transfer guide member 64 and the other end of which is not fixed and which is a free end. When the recording sheet P sent to the delivery transport path 55 by the transport roll pair 3 passes, its free end is elastically deformed so as to leave a transport space (two-dot chain line in the figure). When the recording sheet P sent to the reversing conveyance path 65 passes, the free end side is positioned so as to close the conveyance path of the sending conveyance path 55, and the sheet is not sent to the sending conveyance path 55 side. To prevent paper jams. Code 67
Is a conveyance guide film for a branch portion, and plays a similar role.

In the face-down discharge, the recording paper P after fixing is fed to the delivery conveyance path 55 side and stopped shortly before reaching the reversing conveyance path 56, and then the conveyance roll pair 55a without the delivery conveyance path is used. Is rotated in the reverse direction, so that the sheet is conveyed from the rear end side of the sheet conveyance to the discharge conveyance path 53 via the reversing conveyance path 58 and discharged.

[Other Embodiments] In the first embodiment, a case has been described in which, as the urging spring 77, a spring having an irregular shape in which only both end portions 78 have a coil shape is used. A coil spring of a general form having a coil shape may be used. Further, the biasing spring may be a plate-shaped spring. In the case of this plate-shaped spring, it is preferable to form a housing recess in the longitudinal direction in the hollow portion of the cylindrical shaft 75 so that the plate-shaped spring can be accommodated. Further, when a coil spring having an irregular shape as in the first embodiment is used as the biasing spring 77, the central portion thereof may have any other shape than the linear shape.

In the first embodiment, the case where the sheet conveying device 4 is arranged and used at the branch portion of the conveying path has been described as an example. However, as the conveying roll pairs in the normal conveying paths 51, 53, 55, 56 and 57, It is also possible to use. Further, the sheet conveying apparatus of the present invention is not limited to the sheet conveying path in the main body of the image forming apparatus, and may be applied to a sheet conveying path in an automatic document feeder, a post-processing device, or the like. Furthermore, the sheet conveying apparatus of the present invention is applicable as long as it has a configuration in which the sheet is conveyed by a pair of conveying rolls in which a driving roll and a driven roll are combined.

Further, in the first embodiment, the case where the image forming apparatus is an intermediate transfer type color printer has been described as an example, but other types of printers, copiers, facsimile machines, and multifunction machines may be used.

[0057]

As described above, in the sheet conveying apparatus of the present invention, in particular, since the driven roll of the pair of conveying rolls has the above-described configuration, it is difficult to secure the installation space and the mounting work space. However, the installation and attachment can be performed, and smooth and stable rotation can always be obtained regardless of the roll width. When a coil spring is used as the biasing elastic member, the number of turns of the coil can be reduced to a minimum necessary number. As a result, unnecessary constituent materials are not used and cost is reduced. It is also possible to aim.

Further, since the image forming apparatus of the present invention uses the above-described sheet conveying apparatus of the present invention as a sheet conveying apparatus of the sheet conveying path, the sheet conveying apparatus of the sheet conveying path (particularly the conveying roll) Even if it is difficult to secure the installation space and installation work space for the driven rolls in the pair, the installation and installation can be performed, and the recording medium can be conveyed even in the sheet conveyance path under such bad conditions. Can be performed smoothly and stably.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a color printer according to a first embodiment.

FIG. 2 is a cross-sectional view of a main part showing a configuration of a sheet conveying apparatus and an installation position thereof.

FIG. 3 is a perspective view of a main part showing the sheet conveying device of FIG. 2;

FIG. 4 is a perspective view of a main part showing a pair of conveying rolls of the sheet conveying apparatus.

FIG. 5 is a side view of the transport roll pair shown in FIG. 4;

FIG. 6 is a sectional view taken along line IV-IV of FIG. 4;

FIG. 7 is an exploded perspective view of a driven roll in a transport roll pair.

FIG. 8 is an exploded perspective view showing an attached state of a driven roll in a transport roll pair.

FIG. 9 is a perspective view of a main part showing a conventional sheet conveying apparatus.

FIG. 10 is a perspective view of a main part showing an example of a conveying roll pair in a conventional sheet conveying apparatus.

FIG. 11 is a perspective view of a main part showing another example of a conveying roll pair in a conventional sheet conveying apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drive roll, 2 ... Follower roll, 3 ... Conveyance roll pair,
4. Sheet transport device, 55: Delivery transport path (sheet transport path), 70: Roll body, 71: Through hole, 75: Hollow cylindrical shaft, 76: Slit groove for locking, 77: For biasing Spring (elastic member for urging), 78: Both end portions, 79: Central portion (portion inserted into the cylindrical shaft), 81: Shaft holding portion (holding member), 81c: Shaft holding portion for locking, P ... Recording paper (sheet-like material or recording medium).

Claims (5)

[Claims] 1. A transport roll pair comprising a combination of a drive roll that is driven to rotate and a driven roll that is pressed against and driven by the drive roll, and is passed between the drive roll and the driven roll of the transport roll. In a sheet conveying apparatus that conveys a sheet-like material in a proper state, the driven roll of the pair of conveying rolls is fitted into a roll main body having a through-hole formed in a central portion thereof and penetrated into a through-hole of the roll main body. A hollow cylindrical shaft that rotatably supports the roll body, and is inserted and inserted into the hollow portion of this cylindrical shaft, and both ends are locked and fixed at positions protruding from both ends of the cylindrical shaft. And a biasing elastic member for biasing the roll body elastically in a direction in which the roll body is pressed against the drive roll via the cylindrical shaft. Feeding apparatus. 2. The sheet conveying device according to claim 1, wherein a spring having at least both ends formed in a coil shape is used as the biasing elastic member of the driven roll. 3. The device according to claim 2, wherein a portion of the biasing elastic member inserted into the hollow portion of the cylindrical shaft matches a lower inner wall surface along a longitudinal direction of the cylindrical shaft. A sheet conveying device having a shape that can be abutted. 4. The apparatus according to claim 1, wherein holding members are provided in the vicinity of both sides of the roll body of the driven roll, facing each other at an interval in which the cylindrical shaft is fitted.
The cylindrical shaft is provided with a slit groove into which a part of the holding member is inserted to position the cylindrical shaft when the cylindrical shaft is fitted between the holding members. Sheet transport device. 5. An image forming apparatus for forming an image made of toner on a sheet-shaped recording medium, the apparatus comprising a sheet conveying path for conveying the recording medium. An image forming apparatus using the sheet conveying apparatus according to claim 1 as an apparatus.