US20070018387A1

US20070018387A1 - Sheet conveying device

Info

Publication number: US20070018387A1
Application number: US11/487,267
Authority: US
Inventors: Kiyonori Yamamoto
Original assignee: Kyocera Mita Corp
Current assignee: Kyocera Document Solutions Inc
Priority date: 2005-07-25
Filing date: 2006-07-14
Publication date: 2007-01-25
Also published as: JP2007031027A

Abstract

A sheet conveying device for in an image forming apparatus includes a first guide. A second guide faces the first guide to define a sheet conveyance passage therebetween. A driving shaft is mounted on the first guide and carries driving rollers. A supporting shaft extends substantially orthogonal to a sheet conveying direction. Driven rollers are at opposite ends of the supporting shaft and correspond to the driving rollers. A holder holds the supporting shaft so that the supporting shaft can move towards the driving shaft. Urging members are at opposite sides of an axially center of the supporting shaft for pushing the driven rollers against the driving rollers. The holder is attached to the second guide to swing at a pivotal axis extending in the sheet conveying direction, the pivotal axis is on a plane orthogonally passing the supporting shaft at a center thereof.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a sheet conveying device for use in an image forming apparatus.
2. Description of the Related Art
Conventionally, as disclosed in Japanese Unexamined Patent Publication No. 5-69980, there has been known a sheet conveying device provided with a plurality of driving rollers aligned in a direction substantially orthogonal to a sheet conveying direction, a plurality of driven rollers facing the driving rollers, and a guide member in which the respective driven rollers are mounted. In this sheet conveying device, the driven rollers are mounted in the guide member in a state that the driven rollers are independently urged by a spring member.
Further, Japanese Unexamined Patent Publication No. 6-16303 discloses a sheet conveying device provided with a supporting shaft extending in a direction substantially orthogonal to the sheet conveying direction, for rotatably supporting driven rollers at opposite ends thereof, and a guide member in which the supporting shaft is mounted. In this sheet conveying device, a center portion of the supporting shaft is made contact with a projection formed on the guide member, and the center portion of the supporting shaft is pressed by a holding member in a direction opposite to the projection to thereby allow the supporting shaft to swing at the center portion thereof.
Recently has been proposed a sheet conveying device in which a first guide member and a second guide member are provided facing each other to define a sheet conveying passage therebetween. A driving roller is mounted in the first guide member, and a driven roller is mounted in the second guide member. However, if the configuration disclosed in Japanese Unexamined Patent Publication No. 5-69980 or the configuration disclosed in Japanese Unexamined Patent Publication No. 6-16303 is adopted in such sheet conveying device constructed as above, the following problems can be seen to rise.
First, in the case of adopting the configuration of Japanese Unexamined Patent Publication No. 5-69980, the driven rollers are separately mounted in the second guide member. If the first guide member and the second guide member are not parallel to each other, the driven rollers do not urge uniformly, causing a sheet skew due to the non-uniform urging force.
In order to prevent the sheet skew, it is necessary to raise the strength of the second guide member to suppress bending of the second guide member and to raise the production preciseness of the second guide member to maintain the parallelism between the first guide member and the second guide member. This causes increases in the cost and the weight.
Second, in the case of adopting the configuration of Japanese Unexamined Patent Publication No. 6-16303, even if the first guide member and the second guide member are not parallel to each other, the driven rollers mounted on the opposite end portions of the supporting shaft are respectively urged to the driving rollers owing to the swingness of the supporting shaft. However, in order to make the urging force of the respective driven rollers uniform, it is necessary to make the distance between the first guide member and the second guide member constant while keeping the parallelism thereof. For this reason, there is still the necessity of raising the strength of the second guide member to suppress the bending of the second guide member and raise the production preciseness of the second guide member.

SUMMARY OF THE INVENTION

In view of the above problems, it is an object of the present invention to provide a sheet conveying device which can keep a sheet from skewing without raising the strength and the production preciseness of a guide member.
According to the present invention, a sheet conveying device for conveying a sheet, which is to be installed in an image forming apparatus for forming an image on a sheet, includes: a first guide member; a second guide member facing the first guide member so as to define a sheet conveyance passage therebetween; a driving shaft mounted on the first guide member and carrying driving rollers; a supporting shaft extending in a direction substantially orthogonal to a sheet conveying direction, the supporting shaft rotatably supporting driven rollers at opposite ends thereof, the driven rollers corresponding to the driving rollers, respectively; a holder for holding the supporting shaft in such a manner that the supporting shaft is able to move toward the driving shaft; urging members provided at opposite sides of an axially center of the supporting shaft for urging the supporting shaft in a direction of pushing the driven rollers against the driving rollers. The holder is attached to the second guide member in such a manner that the holder is able to swing at a pivotal axis extending in the sheet conveying direction, the pivotal axis is on a plane orthogonally passing the supporting shaft at a center thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing a configuration of a printer in which a sheet conveying device according to an embodiment of the present invention is installed.
FIG. 2 is a perspective view showing the sheet conveying device seen from an upstream of a sheet conveying direction.
FIG. 3 is a perspective view showing the sheet conveying device with a first guide member and a second guide member being omitted.
FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 2.
FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 4.
FIG. 6 is a perspective view showing the second guide member.
FIG. 7 is a perspective view showing a holder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the best mode of carrying out the present invention is described in detail referring to the drawings.
FIG. 1 shows a printer 10 as an image forming apparatus in which a sheet conveying device 1 according to an embodiment of the present invention is installed. The sheet conveying device 1 may be installed not only in the printer 10, but also in other image forming apparatuses, such as a copying machine, a facsimile machine, or a complex machine.
The printer 10 is operable to form an image on a sheet in accordance with image data sent from a terminal and the like on a way of conveying the sheet along a conveyance passage L. The printer 10 includes, in a box-shaped housing 15, an image forming section 13 in which a toner image is transferred on the sheet after the toner image is formed on a peripheral surface of the. photoconductive drum 131, a sheet supplying section 12 for supplying the sheet to the image forming section 13, and a fixing section.16 for fixing the toner image to the sheet.
The conveyance passage L includes a horizontal portion L1 extending substantially horizontally from front to back and a vertical portion L2 uprising substantially perpendicularly from a tail portion of the horizontal portion L1 so as to be substantially L-shaped in a side view.
The sheet supplying section 12 includes a sheet supplying cassette 121 provided beneath the horizontal portion L1 of the conveyance passage L. In the sheet conveying section 12, sheets accommodated in the sheet supplying cassette 121 are picked up by a picking up roller 12 a, and the sheet is fed to the horizontal portion L1 of the conveyance passage L one by one by sheet supplying rollers 12 b to 12 e, the sheet fed to the conveyance passage L is held by registration rollers 12 f, and the sheet is supplied to the image forming section 13 at a predetermined timing.
The sheet conveying section 12 includes a manual feeding tray 122 detachably mounted in a front portion of the housing 15. In the sheet conveying section 12, it is possible that sheets mounted on the manual feeding tray 122 are picked up by a picking up roller 12 g, and fed to the horizontal portion L1 of the conveyance passage L one by one by the sheet supplying rollers 12 c and 12 e.
The image forming section 13 includes a photoconductive drum 131 provided in a substantial center of the horizontal portion L1 of the conveyance passage L in the sheet conveying direction, a charging section 132 provided above the photoconductive drum 131, a developing section 133 provided before the photoconductive drum 131 in the sheet conveying direction, a transferring section 134 provided beneath the photoconductive drum 131, a cleaning section 135 provided after the photoconductive drum 131 in the sheet conveying direction, a laser scanner unit (LSU) 14 provided above the charging section 132, the cleaning section 135, and the fixing section 16.
The photoconductive drum 131 rotates in a clockwise direction in FIG. 1. After the peripheral surface of the photoconductive drum 131 is uniformly charged by the charging section 132, a laser beam based on the image data is irradiated by the laser scanner unit 14 onto the peripheral surface of the photoconductive drum 131 via a space between the charging section 132 and the developing section 133 so as to form a static latent image thereon. Then, toner particles are supplied by the developing section 133 to form a toner image on the peripheral surface on which the static latent image has been formed.
The sheet supplied by the sheet supplying section 12 is conveyed while being urged to the photoconductive drum 131 by a transferring roller 134 a of the transferring section 134 so that the toner image formed on the peripheral surface of the photoconductive drum 131 is transferred to a surface of the sheet (a transfer-bearing surface), then the sheet is conveyed to the fixing section 16.
Toner particles or residual charge remained on the peripheral surface of the photoconductive drum 131 after completion of the transferring process is removed by the cleaning section 135.
The fixing section 16 includes a heating roller 16a and a pressing roller 16 b. These rollers 16 a and 16 b hold the sheet on which the toner image is transferred so as to fix the toner image to the sheet by the heat and pressure.
The sheet to which the toner is fixed is discharged by a discharging roller 18 to a discharge section 19 formed on an upper surface of the housing 15.
In the printer 10 of the present embodiment, a switchback section 17 is provided between the horizontal portion L1 of the conveyance passage L and the sheet supplying cassette 121 so that an image can be formed on the both surfaces of the sheet.
The sheet conveying device 1 is mounted between the fixing section 16 and the discharging roller 18, and along the conveyance passage L′ of the switchback section 17.
As shown in FIGS. 2 to 5, the sheet conveying device 1 includes a first guide member 8 and a second guide member 9 facing each other having the conveyance passage L or L′ (hereinafter, they are simply called as the conveyance passage L) therebetween.
The first guide member 8 is made of a synthetic resin and the like, and has a substantially rectangular flat plate extending along the conveyance passage L.
The second guide member 9 is formed by applying a pressing force to a steel plate and the like, and includes a main plate 91 facing the first guide member 8, and having the substantially rectangular shape, an end plate 92 extending from an end portion of the main plate 91 in the sheet conveying direction (hereinafter, an X-direction) to a direction bearing off from the first guide member 8 (hereinafter, a downward Z-direction) along a direction substantially orthogonal to the X-direction (hereinafter, a Z-direction) over substantially whole length of the main plate 91, and side plates 93 respectively extending from opposite end portions in a direction substantially orthogonal to the X-direction along the conveyance passage L of the main plate 91 (hereinafter, a Y-direction) to the downward Z-direction. The conveyance passage L is defined between the main plate 91 and the first guide member 8.
The sheet conveying device 1 includes two driving rollers 2 spaced away from a center of the conveyance passage L in the Y-direction with substantially equal distance, and two driven rollers 4 facing the driving rollers 2 in the Z-direction.
The driving roller 2 is made of a rubber material and the like, and penetrated by a driving shaft 3 extending in the Y-direction so that the driving roller 2 is fixedly attached thereto. The driving shaft 3 is rotatably supported by a supporting member (not shown) mounted on a surface opposite to a surface which faces the conveyance passage L of the first guide member 8, and rotated by an un-illustrated driving source in the predetermined rotational number. The first guide member 8 is provided with a window 82 in a position corresponding to the driving roller 2, and a part of the driving roller 2 intrudes in the conveyance passage L through the window 82.
The driven roller 4 is made of a synthetic resin and the like, and has a cylindrical shape. The driven rollers 4 are respectively engaged with the opposite end portions of a circle-bar shaped supporting shaft 5 extending in the Y-direction so as to be rotatably supported at opposite end portions of the supporting shaft 5. The supporting shaft 5 is held in a holder 6, the holder 6 is mounted on a surface opposite to a surface facing the conveyance passage L of the main plate 91 of the second guide member 9. The main plate 91 of the second guide member 9 is formed with a window 95 in a position corresponding to the driven roller 4, and a part of the driven roller 4 intrudes in the conveyance passage L through the window 95 so as to be contactable with the driving roller 2.
As shown in FIG. 7, the holder 6 includes a peripheral wall 61 extending in the Z-direction, and having a cross sectional shape of a rectangular tube extending in the Y-direction, and a bottom wall 62 which closes an opening opposite to the main plate 91 of the peripheral wall 61. The holder 6 has the shape of a container and opens toward a direction opposite to the downward direction of the Z-direction (hereinafter, an upward Z-direction). The size of the holder in the Y-direction is slightly smaller than a distance between the driven rollers 4 so that the holder 6 can be disposed between the driven rollers 4. Inside the holder 6, ribs 63 uprise from the bottom wall 62 at positions bit inner side from the opposite end portions in the Y-direction to connect the opposite long walls of the peripheral wall 61 each other.
In the holder 6, substantially U-shaped bearing recesses 61 a and 63 a are respectively formed in short walls of the peripheral wall 61 and ribs 63 in a manner of opening toward the upward Z-direction in the view from the Y-direction. The width of the bearing recesses 61 a and 63 a is substantially the same as a diameter of the supporting shaft 5. The supporting shaft 5 is engaged with the bearing recesses 61 a and 63 a so as to be movably supported by the holder 6 in the Z-direction while the supporting shaft 5 is covered by the holder 6 from the opposite side of the driving rollers 2.
A drooping portion 95 a which droops from an edge portion of the window 95 downwardly in the Z-direction is provided in an outside of the supporting shaft 5 in the Y-direction. The drooping piece 95 a faces an end surface of the supporting shaft 5 so as to restrict movement of the supporting shaft 5 in the Y-direction. The drooping portion 95 a is formed by cutting a portion corresponding to an area of the window 95 of the main plate 91 and bending the same toward the downward direction of the Z-direction when the window 95 is formed.
Compression springs 7 are respectively provided in a space between the rib 63 and the short wall of the peripheral wall 61. In a case where the supporting shaft 5 is held in the holder 6, the opposite sides of the axially center of the supporting shaft 5 are urged by the compression springs 7 in the upward direction of the Z-direction so as to urge the driven rollers 4 against the driving rollers 2. A cylinder-shaped guide member 62 a for guiding the compression springs 7 projects from the bottom wall 62 in a position between the rib 63 and the short wall of the peripheral wall 61.
Projecting portions 66 which project in the upward direction of the Z-direction from the peripheral wall 61 are respectively provided at the center of the long walls of the peripheral wall 61 in the Y-direction. Ribs 64 which extend in the Z-direction are respectively provided in the both inner surfaces of the peripheral wall 61 in the X-direction and the projecting portions 66. The width of the rib 64 in the X-direction is set in such a manner that a space between the ribs 64 is larger than the diameter of the supporting shaft 5. Shaft restrainers 64 a which project so as to face each other are respectively provided in end surfaces of the ribs 64 in the X-direction and end portions in the upward direction of the Z-direction of the ribs 64, thereby keeping the supporting shaft 5 from leaving from the holder 6. The supporting shaft 5 can be forcibly placed in a space between the shaft restrainers 64 a. In other words, in a case of pressing the supporting shaft 5 into the space between the shaft restrainers 64 a from an outside, the peripheral wall 61 is elastically deformed and the both shaft restrainers 64 a are pushed toward the both sides in the X-directions so that the supporting shaft 5 can pass the space between the shaft restrainers 64 a.
Two pivotal holes 65 a aligned in the Z-direction are provided in both outside surfaces of the peripheral wall 61 in the X-directions and the projecting portion 66.
On the other hand, the second guide member 9 includes a pair of retainers 94 for holding the holder 6 from the both sides in the X-direction at a position corresponding to substantially a center of the conveyance passage L in the Y-direction, namely, substantially a center in the axial direction of the supporting shaft 5. The retainer 94 is formed by cutting portions aligned in the X-direction of the main plate 91 and bending the same toward the downward direction of the Z-direction so as to be opposite to each other, and is elastically deformable in the X-direction. In other words, the retainers 94 can be pressedly widened. When the retainers 94 are released in this situation, the retainers 94 can be restored to original positions by restoring force of the retainers 94. A pivotal stem 94 a which extends in the X-direction and can be engaged with pivotal hole 65 a of a boss 65 of the holder 6 projects respectively in both inner surfaces of the retainers 94. The pivotal stem 94 a is engaged with the pivotal hole 65 a so that the holder 6 can swing about the pivotal stem 94 a.
With the sheet conveying device 1 configured as mentioned above, the holder 6 swings about the pivotal stem 94 a placed in the position corresponding to substantially the center in the axial direction of the supporting shaft 5 so that a parallelism of the driving roller 2 and the driven roller 4 can be ensured if the second guide member 9 and the first guide member 8 are not parallel to each other. Further, the supporting shaft 5 is urged by the compression springs 7 at the opposite sides thereof with respect to the center in the axial direction, and the driven rollers 4 supported by the both end portions of the supporting shaft 5 are urged against the driven rollers 2 with the substantial equal urging force so that a sheet skew can be restrained. The supporting shaft 5 is held in the holder 6 to be movable in the Z-direction. In a case where the holder 6 vibrates due to a vibration generated in the second guide member 9, the vibration is absorbed by the compression springs 7, and can be prevented from transmitting to the supporting-shaft 5 so that the uniformity of the urging force of the driven rollers 4 can be ensured. In other words, the strength of the second guide member 9 can be lowered to thereby reduce the cost and weight. Further, it is not necessary to produce the second guide member 9 with a high degree of accuracy to thereby improve the production yield.
The holder 6 is so formed to cover the supporting shaft 5 from the opposite side of the driving rollers 2 so that the holder 6 can hold the supporting shaft 5 to be movable in the Z-direction with a simple shape. The holder 6 is provided with the shaft restrainers 64 a for restraining the leaving of the supporting shaft 5 so that the holder 6 can be treated as a unit in which the supporting shaft 5 is installed to thereby improve the assembling efficiency.
The supporting shaft 5 can be forcibly placed in the space between the restrainers 64 a so that the supporting shaft 5 can be held in the holder 6 with a simple fingertip operation.
The retainers 94, in an inner surface of which the pivotal stem 94 a respectively projects, are elastically deformable in the X-direction so that the holder 6 can be mounted on the second guide member 9 with the simple fingertip operation.
Two pivotal holes 65 a with which the pivotal stem 94 a is engageable are aligned in the Z-direction so that the urging force of the driven roller 4 can be adjusted only by shifting the position where the pivotal shaft 94 a is engaged with.
Though the shaft restrainers 64 a are provided in the both ribs 64 in the embodiment, the shaft restrainers 6 a may be provided in only one rib 64.
Further, though the supporting shaft is urged by the compression springs 7 in the above embodiment, it is possible to adopt urging means for urging the supporting shaft 5 with the restoring force caused by an elastic deformation.
Further, the pivotal shaft 94 a may project from the both outer surfaces of the holder 6 in the X-direction and the pivotal holes 65 a may be provided in both inner surfaces of the retainers 94.
The number of driven rollers 2 is not limited to two, but the number thereof may be four. In this case, the driven rollers 4 can be provided at a position opposite to the central two driven rollers, or two of set including the supporting shaft 5 supporting the driven rollers 4 at the opposite end portions thereof and the holder 6 may be aligned in the Y-direction. Further, in a case of six driving rollers, three sets of the supporting shaft 5 and the holder 6 can be prepared.
As described above, a sheet conveying device for conveying a sheet, which is to be installed in an image forming apparatus for forming an image on a sheet, comprises a first guide member; a second guide member facing the first guide member so as to define a sheet conveyance passage therebetween; a driving shaft mounted on the first guide member and carrying driving rollers; a supporting shaft extending in a direction substantially orthogonal to a sheet conveying direction, the supporting shaft rotatably supporting driven rollers at opposite ends thereof, the driven rollers corresponding to the driving rollers, respectively; a holder for holding the supporting shaft in such a manner that the supporting shaft is able to move toward the driving shaft; urging members provided at opposite ends thereof for urging the supporting shaft in a direction of pushing the driven rollers against the driving rollers, wherein the holder is attached to the second guide member in such a manner that the holder is able to swing at a pivotal axis extending in the sheet conveying direction, the pivotal axis is on a plane orthogonally passing the supporting shaft at a center thereof.
With this arrangement, in a case where the second guide member and the first guide member are not parallel to each other, the holder swings at a position corresponding to substantially the center of the supporting shaft in the axial direction so that the parallelism of the driving roller and the driven roller can be ensured. Further, the supporting shaft is urged by the urging members at the opposite sides thereof with respect to the center of the supporting shaft in the axial direction so that the driven rollers supported at the opposite end portions of the supporting shaft are urged against the driving rollers with substantially the equal urging force to thereby prevent the sheet skew. Further, the supporting shaft is held by the holder so as to be movable in a predetermined direction (a direction in which the driven roller faces the driving roller). With this construction, in a case where the vibration generated in the second guide member causes to vibrate the holder, the vibration is absorbed by the urging members and prevented from transmitting to the supporting shaft to thereby ensure the uniformity of the urging force of the driven roller. In other words, the strength of the second guide member can be lowered so that the cost and weight can be reduced by lessening the material, and the second guide member is not necessary to produce with the high accuracy, thereby improving the production yield.
It may be preferable that the holder has a bearing recess which is opened toward the driving shaft and in which the supporting shaft is placed movably toward the driving shaft.
With this arrangement, the holder can hold the supporting shaft to be movable toward the predetermined direction with a simple configuration.
It may be preferable that the holder has a shaft restrainer in a position closer to the driving shaft than the supporting shaft placed in the bearing recess for keeping the supporting shaft from leaving from the bearing recess.
With this construction, the supporting shaft is prevented from leaving from the bearing recess by the shaft restrainer so that the holder in which the supporting shaft is placed can be treated as a unit, thereby improving the assembling efficiency.
It may be preferable that the shaft restrainer is provided in the opposite sides of the supporting shaft in the sheet conveying direction, and a gap between the shaft restrainer is smaller than a diameter of the supporting shaft under a specified pressure, but the gap is expandable owing to elastic shifts of the opposite walls when being applied with a pressure greater than the specified pressure.
With this arrangement, the supporting shaft can be forcibly placed in the space between the shaft restrainer so that the supporting shaft can be held by the holder with the simple fingertip operation.
It may be preferable that the second guide member includes a pair of retainers which are opposite to each other in the sheet conveying direction and are adapted for retaining the holder swingably.
With this arrangement, the holder can be retained swingably with the simple configuration.
It may be preferable that the pivotal axis is defined by an engagement of a pivotal stem formed on an outer surface of the holder and a pivotal hole formed in an inner surface of the retainer or an engagement of a pivotal stem formed on the inner surface of the retainer and a pivotal hole formed in the outer surface of the holder.
With this arrangement, the retainers can hold the holder swingably only by engaging the pivotal stem with the pivotal hole.
It may be preferable that the retainer is elastically shiftable in the sheet conveying direction.
With this arrangement, the holder can be forcedly placed in the space between the pair of retainers so that the holder can be mounted on the second guide member with the simple fingertip operation.
It may be preferable that a plurality of pivotal holes are provided in a direction parallel with a plane orthogonally passing the respective axes of the driving shaft and supporting shaft.
With this arrangement, the urging force of the driven roller can be adjusted only by shifting the position with which the pivotal stem is engaged.
Further, in a case of the image forming apparatus in which the sheet conveying device is installed, the above effects can be obtained in the image forming apparatus.
This application is based on patent application No. 2005-213991 filed in Japan, the contents of which are hereby incorporated by references.
As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to embraced by the claims.

Claims

1. A sheet conveying device for conveying a sheet, which is to be installed in an image forming apparatus for forming an image on a sheet, comprising:

a first guide member;

a second guide member facing the first guide member so as to define a sheet conveyance passage therebetween;

a driving shaft mounted on the first guide member and carrying driving rollers;

a supporting shaft extending in a direction substantially orthogonal to a sheet conveying direction, the supporting shaft rotatably supporting driven rollers at opposite ends thereof, the driven rollers corresponding to the driving rollers, respectively;

a holder for holding the supporting shaft in such a manner that the supporting shaft is able to move toward the driving shaft; and

urging members provided at opposite sides of an axially center of the supporting shaft for urging the supporting shaft in a direction of pushing the driven rollers against the driving rollers, wherein the holder is attached to the second guide member in such a manner that the holder is able to swing at a pivotal axis extending in the sheet conveying direction, the pivotal axis is on a plane orthogonally passing the supporting shaft at a center thereof.

2. A sheet conveying device according to claim 1, wherein the holder has a bearing recess which is opened toward the driving shaft and in which the supporting shaft is placed movably toward the driving shaft.

3. A sheet conveying device according to claim 2, wherein the holder has a shaft restrainer in a position closer to the driving shaft than the supporting shaft placed in the bearing recess for keeping the supporting shaft from leaving from the bearing recess.

4. A sheet conveying device according to claim 3, wherein the shaft restrainer includes restraining projections on opposite walls of the bearing recess, the opposite walls face each other in the sheet conveying direction, and a gap between the restraining projections is smaller than a diameter of the supporting shaft under a specified pressure, but the gap is expandable owing to elastic shifts of the opposite walls when being applied with a pressure greater than the specified pressure.

5. A sheet conveying device according to claim 1, the second guide member includes a pair of retainers which are opposite to each other in the sheet conveying direction and are adapted for retaining the holder swingably.

6. A sheet conveying device according to claim 5, wherein the pivotal axis is defined by an engagement of a pivotal stem formed on an outer surface of the holder and a pivotal hole formed in an inner surface of the retainer or an engagement of a pivotal stem formed on the inner surface of the retainer and a pivotal hole formed in the outer surface of the holder.

7. A sheet conveying device according to claim 6, wherein the retainer is elastically shiftable in the sheet conveying direction.

8. A sheet conveying device according to claim 6, wherein a plurality of pivotal holes are provided in a direction parallel with a plane orthogonally passing the respective axes of the driving shaft and supporting shaft.

9. An image forming apparatus comprising a sheet conveying device provided with:

a first guide member;

a driving shaft mounted on the first guide member and carrying driving rollers;

a holder for holding the supporting shaft in such a manner that the supporting shaft is able to move toward the driving shaft;