JPH11139626A - Paper material conveying device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the influence of paper feed precision on paper feed precision of a resist roller pair and to improve conveyance precision of a paper material. SOLUTION: This conveying device is formed such that a paper material (p) is conveyed along a conveying route as the paper material is formed in a loop at the conveyance route between a conveyance roller device 4 (a conveyance means) and a mechanical shutter 11 (a shutter means). In this case, the paper material conveyance speed of the conveyance roller device 4 is adjusted to a speed equal to or lower than the paper material conveyance speed of the resist roller device 2, and during a time in which the rear end part of the paper material passes the conveyance roller device 4, a speed is set to a value at which the loop is maintained.

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 in an image forming apparatus such as a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art A conventional sheet conveying apparatus 100 will be described with reference to FIG. FIG. 6 illustrates a cross-sectional configuration of a main part from a sheet material stacking unit to an image forming unit using a well-known electrophotographic method in the image forming apparatus.

A sheet feeding device 5 for feeding a sheet material from a sheet material stacking section (not shown) to a conveying path H has a feed roller 20 which is driven to rotate in a sheet material conveying direction, and a position facing the feed roller 20. Retard roller 21, which is pressed against,
A torque limiter 22 is coaxially supported on the drive shaft of the retard roller 21.

At the time of sheet feeding, the feed roller 20 is driven to rotate in the sheet conveying direction, and the retard roller 21 and the torque limiter 22 are driven to rotate in the direction opposite to the sheet conveying direction.

However, the retard roller 21 is idled with respect to the drive shaft of the retard roller 21 via the torque limiter 22 due to the torque transmitted from the feed roller 20 which is in pressure contact with the feed roller 2.
Rotate to zero.

Downstream of the sheet feeding device 5, a transport roller device 4 including a driving roller 19 for feeding the sheet material in a vertical direction and a driven roller 18 is disposed. The rotation of the feed roller 20 is controlled by the transport roller device 4. The mechanism is released after the sheet material is nipped. When the driving is released, both the feed roller 20 and the retard roller 21 rotate in a direction opposite to the sheet material conveying direction.

Downstream of the conveying roller device 4, an upstream guide 14a before registration and a downstream guide 14b before registration, made of a molding material, and a rush guide 14c before registration, made of a rigid plate material, are opposed to the above three guides. In this manner, a front guide 14d also serving as a frame of the main body is disposed. The sheet material is bent by the curved shape of the pre-registration upstream guide 14a, and is introduced into the nip of the registration roller device 2 by the pre-registration downstream guide 14b and the pre-registration intrusion guide 14c.

Downstream of the registration roller device 2, a drum 6 and a transfer roller 7 are moved along an upper transfer guide 8 arranged on the printing surface side and a lower transfer guide 9 arranged on the non-printing surface side.
And the image is formed on the sheet material.

Further, a sheet feeding device 3 which is separate from the sheet feeding device 5 and comprises a half-moon shaped sheet feeding roller 15, a separation pad 17 pressed against the sheet feeding roller 15 and a sheet feeding plate 16, is a registration roller device. 2 and is disposed at a position substantially horizontally separated from the second.

The transport roller device 4 will be described with reference to FIG. The drive roller 19 is made of a cylindrical rubber material and has a rotating shaft 2.
3 and coaxially fixed thereto, and rotates integrally with the rotating shaft 23.

The driven roller 18 is made of a cylindrical molding material, is coaxially fixed on a rotating shaft 24, and rotates integrally with the rotating shaft 24. The driven roller 18 is arranged at a position facing the driving roller 19 and is pressed by a coil spring 25 at the roller end.

The driving roller 19 and the driven roller 18
Is divided into two parts, and by applying pressure at the center of the driven roller 18, the deflection of the rotating shaft 24 of the driven roller 18 is reduced and the nip shape of each roller is made uniform.

According to an electric signal from the main body, connection of driving,
The electromagnetic clutch 26 for releasing and releasing includes an input gear 27 that receives drive from the main motor, and an output shaft 28 that is coaxially disposed on the rotation shaft 23 of the drive roller 19 and rotates integrally with the drive roller 19.

Similarly, an output gear 29 coaxially arranged on the rotation shaft 23 of the driving roller 19 and rotating integrally with the driving roller 19 transmits a driving force to the driving system of the sheet feeding device 5 on the upstream side. .

Next, the registration roller device 2 located downstream of the transport roller will be described in detail with reference to FIG.

The driving roller 13 is made of a cylindrical rubber material.
It is coaxially fixed on the rotating shaft 34 and rotates integrally with the rotating shaft 34. The driven roller 12 is a cylindrical molding material 3.
2 and is coaxially fixed on the rotating shaft 33 at a position facing the driving roller 13 and rotates integrally with the rotating shaft 33.

The driving roller 13 and the driven roller 12 are pressed against each other by a coil spring 11 at the end of the roller. The gap between the driven rollers 12 has a function of aligning the leading end of the sheet material immediately before the nip of the roller. A molding material 32 axially and coaxially supported thereon, and a rigid plate material 3 having a weight function of applying a constant stopping force to the molding material 32
1 is provided.

The mechanical shutter 11 is driven by a driven roller 12.
Since it is rotatably supported on the upper side, it can open and close independently of the rotation of the driven roller 12.

The input gear 36 is coaxially fixed on a rotating shaft 34 of the driving roller 13 and rotates integrally with the rotating shaft 34.
The drive from the main motor is transmitted to the drive roller 13.

A registration mechanism in the sheet conveying apparatus will be described with reference to FIGS.

In FIG. 9, the sheet material p nipped by the conveying roller is bent at the curved portion of the upstream guide 14a before the registration, and the downstream guide 14b before the registration and the entry guide 1 before the registration.
The sheet is sent to the nip portion of the registration roller device 2 along 4c.

In FIG. 10, when the leading edge of the sheet is stopped by the mechanical shutter 11, a loop is formed inside the upstream guide 14a before the register and the downstream guide 14b before the register, and the leading edge of the sheet is aligned by the mechanical shutter 11 therebetween.

When the loop completely grows and contacts the entire upstream guide 14a before the register and the downstream guide 14b before the register,
The sheet conveying force F1 of the conveying roller is converted into a sheet conveying force F2 in the direction of the stopping force of the mechanical shutter.

Since the leading end of the sheet is stopped by the mechanical shutter 11 while the loop is formed,
There is no need to stop the rotation of each roller of the registration roller device 2, and an electromagnetic clutch for connecting and releasing the drive by the electric signal from the main body becomes unnecessary.

Therefore, the rotation of the registration roller device 2 and the main motor can be synchronized, and the configuration can be simpler than that of a general registration roller device in which the rotation is temporarily stopped.

In FIG. 11, the sheet material conveying force F2
Is greater than the stopping force of the mechanical shutter 11, the mechanical shutter 11 opens, the leading end of the sheet material enters the nip portion of the registration roller device 2, and the conveyance of the sheet material starts.

The sheet material sent from the sheet feeding device 3 also forms a loop similarly to the registration mechanism, and the sheet material is sent to the developing device 1 after the leading end of the sheet material is aligned by the mechanical shutter 11.

[0028]

However, there is a concern that the following problem may occur in the sheet conveying apparatus for performing the registration of the sheet with such a configuration.

As a first problem, when the paper feed accuracy of the transport roller device 4 is poor, the paper feed accuracy of the transport roller device 4 is reduced due to the relationship between the registration roller device 2 and the sheet material transport speed of the transport roller device 4. This has an adverse effect on the paper feed accuracy of the registration rollers via the material.

As a second problem, when a jam occurs in a state where the sheet material is nipped in the conveying roller device 4 and the user tries to pull out the sheet material (in the direction opposite to the conveying direction), the driving roller 19 The drive is transmitted to the retard roller 21 on the upstream side of the conveying roller device 4 through the output gear 29 fixed to the sheet material, so that the feed roller 20 and the retard roller 21 also rotate in the direction opposite to the sheet material conveying direction, and To give back tension. Therefore,
The force required when pulling out the sheet material increases, making it difficult for the user to clear the jam.

As a third problem, when the sheet feeding device 3 is disposed at a position substantially horizontal to the registration roller device 2, external light entering from the gap between the sheet feeding devices passes through the gap between the registration roller device 2. And easily reaches the vicinity of the drum 6. Since the pre-transfer guides (transfer upper guide 8, transfer lower guide 9, etc.) arranged near the drum 6 reflect the incoming external light, when the developing light on the drum 6 is irradiated with the external light, The toner also gets on the position where the outside light is irradiated,
Damage the image.

As a fourth problem, if there is a guide for bending the sheet material downstream of the transport roller device 4, if the paper feed of the transport roller tends to bring the sheet material to the center, if the sheet material is bent, There is a possibility that sound is generated or wrinkles of the sheet material are generated, and the worst case is a jam.

In particular, as described above, when the transport roller device 4 generates a back tension at the center of the sheet material while the sheet material is being transported, the movement of the sheet material toward the center is promoted.

The present invention has been made in order to solve the above-mentioned problems of the prior art. As a first object, the paper feeding accuracy of the transport roller device on the upstream side of the transport path is reduced by the registration of the resist on the downstream side via the sheet material. An object of the present invention is to eliminate the influence of the roller device on the paper feeding accuracy and improve the sheet material conveyance accuracy.

A second object of the present invention is to provide a drive transmission system that eliminates back tension caused by a retard roller during jam processing and enables an operator to easily perform jam processing.

A third object of the present invention is to provide a configuration for preventing light that has entered from outside the apparatus main body through a transport path from being irradiated on a developing area on a drum and damaging an image.

A fourth object of the present invention is to prevent the sheet material from generating noise, wrinkles, jams and the like when the sheet material is bent downstream of the conveying roller.

[0038]

In order to achieve the above object, according to the present invention, there is provided a pair of conveying rollers having a nip disposed on a conveying path of a sheet material, and attempts to enter the nip. Shutter means having a contact portion which comes into contact with the leading end of the sheet material, stops the sheet material with a predetermined stopping force, aligns the posture thereof, and retreats from the conveying path by the conveying force of the contacted sheet material; Transport means for transporting the material toward the transport roller pair, the sheet material transport speed of the transport means is equal to or less than the sheet material transport speed of the transport roller pair, and the rear end of the sheet material Until the sheet passes through the conveying means, a speed is set so that a loop of the sheet material formed between the conveying roller pair and the conveying means can be maintained.

Thus, the paper feeding accuracy of the conveying means does not affect the paper feeding accuracy of the conveying roller pair via the sheet material, and the paper feeding accuracy is improved.

A first conveying means which is rotated in the conveying direction via a clutch means and conveys the sheet material with a driving source, and a driving force transmitted from the first conveying means via a driving force transmitting means. A second conveying means for conveying the sheet material by force, and a driving force transmitting means provided in the conveying path of the sheet material, wherein the driving force transmitting means is rotated in a direction opposite to the conveying direction in a reverse direction from the first conveying means. A one-way clutch for interrupting the driving force is provided.

According to this, at the time of jam clearance or the like,
When the sheet material is pulled out, the transmission of the driving force between the first and second conveying means is cut off, the pulling force of the sheet material is reduced, and the operability is improved.

It is also preferable that the clutch means and the one-way clutch means are arranged coaxially with the drive shaft of the first transport means.

In a sheet material transporting apparatus which comprises transport means having a transport roller which is driven to rotate and a driven roller which is in pressure contact with the transport roller, and which forms a loop in the sheet material transported by the transport means, Further, the diameter of at least one of the driven rollers is set to be larger in the axial direction at the end side than at the center side of the sheet material to be conveyed.

According to this, the conveying speed at the end portion of the sheet material is faster than the conveying speed at the center side of the sheet material. It is possible to convey the sheet material while always applying tension, and it is possible to prevent the sheet material from being distorted, wrinkled, and jammed due to bending downstream of the conveyance roller.

It is also preferable that a plurality of the conveying means are arranged coaxially substantially orthogonal to the conveying direction on the conveying path of the sheet material.

The present invention is characterized in that a mat member is subjected to a matting process on a guide member constituting a sheet material conveyance path.

It is also preferable that the guide member is a sheet metal member plated with black.

The image forming apparatus is characterized by comprising the above-described sheet material conveying device and image forming means for forming an image on the sheet material conveyed by the sheet material conveying device.

It is preferable that any one of the above-described means is independently selected and appropriately combined.

[0050]

(Embodiment 1) FIG. 1 is a drawing showing a configuration of a main part of a sheet conveying apparatus according to a first embodiment of the present invention. In FIG. 1, the mechanical configuration and the mechanism for performing the registration are the same as those described in the section of the related art, and therefore, the same configurations are denoted by the same reference numerals, and detailed description of the configurations will be omitted. FIG.
FIG. 2 is an enlarged view of a portion D1 in FIG. 1, and a characteristic configuration of the first embodiment will be described with reference to FIGS. 1 and 2.

In the registration mechanism according to the present embodiment, the conveyance of the sheet material of the registration roller device 2 as a conveyance roller pair starts from a state where the sheet material p is in contact with the entire upstream guide 14a before registration and the downstream guide 14b before registration. Therefore, when the sheet material conveyance speed of the conveyance roller device 4 as the conveyance means is faster than the sheet material conveyance speed of the registration roller device 2, the paper feeding accuracy of the conveyance roller device 4 is controlled by the registration roller device via the sheet material p. 2 affects the paper feeding accuracy.

On the other hand, when the sheet material conveyance speed of the conveyance roller device 4 is much lower than the sheet material conveyance speed of the registration roller device 2, the loop formed between the registration roller device 2 and the conveyance roller device 4 disappears. However, since the contact is made in the entire area of the inner guide 14d before the registration, the paper feeding accuracy of the transport roller device 4 also affects the paper feeding accuracy of the registration roller device 2 via the sheet material p.

Therefore, the upper limit of the tolerance of the sheet conveying speed of the registration roller device 2 is V1, the lower limit of the tolerance of the sheet conveying speed of the conveying roller device 4 is V2, and the maximum length of the sheet p in the conveying direction is L. And

Further, the length of the loop when the loop has grown and is completely stuck to the upstream guide 14a before registration and the downstream guide 14b before registration is L3, and the loop has disappeared and has completely stuck to the inner guide 14d before registration. The loop length in the state is L
4 is assumed.

Further, the leading end of the sheet material p is stopped by the contact portion 11a of the mechanical shutter 11 as shutter means,
When the loop has completely grown, the distance from the nip of the feed roller 20 and the retard roller 21 to the rear end of the sheet material is L1.

The sheet material p being conveyed by the conveying roller device 4 has a back tension applied to the sheet material p because the retard roller 21 rotates in the direction opposite to the conveying direction during the conveyance of the sheet material. Become.

At this time, the lower limit of the tolerance of the sheet conveying speed of the conveying roller device 4 is V2 ', and the distance from the nip of the conveying roller device 4 to the nip of the feed roller 20 and the retard roller 21 is L2.

Here, V2> V2 'L = L1 + L2 + L3.

The time T1 required for the trailing edge of the sheet material to pass through the nip between the feed roller 20 and the retard roller 21 is: T1 = L1 / V2 'After the trailing edge of the sheet material has passed through the nip between the feed roller 20 and the retard roller 21, The time T2 required to pass through the nip of the transport roller device 4 can be expressed as T2 = L2 / V2.

In order for the sheet material conveyance speed of the conveyance roller device 4 to be equal to or slower than the sheet material conveyance speed of the registration roller device 2 in consideration of the tolerance, V1 ≧ V2 (1) And even when conveying the largest sheet material p,
The speed relationship at which the loop does not disappear is as follows: L3−L4> (V1−V2 ′) × T1 + (V1−V2) × T2 (2)

V1 and V satisfying the above equations (1) and (2)
2. By calculating V2 ', the sheet conveying speed of the conveying roller device 4 becomes equal to or slower than the sheet conveying speed of the registration roller device 2 in consideration of a tolerance, and the maximum sheet material is conveyed. Even if it does, the speed range in which the loop does not disappear can be set.

In this embodiment, in order to have a margin for the disappearance of the loop, as shown in FIG. 3, the inner guide 14d before registration is cut as much as possible, and the loop is completely eliminated and the inner guide before registration is removed. Loop length L4 when attached to 14d
Is smaller.

Next, the configuration of the transport roller device 4 will be described.
This will be described in detail with reference to FIG.

A one-way clutch 30 as a one-way driving force transmitting means, which is also coaxially arranged on the rotating shaft 23 of the driving roller 19, is provided inside an output gear 29 arranged coaxially on the rotating shaft 23 of the driving roller 19. Is fixed. An output shaft 28 of the electromagnetic clutch 26 is directly connected to an output gear 29, and is rotatably supported on a rotation shaft 23 of the drive roller 19.

During normal sheet conveyance, the driving force from the main motor is applied to the input gear 27 of the electromagnetic clutch 26 first.
Is transmitted to the electromagnetic clutch 2 by an electric signal from the main body.
When the drive of No. 6 is connected, the drive is transmitted to the output shaft 28. Since the output shaft 28 and the output gear 29 rotate integrally,
Feed roller 20 upstream of the transport roller from output gear 29
The drive is transmitted to the drive system of the retard roller 21.
At the same time, the drive of the output shaft 28 is transmitted to the drive roller 19 via the one-way clutch 30 fixed to the output gear 29.

On the other hand, when an attempt is made to pull out the sheet material from the conveyance path in the jam processing, the drive roller 19 rotates with the sheet material. At this time, since the output gear 29 idles with respect to the drive roller 19 by the one-way clutch 30, the drive is not transmitted to the drive system of the feed roller 20 and the retard roller 21 on the upstream side.

Therefore, the influence of the back tension due to the reverse rotation of the retard roller 21 can be eliminated, and the operator can easily perform the jam clearance.

Further, the driven roller 18 is set so that the outer diameter D1 on the sheet material end side is larger than the outer diameter D2 on the sheet material center side even in consideration of the tolerance. With this configuration, the paper transport speed at the end of the sheet material is higher than the paper transport speed at the center of the sheet material, so that tension is always applied in the direction orthogonal to the sheet material feed direction in the sheet material plane. It is possible to feed the sheet material while giving it, and it is possible to prevent the sheet material from being bent, wrinkled, and jammed due to bending.

The transport roller device 4 in this embodiment is arranged at a position where the operator cannot access it, and does not have a pressure release mechanism for clearing the sheet material.

Next, in FIG. 1, the upper transfer guide 8 is separate from the cartridge 10, and is made of a sheet metal subjected to a zinc-nickel alloy black plating process. External light that has entered through the gap of the sheet feeding device 3 passes through the gap of the registration roller device 2,
Although it easily reaches the vicinity of the drum 6, external light is absorbed by the transfer upper guide 8 coated with black, so that the external light is not irradiated to the developing area on the drum 6, and the light-shielding property is increased, and damage to the image is reduced. Can be prevented.

Here, instead of the black plating treatment of the upper transfer guide 8, a black coating may be used, but the black plating treatment is more preferable in consideration of abrasion resistance.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is the same as the first embodiment except that the arrangement of the one-way clutch 30 of the transport roller device 4 is changed. Therefore, the same components are denoted by the same reference numerals. The description is omitted.

The one-way clutch 30 includes the driving roller 19
And the rotating shaft 23, the shaft is coaxially supported with the rotating shaft 23, and the driving roller 19 and the one-way clutch 30 rotate integrally. The output shaft 28 of the electromagnetic clutch 26 is also coaxially supported on the rotating shaft 23, and the output shaft 28 and the rotating shaft 23
Is rotating together. The output gear 29 is coaxially supported on the rotating shaft 23 and rotates integrally with the rotating shaft 23.

At the time of normal sheet conveyance, the driving force from the main motor is first applied to the input gear 2 of the electromagnetic clutch 26.
7, when the drive of the electromagnetic clutch 26 is connected by an electric signal from the main body, the drive is transmitted to the output shaft 28. The drive is transmitted from the output shaft 28 to the rotation shaft 23 of the drive roller 19, and the drive is transmitted from the rotation shaft 23 via the one-way clutch 30. Also, the rotation shaft 23 of the drive roller 19
The output roller 29 rotates integrally with the transport roller device 4.
Feed roller 20 and retard roller 21 on the upstream side of
The drive is transmitted to the drive system.

On the other hand, in the jam processing of the sheet material nipped by the conveying roller device 4, the driving roller 19 rotates in the sheet conveying direction, but the one-way clutch 30 causes the driving roller 19 and the rotating shaft 23 to run idle. As a result, the drive is not transmitted to the output gear 29, and the drive is not transmitted to the drive system of the upstream feed roller 20 and the retard roller 21.

Therefore, the influence of the back tension due to the reverse rotation of the retard roller 21 can be eliminated, and the operator can easily perform the jam clearance. Therefore, the influence of the back tension by the retard roller 21 can be eliminated.

[0077]

As described in the embodiment of the present invention, it is possible to suppress the influence of the paper feeding accuracy of the transporting means on the paper feeding accuracy of the transport roller pair, and to stably and precisely sheet the sheet material. Can be transported.

When a sheet material is withdrawn from the conveyance path during a jam clearance or the like, transmission of driving force between the first and second conveyance means is interrupted, the sheet material withdrawal force is reduced, and operability is reduced. improves.

In the sheet material plane, while always applying tension in a direction orthogonal to the sheet material conveying direction,
The sheet material can be conveyed, thereby preventing the sheet material from being bent, wrinkled, and jammed due to bending.

By applying a matting process to a guide member constituting a transport path leading to the image forming means, the light shielding property of the transport path can be enhanced, and the image quality of an image formed on the sheet material can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a cross-sectional configuration of a main part of a sheet material conveying device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a loop length of the sheet conveying apparatus according to the first embodiment.

FIG. 3 is a diagram illustrating a sheet material guide position of the sheet material conveying device according to the first embodiment.

FIG. 4 is a diagram illustrating a transport roller device of the sheet material transport device according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a transport roller device of a sheet material transport device according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a cross-sectional configuration of a main part of the sheet material conveying device.

FIG. 7 is a diagram illustrating a transport roller device of the sheet material transport device.

FIG. 8 is a diagram illustrating a registration roller device of the sheet material conveying device.

FIG. 9 is a diagram illustrating an initial state of loop formation of the sheet material conveying device.

FIG. 10 is a diagram illustrating a completed state of the loop formation of the sheet conveying apparatus.

FIG. 11 is a diagram illustrating a state in which a sheet material is being conveyed by a registration roller device of the sheet material conveying device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing device 2 registration roller device (transport roller pair) 3 paper feed device 4 transport roller device (transport means) 5 paper feed device 6 drum 7 transfer roller 8 upper transfer guide 9 lower transfer guide 10 cartridge 11 mechanical shutter (shutter means) 12 Driven roller 13 Drive roller 14a Upstream guide before registration 14b Downstream guide before registration 14c Intrusion guide before registration 14d Inner guide before registration 15 Paper feed roller 16 Paper feed plate 17 Separation pad 18 Driven roller 19 Drive roller 20 Feed roller 21 Retard roller 22 Torque limiter Reference Signs List 23 Rotary shaft of drive roller 24 Rotary shaft of driven roller 25 Coil spring 26 Electromagnetic clutch 27 Input gear 28 Output shaft 29 Output gear 30 One-way clutch 31 Rigid plate material 32 Mold material 33 Rotary shaft of driven roller 34 Drive low Rotary shaft 35 coil spring 36 input gear

Claims (8)

[Claims] A conveying roller pair having a nip portion disposed on a conveying path of the sheet material, and abutting against a leading end portion of the sheet material to enter the nip portion, and stopping the sheet material with a predetermined stopping force. Shutter means having a contact portion that retreats from the conveyance path by the conveyance force of the abutted sheet material, and conveyance means for conveying the sheet material toward the conveyance roller pair, The sheet material conveyance speed of the conveyance means is the same as or smaller than the sheet material conveyance speed of the conveyance roller pair, and the conveyance roller pair and the conveyance means are used until the rear end of the sheet material passes through the conveyance means. A sheet material conveying device set at a speed capable of maintaining a loop of a sheet material formed therebetween. 2. A first conveying means which is rotated in a conveying direction via a clutch means and conveys a sheet material between the driving means and a driving source, and which is transmitted from the first conveying means via a driving force transmitting means. A second conveying means for conveying the sheet material by a driving force applied to the sheet material, and the driving force transmitting means is provided with a second conveying means for conveying the sheet material from the first conveying means rotated in a direction opposite to the conveying direction. A sheet material transport device comprising one-way clutch means for interrupting a reverse driving force. 3. The sheet conveying apparatus according to claim 2, wherein the clutch unit and the one-way clutch unit are arranged coaxially with a drive shaft of the first conveying unit. 4. A sheet material conveying apparatus comprising: conveying means having a conveying roller that is driven to rotate and a driven roller that is in pressure contact with the conveying roller, wherein the sheet material conveyed by the conveying means forms a loop. The sheet material conveyance according to claim 1, wherein the diameter of at least one of the conveyance roller and the driven roller is set to be larger in the axial direction at an end side than at a center side of the sheet material to be conveyed. apparatus. 5. A sheet conveying apparatus according to claim 4, wherein a plurality of said conveying means are arranged coaxially substantially orthogonal to a conveying direction on a conveying path of the sheet. 6. A sheet material conveying device, wherein a matting process is performed on a guide member constituting a sheet material conveying path. 7. The sheet conveying apparatus according to claim 6, wherein the guide member is a sheet metal member plated with black. 8. A sheet conveying apparatus according to claim 1, further comprising: an image forming unit configured to form an image on a sheet conveyed by the sheet conveying apparatus. Image forming apparatus.