JPH1159952A - Recording material carrying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably carry a recording material even when the carrying direction of the recording material is deviated in a method wherein a part or a whole of a nip part of roll pairs is releasing on this side in the carrying direction to the roll pairs when a tip of the recording material reaches the nip part of a certain roll pairs. SOLUTION: A recording material is held by nip parts of a plurality of roll pairs 73a-73c, 72a-72c, 71, 78, and the recording material is successively carried from recording material trays 75a-75c storing the recording material to transfer roll pairs 78 to transfer the toner image held on an intermediate transfer belt on the recording material by rotating a plurality of roll pairs. When the tip of the recording material reaches the transfer roll pairs 78, a nip releasing means is controlled so as to release a part of or a whole of nip parts of the other roll pairs 73a-73c, 72a-72c, 71, 78.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording material conveying device, and more particularly, to a recording material conveying device constituted by a plurality of roll pairs.

[0002]

2. Description of the Related Art Conventionally, there has been a recording material transporting apparatus which sandwiches a recording material between nip portions of a plurality of roll pairs and sequentially transports the recording material by rotating at a predetermined rotation speed. For example, such a recording material conveying apparatus is also used in an electrophotographic image forming apparatus.

The basic structure of an electrophotographic image forming process includes a photosensitive member, a charging device, a developing device, a transfer device, a fixing device, a static eliminator, and a cleaner. In a general image forming process, the surface of the photoconductor is uniformly charged by a charger in a dark place. Next, light is applied to a portion other than the image portion by an exposure device to remove the charged charges in the portion where the light is applied,
An electrostatic latent image with a charge remaining on the image area is formed. In the developing section, a toner, which is colored fine particles charged in the opposite polarity to the electrostatic latent image, is attached to the latent image to form a visible image. Next, a recording material is superimposed on the toner image, a charge having a polarity opposite to that of the toner is applied to the recording material from the back side of the recording material by a corona charger, and the toner image is transferred to the recording material by electrostatic force. The transferred toner image is fused with a recording material by applying heat or pressure to form a permanent image. On the other hand, the latent image charge on the photoreceptor after transfer is eliminated by light. The residual toner remaining on the photoreceptor without being transferred is removed by a cleaner. Image formation is performed continuously by repeating a series of processes from charging to cleaning.

In such an electrophotographic image forming apparatus, one of the functions of the recording material transport device is to transport the recording material from a recording material tray containing the recording material to a pair of transfer rolls at a predetermined transfer timing. is there.

[0005] The image carrier such as a photosensitive drum, a photosensitive belt, an intermediate transfer drum and an intermediate transfer belt holds the toner image transferred to the recording material. When the image carrier is transported to the pair of rolls, it adversely affects the steady position and stable rotation of the image carrier, and as a result, a defect may occur in an image to be formed.

In other words, if the direction of the recording material conveyed by the recording material conveying device does not match the rotational direction of the image carrier, the image carrier may be moved when the recording material enters the transfer roll pair. Force is applied in the direction of the misalignment,
The image carrier moves in that direction. Further, when the speed of the recording material conveyed by the recording material conveyance device does not match the speed of the image carrier, a force for pushing the image carrier or pulling when the recording material enters the transfer roll pair is used. The force acts to displace the position and rotation of the image carrier.

[0007] The displacement of the position and rotation of the image carrier due to the conveyance of the recording material is slight, and there is no major problem in image formation performed with a single color toner such as black and white copy. However, when reproducing a color in which toners of a plurality of colors are sequentially superimposed as in so-called full-color image formation, even a slight shift of one color toner changes the color, resulting in a defective image.
This problem has become a very important problem in today's world, as the electrophotographic full-color image forming apparatus has been widely used in various fields and industries, and the required image quality is increasing.

Conventionally, in order to suppress such displacement of the position and rotation of the image carrier, a shift in the conveying direction of the recording material and a difference in speed between the conveyed recording material and the image carrier are prevented. From the viewpoint, various technologies regarding the recording material conveying device have been proposed.

For example, Japanese Patent Application Laid-Open No. 6-1499 discloses that
A technology has been proposed in which the registration roll is slidably mounted in a direction perpendicular to the recording material transport direction, thereby releasing the recording material stress caused by the deviation of the recording material transport direction and preventing the recording material transport direction from shifting. Have been. Japanese Patent Application Laid-Open No. Hei 5-333662 discloses that a difference in speed between a conveyed recording material and an image carrier is prevented by controlling the conveyance speed of the recording material according to the thickness of the recording material. Technology has been proposed. Further, Japanese Patent Application Laid-Open No. 6-100209 discloses that a loop of a recording material is formed in the middle of a recording material conveyance path, and a stress caused by a deviation in the conveyance direction of the recording material is released in the loop. Techniques for preventing misalignment have been proposed.

[0010]

However, all of these techniques reduce the deviation of the recording material in the conveying direction and the difference between the conveying speed and the speed of the image carrier.
The problem has not yet been completely resolved, and image defects due to color misregistration may still occur. On the other hand, the image quality level required for the electrophotographic full-color image forming apparatus is increasing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. It is an object of the present invention to provide a recording material conveying apparatus which is capable of displacing a recording material in a conveying direction. A recording material transport device capable of stably transporting a recording material even if a difference occurs in the rotation speed of each roll pair constituting the recording material transport device, and the recording material transport device is applied to an image forming device An object of the present invention is to provide a recording material transport device of an image forming apparatus capable of stably supplying an image without a defect such as color shift without causing a change in the position and rotation of the image carrier. .

[0012]

In order to achieve the above object, according to the present invention, a plurality of roll pairs (R1, R2,.
, Rn), the recording material is sandwiched between the nip portions, and the recording material is sequentially conveyed to the end roll pair (Rn) by rotating at a predetermined rotation speed. Nip releasing means for releasing, and when the leading end of the recording material reaches the nip portion of a certain roll pair (Ri), the roll pair (R1,. And a control means having a first function of controlling the nip releasing means so as to release a part or all of the nip portion.

[0013] With such a configuration of the recording material conveying device, even if the recording material conveying device is displaced in the conveying direction or the rotational speed of each pair of rolls constituting the recording material conveying device is different. When the leading end of the recording material reaches one roll pair, the nip portion of the other roll pair is released, so that the recording material can be stably conveyed. Also, by applying the recording material transport device to the image forming apparatus, the nip portion of the roll pair is opened when the leading end of the recording material reaches the transfer roll pair,
Even if there is a deviation in the conveying direction of the recording material or a difference between the conveying speed of the recording material and the speed of the image carrier, the position and rotation of the image carrier should not be changed. As a result, an image free from defects such as color misregistration can be stably supplied.

[0014]

Next, preferred embodiments of the present invention will be described based on examples.

Embodiment 1 FIG. 1 shows a configuration of an example of a recording material conveying device of an image forming apparatus to which the present invention is applied. The recording material transport device includes a plurality of roll pairs 73a-c, 72a-c, 71,
78 (R1, R2,..., Rn), the recording material is sandwiched between the nip portions, and is rotated at a predetermined rotation speed. Nip releasing means for releasing a nip portion of a pair of rolls in a recording material transporting device of an image forming apparatus for sequentially transporting a recording material to a transfer roll pair 78 (Rn) for transferring a toner image held on the recording material to a recording material (Not shown), and when the leading end of the recording material reaches the transfer roll pair (Rn), the other roll pairs (R1, R2,..., Rn)
-1) a control means (not shown) having a first function of controlling the nip releasing means so as to release a part or all of the nip portion.

The roll pairs 73a to 73c are a pair of rolls (R ') which are always nipped, and are hereinafter referred to as "feed roll pairs 73a to 73c". That. The roll pairs 72a-c, 71 capable of releasing the nip are hereinafter referred to as "transport roll pairs 7".
2a-c, 71 ".

FIG. 2 shows the relationship between the control means 2 in this embodiment and the nip release means 1 which is the object of control. Here, the nip releasing means 1 is provided with each transport roll pair 7
This is for releasing the nip portion of 2a-c and 71, for example, the configuration is configured by combining a spring and a solenoid, and the nip portion is released and nipped according to the presence or absence of energization to the solenoid. Such a well-known mechanism can be used. When the leading end of the recording material reaches the transfer roll pair 78, the control means 2 sends a control command to the nip release means 1 to release the nip portions of the transport roll pairs 72a to 72c and 71, and releases the nip. The means releases the nip based on the control command.

Here, the method by which the control means 2 determines that the leading end of the recording material has reached the transfer roll pair 78 is, for example, as follows.
The transfer roll pair may be provided with a sensor for detecting the entry of the recording material, but in the present embodiment, the leading end of the recording material receives the signal from the control unit that controls the process of the entire image forming apparatus, and the leading end of the recording material is transferred. It is determined that the number has reached 78. With such a configuration,
There is no need to provide a new sensor or the like, which is economically advantageous.

Next, the operation of the recording material transporting apparatus when forming a full-color image using four color toners of yellow, magenta, cyan and black will be described, including the operation of the image forming apparatus. First, a yellow toner image (Y) is formed on the photosensitive drum 80 rotating in the direction shown in FIG. 1 by a known electrophotographic process. The formed toner image (Y) reaches the primary transfer position with the rotation of the photosensitive drum 80, and is transferred to the intermediate transfer belt 77 by the primary transfer roll pair 81.

When the primary transfer position is reached again with the rotation of the intermediate transfer belt 77, the magenta toner image (M) is primary-transferred onto the yellow toner image (Y). Hereinafter, similarly, the cyan toner image (C) and the black toner image (Bk) are superimposed on the intermediate transfer belt 77 to form a full-color toner image (YMCBk).
When the leading end of the full-color toner image (YMCBk) approaches the (secondary) transfer roll pair 78, the transfer roll pair 78 which has been opened up to that time forms a nip at a predetermined timing, and further records from the recording material tray. The material is conveyed to the (secondary) transfer roll pair 78 at a predetermined timing, and the (secondary) transfer roll pair 78 transfers the (secondary) full-color toner image (YMCBk) from the intermediate transfer belt 77 to the recording material. Is done.

In this embodiment, when a full-color image is formed, the nip of all the roll pairs 71 and 72a-c is released when the leading end of the recording material reaches the (secondary) transfer roll pair 78. Is what you do. Here, in the present embodiment, when forming an image with a single color toner such as a black and white copy, nip release is not performed. This is because there is no room for color misregistration in single-color image formation, and there is no major problem in image quality even with a conventional recording material transport apparatus.

Next, the recording material enters the (secondary) transfer roll pair 78 and the nip between the roll pairs 71 and 72a-c is released.
Further, the timing of the (primary) transfer from the yellow, magenta, cyan, and black photosensitive drums 80 to the intermediate transfer belt 77 will be described with reference to the timing chart of FIG.

At time T, the leading end of the recording material conveyed from the recording material tray 75 reaches the (secondary) transfer roll pair 78. Then, the control means 2 generates a control signal for releasing the nip to the nip releasing means 1. The nib releasing means 1 receiving the signal releases the nip portion of the roll pair, and the nip portions of all the roll pairs 71, 72a to 72c are released.

As described above, when the recording material reaches the (secondary) transfer roll pair 78, the nip portions of all the roll pairs 71 and 72a to 72c are released, thereby causing a shift in the recording material conveyance direction. However, the rotation of the transport roll while nipping the recording material prevents the recording material from being pushed into the intermediate transfer belt in the deviated direction, and the difference between the transport speed of the recording material and the speed of the image carrier. Even when the recording material is nipped, the transport roll rotates while the recording material is nipped, so that the recording material is not pushed or pulled into the intermediate transfer belt 77, and the position and rotation of the intermediate transfer belt 77 are not changed, and As a result, an image free from defects such as color misregistration can be supplied stably.

FIG. 3 also shows the timing of the (primary) transfer from the photosensitive drums 80 of yellow, magenta, cyan, and black to the intermediate transfer belt 77. That is, in the present embodiment, the timing of the primary transfer of the black toner image (Bk) partially overlaps the timing of the recording material entering the (secondary) transfer roll pair 78. This is because a full-color toner image (YMCBk) is formed from the primary transfer position to the secondary transfer position on the intermediate transfer belt 77, and a (secondary) transfer roll pair 78 is formed from the leading end of the toner image (YMCBk). Indicates that the (primary) transfer in which the black toner image (Bk) is superimposed on the yellow, magenta, and cyan toner images (YMC) is performed at the primary transfer position even when the toner image is transferred onto the recording material. . Therefore, when the nip portion of the roll pair 78 is not released as in the related art, the recording material is shifted or the intermediate transfer belt 7 is not moved.
7 enters the (secondary) transfer roll pair 78 with a difference in speed with respect to 7, causing fluctuations in the position and rotation of the intermediate transfer belt 77, resulting in defective images such as color misregistration. However, such a defective image does not occur in this embodiment.

In this embodiment, the toner images of a plurality of colors formed on the photosensitive drum 80 are sequentially stacked (primarily) transferred onto the intermediate transfer belt 77 and then collectively applied to the recording material (secondary). Although the recording material conveying device of the image forming apparatus that forms a color image by transferring is described as an example, the present invention is not limited to this.
An image forming apparatus that forms a color image by laminating and developing a plurality of color toner images on a belt-shaped photosensitive member and transferring the toner images collectively to the recording material, and after adsorbing or holding the recording material on a transfer drum An image forming apparatus for forming a color image by stacking and transferring toner images of a plurality of colors on a recording material, an image having a plurality of photoconductors, and forming a color image by sequentially transferring the toner images to the recording material Forming device, having a plurality of photoconductors, sequentially transferring (primary) toner images of a plurality of colors to an intermediate transfer belt, and then transferring the images (secondary) collectively to a recording material to form a color image Even when the present invention is applied to a recording material transporting apparatus such as an image forming apparatus, the effect of preventing color misregistration can be similarly exerted.

However, in the recording material conveying apparatus according to the present embodiment, the recording material is discharged from the recording material trays 75a to 75c by the feed roll pairs 73a to 73c which are always nipped. The size of the recording material that can be stored in the trays 75a to 75c is limited.

That is, as shown in FIG. 4A, when the leading end of the conveyed recording material reaches the (secondary) transfer roll pair 78, the rear end of the recording material is nipped by the feed roll pair 73. If not, there is no problem.
In the state where the rear end of the recording material is still nipped by the feed roll pair 73 as shown in FIG.
Even if the nip portions a to c are released, the effects of the present invention described above cannot be achieved. On the other hand, the roll pair 71, 72
It is conceivable that the nip portion of the feed roll pair 73 is also released in accordance with the timing of releasing the nip portions a to c. However, if the nip portion of the feed roll pair 73 is released, double feeding of the recording material may be caused. Not valid.

Therefore, the length of the recording material accommodated in each recording material tray in the transport direction must be shorter than the length of the transport path from the feed roll pair 73 to the (secondary) transfer roll pair 78. Thus, each recording material tray 75a
If the size of the recording material that can be accommodated in the recording material is limited, the state shown in FIG. 4A is always obtained, and when the leading end of the recording material reaches the (secondary) transfer roll pair 78, Since the rear end of the recording material is conveyed away from the feed roll pair 73, the effects of the present invention can be obtained.

For example, the length La of the transport path from the feed roll pair 73a to the (secondary) transfer roll pair 78 is 2
If 57 [mm] <La <297 [mm], the length of the recording material that can be stored in the recording material tray 75a in the transport direction is shorter than that, that is, A5SEF, A5
It is necessary to limit to 4LEF, A5LEF and the like. Similar restrictions are imposed on recording materials that can be stored in the recording material trays 75b and 75c.

That is, the recording 7 is transferred to the recording material tray 75a by the feed roll pairs 73a to 73c which are always nipping.
, The recording material to be stored in each recording material tray needs to satisfy such conditions.

In this embodiment, the case where the recording material conveying apparatus according to the present invention is applied to an electrophotographic image forming apparatus is shown, but the scope of the present invention is not limited to this. A recording material conveying device that sandwiches the recording material between the nip portions of a plurality of roll pairs and sequentially conveys the recording material to a terminal roll pair by rotating at a predetermined rotation speed, for example, a recording material conveying device for printing This also enables stable conveyance of the recording material.

Embodiment 2 The recording material transporting apparatus according to the present embodiment can provide the same effects as the recording material transporting apparatus described in Embodiment 1, and further has the recording effect described in Embodiment 1. It compensates for the shortcomings of the material transport device. That is, the present invention proposes a recording material transport device that can exhibit the effects of the recording material transport device described in the first embodiment without limiting the size of the recording material accommodated in each recording material tray. FIG. 5 shows a configuration of the recording material transporting apparatus according to the present embodiment. Here, the same components as those described in the first embodiment are denoted by the same reference numerals, and description of the configuration and operation will be omitted.

The recording material transporting device according to the present embodiment is, in addition to the configuration of the recording material transporting device according to the first embodiment, provided between the recording material tray and the pair of transfer rolls to temporarily transfer the recording material to the recording material tray. And a path selecting means 4 for selecting whether or not to convey the recording material to the pair of transfer rolls via the switchback conveying path 3.
And a rotation switching means (not shown) for switching the rotation direction of the pair of rolls, in which the recording material is discharged from the recording material tray by the feed roll pairs 73a to 73c which are always nipped. If the length of the recording material accommodated in the material tray in the conveyance direction is longer than the length of the conveyance path from the pair of rolls 73a to 73c to the pair of transfer rolls, the recording material is transferred to the transfer roll via the switchback conveyance path. It has a second function of controlling the path selection means 4 and the rotation switching means so as to convey the pair.

The switchback transport path 3 is provided between the recording material tray and the pair of (secondary) transfer rolls, and is for temporarily discharging the recording material out of the recording material tray.
The provision of the switchback transport path 3 ensures that the recording material is discharged out of the recording material tray and is released from the nip formed by the pair of feed rolls 73a to 73c. Further, the discharged recording material can be made less likely to be caught by other components of the image forming apparatus or to cause a jam.

FIG. 6 shows the relationship between the control means 2 in this embodiment and the nip release means 1, the path selection means 4, and the rotation switching means 5 which are the objects of control. The path selection means 4 selects whether or not to convey the recording material discharged from the recording material tray to the (secondary) transfer roll pair via the previous switchback conveyance path 3. It can be configured by rotating a member that can open or close the entrance of the device. The rotation switching means 5 switches the direction of rotation of the rolls of the transport roll pairs 72a to 72c. The control unit 2 can determine in advance whether or not the recording material is discharged from the recording material tray by the feed roll pairs 73a to 73c which are always nipped, depending on the configuration of the image forming apparatus. In addition, the length of the recording material accommodated in each of the recording material trays 75a to 75c in the transport direction is controlled because a sensor for detecting the size of the recording material accommodated in the ordinary recording material trays 75a to 75c is provided. Means 2 can know it. further,
The length of the transport path from the pair of rolls 73a to 73c to the pair of transfer rolls 78 can be known in advance in designing the image forming apparatus. Therefore, the control means can determine the length of the two lengths from these facts.

Hereinafter, a case where the length of the recording material accommodated in the recording material tray a in the conveyance direction is longer than the length of the conveyance path from the pair of rolls 73a to the pair of transfer rolls 78, and The operation of the recording material conveying apparatus according to the present embodiment when forming an image will be described with reference to FIG.

First, as shown in FIG.
The recording material conveyed from 5a by the feed roll pair 73a is conveyed upward by the roll pair 72a.
Here, the control means 2 sends a control command to the route selecting means 4 so as to open the inlet to the switchback path, and the route selecting means 4 opens the inlet. Then, the recording material once enters the switchback path by the feed roll 73a and the roll pair 72a (see the arrow). And
At a certain timing until the rear end of the recording material passes through the feed roll 73a and reaches the roll pair 72a, the roll pair 7
Control means 2 so that the rotation directions of 2a to 2c are reversed.
Transmits a control command to the rotation switching means 5,
Switches its rotation. Then, the recording material is discharged from the switchback conveyance path (see the arrow).

The recording material is directly transferred to a pair of transport rolls 72a to 72a.
While being held at c, the paper is conveyed backward in the lower part of the figure (see the arrow), and the tip ends out of the switchback conveyance path. FIG. 7B shows this state. Next, the control means 2 sends a control command to the path selecting means 4 so as to close the inlet to the switchback path, and the path selecting means 4 closes the inlet. Then, the control means 2 transmits a control command to the rotation switching means 5 so that the rotation directions of the roll pairs 72a to 72c are further reversed, and the rotation switching means 5 switches the rotation. Then, the recording material is conveyed upward in the figure (see arrow), and is conveyed to the transfer roll pair 78 through a normal conveyance path as shown in FIG. 7C (see arrow). The subsequent control such as the release of the nip between the pair of transport rolls 71 and 72a to 72c is the same as that in the first embodiment.

By performing such an operation, it is possible to stably supply an image free from image defects such as color misregistration without restricting the size of the recording material accommodated in each recording material tray. In addition, when forming an image using a single color toner such as a black and white copy, it is unlikely that a problem occurs in the image quality, so that the above-described operation is not required, and the speed of the image forming apparatus is impaired. Nor. Further, even when full-color image formation is performed, a plurality of color toner images are formed on an image carrier such as a photoconductor or an intermediate transfer body as in this embodiment, and the toner images are collectively transferred to a recording material. When the recording material transporting apparatus according to the present invention is applied to such an image forming apparatus, the speed of image formation can be reduced by performing the previous switchback operation while the toner image is held on the image carrier one by one. Does not hurt.

Embodiment 3 The recording material conveying apparatus according to the present embodiment can provide the same effects as the recording material conveying apparatus described in Embodiment 2, and further has the recording effect described in Embodiment 2. An object of the present invention is to provide a recording material transporting device that can be manufactured more economically and advantageously than a material transporting device. FIG. 8 illustrates a configuration of the recording material transporting apparatus according to the present embodiment. Here, the same components as those of the recording material conveying apparatus described in the first and second embodiments are denoted by the same reference numerals, and the description of the configuration and operation will be omitted.

The recording material transporting apparatus according to the present embodiment is provided between the recording material tray and the transfer roll pair, in addition to the configuration of the recording material transporting apparatus described in the first embodiment, and temporarily records the recording material. A recording material reversing device 6 that can be discharged out of the tray and inverts the recording material, and a path selecting unit that selects whether or not to convey the recording material to the transfer roll pair via the recording material reversing device The control means 2 controls the conveying direction of the recording material accommodated in each recording material tray when the recording material is discharged from the recording material tray by the feed roll pairs 73a to 73c which are always nipped. If the length is longer than the length of the transport path from the pair of rolls 73 a to 73 c to the pair of transfer rolls 78, the recording material is transferred to the recording material reversing device 6.
And has a third function of controlling the path selecting means 4 so as to convey it to the transfer roll pair 78 via

Here, the recording material reversing device 6 comprises a recording material reversing path 61 and a pair of reversing rolls 62 and is usually provided after the secondary transfer of the image forming apparatus.
In the present invention, it is provided from the recording material trays 75a to 75c to the transfer roll pair 78. Further, the rotation of the rolls of the pair of reversing rolls can be switched.

FIG. 9 shows the relationship between the control means 2 and the nip releasing means 1 and the route selecting means 4 to be controlled in this embodiment. The control of the nip releasing means is shown in the embodiment. In the first embodiment, since the control of the route selecting means 4 has been described in the second embodiment, the description thereof is omitted here.

Hereinafter, the case where the length of the recording material accommodated in the recording material tray a in the conveyance direction is longer than the length of the conveyance path from the roll pair 73a to the transfer roll pair 78, and the recording material The operation of the recording material conveying apparatus according to the present embodiment when forming an image will be described with reference to FIG. The operation of the recording material reversing device at this time is the same as the operation at the time of normal double-sided image formation.

As shown in FIG. 10A, the length of the recording material accommodated in the recording material tray a in the transport direction is the roll pair 73a.
When the control unit 2 determines that the recording material is to be full-color image-formed when the length is longer than the length of the conveyance path from the transfer roller pair 78 to the transfer roll pair 78, the control unit 2 Is transmitted to the route selecting means 4 so as to open the opening, and the route selecting means 4 opens the inlet. Then, the recording material is fed roll 73a, roll pair 7
2a, once enter the recording material reversing device 6 by the reversing roll pair 62 (see arrow). Then, at a certain timing after the rear end of the recording material passes through the feed roll 73a and further passes through the path selecting means 4, the reversing roll pair 6
The rotation direction of 2 is reversed.

At the same time, as shown in FIG. 10B, the path selecting means 4 closes the inlet of the recording material reversing device 6, and the recording material is transferred 78 while being held by the transport roll pair 71 and the reversing roll pair 62. Transported to Thereafter, when the recording material reaches the transfer roll pair 78, the control for releasing the nip portion of the roll pair is the same as in the first embodiment. However, in this embodiment, the recording is performed when the k material reaches the transfer roll. What holds the material
There are a transport roll pair 71 and a reversing roll pair 62.
The difference is that if the nip portion of one roll pair is released, the effect described in the first embodiment can be obtained.

The following effects can be obtained by using the recording material conveying device having such a configuration. First, when the leading end of the recording material reaches the (secondary) transfer roll pair, the nip portion between the transport roll pair 71 and the reversing roll pair 62 is released, so that an image free from image defects such as color misregistration is stably supplied. be able to. Further, in order to discharge the recording material from the recording material tray and hold the recording material in the recording material reversing device, it is necessary to limit the size of the recording material accommodated in each recording material tray as in the recording material transport device according to the first embodiment. Absent. Further, the recording material reversing device is provided in many image forming apparatuses, and the above-described effect can be obtained only by changing the installation location, which is economically advantageous. Further, when the leading end of the recording material reaches the transfer roll pair 78, only the transport roll pair 71 and the reversing roll pair hold the recording material.
And many transport roll pairs 71 and 72a to
It is economically advantageous because c does not need to have the nip release means 1 respectively. Further, the recording material reversing device has a structure for switching the direction of rotation of the reversing roll in the first place, and as in the second embodiment, the recording material reversing device further includes a rotation switching unit 5 for each of the plurality of transport roll pairs 72a to 72c. There is no need, which is economically advantageous.

[0049]

As described above, according to the first aspect of the present invention, even if there is a deviation in the conveying direction of the recording material, the rotational speed of each pair of rolls constituting the recording material conveying device can be reduced. Provided is a recording material transporting device that can stably transport a recording material because a nip portion of another roll pair is released when the leading end of the recording material reaches one roll pair even if a difference occurs. be able to.

According to the second aspect of the present invention, the nip portion of the pair of rolls is opened when the leading end of the recording material reaches the pair of transfer rolls.
Further, even if a difference between the conveyance speed of the recording material and the speed of the image carrier occurs, it is possible to prevent the position and rotation of the image carrier from fluctuating. It is possible to provide a recording material transporting device of an image forming apparatus that stably supplies an image free from defects.

According to the third aspect of the present invention, even when the recording material is conveyed from the recording material tray to the transfer roll pair by the feed roll which is always nipped, the recording accommodated in each recording material tray is performed. By limiting the size of the recording material, it is possible to provide a recording material conveying device of an image forming apparatus capable of achieving the effects of the invention described in claim 1.

According to the fourth aspect of the present invention, the recording material is temporarily discharged from the recording material tray via the switchback conveyance path and then conveyed to the pair of transfer rolls. It is possible to provide a recording material transport device of an image forming apparatus capable of achieving the effects of the invention described in claim 2 without limiting the size of the material.

According to the fifth aspect of the invention, by providing the recording material reversing device of many image forming apparatuses between the recording material tray and the transfer roll pair, it is economically advantageous. Moreover, it is possible to provide a recording material transport device of an image forming apparatus capable of achieving the effect of the invention described in claim 2 without limiting the size of the recording material accommodated in each recording material tray.

[Brief description of the drawings]

FIG. 1 illustrates a configuration of a recording material conveying device of an image forming apparatus according to a first embodiment.

FIG. 2 is a block diagram illustrating a relationship between a control unit and a control target according to the first embodiment;

FIG. 3 is a timing chart illustrating the timing of full-color image formation in the image forming apparatus to which the recording material conveying apparatus according to the first embodiment is applied.

FIG. 4 is a diagram illustrating a problem that may occur depending on the size of a recording material.

FIG. 5 illustrates a configuration of a recording material conveying device of the image forming apparatus according to the second embodiment.

FIG. 6 is a block diagram illustrating a relationship between a control unit and a control target according to the second embodiment.

FIG. 7 is a diagram for explaining the operation of the recording material conveying device of the image forming apparatus according to the second embodiment;

FIG. 8 illustrates a configuration of a recording material conveying device of an image forming apparatus according to a third embodiment.

FIG. 9 is a block diagram illustrating a relationship between a control unit and a control target according to the first embodiment.

FIG. 10 is a diagram for explaining an operation of the recording material conveying device of the image forming apparatus according to the third embodiment;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nip release means, 2 ... Control means, 3 ... Switch back conveyance path, 4 ... Path selection means, 5 ... Rotation switching means, 6 ... Recording material reversing device

(72) Inventor Satoshi Fukada 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Shuji Iseki 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd.

Claims (5)

[Claims] A plurality of roll pairs (R1, R2,..., R
n), the recording material is sandwiched between the nip portions, and the recording material is rotated at a predetermined rotation speed to thereby rotate the recording material to the end roll pair (R
n) a nip releasing means for releasing the nip portion of each roll pair; and a roll pair when the leading end of the recording material reaches the nip portion of a certain roll pair (Ri). (Ri) control means having a first function of controlling the nip release means so as to release a part or all of the nip portion of the roll pair (R1,..., Ri-1) before the transport direction. A recording material transporting device. 2. A plurality of roll pairs (R1, R2,..., R
n) a pair of transfer rolls for transferring the toner image held on the image carrier from the recording material tray containing the recording material to the recording material by rotating the recording material at a predetermined rotation speed by sandwiching the recording material in the nip portion; A nip release means for releasing a nip portion of a roll pair in a recording material transport device of an image forming apparatus for sequentially transporting a recording material to (Rn); , A control means having a first function of controlling the nip releasing means so as to release a nip part or all of the other roll pairs (R1, R2,..., Rn-1). A recording material conveying device for an image forming apparatus, comprising: 3. Roll pair (R ') which is always nipped
When the recording material is discharged from the recording material tray, the length of the recording material contained in each recording material tray in the transport direction is determined by the length of the transport path from the roll pair (R ′) to the transfer roll pair (Rn). 3. The recording material transporting device of the image forming apparatus according to claim 2, wherein the length is limited to be shorter than the length. 4. A switchback conveyance path which is provided between the recording material tray and the transfer roll pair, and temporarily discharges the recording material out of the recording material tray, and a recording material via the switchback conveyance path. A path selection unit for selecting whether or not to convey the recording material to the transfer roll pair; and a rotation switching unit for switching the rotation direction of the roll pair. The control unit controls the recording material by a roll pair (R ′) that is always nipped. In the case where the recording material is discharged from the tray, the length of the recording material accommodated in each recording material tray in the transport direction is longer than the length of the transport path from the roll pair (R ′) to the transfer roll pair (Rn). A second function of controlling the path selection means and the rotation switching means so as to convey the recording material to the transfer roll pair via the switchback conveyance path when the recording material is long. Item 2 Recording material conveying device of the image forming apparatus. 5. A recording material reversing device which is installed between a recording material tray and a transfer roll pair, and which can once discharge a recording material out of the recording material tray and reverses the recording material. Path selecting means for selecting whether or not to convey to the transfer roll pair via the recording material reversing device, wherein the control means records from the recording material tray by the roll pair (R ') which is always nipped. When the recording material is ejected and the length of the recording material accommodated in each recording material tray in the transport direction is longer than the length of the transport path from the roll pair (R ′) to the transfer roll pair (Rn). 3. The apparatus according to claim 2, further comprising a third function of controlling the path selecting means so as to convey the recording material to the transfer roll pair via the recording material reversing device.
3. A recording material transport device for an image forming apparatus according to claim 1.