JP7187803B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art Japanese Patent Laid-Open Nos. 2002-300001 and 2003-200020 disclose, for example, the following technologies related to paper feeding in which a sheet is conveyed by passing through impingement rolls, which are generally called registration rolls, registration rollers, or the like. are known.

In Patent Document 1, a registration roller is arranged in a transfer path of a transfer sheet, and a first transfer roller is arranged upstream of the registration roller and substantially in the center in the width direction of the transfer sheet conveyed on a support shaft. and a second transport roller arranged upstream of the first transport roller and releasing the transfer paper from a state in which the transfer paper is sandwiched when the transfer paper is slackened before the registration roller. In the second transport roller, when the transfer paper is slackened in front of the registration roller, the length of the transfer paper in the transport direction is short, and even if the transfer paper contacts the registration roller, the end of the transfer paper is When the transfer paper is not sandwiched between the second rollers, it is in a pressure holding state, and even if the length of the transfer paper in the conveying direction is long and the transfer paper comes into contact with the registration rollers, the end of the transfer paper is sandwiched between the second rollers. In some cases, there is described a paper conveying device provided with pressurizing means for releasing the transfer paper from the sandwiched state.

Japanese Patent Application Laid-Open No. 2002-200001 discloses a paper feed unit that feeds paper, a first paper detection sensor provided downstream of the paper feed unit, a loop forming roller that forms a loop in the fed paper, and a image forming unit for forming an image on the paper; a second paper detection sensor provided near the registration roller; The forming apparatus has control means for controlling whether or not to temporarily stop the paper based on determination of whether or not the paper reaches the first paper detection sensor after a predetermined time has passed since the paper feeding means started to feed the paper. , the control means measures the arrival time from the start of paper feeding to the second paper detection sensor when the paper is temporarily stopped, and corrects the time of the temporary stop based on the arrival time. is described.

Japanese Patent No. 3749778 Japanese Patent Application Laid-Open No. 2005-314020

In the present invention, paper supplied from a supply roll that feeds and supplies paper stored in a storage section is conveyed to a pair of impingement rolls via a pair of transport rolls, and the front end of the paper is conveyed to the impingement rolls. When sending to the image forming section after the abutment, the operation to relatively reduce the contact pressure of the transport rolls for all the sheets whose leading edge is in contact with the impingement rolls while being sandwiched by the transport rolls is performed each time An object of the present invention is to provide an image forming apparatus capable of efficiently suppressing oblique feeding of paper on an impingement roll compared to a conventional image forming apparatus.

The image forming apparatus of this invention (A1) is
an image forming unit that forms an image on paper;
a storage unit that stacks and stores sheets to be supplied to the image forming unit;
a supply roll that feeds and supplies the paper stored in the storage unit;
a pair of abutment rolls that abut the leading edge of the paper supplied from the supply roll and then send the sheet to the image forming unit;
a pair of transport rolls arranged in a paper transport path connecting between the storage section and the impingement roll, and transporting the paper supplied from the supply roll toward the impingement roll;
changing means for changing the contact pressure of the contacting portions of the pair of transport rolls;
with
A plurality of the transport rolls are arranged on the transport path,
Among the plurality of transport rolls, the transport roll arranged closest to at least the supply roll has a contact pressure at a normal time of the contact pressure, which is a first contact when a sheet other than a specific type is supplied. is set to a second contact pressure lower than the pressure,
The changing means changes the contact pressure of at least the transport roll arranged closest to the supply roll from the second contact pressure to the second contact pressure when paper other than the specific type is supplied as the paper. 1 contact pressure.

The image forming apparatus of this invention (A2) is the image forming apparatus of the above invention A1, wherein the specific type of paper has a basis weight within a predetermined numerical range and a transport direction length equal to or greater than a predetermined value. and/or at least one of

The image forming apparatus of the present invention (A 3 ) is the image forming apparatus of the above invention A1 or A2 , further comprising measuring means for measuring a transport speed when the supply roll feeds the paper and supplies it to the transport roll; adjusting means for adjusting the rotation speed of the supply roll so as to approach a preset conveying speed according to the measurement result of the means.
The image forming apparatus of this invention ( A4) is the image forming apparatus of the above invention A3 , wherein the measuring means has a plurality of detecting means for detecting passage of the leading edge of the paper, and the plurality of detecting means comprise the above-described They are arranged in a line with a gap in the paper transport direction in the section from the supply roll of the transport path to the first transport roll.

According to the image forming apparatus of the invention A1, the paper supplied from the supply roll that feeds and supplies the paper stored in the storage unit is transported to the pair of abutment rolls via the pair of transport rolls, When the leading edge of the paper hits the impingement roll and is sent to the image forming section, the contact pressure of the transport roll is relatively applied to all of the paper whose leading edge is in contact with the impingement roll while being sandwiched between the transport rolls. It is possible to efficiently suppress the skewed feeding of the paper on the impingement roll compared to the case where the reduction operation is performed each time. Further, according to the image forming apparatus of the invention A1, compared to the case where the contact pressure of at least the transport roll arranged closest to the supply roll among the plurality of transport rolls is not changed, the amount of paper on the impingement roll is reduced. Oblique feeding can be suppressed.

According to the image forming apparatus of the invention A2, the paper supplied from the supply roll that feeds and supplies the paper stored in the storage unit is conveyed to the pair of abutment rolls via the pair of transport rolls, and the When sending the paper to the image forming section after the leading edge of the paper hits the impingement roll, the contact pressure of the transport roll is relatively reduced for all the paper whose leading edge is in contact with the impingement roll while being sandwiched between the transport rolls. It is possible to efficiently suppress the skewed feeding of the paper on the impingement roll compared to the case of performing the operation for each time .

According to the image forming apparatus of the invention A3 , the contact pressure of the conveying roll is set to the second contact pressure lower than the first contact pressure by the changing means, compared with the case where the measuring means and the adjusting means are not provided. Even if it is changed, the paper can be transported from the supply roll to the first transport roll in a stable time.
According to the image forming apparatus of invention A4, compared to the case where the paper transport speed is not calculated from the time required for passing through the above two points, the paper is transported from the supply roll to the first transport roll in a more stable time. can be transported.

1 is a conceptual diagram showing a configuration of an image forming apparatus according to Embodiment 1 and the like; FIG. 2 is a conceptual diagram showing a configuration of part of the image forming apparatus of FIG. 1; FIG. (a) is a conceptual diagram showing the configuration and state of the change means and the transport rolls set to the first contact pressure, and (b) is the configuration and state of the change means and the transport rolls set to the second contact pressure. It is a conceptual diagram showing. 4 is a flow chart showing the operation of a changing means according to Embodiment 1. FIG. FIG. 2 is a conceptual diagram showing a state in which oblique feeding of an impingement roll is suppressed even when a specific type of paper is conveyed in an oblique state in the image forming apparatus of FIG. 1 ; 4 is a conceptual diagram showing a modification of the image forming apparatus according to Embodiment 1; FIG. 6 is a conceptual diagram showing a partial configuration of an image forming apparatus according to Embodiment 2; FIG. 8 is a conceptual diagram showing a modification of the image forming apparatus according to Embodiment 2; FIG. 10 is a flow chart showing the operation of a changing unit in the image forming apparatus according to Embodiment 3; FIG. 10 is a conceptual diagram showing skewed feed of an impingement roll that occurs when a sheet is conveyed in an obliquely inclined state in an image forming apparatus for comparison;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[Embodiment 1]
1 and 2 show an image forming apparatus according to Embodiment 1. FIG. FIG. 1 shows the overall configuration of the image forming apparatus, and FIG. 2 shows the configuration of a part of the image forming apparatus (conveyance route from the sheet containing section to the image forming section).
Arrows indicated by symbols X, Y, and Z in each drawing indicate directions of width, height, and depth of a three-dimensional space assumed in each drawing. In addition, in FIGS. 1, 2, etc., the circle mark at the portion where the arrows in the X and Y directions intersect indicates that the Z direction is vertically downward in the drawings.

<Configuration of Image Forming Apparatus>
As shown in FIG. 1, the image forming apparatus 1 according to the first embodiment includes an image forming unit 2 for forming an image on a sheet 9 based on image information, and an image forming unit 2 in the internal space of the housing 10. It is provided with a storage section 4 that stacks and stores the sheets 9 to be supplied, and a transport section 5 that transports the sheets 9 through a required transport path.
Here, the image information is, for example, information related to images such as characters, graphics, photographs, and patterns. The housing 10 is a structure formed into a desired shape by various support members, exterior materials, and the like. The housing 10 has a discharge/receiving section 12 formed on a part of the upper surface thereof, in which the sheets 9 to be discharged after the image is formed are stacked and stored.

The image forming unit 2 is configured as an electrophotographic image forming unit that forms an image made of a developer on a sheet of paper 9 . The image forming unit 2 includes an image forming unit 20 that creates an unfixed image (toner image) made of developer based on image information and transfers it onto a sheet of paper 9 , and an unfixed image that has been transferred by the image forming unit 20 . A fixing section 35 for fixing the toner image on the paper 9 is provided.

Among them, the imaging unit 20 includes a charging device 22, an exposure device 23, a developing device 24, a transfer device 25, a cleaning device 26, and the like around a photosensitive drum 21, which is a drum-shaped photosensitive body that rotates in the direction indicated by the arrow. It is a part configured by arranging devices. In the image forming section 20, a portion where the photosensitive drum 21 and the transfer device 25 contact or face each other becomes a transfer position TP where the paper 9 is passed and the toner image is transferred.

In addition, the fixing unit 35 includes a heating rotator 37 that rotates in the direction indicated by the arrow, a pressurizing rotator 38 that contacts the heating rotator 37 under pressure and is driven to rotate, and the like. It is a part configured by arranging devices. In the fixing section 35, the portion where the heating rotator 37 and the pressure rotator 38 come into contact is a fixing processing section (fixing section) that passes the sheet 9 onto which the toner image has been transferred and performs fixing processing such as heating and pressing. Nip) becomes FN.

The accommodation portion 4 includes three accommodation portions, for example, a first accommodation portion 4A, a second accommodation portion 4B, and a third accommodation portion 4C.

Both the first accommodation portion 4A and the second accommodation portion 4B are cassette-type accommodation portions provided at positions below the image forming portion 2 of the housing 10. 44 and the like are arranged.

Each of the storage cassettes 41 and 42 has stacking plates 41a and 42a for stacking and storing a plurality of sheets of paper 9 in a required direction, and is a storage member attached to the outside of the housing 10 in a state in which it can be pulled out. is. Both of the supply devices 43 and 44 feed the sheets 9 stacked on the stacking plates 41a and 42a of the storage cassettes 41 and 42 one by one from above and supply them toward the image forming section 20 of the image forming section 2. It is a device.
Further, the supply devices 43 and 44 include delivery rolls 43a and 44a for delivering the stacked paper 9 from above, supply rolls 43b and 44b for supplying the paper 9 delivered from the delivery rolls 43a and 44a, and the delivery roll 43a. , 44a are provided with handling rolls 43c, 44c, etc. for handling the plurality of sheets of paper 9 fed out by one sheet.

The third storage section 4C is a tray-type storage section provided outside of the side surface of the housing 10, and is configured by arranging devices such as a storage tray 46 and a supply device 47. As shown in FIG.

The storage tray 46 is also referred to as a so-called manual feed tray, and is a collapsible type that is attached to the outside of the housing 10 so that it can be used in a state of being laid down while stacking and storing a plurality of sheets of paper 9 in a desired direction. is a housing member. The supply device 47 is a device that feeds and supplies the sheets 9 stored on the storage tray 46 one by one from above. The accommodation tray 46 and the supply device 47 are arranged at a position based on the paper entrance 13 provided on one side of the housing 10 .
Further, the supply device 47 is provided with a delivery roll 47a, a supply roll 47b, a handling roll 47c and the like, in substantially the same manner as in the case of the supply devices 43 and 44 described above.

As shown in FIG. 1, the transport section 5 includes the following five transport sections: a first transport section 5A, a relay transport section 5B, a discharge transport section 5C, a second transport section 5D and a third transport section 5E. ing.

The first conveying portion 5A is a conveying portion that forms a conveying path for paper feeding (a path indicated by a dashed-dotted line curve) that connects the first accommodating portion 4A and the registration rolls 51 . The first transport unit 5A includes a pair of transport rolls 53 arranged between (the supply roll 43b of) the supply device 43 of the first storage unit 4A and the registration roll 51, and the paper 9A while securing a transport space for the paper 9A. and a paper guide member (not shown) for guiding the paper.

The relay conveying portion 5B is a conveying portion that forms a relay conveying path that connects between the registration roll 51 and the sheet introduction portion side and inside of the image forming portion 2 . The relay transport section 5B includes a sheet guide member (not shown) arranged between the registration roll 51 and the transfer position TP of the image forming section 20, and a sheet guide member arranged between the image forming section 20 and the fixing section 35. etc.
The discharge transport section 5</b>C is a transport section that forms a transport path for discharge that connects the paper discharge side of the image forming section 2 and the discharge roll 52 . The discharge/conveyance section 5C is composed of a pair of conveyance rolls 54 arranged between the fixing section 35 and the pair of discharge rolls 52, a paper guide member (not shown), and the like.

The second transport section 5D is a transport section that forms a transport path for paper feeding that connects the second storage section 4B and the registration rolls 51 . The second conveying section 5D includes a pair of conveying rolls 55 and 56 arranged between (the supply roll 44b of) the supply device 44 of the second storage section 4B and the confluence portion of the first conveying section 5A; It is composed of a paper guide member (not shown) that guides the paper 9B while forming a transport space for the paper 9B.
The third conveying portion 5E is a conveying portion that forms a conveying path for paper feeding that connects between the third storage portion 4C and the registration rolls 51 . The third conveying portion 5E forms a conveying path that also joins the second conveying portion 5D at a junction J2 located upstream of the junction J1. Further, the third transport section 5E includes a pair of transport rolls 56 arranged between the junction J2 with the second transport section 5D and the junction J1 with the first transport section 5A, and a transport space for the paper 9C. and a paper guide member (not shown) that guides the paper 9C while forming a . The transport roll 56 in the third transport section 5E also serves as one transport roll 56 in the second transport section 5D.

The registration rolls 51 are a pair of protrusions that feed the sheets 9 (A to C) supplied from the storage sections 4A to 4C to the image forming section 2 (the transfer position in the image forming section 20) after abutting the leading edges of the sheets. An example of this roll.
The discharge rolls 52 are a pair of rolls for discharging the paper 9 on which the image is formed from the paper discharge port 14 provided on the side surface of the housing 10 and storing it in the discharge storage section 12 .

The pair of registration rolls 51 is a combination of two rolls, a driving roll that rotates and a driven roll that contacts and rotates following the driving roll. Both the driving roll and the driven roll are composed of a rotating shaft and a plurality of roll bodies fixed to the rotating shaft.
Further, the pair of discharge rolls 52 and the transport rolls 53 and 54 are also a combination of two rolls, a drive roll and a driven roll, in substantially the same manner as the registration roll 51 .

<Image forming operation by image forming apparatus>
In this image forming apparatus 1, an image forming operation is performed as follows.

First, in the image forming apparatus 1, when a control means (not shown) receives a command requesting an image forming operation from an externally connected device or the like, the movable portions such as the image forming section 2, the housing section 4, and the conveying section 5 are operated at the required timing. Start. Here, as a representative example, the operation of forming an image on one side of the paper 9A supplied from the first container 4A will be described.

In the image forming section 2, as shown in FIG. 1, in the image forming section 20, the photosensitive drum 21 starts rotating in the direction indicated by the arrow, and the charging device 22 sets the outer peripheral surface of the photosensitive drum 21 to a desired potential. After charging, the exposing device 23 irradiates the charged outer peripheral surface of the photosensitive drum 21 with light (broken line arrow) corresponding to the image signal subjected to image processing to form an electrostatic latent image. After that, the developing device 24 in the image forming section 20 develops the electrostatic latent image by supplying and adhering toner of a desired color (for example, black) as developer. As a result, a toner image of a desired color is formed on the outer peripheral surface of the photosensitive drum 21 .

On the other hand, in the first conveying section 5A, the sheet 9A stored in the storage cassette 41 of the first storage section 4A is supplied to the image forming section 2 by the feeding device 43 in accordance with the operation timing of the image forming section 20 in the image forming section 2. is supplied toward the transfer position TP of the image forming unit 20 at. At this time, in the first transport unit 5A, after the paper 9A supplied from the first storage unit 4A by the supply device 43 is sent to the registration roll 51 via the transport roll 53, the registration roll 51 feeds it to the image forming unit at a required timing. 20 to the transfer position TP.

Subsequently, in the image forming section 20, the transfer device 25 transfers the toner image formed on the photosensitive drum 21 of the image forming section 20 onto the sheet 9A supplied from the first storage section 4A at the transfer position TP. In the image forming unit 20, the cleaning device 26 removes unnecessary substances such as toner and paper dust adhering to the outer peripheral surface of the photosensitive drum 21 after transfer, etc., to prepare for the next image forming process.

Subsequently, in the image forming section 2, the sheet 9A onto which the toner image has been transferred by the image forming section 20 is sent to the fixing section 35 via the relay conveying section 5B, and introduced into the fixing processing section FN in the fixing section 35. and let it pass. As a result, the toner image on the paper 9A is heated under pressure, melted, and fixed on the paper 9A.

Finally, the paper 9A after fixing is discharged from the fixing section 35 to the discharge/conveyance section 5C via the discharge/conveyance section 5C and is received in the discharge/container section 12 . At this time, the sheet 9 ejected from the fixing section 35 after fixing is conveyed by the transport rollers 54 in the ejection transport section 5C, and then ejected to the ejection storage section 12 through the paper ejection port 14 by the ejection rollers 52. .

By performing the series of operations described above, an image of a desired color is formed on one side of one sheet 9A, and the basic image forming operation is completed.
Further, in this image forming apparatus 1, when a command requesting image forming operation for a plurality of sheets of paper 9A is issued, the series of operations described above are similarly repeated for the number of sheets.
Further, in the image forming apparatus 1, there is a request for an image forming operation on the paper 9B accommodated in the second accommodation portion 4B and a request for an image forming operation on the paper 9C accommodated in the third accommodation portion 4C. In this case, the above-described series of operations are performed in substantially the same manner for the sheets 9B and 9C respectively supplied from the second container 4B or the third container 4C.

<Diagonal feeding of paper on the register roll>
By the way, in such an image forming apparatus 1, as illustrated in FIG. A phenomenon (oblique feeding of the registration rolls 51) may occur in which the sheet is fed in an oblique direction instead of in the direction along the conveying direction C.

The diagonal feeding of the registration rolls 51 will be described by taking as an example a case in which the sheet 9A stored in the first storage section 4A is transported via the first transport section 5A.

First, when the paper 9A stored in the first storage unit 4A is transported by the first transport unit 5A, it is transported to the pair of transport rolls 53 by the transport force of the supply roll 43b of the supply device 43, and then The sheet is conveyed to the pair of registration rolls 51 by the conveying force of the conveying rolls 53 .
Subsequently, while the sheet 9A is being conveyed by the conveying rolls 53, the leading edge 9a of the sheet 9A is temporarily stopped by abutting against a pair of registration rolls 51 (between the driving roll and the driven roll). After that, the registration roll 51 starts to rotate at a required timing, and is sent to the image forming section 2 .

In this case, as illustrated in FIG. 10(a), when the paper 9A is conveyed to the registration rolls 51 in an attitude inclined with respect to the original conveying direction C, the paper 9A is shown in FIG. 10(b). As shown in the example, between the stopped registration roll 51 and the conveying roll 53 being conveyed, it is in a curved state so as to temporarily bend from the end 9c on the side that hits the registration roll 51 first to the opposite end 9d. . Reference numeral 9t in the drawing indicates a curved portion of the paper 9. FIG. Reference numeral 90 indicated by a dashed rectangle in the figure indicates the paper being fed in a normal feeding attitude until the leading edge thereof reaches the registration rolls 51 .
Subsequently, the paper 9A begins to be fed from the registration rolls 51 when the registration rolls 51 begin to rotate.
At this time, the sheet 9A is sent out in a posture in which the front portion, which becomes the leading edge 9a, is substantially parallel to the axial direction B of the rotating shaft 510 of the registration roll 51, as illustrated in FIG. 10(c). At this time, the sheet 9A is fed with the curved portion 9t remaining in the transport path between the registration rolls 51 and the transport rolls 53 at the trailing end 9b of the sheet 9A. This curved portion 9 t disappears when the trailing edge 9 b of the paper 9 A exits the transport roll 53 .
Therefore, the sheet 9A conveyed in this oblique posture is corrected by the registration rollers 51 in its skewed conveying posture, and is conveyed in a normal conveying posture along the original conveying direction C as a whole. Become so.

However, in this case, depending on the type of paper 9A, the amount (size) of the curved portion 9t generated between the registration rolls 51 and the transport rolls 53 may vary in the axial direction B as shown in FIG. Since the left and right ends 9c and 9d are different, as shown in FIG. The sheet is fed relatively faster with respect to the registration rolls 51 than the side of the end portion 9d.
As a result, depending on the type of paper 9A, as shown in FIG. Skew feeding of the registration rolls 51 occurs.

Incidentally, the diagonal feeding of the registration rolls 51 occurs when the binding force between the pair of transport rolls 53 existing on the upstream side in the transport direction C of the registration rolls 51 and holding the sheet 9A is always strong. tends to be easy.
Further, the diagonal feeding of the registration rolls 51 is performed when the sheets 9B stored in the second storage section 4B are transported to the registration rolls 51 via the second transport section 5E, and when the sheets 9B are stored in the third storage section 4C. This may also occur when the sheet 9C on the sheet is conveyed to the registration roll 51 via the third conveying portion 5E.

<Detailed Configuration of Image Forming Apparatus>
Therefore, in the image forming apparatus 1, as shown in FIGS. 2, 4, etc., a changing means 6A is provided for changing the contact pressure of the portion where the pair of transport rolls 53 in the first transport section 5A are in contact. After that, the changing means 6A changes the contact pressure CP of the transport roll 53 to the first contact pressure CP applied when the paper 9 other than the specific type is supplied when a specific type of paper is supplied as the paper 9. is changed to a second contact pressure CP2 (<CP1) that is lower than the contact pressure CP1 of the first contact pressure.

First, the pair of transport rolls 53 is composed of a driving roll 531 and a driven roll 532, as shown in FIG.
Among these, the driving roll 531 of the transport roll 53 is composed of a rotating shaft 531a and a plurality of roll bodies 531b fixed to the rotating shaft 531a. placed as possible. Further, the drive roll 531 rotates in the direction in which the paper 9 is conveyed by transmitting the power of the electric motor 535 to the rotation shaft 531a through the rotation transmission mechanism 536 .

On the other hand, the driven roll 532 of the transport roll 53 is composed of a rotating shaft 532a and a plurality of roll bodies 532b fixed to the rotating shaft 532a. It is mounted so as to be displaceable in a direction toward and away from the drive roll 531 (direction indicated by a double arrow in FIG. 3). The driven roll 532 has its roll body 532b pressurized by the spring 61 through the bearing 534 and the rotating shaft 532a and pressed against the roll body 531b of the driving roll 531. As a result, the driving roll 531 rotates. It contacts with a required contact pressure CP and is driven to rotate.

As shown in FIG. 3, the changing means 6A is constructed using a device that adjusts the length L of the spring 61 for pressing the driven roll 532 of the transport roll 53 against the drive roll 531 by means of a cam mechanism. there is

For example, the changing means 6A drives the contact member 63 contacting one end of the spring 61 that presses the bearing 534 of the driven roll 532 in the direction to approach the driving roll 531 by moving two eccentric cams 62 as cam mechanisms. It is configured to be displaced toward and away from the roll 531 .

A coil spring, for example, is used as the spring 61 .
The two eccentric cams 62 are cams having a long diameter portion 62a and a short diameter portion 62b, and are fixed to a rotating shaft 64 rotatably attached to a predetermined portion of a supporting member (not shown). Further, the two eccentric cams 62 are rotated by the power of the electric motor 65 transmitted from the rotation transmission mechanism 66 via the rotating shaft 64, so that the long diameter portion 62a and the short diameter portion 62b are brought into contact with the contact member 63, respectively. Let it stop.
The rotating shaft 64 is rotatably supported by a supporting member (not shown) so as to be kept at a constant distance from the rotating shaft 531a of the drive roll 531 in the transport roll 53. As shown in FIG. The long-diameter portion 62a of the eccentric cam 62 is a portion that functions as a cam and has a relatively large radius. The short diameter portion 62b of the eccentric cam 62 is a portion having a relatively small radius among the portions functioning as a cam.

When the contact pressure CP of the transport roll 53 is set to a relatively high first contact pressure CP1, the changing means 6A makes contact with the long diameter portion 62a of the eccentric cam 62 as shown in FIG. 3(a). The electric motor 65 is actuated to come into contact with the member 63 and stop.
As a result, in the changing means 6A, the long-diameter portion 62a of the eccentric cam 62 displaces the contact member 63 in the direction of approaching the drive roll 531, so the length L of the pressure spring 61 is relatively short. At L1, the pressure spring 61 is in a state of generating a relatively large pressure force F1.
As a result, the contact pressure CP of the transport roll 53 is changed to the first contact pressure CP1 relatively higher than the second contact pressure CP2.

Further, when the contact pressure CP of the transport roll 53 is set to a second contact pressure CP2 (<CP1) lower than the first contact pressure CP1, the changing means 6A changes the contact pressure as shown in FIG. Then, the electric motor 65 is operated so that the short diameter portion 62b of the eccentric cam 62 comes into contact with the contact member 63 and stops.
As a result, in the changing means 6A, the short diameter portion 62b of the eccentric cam 62 displaces the contact member 63 in the direction away from the drive roll 531, so that the length L of the pressure spring 61 becomes relatively long L2 ( <L1), the pressure spring 61 generates a relatively small pressure force F2 (<F1).
As a result, the contact pressure CP of the transport roll 53 is changed to a second contact pressure CP2 (<CP1) that is relatively lower than the first contact pressure CP1. The transport rolls 53 at the second contact pressure CP2 are set to a state in which at least the driving roll 531 and the driven roll 532 can transport the paper 9 to the registration rolls 51 while sandwiching the paper 9 therebetween.

Incidentally, in the image forming apparatus 1, the normal contact pressure CP of the transport roll 53 is set to be the first contact pressure CP1 applied when the paper 9 other than the specific type is supplied ( FIG. 3(a)). The normal time is the time before the image forming operation is performed by the image forming apparatus 1 or the time when the image forming operation is not performed.

Further, as shown in FIG. 2, the operation of the changing means 6A (actually, the operation of the electric motor 65) is controlled by the control means 16 as will be described later.
The control means 16 comprises arithmetic processing means, storage means, input/output means and the like. An image forming operation request command is input to the control means 16 . This control means 16 may be a dedicated one for controlling the operation of the electric motor 65 in the changing means 6A, but it is constructed as a part of the control means for controlling the overall operation of the image forming apparatus 1. may

Also connected to the control means 16 is an identification means 60 for identifying whether or not the type of paper 9 used in the image forming operation is a specific type.
As a result, the operation of the electric motor 65 is controlled by the control means 16 according to the information about the type of paper 9 obtained from the identification means 60 in the changing means 6A.

For example, the identification means 60 is configured as a means for obtaining and identifying information about the type of paper 9 included in an image forming operation request command input from the outside of the image forming apparatus 1 . Further, the identifying means 60 is not particularly limited, and obtains input information regarding the type of paper 9 input or selected from the input section 61 of the operation panel of the image forming apparatus 1 before the image forming operation is started. A means for identifying (60A) and a means (60B) for identifying by obtaining information detected by detecting means 62 for detecting the type of paper 9 stored in the storage cassette 41 of the first storage section 4A before the start of the image forming operation. ) may be configured as Further, the identification means 60 may be configured as a combination of these identification means (60A, 60B) and the like.

The specific type of paper 9 identified by the identifying means 60 is a type of paper that tends to skew the paper 9 on the registration rolls 51 .

Criteria for determining whether or not the paper is of a specific type include, for example, the basis weight, the length in the transport direction, and the like. Further, if there is a tendency that the skewed feed is likely to occur, either the case of limiting to one parameter or the case of combining a plurality of parameters may be used. The basis weight may be within a predetermined specific numerical range. The basis weight is, for example, in the range of 60 to 80 gsm (g/m ² ). In addition, the length during transportation may be a length in the transportation direction equal to or greater than a predetermined value. The transported length is equal to or greater than the length in the transport direction C when, for example, a Japanese Industrial Standards A3 size sheet is fed longitudinally (feeding with the short side leading).

<Operation of change means>
The changing unit 6A in the image forming apparatus 1 operates as follows.

In the image forming apparatus 1, as shown in FIG. 4, when the control means 16 receives the image forming operation request command (step 10: S10), whether or not the specific type of paper 9 is used in the image forming operation is determined. is determined (S11).

At this time, the control means 16 acquires the identification information regarding the type of the paper 9 from the identification means 60 and makes a determination. At this time, as the specific type of paper, for example, either one of the case where the basis weight is within the predetermined specific numerical range and the case where the length in the transport direction is equal to or greater than the above predetermined value is adopted. or both. Further, when the parameter of the paper is out of the numerical range defined in the image forming apparatus 1, it may be determined that the paper is of a specific type.

In step 11 (S11), if it is determined that the paper 9A contained in the first container 4A used for the image forming operation is a specific type of paper, the control means 16 causes the change means 6A to operate. is controlled to change the contact pressure CP of the transport roll 53 from the first contact pressure CP1 to the second contact pressure CP2 (S12).
Here, it is assumed that the requested image forming operation uses the paper 9A contained in the first container 4A, and the paper 9A is of a specific type.

At this time, the changing means 6A drives the electric motor 65 to rotate the two eccentric cams 62 so that the short diameter portion 62b of each eccentric cam 62 is brought into contact with the contact member 63 as shown in FIG. 3(b). Acts to stop on contact.
As a result, the contact pressure CP of the transport roll 53 is changed from the first contact pressure CP1 shown in FIG. 3(a) to the relatively low second contact pressure CP2 shown in FIG. 3(b). .

Subsequently, the image forming apparatus 1 executes the requested image forming operation (S13). This image forming operation is continued until all the series of image forming operations for the requested same type of paper 9A are completed (S14).

In the image forming operation at this time, the paper 9A stored in the first storage section 4A passes through the pair of transport rolls 53 changed from the supply roll 43b of the supply device 43 to the second contact pressure CP2. is sent to the register roll 51 of .
In this case, even if the sheet 9A is conveyed to the registration rolls 51 in an attitude inclined with respect to the original conveying direction C as illustrated in FIG. The paper 9A to be fed is not fed obliquely from the registration rolls 51 as described below, but is fed in a normal transport posture along the original transport direction C. FIG.

That is, as shown in FIG. 5(b), the sheet 9A sent in an oblique posture is positioned between the stopped registration roll 51 and the conveying roll 53 being conveyed. After the sheet is temporarily bent from the portion 9c to the opposite end 9d, the sheet begins to be fed from the regi rolls 51 as the regi rolls 51 begin to rotate.
At this time, the sheet 9A is sent out in a posture in which the front portion, which becomes the leading edge 9a, is substantially parallel to the axial direction B of the rotation shaft 510 of the registration roll 51, as illustrated in FIG. 5C.
Also, the sheet 9A at this time is fed with the curved portion 9t remaining in the transport path between the registration rolls 51 and the transport rolls 53 at the rear portion, which becomes the trailing edge 9b. At this time, since the conveying roll 53 is at the relatively low second contact pressure CP2, the curved portion 9t of the paper 9A is slightly shifted upstream in the conveying direction C from the conveying roll 53 and becomes smaller. As a result, the curved portion 9t does not strongly push the leading edge 9a of the paper 9A toward the downstream side in the conveying direction C (toward the registration rolls 51).

Therefore, the sheet 9A transported in this oblique posture is corrected between the registration roll 51 and the transport roll 53 so that the skewed transport posture is corrected as shown in FIG. 5(d). , the sheet is conveyed in a normal conveying posture along the original conveying direction C without being obliquely conveyed from the registration rolls 51.例文帳に追加

In this case, for example, as the specific type of paper 9A, the so-called plain paper whose basis weight is in the numerical range of 60 to 80 gsm, or the length of A3 size paper in the transport direction C when fed longitudinally Even when the paper having the above length is used, the paper 9A of that type can be fed in a normal conveying posture without being skewed from the registration rolls 51.例文帳に追加
As a result, in the image forming section 2 at this time, an image can be formed in a good state in which parallelism to the paper is maintained on the paper 9A that is fed in a normal conveying posture.

Subsequently, in the image forming apparatus 1, when all the requested series of image forming operations are completed, the control means 16 confirms whether the contact pressure CP of the transport roll 53 is the normal first contact pressure CP1. (S15).

In the image forming operation at this time, since the paper 9A used is a specific kind of paper, in step 12 (S12), the contact pressure CP of the transport roll 53 changes from the first contact pressure CP1 to the second contact pressure CP2. has been changed to
Therefore, in this case, the control means 16 controls the operation of the changing means 6A to change the contact pressure CP of the transport roll 53 from the second contact pressure CP2 to the normal first contact pressure CP1. An operation is performed (S16).

On the other hand, in step 11 (S11), it was determined that the paper 9A contained in the first container 4A used for the image forming operation is not of the specific type, that is, is of a type other than the specific type. In this case, the operation of changing the contact pressure CP of the transport roll 53 by the changing means 6A is not performed, and the requested image forming operation is performed (S13).
Here, it is assumed that the requested image forming operation uses the paper 9A contained in the first container 4A, and the paper 9A is of a type other than the specific type.

In the image forming operation at this time, the paper 9A accommodated in the first accommodation unit 4A passes from the supply roll 43b of the supply device 43 through the pair of transport rolls 53 under the first contact pressure CP1 to the pair of registration rolls. sent to 51.
In this case, even if the sheet 9A is conveyed to the registration rolls 51 in an attitude inclined with respect to the original conveying direction C as illustrated in FIG. The sheet 9A to be fed is corrected for its inclined transport posture between the registration rolls 51 and the transport rolls 53 under the first contact pressure CP1, and as shown in FIG. It is sent in a normal conveying posture along the original conveying direction C without being conveyed.

In this case, for example, as the paper 9A other than the specific type, a thick paper with a basis weight exceeding 80 gsm, or a length in the transport direction C that is shorter than the length of A3 size paper when it is fed longitudinally. Even when using paper (for example, when A4 size paper is fed sideways), it is unlikely that any of the paper 9A of that type will be fed diagonally from the registration rolls 51, and the normal feeding direction C along the original feeding direction C is unlikely. It is sent in the transport posture.

Subsequently, in the image forming apparatus 1, when all the requested series of image forming operations are completed, the control means 16 confirms whether the contact pressure CP of the transport roll 53 is the normal first contact pressure CP1. (S15).
However, when this image forming operation is performed, the contact pressure CP of the transport roll 53 is not changed by the changing means 6A, and is the first contact pressure CP1 of the normal time.
Therefore, in this case, the operation (S16) of changing the contact pressure CP of the transport roll 53 back to the normal first contact pressure CP1 by the changing means 6A is not performed.

As described above, in the image forming apparatus 1, the paper 9A accommodated in the first accommodation section 4A is conveyed from the supply roll 43b to the registration roll 51 via the conveyance roll 53, and the leading edge 9a of the paper is conveyed to the registration roll 51. When the paper 9A is sent to the image forming section 2 after being bumped, only when the paper 9A is of a specific type, the changing means 6A changes the contact pressure CP of the transport roll 53 to a relatively low second contact pressure CP2. This prevents the paper 9A from being skewed from the registration rolls 51. As shown in FIG. Further, when the paper 9A is of a type other than the specific type, the changing operation by the changing means 6A is unnecessary, and the paper 9A of the type other than the specific type is not skewed from the registration rolls 51. - 特許庁
Therefore, according to the image forming apparatus 1, when the sheet 9A stored in the first storage section 4A is transported to the registration rolls 51 via the transport rolls 53, the transport rolls 53 move all of the sheets 9A. As compared with the case where the operation of relatively reducing the contact pressure CP is performed each time, the skew feeding of the paper on the registration rolls 51 is efficiently suppressed.

Further, in the image forming apparatus 1, for example, the operation of changing the contact pressure CP of the transport roll 53 to a relatively low second contact pressure CP2 (the operation of returning the second contact pressure CP2 to the first contact pressure CP1) ) to all the sheets 9A supplied from the first storage unit 4A each time, there is no need for a high-output drive source (such as a high-output electric motor or solenoid) or a large-scale mechanism. becomes.
Therefore, in the image forming apparatus 1, it is possible to avoid an increase in cost and an increase in the size of the means for changing the contact pressure CP, which would be caused by adopting the high-output drive source.

<Modification of Embodiment 1>
In the image forming apparatus 1, as shown in FIG. 1 or FIG. When specific types of paper are supplied as the paper 9B and 9C accommodated in the section 4C, the contact pressure CP on the transport rolls 55 and 56 is changed from the first contact pressure CP1 to the second contact pressure CP2. Changing means 6B and 6C for changing to (<CP1) can be provided.
In this case, the changing means 6B and 6C are configured with a mechanism using a cam mechanism shown in parentheses in FIG. Each operation is controlled by the control means 16 to which the identification means 60 is connected.

In the image forming apparatus 1 of this modified example, only when the sheets 9B and 9C supplied from the second container 4B or the third container 4C are used for the image forming operation and are of a specific type , changing means 6B and 6C change the respective contact pressures CP on the transport rolls 55 and 56 from the first contact pressure CP1 to the second contact pressure CP2 (<CP1).
As a result, when an image forming operation is performed on the sheets 9B and 9C supplied from the second storage section 4B or the third storage section 4C, the sheets 9B and 9C are conveyed to the registration rolls 51 in an oblique posture. Even in such a case, the skew feeding of the registration rolls 51 with respect to the sheets 9B and 9C is efficiently suppressed.

Further, in the image forming apparatus 1 of this modified example, when the sheet 9B stored in the second storage section 4B is transported to the registration roll 51 through the second transport section 5D, as shown in FIGS. Two transport rolls 55 and 56 are present in the second transport section 5D.
In this case, when the paper 9B is a specific type of paper, the contact pressures CP on the transport rolls 55 and 56 are changed from the first contact pressure CP1 to the second contact pressure CP2 (<CP1 ), it may be configured as follows.
That is, in this case, only the contact pressure CP of the transport roll 55 arranged closest to the supply roll 44b of the second storage section 4B is changed from the first contact pressure CP1 to the second contact pressure by the changing means 6B. It can also be configured to change to CP2 (<CP1).
Even with such a configuration, the diagonal feed of the registration rolls 51 with respect to the sheet 9B supplied from the second storage section 4B is efficiently suppressed. Moreover, in the case of such a configuration, the operation of changing the contact pressure CP of the transport roll 56 from the first contact pressure CP1 to the second contact pressure CP2 (<CP1) by the changing means 6C becomes unnecessary.

[Embodiment 2]
FIG. 7 shows part of an image forming apparatus according to the second embodiment.
The image forming apparatus according to the second embodiment has the same configuration as the image forming apparatus 1 according to the first embodiment, except that measuring means and adjusting means, which will be described below, are additionally provided.

First, in the image forming apparatus 1 according to the first embodiment, when the image forming operation is performed using the specific type of paper 9A, the contact pressure CP of the transport roll 53 is set to the normal first contact pressure by the changing unit 6A. The contact pressure is changed to a second contact pressure CP2 relatively lower than CP1.
In this case, the conveying ability of the conveying roll 53 under the second contact pressure CP2 is lower than when it is set at the normal first contact pressure CP1. Therefore, the transport speed at which the specific type of paper 9A is transported from the supply roll 43b of the first storage section 4A to the registration roll 51 via the transport roll 53 is governed by the transport capability of the supply roll 43b. .

However, the supply roll 43b generally has low wear resistance, and the roll diameter tends to fluctuate due to wear.
For example, from the viewpoint of supplying the paper 9A supplied from the storage cassette 41 by the supply roll 43b at a required interval, the paper 9A supplied by the supply roll 43b is sandwiched between the transport rolls 53 and transported by the transport rolls 53. is started, the rotation of the supply roll 43b is stopped, and the sheet 9A is conveyed so as to be pulled out from the supply roll 43b (between the separating roll 43c). Local variations in roll diameter may also occur.
Therefore, the timing at which the paper 9A is supplied by the supply roll 43b and handed over to the registration roll 51 via the transport roll 53 is the time when the image forming apparatus 1 (the supply roll 43b) is started to be used and the time when the image forming apparatus 1 is repeatedly used. There may be variations after

The timing of handing over the paper to the registration rolls 51 is important in correcting the conveying posture of the paper 9A by the registration rolls 51 .
Therefore, in the image forming apparatus 1, even when the contact pressure CP of the transport roll 53 is changed to the relatively low second contact pressure CP2 by the changing means 6A, the paper 9A at that time is placed on the registration roll 51. It is required to suppress variations in handover timing and improve its accuracy (reduce variations).

Therefore, in the image forming apparatus 1 according to Embodiment 2, as shown in FIG. A measuring means 7A for measuring a conveying speed V when feeding up to the conveying roll 53 in the first conveying section 5A, and a conveying speed Vx preset with a rotational speed S of the supply roll 43b according to the measurement result of the measuring means 7A. is newly provided with adjustment means 8A for adjusting so as to approach to .

The measuring means 7A includes detecting means 71 and 72 for detecting the required time Tm required for the leading edge 9a of the paper 9A to pass through the two points P1 and P2 in the first conveying section 5A, and the required time Tm detected by the detecting means 71 and 72. Calculation means 73 for calculating the conveying speed V of the paper 9A on the supply roll 43b from the time Tm.

Among them, the detecting means 71 and 72 are set to be arranged in a line with a predetermined interval Lm in the conveying direction C of the paper 9A in the section from the supply roll 43b to the first conveying roll 53 in the first conveying section 5A. means for detecting that the leading edge 9a of the sheet 9A has passed through the two points P1 and P2. The detection means 71 and 72 are, for example, reflective photosensors. The required time Tm required for the leading edge 9a of the paper 9A to pass through the two points P1 and P2 is obtained from the difference between the times when the detection means 71 and 72 detect the passage of the leading edge 9a of the paper 9A.

The calculation means 73 divides the interval Lm between the two points P1 and P2 by the required time Tm obtained from the detection means 71 and 72, thereby calculating the transport speed V (=Lm/Tm) of the paper 9A on the supply roll 43b. ) is a means of calculating
The calculating means 73 of the measuring means 7A is connected to the control means 16 for controlling the operation of the changing means 6A, as shown in FIG. It has become. The calculation means 73 may be configured to be included as a part of the function of the adjustment means 8A.

The adjustment means 8A adjusts the rotation speed S of the supply roll 43b so that the transport speed V of the supply roll 43b to the transport roll 53 obtained by the measurement means 7A approaches the preset transport speed Vx of the supply roll 43b. It is a means.
The adjustment means 8A is configured as a part of the function of the control means 16 described above. The adjusting means 8A also transmits information for adjusting the rotation speed S of the supply roll 43b to the drive means 18 that drives the supply device 43. As shown in FIG.

This adjusting means 8A operates as follows.
First, when the conveying speed V measured by the measuring unit 7A is slower than the preset conveying speed Vx, the adjusting unit 8A adjusts the rotation speed S of the supply roll 43b at a predetermined necessary ratio according to the difference. Adjust to speed up. Conversely, if the conveying speed V measured by the measuring means 7A is faster than the preset conveying speed Vx, the rotation speed S of the supply roll 43b is adjusted to be reduced at a predetermined necessary ratio according to the difference. do.

Moreover, the measuring means 7A and the adjusting means 8A are operated at least when the image forming operation is performed in a state where the contact pressure CP of the transport roll 53 is changed to the relatively low second contact pressure CP2 by the changing means 6A. is configured to

Furthermore, the adjustment of the rotation speed S of the supply roll 43b by the adjusting means 8A is performed by feedback as follows.
For example, the adjustment amount of the rotation speed S obtained from the result of the conveying speed V for the previous sheet 9A in a series of image forming operations (job) is the rotation of the supply roll 43b for the next sheet 9A in the same image forming operation (job). This is done so as to be reflected in the adjustment of the speed S. In addition, the average value of the adjustment amount of the rotation speed S obtained from the result of each conveying speed V for a plurality of sheets of paper 9A in the preceding series of image forming operations (preceding job) is This may be reflected in the adjustment of the rotation speed S of the supply roll 43b with respect to the paper 9A in the image forming operation (subsequent job).

In this image forming apparatus 1, when the contact pressure CP of the transport roll 53 is changed to a second contact pressure CP2 lower than the first contact pressure CP1 by the changing means 6A, the paper 9A on the supply roll 43b is Even if the conveying speed V fluctuates, the rotating speed S of the supply roll 43b is adjusted by the measuring means 7A and the adjusting means 8A so as to approach the predetermined conveying speed Vx. As a result, in the image forming apparatus 1, the sheet 9A is conveyed at the required conveying speed Vx under the control of the conveying performance of the supply roll 43b rotating at the rotational speed S adjusted by the adjusting means 8A. become.
Therefore, according to this image forming apparatus 1, compared to the case where the measuring means 7A and the adjusting means 8A are not provided, the paper 9A is transferred from the supply roll 43b to the transport roll 53 under the second contact pressure CP2. Finally, it is conveyed in a stable time (delivery timing) until it reaches the registration rolls 51 .

In the image forming apparatus 1, the leading end of the sheet 9A is measured by the measuring means 7A at the two points P1 and P2 set in the section from the supply roll 43b in the first transport section 5A to the transport roll 53 that reaches first. The current transport speed V of the paper 9A is calculated from the required time Tm when the paper 9a passes.
Therefore, according to the image forming apparatus 1, compared with the case where the conveying speed V of the sheet 9A is not calculated from the required time Tm when passing through the two points P1 and P2, the sheet 9A is transported from the supply roll 43b first. It is conveyed to the conveying rolls 53 and finally to the registration rolls 51 in a more stable time. The case where the conveying speed V of the paper 9A is not calculated from the required time Tm when passing through the two points P1 and P2 is when passing through the two points before and after the conveying roll 53 of the first conveying section 5A. It also includes the case of calculating the transport speed of the paper 9A from the required time.

Moreover, in this image forming apparatus 1, the leading edge 9a of the paper 9A passes through the measuring means 7A by means of the detection means 71 and 72 arranged at the two points P1 and P2 which are set to line up in the conveying direction C of the paper 9A. The required time Tm is detected.
Therefore, according to the image forming apparatus 1, even if the paper 9A is transported in an oblique posture from the supply roll 43b, the leading edge 9a of the paper 9A transported in that tilted posture is substantially the same. Passage of sites can be detected.
As a result, the required time Tm can be measured more accurately than when the passage of the leading edge 9a of the paper 9A is not detected by the detection means 71 and 72 arranged in a line in the conveying direction C of the paper 9A. The conveying speed of the roll 43b is accurately measured. Further, the adjustment of the adjusting means 8A based on the measurement results of the detecting means 71 and 72 is also performed accurately.

<Modification of Embodiment 2>
In the image forming apparatus 1 according to the second embodiment, as shown in FIG. 8, the measuring means 7A is also provided in the second conveying section 5D and the third conveying section 5E so as to correspond to the first conveying section 5A. And as with the adjusting means 8A, measuring means 7B, 7C and adjusting means 8B, 8C can be provided, respectively.

In this case, the measuring means 7B measures the transport speed when the supply roll 44b of the second storage section 4B feeds out the paper 9B and supplies it to the transport roll 55 which reaches first. The measuring means 7B detects the required time Tm when the leading edge 9a of the paper 9B passes through two points set in the section from the supply roll 44b to the transport roll 55 by means of the two detection means 71 and 72. The current transport speed V of the supply roll 44b relative to the paper 9B is calculated by the calculation means 73 using information on the detected required time Tm.
The adjustment unit 8B adjusts the rotation speed S of the supply roll 44b to a preset conveyance speed Vx of the supply roll 44b according to the measurement result (conveyance speed V of the supply roll 44b) obtained by the measurement unit 7B. adjust.

The measuring means 7C measures the transport speed when the supply roll 47b of the third storage section 4C feeds out the paper 9C and supplies it to the transport roll 56 which reaches first. The measuring means 7C detects the required time Tm when the leading edge 9a of the paper 9C passes through two points set in the section from the supply roll 47b to the transport roll 56 with the two detection means 71 and 72, and The information on the detected required time Tm is used to determine the current transport speed V of the supply roll 47b for the paper 9C by the calculation means 73. FIG.
The adjustment unit 8C adjusts the rotation speed S of the supply roll 47b to a preset conveyance speed Vx of the supply roll 47b according to the measurement result (conveyance speed V of the supply roll 47b) obtained by the measurement unit 7C. adjust.

The adjustment means 8B and the adjustment means 8C are configured as part of the functions of the control means 16 as shown in FIG. 8, similarly to the adjustment means 8A. Further, although neither of the calculation means 73 of the measurement means 7B and 7C is specifically shown in FIG. They are connected to portions functioning as adjusting means 8C.

In the image forming apparatus 1 of this modified example, when the contact pressure CP of the transport rolls 55 and 56 is changed to the second contact pressure CP2 lower than the first contact pressure CP1 by the changing means 6B, the supply roll Even if the conveying speed V of the sheet 9B of the sheet 44b fluctuates, the rotational speed S of the supply roll 44b is adjusted by the measuring means 7B and the adjusting means 8B so as to approach the predetermined conveying speed Vx. .
For this reason, according to the image forming apparatus 1, the sheet 9B passes from the supply roll 44b to the transport roll 55 and finally through the transport roll 56 to the registration rolls, compared to the case where the measuring means 7B and the adjusting means 8B are not provided. It is transported at a stable time (delivery timing) until it reaches 51.

Further, in the image forming apparatus 1 of this modified example, when the contact pressure CP of the transport roll 56 is changed to the second contact pressure CP2 lower than the first contact pressure CP1 by the changing unit 6C, the contact pressure of the supply roll 47b is Even if the conveying speed V of the paper 9C fluctuates, the measuring means 7C and the adjusting means 8C adjust the rotating speed S of the supply roll 47b to approach the predetermined conveying speed Vx.
Therefore, according to the image forming apparatus 1, the required time for the sheet 9C to reach the registration roll 51 from the supply roll 47b via the transport roll 56 is stable compared to the case where the measurement means 7C and the adjustment means 8C are not provided. It can be transported at (delivery timing).

[Embodiment 3]
FIG. 9 shows the operation of the changing means in the image forming apparatus according to the third embodiment.
The image forming apparatus according to the third embodiment sets and changes the contact pressure CP of the transport rolls 53, 55, 56 in the normal state to a relatively low second contact pressure CP2, and changes the change means 6A, 6B, 6C. The configuration is the same as that of the image forming apparatus 1 according to Embodiments 1 and 2 (including modifications thereof) except that part of the operation is changed.

In the image forming apparatus 1, the normal contact pressure CP of the transport rolls 53, 55, 56 is relatively is set to a second contact pressure CP2 (<CP1) which is relatively low. The second contact pressure CP<b>2 at this time is set to a level of contact pressure that can exhibit the transport capability of sandwiching the specific type of paper 9 and transporting it to the next registration roll 51 or transport roll 56 .

As for the changing means 6A, 6B, and 6C, as shown in FIG. 9, when a sheet other than the specified type is supplied as the sheet 9, the contact pressure of the conveying rolls 53, 55, and 56 is set to the normal contact pressure. It is configured to change from the second contact pressure CP2 to the first contact pressure CP1.

<Operation of change means>
The operation of the changing means 6A, 6B, 6C is as follows.
In the image forming apparatus 1 provided with at least one of the changing means 6A, 6B, 6C, as shown in FIG. 9, when the control means 16 receives an image forming operation request command (S20), the image forming operation specified (S21).

If it is determined in step 21 that the sheets 9A to 9C contained in any one of the first containing section 4A to the third containing section 4C used for the image forming operation are of a specific type, The operation for changing the contact pressure CP of the transport rolls 53, 55, 56 by the changing means 6A-6C is not performed, and the requested image forming operation is performed (S22). This image forming operation is continued until all the requested series of operations are completed (S23).

In the image forming operation at this time, the sheets 9A to 9C accommodated in the respective accommodating portions 4A to 4C are subjected to the second contact pressure CP2 from the supply rolls 43b, 44b, 47b of the respective supply devices 43, 44, 47. It is sent to a pair of registration rolls 51 via one of the pair of transport rolls 53, 55, 56 in the .
In this case, any one of the specific types of paper 9A to 9C supplied for use in the image forming operation may be conveyed to the registration rolls 51 in a posture that is inclined with respect to the original conveying direction C. Even (FIG. 5A), the sheets 9A to 9C fed in the oblique posture are conveyed by the transport rolls 53, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 51, 5, 5, 5, 5, 5, 5, 56, and is sent in a normal conveying attitude along the original conveying direction C without being obliquely conveyed from the registration rolls 51 (FIG. 5(d)).

Subsequently, when all the requested series of image forming operations are completed, the control means 16 confirms whether or not the contact pressure CP of each of the transport rolls 53, 55 and 56 is the normal second contact pressure CP2. (S24).

However, when this image forming operation is performed, the contact pressure CP of none of the transport rolls 53, 55, 56 is changed by the changing means 6A, 6B, 6C, and the normal second contact pressure CP2 It has become.
Therefore, in this case, the contact pressure CP of the transport rolls 53, 55, 56 is changed back to the normal second contact pressure CP2 by any of the changing means 6A, 6B, 6C (S26). can't break

On the other hand, in step 21, the sheets 9A to 9C accommodated in any one of the first accommodating section 4A to the third accommodating section 4C used for the requested image forming operation are not of the specific type. If it is determined that the paper is not of the type), the contact pressure CP of any one of the transport rolls 53, 55, and 56 is changed from the second contact pressure CP2 in the normal state to the first contact pressure by the changing means 6A to 6C. CP1 is changed (S25).
That is, any one of the transport rolls 53, 55, 56 at this time is changed to the first contact pressure CP1 relatively higher than the second contact pressure CP2 as shown in FIG. 3(a).

Subsequently, the image forming apparatus 1 executes the requested image forming operation (S22), and continues the image forming operation until the requested series of operations are all completed (S23).

In the image forming operation at this time, the sheets 9A to 9C accommodated in the respective accommodating units 4A to 4C are subjected to the first contact pressure CP1 from the supply rolls 43b, 44b, 47b of the respective supply devices 43, 44, 47. It is sent to a pair of registration rolls 51 via one of the pair of transport rolls 53, 55, 56 in the .
In this case, any one of the non-specific types of paper 9A to 9C supplied to be used for the image forming operation may be conveyed to the registration rolls 51 in a posture inclined with respect to the original conveying direction C. Even (FIG. 5A), the sheets 9A to 9C sent in the oblique posture are conveyed by the transport rolls 53, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 51, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6 56, and is sent in a normal conveying attitude along the original conveying direction C without being obliquely conveyed from the registration rolls 51 (FIG. 5(d)).

In Embodiments 1 to 3, the image forming apparatus 1 is an image forming apparatus that forms a monochromatic image composed of a developer, but the present invention is an image forming apparatus that forms a color (multicolor) image. can also be applied to
In addition, the image forming apparatus of the present invention is not limited to the image forming apparatus 1 provided with the image forming unit 2 for forming a toner image made of developer, and may be made of other material such as ink. It may be an image forming apparatus having an image forming unit that forms an image.

REFERENCE SIGNS LIST 1 ... image forming apparatus 2 ... image forming section 4 ... housing section 5 ... conveying section (an example of a conveying route)
6 ... changing means 7 ... measuring means 8 ... adjusting means 9 ... paper (an example of a recording medium)
9a... Tips 43b, 44b, 47b... Supply roll 51... Registration roll (an example of abutment roll)
53, 55, 56... Conveying rolls (conveying rolls that arrive first)
71, 72...Detecting means C...Conveyance direction Lm...Required intervals P1, P2...2 points

Claims (4)

an image forming unit that forms an image on paper;
a storage unit that stacks and stores sheets to be supplied to the image forming unit;
a supply roll that feeds and supplies the paper stored in the storage unit;
a pair of abutment rolls that abut the leading edge of the paper supplied from the supply roll and then send the sheet to the image forming unit;
a pair of transport rolls arranged in a paper transport path connecting between the storage unit and the impingement roll, and transporting the paper supplied from the supply roll toward the impingement roll;
changing means for changing the contact pressure of the contacting portions of the pair of transport rolls;
with
A plurality of the transport rolls are arranged on the transport path,
Among the plurality of transport rolls, the transport roll positioned closest to at least the supply roll has a contact pressure at a normal time of the contact pressure, which is a first contact when a sheet other than a specific type is supplied. is set to a second contact pressure lower than the pressure,
The changing means changes the contact pressure of at least the transport roll arranged closest to the supply roll from the second contact pressure to the second contact pressure when paper other than the specific type is supplied as the paper. An image forming apparatus that changes to a contact pressure of 1. 2. The image forming apparatus according to claim 1 , wherein the specific type of paper is at least one of paper having a basis weight within a predetermined numerical range and paper having a transport direction length equal to or greater than a predetermined value . measuring means for measuring a transport speed when the supply roll feeds the paper and supplies it to the transport roll;
adjusting means for adjusting the rotation speed of the supply roll so as to approach a preset conveying speed according to the measurement result of the measuring means;
The image forming apparatus according to claim 1 or 2 , comprising : The measuring means has a plurality of detecting means for detecting passage of the leading edge of the paper, and the plurality of detecting means conveys the paper within the section of the conveying path from the supply roll to the first conveying roll. 4. The image forming apparatus according to claim 3, wherein the image forming apparatus is arranged in a line with a space in the direction .

Images