JP2023055371A - Document feeding device and image forming device - Google Patents

Abstract

To prevent a document from being skewed when the document roughly stacked on a document tray is conveyed.SOLUTION: Document feeding units 3, 33 respectively include: a document tray 301 on which a document D is placed; a feeding roller 303 that feeds the document placed on the document tray in a feeding direction; friction members 306, 310 that are arranged upstream of the feeding roller in a feeding direction and impart feeding resistance R2, R3 to the document; and contact/separation mechanisms 320, 420 that bring the feeding roller into contact with the document after the friction members are brought into contact with the document placed on the document tray. The friction members are arranged upstream from the feeding roller in the feeding direction within a range of a distance equal to or less than 2/3 of a length in the feeding direction of a minimum size document that can be conveyed by the document feeding units.SELECTED DRAWING: Figure 5

Description

The present invention relates to a document conveying device and an image forming device.

Generally, an image forming apparatus has a document conveying section and a document reading section in the upper part of the main body, and has an image forming part and a feeding section in the lower part of the main body. The document conveying section conveys the document to the document reading section. The document reading section reads a document conveyed from the document conveying section and transmits image data to the image forming section. The image forming section forms an image on a recording medium fed from the feeding section according to the image data.

Some of the document conveying units have a mixed loading function in which documents of different sizes are placed in a mixed state. In such a document conveying unit, the feeding roller is provided at a position (usually, the central portion in the document width direction) at which a frequently used size of the document can be properly conveyed. For this reason, for example, when the feeding roller conveys a document of a size smaller than a frequently used size that is roughly arranged on the document conveying unit, the center of the document in the width direction orthogonal to the document conveying direction and the feeding roller A turning moment is generated in the document due to deviation from the center of the roller. As a result, a small size document is conveyed while rotating, and a so-called oblique document conveyance phenomenon (skew) occurs. For this reason, if the skew of the document increases while the document reading section is reading the document that is being transported by the document transport section, a document reading error may occur, and a document jam may occur in the document transport path. ) is likely to occur.

Even if the document transport section is provided with side regulating plates on both sides for regulating the position of the document placed on the document tray in the width direction, when documents of different sizes are placed together, the small size document may Only one side edge in the width direction is regulated by one side regulating plate. As a result, the effect of regulating the position of the document by the side regulating plate is remarkably reduced, so that there is also a problem that the document is skewed while the document is being conveyed by the feeding roller.

In order to solve these problems, Patent Document 1 discloses a friction applying member (driven roller member) provided outside one end of a feeding roller in the width direction and upstream of the feeding roller in the conveying direction. is disclosed. The feeding roller is provided at the center of the document tray in the width direction so as to face the leading edge of the mixed document bundle stacked on the document tray. The frictional force imparting member abuts against the surface of the document outside one end of the feeding roller in the width direction and upstream of the feeding roller in the transport direction to impart frictional force to the document.

JP 2005-314063 A

In Patent Document 1, the mixed document bundle is placed on the document tray so that the side edges of each document of the mixed document bundle are in contact with one of side regulation plates arranged on both sides of the feed roller in the width direction. be done. Then, the document is fed by the feeding roller while applying a frictional force to the document by a frictional force imparting member provided outside one end of the feeding roller in the width direction and upstream of the feeding roller in the conveying direction. send. As a result, the document is prevented from skewing by the friction applying member while being restricted by one of the side regulating plates.

However, when the side edges of the small-size documents in the mixed document bundle are placed roughly on the document tray without contacting the side regulating plate, the conventional technology does not allow the small-size documents to The skew of the document may increase due to the frictional force applied by the frictional force applying member. In order to start the document feeding operation, when the feeding roller comes into contact with a small size document that is roughly placed (rough set arrangement) on the document tray, the feeding roller causes unevenness in the width direction. An urging force acts on the document, causing the document to turn and cause the skew of the document.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a document feeder capable of preventing the document from being skewed when the document is not regulated by the side regulating plate and is roughly placed on the document tray.

A document feeder according to an embodiment of the present invention includes:
a document tray on which documents are placed;
a conveying member that conveys the document placed on the document tray in a conveying direction;
a friction member arranged upstream of the conveying member in the conveying direction and applying a conveying resistance force to the document;
a mechanism for bringing the conveying member into contact with the document after the friction member is brought into contact with the document placed on the document tray;
with
The friction member is arranged upstream from the conveying member in the conveying direction, within a range of distance equal to or less than two-thirds of the length of the minimum size document that can be conveyed by the document conveying device in the conveying direction. characterized by

According to the present invention, it is possible to prevent the document from being skewed when the document placed roughly on the document tray without being regulated by the side regulating plate is conveyed.

FIG. 2 is a cross-sectional view of the image forming apparatus according to the first embodiment; FIG. 2 is a plan view of a conventional document tray in which documents of different sizes are arranged in a rough set. FIG. 10 is a plan view of a conventional document tray for explaining skew feeding of a small size document D1; FIG. 10 is a plan view of a document tray provided with a conventional friction member; FIG. 2 is a plan view of a document tray provided with a friction member according to the first embodiment; FIG. 7 is a diagram showing the relationship between the skew amount and the distance between the friction member and the feed roller according to the first embodiment; FIG. 4 is an explanatory view of a contact/separation mechanism for bringing the friction member of the first embodiment into contact with a document; FIG. 8 is a plan view of a document tray provided with a friction member according to a second embodiment; FIG. 9 is an explanatory diagram of a contact/separation mechanism that causes the friction member of the second embodiment to contact a document;

Embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

(First embodiment)
FIG. 1 is a cross-sectional view of an image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 is a digital color copier that reads an image of a document and forms a color image on a recording medium by electrophotography according to the image data. Image forming apparatus 100 includes image forming section 1 , document reading section 2 arranged above image forming section 1 , and document conveying section 3 (document conveying device) placed on document reading section 2 . Prepare. The document transport section 3 has a document tray 301 on which documents are placed. The document conveying unit 3 feeds the document D set on the document tray 301 with the image surface facing upward, one by one from the first page by the feeding roller 303 (conveying member). The document D passes over the scanning glass 200 of the document reading section 2 through a curved conveying path, and is ejected onto the document ejection tray 302 .

The document reading section 2 has a scanner unit 202 for reading an image of a document. The document reading section 2 reads the document D conveyed on the flow reading glass 200 by the document conveying section 3 with the scanner unit 202 held at a predetermined position. Specifically, the scanner unit 202 irradiates the reading surface of the document D with light from the lamp 203 . Reflected light from document D is guided to lens 207 by mirrors 204 , 205 and 206 . Light passing through the lens 207 forms an image on the imaging surface of the image sensor 208 . The image sensor 208 converts incident light into digital signals and outputs them as image data. Further, the user can lift the document conveying unit 3 without conveying the document by the document conveying unit 3 and set the document D on the platen glass 201 . The scanner unit 202 can read the image of the document while moving under the platen glass 201 on which the document D is set.

The image forming unit 1 includes an image forming unit 10 that forms Y (yellow), M (magenta), C (cyan), and K (black) images. The photosensitive drum 11 rotates clockwise. The charging roller 12 uniformly charges the surface of the photosensitive drum 11 . The laser scanner 13 emits laser light onto the uniformly charged surface of the photosensitive drum 11 according to the image data output from the document reading unit 2 to form a latent image on the surface of the photosensitive drum 11 . The developing device 14 develops the latent image with toner to form a toner image on the surface of the photosensitive drum 11 . The toner image on the photosensitive drum 11 is sequentially transferred to the intermediate transfer belt 31 by applying a predetermined pressure and an electrostatic load bias from the primary transfer roller 17 . A small amount of toner remaining on the photosensitive drum 11 after transfer is removed by the drum cleaner 15 .

On the other hand, recording media (hereinafter referred to as sheets) P are fed one by one from a feeding cassette 20 and conveyed to a registration roller pair 23 by a feeding pull-out roller pair 24 and a pre-registration roller pair 22 . The leading edge of the sheet P contacts the stopped registration roller pair 23, a loop is formed in the sheet P, and skew feeding of the sheet P is corrected. Thereafter, the registration roller pair 23 rotates the sheet so that the leading edge of the sheet P and the leading edge of the toner image on the intermediate transfer belt 31 are aligned at the nip portion between the intermediate transfer belt 31 and the secondary transfer outer roller 35 . transport P. The color toner image on the intermediate transfer belt 31 is applied with a predetermined pressure and an electrostatic load bias at the nip portion between the inner secondary transfer roller 34 and the outer secondary transfer roller 35 which are arranged opposite to each other. Thus, it is transferred to the sheet P. A small amount of toner remaining on the intermediate transfer belt 31 after transfer is removed by a belt cleaner 36 .

The toner image transferred onto the sheet P is fixed onto the sheet P by being heated and pressed by the fixing device 40 . The sheet P on which the image is formed is conveyed by the inner discharge roller pairs 42 and 43 and discharged onto the discharge tray 50 by the discharge roller pair 41 . The image forming apparatus 100 is formed to have an in-body discharge configuration in which a discharge tray 50 is provided between the image forming section 1 and the document reading section 2 . However, the image forming apparatus 100 is not limited to the in-body discharge configuration, and the image forming apparatus 100 may have a configuration in which the sheet P on which an image is formed is discharged to a discharge tray provided protruding from the side surface of the image forming apparatus 100. good too.

(Description of rough set arrangement of originals D of different sizes)
The document conveying unit 3 transports a plurality of different size documents D (D1, D2, D3) roughly placed on the document tray 301 to the reading position (predetermined position) of the document reading unit 2 (image reading unit). It has a mixed loading function that can be transported. First, the conventional document conveying section 53 will be described. FIG. 2 is a plan view of a conventional document tray 301 in which documents D of different sizes are arranged in a rough set. As shown in FIG. 2, the document tray 301 includes a pair of side regulating plates 305 (a pair of regulating members) that regulate the position of the document D placed on the document tray 301 in the width direction. The width direction is a direction perpendicular to the transport direction (feeding direction) of the document D and parallel to the surface of the document D. As shown in FIG. The side regulating plate 305 is configured to be steplessly movable in the width direction of the document tray 301 so as to always be symmetrical with respect to the center in the width direction of the document tray 301 . The pair of side regulating plates 305 function as a pair of aligning members that align the center of the document D placed on the document tray 301 with the center of the document tray 301 in the width direction.

In the conventional technique, one end in the width direction of different size documents D (D1, D2, D3) mixedly placed on the document tray 301 is brought into contact with, for example, the side regulation plate 305 on the back side, and the documents D are separated. , the document is prevented from skewing. As shown in FIG. 2, when the small-size document D1 is rough-set on the document tray 301 without being restricted by any of the side regulating plates 305 at both side edges in the width direction, the small-size document D1 is skewed. row conveyed. In the prior art, in order to prevent the small-sized document D1 from being conveyed obliquely, the user places one end of the small-sized document D1 in the width direction in contact with the side regulation plate 305 on the far side and places it on the document tray 301 . It is necessary to arrange the small size document D1 on the .

(Description of Oblique Feeding Phenomenon (Skew) of Small Size Document D1)
The small size document D1 is placed at an arbitrary position in the width direction on the document tray 301 (rough set placement) without being regulated by any of the side regulating plates 305 at both side edges in the width direction. In FIG. 2, the center of the small size document D1 (center of gravity position G1) in the width direction is deviated from the center of the feed roller 303 by the amount of deviation X1 to the rear side, and the vicinity of the front corner in the width direction of the small size document D1 is shifted. , the feeding roller 303 is arranged to abut on.

FIG. 3 is a plan view of a conventional document tray 301 for explaining skew feeding of the small size document D1. Documents D (D1, D2, and D3) of different sizes are arranged on a document tray 301 in the conventional document transport section 53 shown in FIG. As shown in FIG. 3, different-sized originals D (D1, D2, D3) mixed on the conventional original tray 301 are arranged along the transport direction of the originals D, the small size original D1, the original D2, and the maximum size original D1. The document D3 is conveyed one by one by the feeding roller 303 in order. However, when the documents D (D1, D2, and D3) are arranged in rough set, the small size document D1 and the document D2 other than the maximum size document D3 are restricted at both side edges in the width direction by the pair of side restriction plates 305. It has not been.

Both side edges of the small size document D1 in the width direction are not regulated by the side regulating plate 305, and the center (center of gravity position G1) of the small size document D1 is displaced from the center of the feed roller 303 by the amount X1. is in contact with the vicinity of the front corner in the width direction of the small size document D1. At this time, when the small-sized original D1 is conveyed by the conveying force F of the feeding roller 303, the force balance with the conveying resistance force R1 generated in the small-sized original D1 causes the small-sized original D1 to move around the center of gravity position G1 of the small-sized original D1. A clockwise turning moment M1 is produced. The small size document D1 is rotated clockwise to the position of the small size document D1' indicated by the two-dot chain line in FIG. 3 by the turning moment M1. The small-sized document D1' is conveyed while the leading end thereof in the conveying direction of the small-sized document D1' is rotated by a skew amount α.

The transport resistance R1 generated on the small size document D1 is defined by the following equation 1 using the coefficient of friction μ1 and the load W1.
R1=μ1×W1 (Formula 1)
Here, the coefficient of friction μ1 is the coefficient of friction between the lower surface of the small size document D1 and the upper surface of the document D2 stacked immediately below the small size document D1. A load W1 is a load applied by the feeding roller 303 to the small-size document D1. A load W1 is a load acting on the small-size document D1 from above toward the document tray 301 at the center of the feeding roller 303 indicated by a black circle in FIG.

Also, the turning moment M1 generated around the center of gravity G1 of the small size document D1 being conveyed by the feeding roller 303 is defined by the following equation 2 using the conveying force F of the feeding roller 303 and the deviation amount X1. be done.
M1=F×X1 (Formula 2)

The turning moment M1 decreases as the amount of deviation X1 between the center of the small size document D1 in the width direction (center of gravity position G1) and the center of the feeding roller 303 decreases. When the small-size original D1 is conveyed by the feed roller 303 and turned by the turning moment M1 to reduce the deviation amount X1, the turning moment M1 becomes smaller. That is, while the small size original D1 is being conveyed by the feeding roller 303, the skew feeding phenomenon continues until the deviation amount X1 between the center of the small size original D1 (center of gravity position G1) and the center of the feeding roller 303 is eliminated. (skew).

(Description of Large Skew Feeding of Small Size Document D1 in Rough Set Arrangement in Conventional Configuration)
FIG. 4 is a plan view of document tray 301 provided with conventional friction member 406 . When different size documents D (D1, D2, D3) are roughly set on the document tray 301 in the conventional document transport section 63 shown in FIG. The state in which the sheet is conveyed by pressing is described below. The conventional friction member 406 is provided outside one end (front end) of the feed roller 303 in the width direction and in contact with the document D upstream of the feed roller 303 in the transport direction. there is Therefore, depending on the position of the small size document D1 rough set on the document tray 301, the conventional friction member 406 increases the skew of the small size document D1 and prevents the skew of the small size document D1 being conveyed. Sometimes I can't.

The small size document D1 is rough set on the document tray 301 without being restricted by any of the side restriction plates 305 at both side edges in the width direction. In FIG. 4, the center of the small size original D1 (center of gravity position G1) in the width direction is deviated from the center of the feed roller 303 by the amount of deviation X1 toward the near side of the width direction of the small size original D1. , the feeding roller 303 is arranged to abut on. At this time, when the small-sized document D1 is conveyed by the conveying force F of the feeding roller 303, the conveying resistance R1 generated in the small-sized original D1 causes the small-sized original D1 to turn counterclockwise around the center of gravity position G1 of the small-sized original D1. A moment M1 is produced.

Further, the friction member 406 abuts the small-size document D1 on the upstream side of the feed roller 303 by a distance X2 in the transport direction, with the center in the width direction forward of the center of the feed roller 303 by the shift amount X3. At this time, when the small-sized document D1 is conveyed by the conveying force F of the feeding roller 303, the frictional force applied to the small-sized original D1 by the friction member 406 causes the conveying resistance R2 to act on the small-sized original D1. A counterclockwise turning moment M2, which is the same as the turning moment M1, is generated on the small-size document D1 with the friction member 406 as the center.

The transport resistance R2 acting on the small-size document D1 by the friction member 406 is defined by the following equation 3 using the friction coefficient μ1 and the load W2.
R2=μ1×W2 (Formula 3)
Here, the coefficient of friction μ1 is the coefficient of friction between the lower surface of the small size document D1 and the upper surface of the document D2 stacked immediately below the small size document D1. A load W2 is a load applied by the friction member 406 to the small size document D1 in the direction toward the document tray 301 from above at the center of the friction member 406 indicated by a black circle in FIG.

A turning moment M2 generated about the friction member 406 with respect to the small-size document D1 being conveyed by the feeding roller 303 is defined by the following equation 4 using the conveying resistance R2 and the deviation amount X3. .
M2=R2×X3 (Formula 4)

Due to the turning moment M2 generated by the conventional friction member 406, the skew of the small size document D1 increases. The small size document D1 is rotated counterclockwise to the position of the small size document D1' indicated by the two-dot chain line in FIG. 4 by the turning moment M1 and the turning moment M2. The small-sized document D1' is conveyed while the leading end portion thereof in the conveying direction of the small-sized document D1' turns with a large skew amount β.

(Description of document skew prevention in the first embodiment)
The document conveying unit 3 of the first embodiment transports a plurality of different size documents D (D1, D2, D3) roughly placed on the document tray 301 to the reading position (predetermined position) of the document reading unit 2. It has a mixed loading function that can be transported. The document conveying section 3 includes a skew prevention mechanism that prevents the document from skewing even in a rough set arrangement in which both side edges of the document D in the width direction are not regulated by the side regulating plates 305 . FIG. 5 is a plan view of the document tray 301 provided with the friction member 306 (frictional force imparting member) of the first embodiment. FIG. 5 shows an example of a state in which documents D (D1, D2, D3) of different sizes are roughly set on the document tray 301 and the small size document D1 is conveyed. When documents of different sizes are placed together on the document tray 301, the small size document D1 is placed on the document tray 301 without abutting both side edges in the width direction of the small size document D1 against the side regulating plates 305. Sometimes. The document conveying section 3 is configured so as to allow a rough set arrangement. In the rough set arrangement, the small size document D1 is placed within a range in which the feeding roller 303 can contact in the width direction of the small size document D1 without abutting the side regulating plates 305 on both side edges of the small size document D1 in the width direction. Free initial placement of D1 is allowed.

In the document conveying unit 3 of the first embodiment, the document D is placed on the document tray 301 within a range where the document D can come into contact with the feeding roller 303 provided at the center of the document tray 301 in the width direction, in view of improving user operability. placed above. For example, as shown in FIG. 5, the small size document D1 is placed on the document tray 301 without being restricted by any of the side restriction plates 305 at both side edges in the width direction. The document conveying section 3 according to the first embodiment can convey the small size document D1 in a rough set arrangement in which the small size document D1 can be arranged at any position in the width direction.

If the center (the center of gravity position G1) of the small size document D1 and the center of the feed roller 303 are misaligned in the conventional document transport section 63 described above with reference to FIG. The friction member 406 causes an oblique transport phenomenon (skew). On the other hand, in the document conveying unit 3 of the first embodiment shown in FIG. 5, the friction member 306 is placed on the document D at the center of the feeding roller 303 in the width direction and on the upstream side of the feeding roller 303 in the conveying direction. provided to abut. In the width direction, the center of the friction member 306 may coincide with the center of the feeding roller 303, but may be shifted within a predetermined error range. The friction member 306 applies a transport resistance R2 to the document D (D1, D2, D3). Even if the center (center of gravity position G1) of the small size document D1 and the center of the feed roller 303 are misaligned in the width direction, the friction member 306 can prevent the skew of the small size document D1.

In the first embodiment, the friction member 306 is provided with a roller member so as to apply a frictional force to the document D, but not to damage the document D. As shown in FIG. The roller member rotates following the movement of the document D in the transport direction. In FIG. 5, the small size document D1 is not regulated by the side regulating plates 305 at both side edges in the width direction, and the center (center of gravity position G1) of the small size document D1 is displaced from the center of the feeding roller 303 by the amount X1. It is placed on the document tray 301 with a shift. The feeding roller 303 is in contact with the small size document D1 near the front corner of the small size document D1 in the width direction. At this time, as shown in FIG. 5, when the small-sized document D1 is conveyed by the conveying force F of the feeding roller 303, a clockwise turning moment M1 is generated around the center of gravity position G1 of the small-sized document D1.

Further, the friction member 306 is configured to abut against the small-size document D1 at a position a distance X2 from the feeding roller 303 on the upstream side of the feeding roller 303 in the transport direction. At this time, when the small-size original D1 is conveyed by the conveying force F of the feeding roller 303, the friction member 306 generates a counterclockwise turning moment M1 generated around the center of gravity G1 of the small-size original D1 in the opposite direction. A clockwise turning moment M2 is produced.

The transport resistance R2 acting on the small-size document D1 by the friction member 306 is defined by the following equation 5 using the friction coefficient μ1 and the load W2.
R2=μ1×W2 (Formula 5)
Here, the coefficient of friction μ1 is the coefficient of friction between the lower surface of the small size document D1 and the upper surface of the document D2 stacked immediately below the small size document D1. A load W2 is a load applied by the friction member 306 to the small size document D1 in the direction toward the document tray 301 from above at the center of the friction member 306 indicated by a black circle in FIG.

A turning moment M2 generated around the friction member 306 with respect to the small size document D1 being conveyed by the feeding roller 303 is defined by the following equation 6 using the conveying resistance R2 and the deviation amount X1. .
M2=R2×X1 (Formula 6)

The turning moment M2 generated by the friction member 306 cancels out the turning moment M1 generated clockwise around the center of gravity position G1 of the small size document D1 conveyed by the feeding roller 303. FIG. Therefore, according to the first embodiment, even if the center (center of gravity position G1) of the small size document D1 is displaced from the center of the feeding roller 303, skewing of the small size document D1 can be prevented. .

In the first embodiment, the transport resistance R2 generated by the friction member 306 is less than or equal to the transport force F of the feed roller 303 so that the feed roller 303 can transport the small-size document D1. It is necessary to set the transport resistance R2 as follows. Here, if the coefficient of friction μ2 between the friction member 306 (roller member that is driven to rotate) and the small-size document D1 is increased, the turning of the small-size document D1 is restricted, and the skew prevention effect of the small-size document D1 is enhanced. can be expected.

Also, the roller member of the friction member 306 uses a rubber material as a material with a high coefficient of friction, but a sponge material or a resin material may also be used. There are no restrictions with respect to the material of the roller members. According to the first embodiment, the small size document D1 is transported to the position of the small size document D1' indicated by the chain double-dashed line in FIG. 5 without causing skew.

(Verification by simulation in this embodiment)
In order to verify the skew prevention of the small size document D1 by the friction member 306, the following simulation conditions were used as an example for each component parameter, and a transport simulation of the small size document D1 was performed using the non-linear structural analysis tool Abaqus.

(Feeding roller 303)
・ Outer diameter 24 [mm], elastic part thickness 3 [mm], width 20 [mm]
・Young's modulus of elastic part 0.4 [MPa], Poisson's ratio 0.4
- Biasing load to small size document D1 0.5 [N]
・Coefficient of friction with the small size document D1 0.3

(Friction member 306 (roller member driven to rotate))
・ Outer diameter 24 [mm], elastic part thickness 3 [mm], width 20 [mm]
・Young's modulus of elastic part 0.4 [MPa], Poisson's ratio 0.4
- Biasing load to small size document D1 0.25 [N]
・Coefficient of friction with the small size document D1 0.3

(Small size original D1)
・Width direction length 100 [mm], transport direction length 200 [mm], thickness 0.1 [mm]
・Young's modulus 1800 [MPa], Poisson's ratio 0.4
・Coefficient of friction with the lower surface 0.2
However, the condition was set so that the plurality of originals D (D2, D3) stacked on the lower surface of the small-sized original D1 were not considered.

Also, the small size document D1 is arranged with a deviation amount X1=40 [mm] between the center of the small size document D1 and the center of the feeding roller 303 in the width direction. After the small size original D1 was conveyed by 160 [mm] in the conveying direction by the feeding roller 303, the skew amount α [deg] of the leading end of the small size original D1 in the conveying direction was output.

(Arrangement Range of Friction Member 306)
FIG. 6 is a simulation result showing the relationship between the distance X2 between the friction member 306 and the feeding roller 303 of the first embodiment and the skew amount α [deg] of the leading edge of the small-size document D1 in the transport direction. As shown in FIG. 6, the skew amount α of the leading edge of the small-size document D1 in the transport direction changes according to the distance X2 between the friction member 306 and the feeding roller 303. As shown in FIG. As the position of the friction member 306 approaches the position of the center of gravity G1 (X2=88 [mm] in FIG. 6) of the small size document D1 from the position of the feeding roller 303, the skew amount α of the leading end of the small size document D1 in the transport direction. tends towards the minimum. Further, when the position of the friction member 306 moves away from the center of gravity G1 of the small-size document D1 toward the upstream side in the transport direction, the skew amount α of the leading end in the transport direction of the small-size document D1 sharply increases.

Here, when the distance X2 is 0 (X2=0), the skew amount .alpha. 8 [deg] (α=1.8). If the skew amount α = 1.2 [deg], which can be expected to have a skew prevention effect of 30% or more from the skew amount α = 1.8 [deg] of the conventional configuration, is set as the threshold value, the friction as shown in FIG. A distance X2 between the member 306 and the feed roller 303 is set to 120 [mm] or less (X2≦120). Also, the distance X2 between the friction member 306 and the feeding roller 303 is preferably set to be greater than 12 [mm] (12<X2≦120).

Here, the effective range of the layout of the friction member 306 dimensionless with the length of the small-size document D1 in the conveying direction is defined by the following Equation 7.
Effective range ≤ (radius of feed roller 303 + distance X2 between friction member 306 and feed roller 303 indicating skew amount α equal to or less than threshold value)/(conveyance direction length of small size document D1) (equation 7)

By substituting the values used in the simulation conditions described above into Equation 7, a non-dimensional effective range of the arrangement of the friction member 306 based on the length of the small size document D1 in the transport direction can be obtained.
Effective range ≤ (12 [mm] + 120 [mm]) / (200 [mm]) = 0.66
Effective range ≤ 0.66 (≈ 2/3)

Also, the lower limit of the effective range may be, for example, as follows.
(12 [mm] + 12 [mm]) / (200 [mm]) = 0.12 < effective range 0.12 (= 3/25) < effective range

According to the first embodiment, in the document transport section 3 having the function of mixing document sizes and capable of rough setting arrangement of the document D, the small size document D1 whose both side edges in the width direction are not regulated is transported. It is possible to prevent skewing of time. The friction member 306 is arranged within a range of a distance of 2/3 or less of the length of the minimum size document from the feed roller 303 toward the upstream in the transport direction of the document D. FIG. Further, the friction member 306 is arranged within a range of distance larger than 3/25 of the length of the minimum size document from the feed roller 303 toward the upstream in the transport direction of the document D. FIG. As a result, the document conveying unit 3 can reduce the skew amount of the document D regardless of the position of the document D placed on the document tray 301 . While the frictional force imparting member in the conventional technology may increase the amount of skew feeding of the document D that is rough set, the friction member 306 of the document conveying section 3 of the first embodiment does not convey the document D. It is possible to reduce the amount of skew at time.

(Contact/separation mechanism of the first embodiment)
The document conveying section 3 of the first embodiment is configured so as to allow a rough set arrangement in which both side edges in the width direction of the document D are not restricted, and the document D caused by an uneven biasing force in the width direction of the document D. A configuration is provided to prevent swiveling. 7A and 7B are explanatory diagrams of the contact/separation mechanism 320 for contacting the document D with the friction member 306 of the first embodiment.

FIG. 7A is a cross-sectional view of the contact/separation mechanism 320 (mechanism) in the separated state in which the friction member 306 and the feed roller 303 of the first embodiment are separated from the small-size document D1. As shown in FIG. 7A, a plurality of originals D of different sizes including a small-sized original D1 are rough-set on the original tray 301 . The feeding unit 309 integrally holds the feeding roller 303 and the drawing roller 307 . The pull-out roller 307 is arranged downstream of the feed roller 303 in the document D transport direction. The separation unit 304 is arranged downstream of the document tray 301 in the document D transport direction. The separating unit 304 separates the document D fed by the feeding roller 303 sheet by sheet. The friction member 306 is arranged upstream of the feed roller 303 in the document D transport direction. In the first embodiment, the friction member 306 is a roller member that rotates around the rotation axis C3 following the movement of the document D fed by the feeding roller 303 . The friction member 306 is rotatably provided at the upstream end of a swing arm 308 that is swingably provided in the feeding unit 309 .

FIG. 7B is a cross-sectional view of the contact/separation mechanism 320 in the first contact state in which the feeding roller 303 is separated from the small size document D1 and the friction member 306 is in contact with the small size document D1. . When the transport control of the document D set on the document tray 301 is started, the feeding unit 309 is rotated clockwise as shown in FIG. Rotate CW. In the first embodiment, the swing axis C1 is the rotation axis of the pull-out roller 307 . A swing arm 308 provided in the feeding unit 309 swings in the clockwise direction CW integrally with the feeding unit 309 rotating in the clockwise direction CW. The friction member 306 abuts on the small size document D1. At this time, the friction member 306, which is closer to the center of gravity G1 (FIG. 5) of the small-sized document D1 than the feeding roller 303, contacts the small-sized document D1 before the feeding roller 303. It is possible to prevent the small-size document D1 from turning.

FIG. 7C is a cross-sectional view of the contact/separation mechanism 320 in the second contact state (document transportable state) in which both the feed roller 303 and the friction member 306 are in contact with the small size document D1. . The feeding unit 309 rotates in the clockwise direction CW shown in FIG. 7C about the swing axis C1 until the feeding roller 303 contacts the small-size document D1. At this time, the swing arm 308 swings in the counterclockwise direction CCW shown in FIG. As a result, the feed roller 303 comes into contact with the small size document D1. As shown in FIG. 7C, the feed roller 303 and the friction member 306 contact the small-size document D1 at a distance X2 between the feed roller 303 and the friction member 306. As shown in FIG. The feeding roller 303 contacts the small-size document D1 with a load W1. The friction member 306 contacts the small size original D1 with a load W2. The feeding roller 303 conveys the small size document D1 to the position of the small size document D1' indicated by the two-dot chain line without skew by a drive unit (not shown).

That is, according to the first embodiment, after the friction member 306 near the center of gravity position G1 of the document D contacts the upper surface of the document D from above and urges the document D toward the document tray 301, the feeding roller 303 is moved. The document D is brought into contact. As a result, it is possible to prevent the document D from turning due to the feeding roller 303 contacting the document D with a non-uniform contact force in the width direction. Therefore, according to the first embodiment, when the feeding roller 303 abuts on the document D in the prior art, the document D is rotated by an uneven contact force (biasing force) in the width direction of the document D. It is possible to solve the problem of misalignment.

In the first embodiment, the friction member 306 is a roller member that rotates following the movement of the document D, but the friction member 306 is not limited to this. The friction member 306 may be a wide roller member longer than the feeding roller 303 in the width direction. The friction member 306 may be configured to provide load resistance to the rotation axis C3 of the roller member. The friction member 306 may be composed of a plurality of roller members.

The document conveying unit 3 (document conveying device) in the first embodiment has a document size mixture function capable of placing a plurality of different size documents D (D1, D2, D3) together on the document tray 301. . The document conveying unit 3 is configured to allow a rough set arrangement in which a free initial arrangement of the document D is allowed within a range in which the feeding roller 303 contacts the document D placed on the document tray 301 in the width direction. there is The document conveying section 3 can prevent the small-sized document D1, which is not regulated by the side regulating plates 305 on both sides in the width direction, from being skewed during conveyance.

According to the first embodiment, the friction member 306 is provided within a range of a distance of 2/3 or less of the length of the minimum size document in the direction of transport from the feed roller 303 toward the upstream in the direction of transport of the document D. . The minimum size document is the minimum size document that can be image-formed by the image forming apparatus 100 and transported by the document transport unit 3 . The friction member 306 is separated from the feed roller 303 by a distance greater than 1/2 of the sum of the outer diameter of the roller member of the friction member 306 and the outer diameter of the feed roller 303 so as not to contact the feed roller 303 . Stay away. The friction member 306 is preferably arranged within a range of distance greater than 3/25 of the length of the minimum size document from the feed roller 303 toward the upstream in the document D transport direction. The document conveying unit 3 can prevent the document D from being skewed regardless of the position of the document D placed on the document tray 301 . According to the first embodiment, it is possible to solve the problem that the prior art frictional force imparting member increases the skew feeding of the rough-set document and cannot prevent the skew feeding of the document during transport. According to the first embodiment, it is possible to prevent the document D from being skewed when the document D placed roughly on the document tray 301 without being regulated by the side regulating plate 305 is conveyed.

(Second embodiment)
The second embodiment will be described below with reference to FIGS. 8 and 9. FIG. In the second embodiment, the same reference numerals are given to the same configurations as in the first embodiment, and the description thereof is omitted. The image forming apparatus 100 of the second embodiment is the same as that of the first embodiment, so description thereof is omitted. As in the first embodiment, the document conveying unit 33 of the second embodiment feeds a plurality of different size documents D (D1, D2, D3) roughly placed on the document tray 301 to the document reading unit 2. It has a mixed loading function that can transport to a reading position (predetermined position). Further, as in the first embodiment, the document conveying section 33 of the second embodiment prevents the skew of the document D even in a rough set arrangement in which both side edges in the width direction of the document D are not regulated by the side regulating plates 305 . Equipped with a skew prevention mechanism. FIG. 8 is a plan view of the document tray 301 provided with the friction member 310 (frictional force imparting member) of the second embodiment. FIG. 8 shows an example of a state in which documents D (D1, D2, and D3) of different sizes are roughly set on the document tray 301 and the small size document D1 is conveyed.

The friction member 310 of the second embodiment is a flexible sheet member. A friction member 310 as a flexible sheet member is provided at the upstream end of a swing arm 308 that is swingably provided in the feeding unit 309 . The second embodiment in which the friction member 310 as a flexible sheet member is provided upstream of the feeding roller 303 also has the same effect as the first embodiment.

In the document conveying unit 33 of the second embodiment shown in FIG. 8, the friction member 310 is provided so as to contact the document D at the center of the feeding roller 303 in the width direction and on the upstream side of the feeding roller 303 in the conveying direction. It is The friction member 310 applies a transport resistance R3 to the document D (D1, D2, D3). Even if the center (center of gravity position G1) of small size document D1 and the center of feeding roller 303 are misaligned in the width direction, friction member 310 can prevent skew of small size document D1.

In the second embodiment, the friction member 310 applies a frictional force to the document D, but is provided with a flexible sheet member having good slidability so that the document D is not damaged. In FIG. 8, the small size document D1 is not restricted by the side regulating plates 305 at both side edges in the width direction, and the center (center of gravity position G1) of the small size document D1 is displaced from the center of the feeding roller 303 by the amount X1. It is placed on the document tray 301 with a shift. The feeding roller 303 is in contact with the small size document D1 near the front corner of the small size document D1 in the width direction. At this time, as shown in FIG. 8, when the small size original D1 is conveyed by the conveying force F of the feeding roller 303, a clockwise turning moment M1 is generated about the center of gravity position G1 of the small size original D1.

Further, the friction member 310 is configured to abut against the small-size document D1 at a position a distance X2 from the feeding roller 303 on the upstream side of the feeding roller 303 in the transport direction. At this time, when the small-size original D1 is conveyed by the conveying force F of the feeding roller 303, the friction member 310 generates a counterclockwise turning moment M1 generated around the center of gravity G1 of the small-size original D1 in the opposite direction. A clockwise turning moment M3 occurs.

A transport resistance force R3 acting on the small size document D1 by the friction member 310 is defined by the following equation 8 using the friction coefficient μ1 and the load W3.
R3=μ1×W3 (Formula 8)
Here, the coefficient of friction μ1 is the coefficient of friction between the lower surface of the small size document D1 and the upper surface of the document D2 stacked immediately below the small size document D1. A load W3 is a load applied by the friction member 310 to the small-size document D1 in a direction toward the document tray 301 from above at the center of the friction member 310 indicated by a black circle in FIG.

A turning moment M3 generated in the friction member 310 with respect to the small size document D1 conveyed by the feeding roller 303 is defined by the following equation 9 using the conveying resistance R3 and the deviation amount X1.
M3=R3×X1 (Formula 9)

The turning moment M3 generated by the friction member 310 cancels out the turning moment M1 generated clockwise around the center of gravity position G1 of the small-sized document D1 conveyed by the feeding roller 303 . Therefore, according to the second embodiment, even if the center (center of gravity position G1) of the small size document D1 is shifted from the center of the feeding roller 303, skewing of the small size document D1 can be prevented. .

In the second embodiment, the transport resistance force R3 generated by the friction member 310 is set equal to or less than the transport force F of the feed roller 303 so that the feed roller 303 can transport the small-size document D1. R3 needs to be set. Here, if the coefficient of friction μ3 between the friction member 310 (flexible sheet member) and the small-size document D1 is increased, the rotation of the small-size document D1 can be restricted, and the skew prevention effect of the small-size document D1 can be enhanced. I can expect it.

Also, the sheet member of the friction member 310 is made of PET (polyethylene terephthalate) resin as a material with good slidability, but other materials may be used. There are no restrictions on the material of the sheet member. According to the second embodiment, the small size document D1 is transported to the position of the small size document D1' indicated by the chain double-dashed line in FIG. 8 without causing skew.

According to the second embodiment, the document conveying section 33 having the function of mixing document sizes and capable of rough setting arrangement of the document D conveys the small size document D1 in which both side edges in the width direction are not regulated. It is possible to prevent skewing of time. The friction member 310 is arranged within a range of two-thirds or less of the length of the minimum size document from the feed roller 303 toward the upstream in the transport direction of the document D. As shown in FIG. As a result, the document conveying unit 33 can reduce the skew amount of the document D regardless of the position of the document D placed on the document tray 301 .

(Contact/separation mechanism of the second embodiment)
9A and 9B are explanatory diagrams of a contact/separation mechanism 420 for contacting the document D with the friction member 310 of the second embodiment. FIG. 9A is a cross-sectional view of the contact/separation mechanism 420 (mechanism) in the separated state in which the friction member 310 and the feed roller 303 of the second embodiment are separated from the small-size document D1. As shown in FIG. 9A, a plurality of originals D of different sizes including a small-sized original D1 are rough-set on the original tray 301 . A friction member 310 as a flexible sheet member is arranged upstream of the feeding roller 303 in the direction in which the document D is conveyed. The friction member 310 is provided at the upstream end of a swing arm 308 that is swingably provided on the feeding unit 309 .

FIG. 9B is a cross-sectional view of the contact/separation mechanism 420 in the first contact state in which the feeding roller 303 is separated from the small size document D1 and the friction member 310 is in contact with the small size document D1. . When the transport control of the document D set on the document tray 301 is started, the feeding unit 309 is rotated clockwise as shown in FIG. Rotate CW. In the second embodiment, the swing axis C1 is the rotation axis of the pull-out roller 307 . A swing arm 308 provided in the feeding unit 309 swings in the clockwise direction CW integrally with the feeding unit 309 rotating in the clockwise direction CW. The friction member 310 abuts against the small size document D1. At this time, since the friction member 310 closer to the center of gravity G1 (FIG. 8) of the small size document D1 than the feeding roller 303 contacts the small size document D1 before the feeding roller 303, the contact of the feeding roller 303 causes It is possible to prevent the small-size document D1 from turning.

FIG. 9C is a cross-sectional view of the contact/separation mechanism 420 in the second contact state (document transportable state) in which both the friction member 310 and the feed roller 303 are in contact with the small size document D1. . The feeding unit 309 rotates in the clockwise direction CW shown in FIG. 9C about the swing axis C1 until the feeding roller 303 comes into contact with the small size document D1. At this time, the swing arm 308 swings in the counterclockwise direction CCW shown in FIG. As a result, the feed roller 303 comes into contact with the small size document D1. As shown in FIG. 9C, the feed roller 303 and the friction member 310 contact the small-size document D1 at a distance X2 between the feed roller 303 and the friction member 310. As shown in FIG.

A swing shaft C2 provided at the downstream end of the swing arm 308 is provided with a torsion spring (not shown) that applies a biasing force to the swing arm 308 so that the friction member 310 contacts the small-size document D1 with a load W3. ) is provided. The feeding roller 303 contacts the small size document D1 with a load W1, and the friction member 310 contacts the small size document D1 with a load W3 at a distance X2 from the feeding roller 303 to the upstream side. The feeding roller 303 conveys the small size document D1 to the position of the small size document D1' indicated by the two-dot chain line without skew by a drive unit (not shown).

That is, according to the second embodiment, after the friction member 310 near the center of gravity position G1 of the document D contacts the upper surface of the document D from above and urges the document D toward the document tray 301, the feeding roller 303 is moved. The document D is brought into contact. As a result, it is possible to prevent the document D from turning due to the feeding roller 303 contacting the document D with a non-uniform contact force in the width direction.

In the second embodiment, the friction member 310 is a flexible sheet member, but the friction member 310 is not limited to this. The friction member 310 may be a wide sheet member longer than the feeding roller 303 in the width direction, or may be a sheet member having a width equal to or less than the length of the feeding roller 303 in the width direction. The friction member 310 may have a configuration in which a load (load resistance) applied to the document D is adjusted by stacking a plurality of sheet members. The friction member 310 may be configured by arranging a plurality of sheet members in the width direction, or may be configured by arranging a plurality of sheet members in the document D transport direction.

In the second embodiment, as in the first embodiment, the friction member 310 extends from the feeding roller 303 toward the upstream side in the direction of transport of the document D, within a range of 2/3 or less of the length of the minimum size document in the direction of transport. It should be provided inside. The friction member 310 is preferably separated from the feeding roller 303 so as not to contact the feeding roller 303 . The friction member 306 is preferably arranged within a range of distance greater than 3/25 of the length of the minimum size document from the feed roller 303 toward the upstream in the document D transport direction. According to the second embodiment, it is possible to prevent the document D from being skewed when the document D placed roughly on the document tray 301 without being regulated by the side regulating plate 305 is conveyed.

3, 33 . . . Document conveying section 301 .. Document tray 303 . Documents R2, R3 Conveyance resistance forces 320, 420 Contact/separation mechanism

Claims (12)

a document tray on which documents are placed;
a conveying member that conveys the document placed on the document tray in a conveying direction;
a friction member arranged upstream of the conveying member in the conveying direction and applying a conveying resistance force to the document;
a mechanism for bringing the conveying member into contact with the document after the friction member is brought into contact with the document placed on the document tray;
A document conveying device comprising
The friction member is arranged upstream from the conveying member in the conveying direction, within a range of distance equal to or less than two-thirds of the length of the minimum size document that can be conveyed by the document conveying device in the conveying direction. A document feeder characterized by: The friction member is arranged upstream from the conveying member in the conveying direction within a range of a distance of more than 3/25 and 2/3 or less of the length of the minimum size document in the conveying direction. 2. The document conveying device according to claim 1. The mechanism includes a separated state in which the conveying member and the friction member are separated from the document placed on the document tray, and a first separation state in which the conveying member is separated from the document and the friction member contacts the document. 3. The document conveying apparatus according to claim 1, wherein the document conveying apparatus is configured to take a contact state and a second contact state in which the conveying member and the friction member contact the document. 4. The document conveying apparatus according to claim 3, wherein the conveying member conveys the document when the mechanism is in the second contact state. 5. The document conveying apparatus according to claim 1, wherein the conveying resistance of the friction member is equal to or less than the conveying force of the conveying member. 6. The document conveying apparatus according to claim 1, wherein the friction member includes a roller member that rotates following movement of the document conveyed by the conveying member. 6. The document conveying device according to claim 1, wherein the friction member includes a flexible sheet member. Aligning the center of the document placed on the document tray with the center of the document tray in a width direction that is perpendicular to the transport direction and parallel to the surface of the document placed on the document tray. 8. The document conveying apparatus according to claim 1, further comprising a pair of aligning members for aligning the document. When a plurality of originals of different sizes are stacked on the original tray, both side edges of the small-sized original in the width direction do not contact the pair of aligning members, and the small-sized original is moved in the width direction. 9. The document conveying apparatus according to claim 8, wherein the document conveying apparatus is configured so as to be roughly set on the document tray within a range where the conveying member can come into contact with the conveying member. 10. The document conveying device according to claim 8, wherein the center of the friction member coincides with the center of the conveying member in the width direction. 11. The apparatus according to any one of claims 1 to 10, further comprising a separating section disposed downstream of the document tray in the transport direction and separating one by one the plurality of documents transported by the transport member. Document transport device described. a document conveying device according to any one of claims 1 to 11;
an image reading unit that reads an image of a document conveyed by the document conveying device;
an image forming unit that forms an image on a recording medium according to the image data read by the image reading unit;
An image forming apparatus comprising:

Images