JPH0585630A - Sheet feeding device - Google Patents

Abstract

PURPOSE:To maintain a stable feed function by setting a ratio or a circumferential speed of a separation roller to a circumferential speed of an inverse rotation roller, an angle from a forward end of a separated stand-by sheet to the most upstream position of feed of a protruding part about a center of an axis of the separation roller, and a non-drive transmission angle of a one-way clutch to be in a specified relation. CONSTITUTION:A separation roller 25 is protruded up from a surface of a lower document guide 29. A ratio of a circumferential speed of the separation roller 25 to a circumferential speed of an inverse rotation roller 1 is set to be alpha, an angle of a range from a shaft end C of the separation roller 25 to the most upstream position D of feed of a protruding part of the separation roller 25 in an outer circumferential surface of the protruding part formed about a center of an axis of the separation roller 25 is set to be theta0, and a non-drive transmission angle of a spring clutch, that is a backlash angle, is set to be thetaBK, where thetaBK<(alpha+1)theta0 is satisfied. In this condition, a forward end of a sheet 31b on the back prevented from getting in contact with the separation roller 25 to be returned excessively for realizing a preferable feed. Mounting defective, feed defective, or diagonal feed will not occur for a sheet 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device used in a document feeding system such as a facsimile and a copying machine.

[0002]

2. Description of the Related Art FIGS. 13A and 13B show a conventional sheet feeding apparatus. The sheet stacking table 100 is provided horizontally, and below the sheet stacking table 100, a separation roller 101 that rotates counterclockwise in the forward direction is provided. The positive rotation transmits the driving force of a driving source (not shown) through a one-way clutch (not shown). Further, a reverse rotation roller 102 that rotates forward in the counterclockwise direction is provided above the stacking table 100 and at a position facing the separation roller 101.

On the other hand, on the downstream side of the separating roller 101 in the feeding direction, the feeding roller 103 which rotates in the counterclockwise direction in the normal direction.
And the pinch roller 10 that rotates following the feed roller 103.
4 and are provided.

In the above structure, the separation roller 101 rotates normally and the reverse rotation roller 102 also rotates normally. As a result, the lowermost sheet 105 is separated by the separation roller 101.
Only the sheet is fed to the downstream side as indicated by the arrow, and the feeding of the other sheets 106 and 107 is restricted by the reverse rotation roller 102.

Further, by setting the peripheral speed of the feed roller 103 higher than that of the separation roller 101,
It is configured such that the rear end of the downstream sheet 105 and the front end of the upstream sheet 106 are reliably spaced from each other.

Furthermore, the sheet 105 is fed by the feed roller 10.
3. While feeding by the pinch roller 104, the separation roller 101 is released from the transmission of the driving force by the one-way clutch, and is rotated following the frictional resistance with the sheet.

[0007]

However, in the above-mentioned conventional example, the trailing edge of the sheet is separated by the separating roller 10 as shown in FIG.
The separation roller 101 follows the reverse rotation roller 102 in the clockwise direction immediately after the contact point between the reverse rotation roller 102 and the reverse rotation roller 102 is removed and until the driving force is transmitted to the separation roller 101 via the one-way clutch. It will rotate in reverse.

As a result, the separation roller 101 pushes back the sheet in the feeding standby state to the upstream side, which may cause sheet stacking failure, feeding failure, skew feeding, and the like.

An object of the present invention is to solve the above problems, and an object of the present invention is to provide a sheet feeding apparatus in which the amount of pushing back the sheet due to the reverse rotation of the separation roller is reduced as much as possible.

[0010]

To achieve the above object, the present invention is directed to a separation roller having an outer peripheral surface in contact with a sheet, and a normal rotation drive of the separation roller for feeding the sheet in a predetermined direction. A separating clutch, the separating roller is disposed at a position where the outer peripheral surface of the separating roller protrudes from the sheet stacking table, and a reverse rotation roller that rotates in the forward direction is provided at a position facing the separating roller. In a sheet feeding device provided with a feed roller that rotates in the forward direction on the downstream side in the feeding direction, the peripheral speed of the feed roller is set to be higher than the peripheral speed of the separation roller, and the reverse rotation is performed. The ratio of the peripheral speed of the separating roller to the peripheral speed of the roller is α, and is the outer peripheral surface of the protruding portion of the separating roller, from the leading edge of the sheet waiting for separation to the most upstream position in the feeding direction of the protruding portion. Region, the angle formed about the axis of the separating roller and theta _0, when the non-drive transmission angle of the one-way clutch and theta _BK, characterized in that the _{θ BK <(α + 1)} θ 0 ..

A spring clutch may be used as the one-way clutch.

[0012]

In the present invention based on the above construction, the separation roller and the reverse rotation roller rotate in the forward direction, and only one sheet on the stacking table is fed to the downstream side due to the frictional resistance with the separation roller. Since the peripheral speed of the feed roller is higher than the peripheral speed of the separation roller from the time when the leading edge of the sheet comes into contact with the feed roller, the sheets are fed at intervals one by one.

Further, when the trailing edge of the sheet fed to the downstream side comes out of the contact point between the separation roller and the reverse rotation roller, the separation roller follows the reverse rotation roller until the driving force is transmitted by the one-way clutch. Reverse rotation, but θ _BK <(α +
1) The amount of reverse rotation is small due to the relationship of θ ₀ , and the sheet does not separate from the outer peripheral surface of the separation roller.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. 1 is a plan view of a facsimile apparatus to which the present invention is applied, and FIG.
1A is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 2B is a partial front view seen from the direction of arrow B in FIG. In the figure, 29 is a lower document guide as a sheet stacking table,
It has an inclined portion 29a on the upstream side in the feeding direction and a horizontal portion 29b connected to the downstream side of the inclined portion 29a.

Below the inclined portion 29a, there is provided a separation roller 25 which rotates around the support shaft 27, and the horizontal portion 2 is provided.
A feed roller 26 that rotates around a support shaft 28 is provided below 9b. The separation roller 25 and the feed roller 26 are made of silicone rubber. Further, the separation roller 25 and the feed roller 26 are positively rotated in the arrow direction, that is, the counterclockwise direction by a drive source (not shown). Now, Fig. 8
As shown in (A), the sleeve 54 of the separation roller 25 incorporates a spring clutch 34b that allows the roller to overrun in the sheet feeding direction.
A gear 36 fixed by a key 38 is attached to the drive shaft 37. This gear 36 is a gear 3 attached to the shaft 27.
It meshes with 5. When the paper sheet 31 is being fed by the feed roller 26 having a peripheral speed faster than that of the separation roller 25, the separation roller 25 rotates along with the paper sheet 31.

On the other hand, above the lower original guide 29,
A plate-shaped upper original guide 17 formed in a substantially bow shape corresponding to the shape of the lower original guide 29 is provided. Upper document guide 17
A fulcrum 33 is connected to a main body frame (not shown) on the downstream side of, and is held at a constant height with respect to the lower original guide 29 by a locking means (not shown) as shown in FIG.
Further, when the locking means is released, the upper document guide 17 can be lifted upward as shown in FIG. 3 around the fulcrum 33.

A pair of side plates 12 and 13 are provided on the upper surface of the upper original guide 17 so as to face each other. This side plate 12, 13
Is made of polyacetal, connected by stay 14,
The stay 14 is attached to the side plates 12 and 1 by screws 16b and 16d.
It is fixed to 3.

A reversing roller 1 is provided at a position facing the separating roller 25, that is, between the side plates 12 and 13. The reverse roller 1 is made of silicone rubber and has a stay 14
It is attached so as to be rotatable relative to an axis 8 parallel to the axis.
Both ends of the shaft 8 are attached to the side plate 1 by screws 16a and 16c.
It is fixed to 2 and 13.

A pinch roller 2 made of silicon rubber is provided at a position facing the feed roller 26. The pinch roller 2 is attached to the shaft 9, which is the side plate 1.
Both ends were rotatably supported by 2 and 13. Axis 9 is roller 15
It is inserted in a and 15b.

A gear 3 is attached to the shaft 9 of the pinch roller 2 and meshes with the gear 4. The gear 4 is rotatably attached to a shaft 10 attached to a side plate 13. Further, a gear 4a having a smaller diameter than the gear 4 is integrally attached to the gear 4.

On the other hand, a shaft 11 is rotatably attached to the side plate 13, and a gear 5 is fixed to one end of the shaft 11 by a pin. The gear 5 meshes with the gear 4a. Further, a gear 6 is provided at the other end of the shaft 11, and the gear 6
Meshes with a gear 7 mounted on a shaft 8. Between the gear 6 and the shaft 11 has a built-in torque limiter 32, set to the reverse rotation roller 1 value T _R more torque is adapted to take the slip. Reverse roller 1 to screw 16
a, 16b, 16c, 16d and torque limiter 32
This constitutes an independent reverse rotation roller unit Y.

The upper original guide 17 and the lower original guide 29
Conveying rollers 50 and 51 are provided on the downstream side of. The transport roller 50 is rotatably attached to the shaft 52. 18a and 18b are behind the leaf springs provided along the feeding direction, and one end side of the leaf springs 18a and 18b is a roller 15
a and 15b, and the other end side is placed on the shaft 52.

A leaf spring stay rear portion 19 is provided between the pinch roller 2 and the conveying roller 50, and the leaf spring stay rear portion 19 is fixed to the upper original guide 17 by a screw 20. The pinch roller 2 is pressed toward the feed roller 26 by pressing the center of the leaf spring rear portion 18b downward at one end.

Further, the leaf spring stay front 22 is fixed to the upper document guide 17 with a screw 23. Further, front leaf springs 21a and 21b are fixed to the front leaf spring stays 22 by screws 53, and the shaft 8 and the reverse rotation roller 1 are pressed toward the separation roller 25 side by the elastic force of the front leaf springs 21a and 21b.

Upper document guide 1 upstream of the reverse roller 1
On the lower surface of 7, the guides 24a, 2
4b is provided. The guides 24a and 24b are made of low-rigidity members.

In the above structure, the sheet on the upper surface of the lower original guide 29, that is, the sheet 31 is fed to the downstream side from the lowermost sheet by the rotation of the separating roller 25 in the counterclockwise direction. Then, the paper sheet 31 passes between the pinch roller 2 and the feed roller 26 and is further transported to the downstream side.

In the present invention, the separation roller 25
Project upward from the surface of the lower original guide 29.
Further, the ratio of the peripheral speed of the separation roller 25 to the peripheral speed of the reverse rotation roller 1 is α, and as shown in FIGS. A region from the leading edge C of the rear five trailing paper sheets to the most upstream position D of the protruding portion in the feeding direction is defined by an angle θ _{0 about} the axis of the separating roller 25, and the non-drive transmission angle of the spring clutch. ,
That is, when the backlash angle is θ _BK , θ _BK <(α + 1) θ ₀ .

On the other hand, the frictional force between the rollers or between the rollers and the paper sheet is applied between the reverse roller 1 and the separation roller 25 ... Between the F ₁ pinch roller 2 and the feed roller 26 ... Between the F ₂ reverse roller 1 and the paper sheet 31. and F ₃ separation roller 25 and the paper sheet 31 between ... F ₄ between two paper 31 ... F ₅ pinch roller 2 between the paper 31 ... F ₆ feed roller 26 between the paper 31 ... F _7, the reverse roller 1 , Radii of the pinch rollers 2 are r ₁ and r ₂ , respectively, and a reduction ratio from the pinch roller 2 to the reverse rotation roller 1 is η, each value is a friction coefficient of each roller and leaf springs 18a, 18b, 21a, 21b. Therefore, F ₁ r ₁ > T _R (i) F ₃ r ₁ > T _R > F ₅ r ₁ (ii) F ₄ > F ₅ (iii) ηF ₂ r ₂ > T _R (iv) ηF _{Since 6} r ₂ > T _R (v) ηF ₇ r ₂ > T _R (vi), the paper for the lower original guide 29 is set. This automatic paper feeder operates as follows according to the set of leaves. (1) When there is no sheet (see FIG. 5) i) and iv), the reverse rotation roller 1 and the pinch roller 2 rotate with the separation roller 25 and the feed roller 26, respectively, and the torque limiter 32 slides. (2) When there is only one sheet (see FIG. 6) ii) (F ₃ r ₁ > T _R ), v), vi) the reverse roller 1
And the pinch roller 2 rotates together with the separation roller 25 and the feed roller 26 via the paper sheet 31, and the torque limiter 32 slides (performs the same operation as (1)). (3) When there are two or more sheets (see FIG. 7) ii), iii), v), and vi), the pinch roller 2 rotates with the feed roller 26 via the sheet, and the reverse roller 1 Rotates in the forward direction to return the paper sheets other than the bottommost paper sheet to the upstream direction in the paper sheet conveyance direction. The torque limiter 32 does not slip, but slips between paper sheets.

Now, the radius of the reverse roller 1 is r _R , the angular velocity is ω _R , the radius of the separating roller 25 is r _B , and the separating roller shaft 2 is
The angular velocity of 7 is ω _B, and the trailing edge of the leading leaf 31a is the trailing leaf 3
1 sec after passing the point C at the tip of the 1b, the separation roller 2
When the reverse roller 5 reverses θ (rad) with the reverse roller 1, the spring clutch 34b is activated and the reverse rotation of the separation roller 25 is shown in FIG.
If it stops as in (B), the amount of displacement of each roller and shaft during this t seconds is (rotation amount of reverse rotation roller 1) = r _R ω _R t ... (Reverse rotation amount of separation roller 25) = r _B θ. (Rotation angle of separation roller shaft 27) = ω _B t. However, since the (reverse rotation amount of the roller 1) = (amount of the reverse rotation of the separation roller 25) ... (rotation angle of the separation roller shaft 27) + theta = theta _BK ... have a relationship, - a, when fitted to eventually r _B θ = r _R ω _R t ... ω _B t + θ = θ _BK ...

[0030]

[Equation 1] Becomes

The return amount of the leading edge of the rear sheet 31b is equal to the reverse rotation amount r _B θ () of the separating roller 25,
In order that the set state of b is not disturbed and the feeding failure does not occur, even if the rear sheet 31b is returned, the leading edge of the rear sheet 31b is separated by the separation roller 2
The state of being in contact with No. 5 is desirable, and this condition is represented by θ <θ ₀ . If θ> θ ₀ , the rear sheet 31
This is because the tip of b is returned to the point D in FIG. 12 and causes non-feeding. Substituting into equation 10

[0032]

[Equation 2] Therefore, this equation 11 is a constant relationship between α, θ ₀ , and θ _BK for preventing the occurrence of the above-described feeding failure. In the present embodiment, the values of α, θ _BK and θ ₀ are 1, 0.
Since 4 rad (23 °) and 0.7 rad (40 °), the conditional expression 11 is satisfied as 0.4 <(1 + 1) × 0.7 = 1.4, and the rear paper sheet 31b as shown in FIG. The leading end of the sheet is not returned too much (contacts the separation roller 25), and good sheet feeding is realized. Therefore, the stacking failure of the paper sheet 31 and the poor feeding,
No skew occurs.

Further, in this embodiment, since the reverse roller 1, the pinch roller 2, the separating roller 25 and the feed roller 26 are made of the same silicone rubber, F ₁ , F ₂ , F
The management of ₃ , F ₄ , F ₆ , and F ₇ can be performed in a unified manner, and it is easy to maintain the conditions (i) to (vi). If the material of each roller is disjointed, the frictional force of each roller will fluctuate due to variations in manufacturing, differences in friction coefficient for various paper sheets, and differences in changes over time. It becomes difficult to maintain the conditions (i) to (vi).

In this example, the lower original guide 29
The paper is set with an appropriate inclination so that the set paper sheet slides down to the separation roller by its own weight. Further, even curled paper sheets can be set by the guides 24a and 24b without the tip being turned up.

The reverse rotation roller unit A is lifted together with the upper document guide 17. Conversely, the upper document guide 1
When 7 is lowered, the reversing roller unit A also descends, and the reversing roller 1 and the pinch roller 2 again come into contact with the separating roller 25 and the feeding roller 26, respectively, thereby forming a reversing type ADF. In this way, the release between the rollers is easily realized without using a complicated mechanism, so the failure rate and the manufacturing cost are low.

In this embodiment, the torque limiter 32 is used to eliminate the slippage between the reverse rotation roller 1 and the separation roller 25 or the slippage between the reverse rotation roller 1 and the sheet, so that the reverse rotation roller 1 and the separation roller 25 are worn. Is very low and the durability of the device is improved. Also, the side plates 12, 1
Since 3 is made of polyacetal and also serves as the bearing of the pinch roller 2, the cost is low and the assembling property is improved. In addition, since each roller is made of silicone rubber, the friction coefficient is not significantly reduced even with respect to the silicone oil adhering to the copy paper, and the copy paper with the silicone oil adhered can be stably fed. There is. (Second Embodiment) In the above-described embodiment, the torque limiter 32 is used.
However, the torque limiter may be omitted. In this case, the frictional force between the rollers or between the rollers and the paper sheet is determined by the friction coefficient of each roller and the leaf springs 18a, 18b, 21a,
According to 21b, ηF ₂ > F ₁ … (vii) F ₄ > F ₃ … (viii) ηF ₇ > F ₃ … (ix) ηF ₆ > F ₃ … (x) F ₃ > F ₅ … (xi) When set, the automatic paper feeder operates as follows. (1) When there is no sheet (see FIG. 9) (vii), the reverse roller 1 and the separating roller 25 slip. If the feed roller 26 slips, the feed accuracy is reduced due to wear, which is not good. (2) When there is one sheet (see FIG. 10) (viii) to (x), the reverse rotation roller 1 and the sheet 31 slip. (3) When there are two or more sheets (see FIG. 11) (viii) and (xi), the sheets 31 other than the lowest one are returned upstream in the sheet conveying direction, and only the lowest sheet 31 is returned. It is separated and sent by the feed roller 26. In any of the above cases (1) to (3), the reverse rotation roller 1 always continues reverse rotation.

The conditional expression 11 is satisfied in this example as well. However, since the torque limiter is not used, the position of the leading edge of the trailing trailing sheet is slightly different from that in FIG.
It should be noted that θ ₀ has a slightly small value as in (A). Incidentally, θ _{0 at} this time is 0.4 rad (23 °) in this example, and the conditional expression 11 is satisfied as 0.4 <(1 + 1) × 0.4 = 0.8.

In order to realize the condition (viii) of the frictional force of this embodiment, F ₄ (friction force between the separation roller 25 and the paper sheet 31) is set to F ₃ (between the reverse rotation roller 1 and the paper sheet 31). Frictional force). Since the reverse rotation roller 1 and the separation roller 25 are in pressure contact with each other with the paper sheet 31 sandwiched between them, the magnitude of the friction coefficient of both rollers directly becomes the magnitude of the friction force. The friction coefficient must be larger than the friction coefficient between the reverse roller 1 and the paper sheet 31.

In order to stably maintain this magnitude relationship, it is advisable to use the same type of rubber (for example, silicon) as the material of both rollers and change the hardness. Generally, rubber has a higher friction coefficient when the hardness is lower, and therefore the separating roller 25 may be made softer.

The one-way clutch may be a needle clutch as shown in FIG. 12 (B). Although it is slightly more expensive than the spring clutch, the backlash angle θ _BK is very small, so that the returning amount of the rear sheet is almost 0, and the sheet feeding performance is more stable.

Although α = 1 in the above embodiment, conditional expression 11 can be easily satisfied by increasing α within the range allowed by the separation performance, that is, by lowering the peripheral speed of the reverse rotation roller 1. In order to increase α, the distance between the separation roller 25 and the feed roller 26 is increased, the reverse rotation roller 1 returns a plurality of overlapping sheets, and only the lowest one sheet is fed to the feed roller 26. You should be able to earn time up to. A large value such as α = 2 or α = 3 is sufficiently possible depending on how this distance is taken.

In the above embodiment, the one-way clutch 34a or 34b is arranged on the separating roller shaft 27, but it can be arranged further upstream of the drive system to reduce the apparent backlash. That is, if the reduction ratio from the point where the one-way clutch is arranged to the separation roller 25 is K, the apparent backlash angle θ ′ _BK of the separation roller 25 is

[0043]

[Equation 3] Becomes According to this method, even if a spring clutch having a relatively large backlash is used, it is possible to easily satisfy the conditional expression 11 by reducing the apparent backlash.

[0044]

Since the present invention has the above-described structure, from immediately after the trailing edge of the sheet comes out of the contact point between the reverse rotation roller and the separation roller until the separation roller rotates in the forward direction, Even if the separation roller rotates following the reverse rotation roller, the return amount of the sheet is small, and the leading edge of the standby sheet is in contact with the outer peripheral surface of the separation roller.

Therefore, the stacking failure, the feeding failure, and the skew feeding do not occur, and the stable feeding function can be maintained.

[Brief description of drawings]

FIG. 1 is a plan view in which the present invention is applied to an automatic paper feeder for facsimile.

2A is a cross-sectional view taken along the line AA of FIG.
FIG. 1B is a partial side view of FIG. 1 viewed from the direction of arrow B.

FIG. 3 is a diagram showing a state where an upper original guide of FIG. 2 is lifted.

4A and 4B are schematic cross-sectional views showing the vicinity of a contact point between a reverse rotation roller and a separation roller.

FIG. 5 is a cross-sectional view showing an operation without a sheet in the first embodiment.

FIG. 6 is a cross-sectional view showing the operation of a single sheet in the first embodiment.

FIG. 7 is a cross-sectional view showing an operation motion of two or more sheets in the first embodiment.

8A is a cross-sectional view of the spring clutch used in the first embodiment, and FIG. 8B is a perspective view of the upper document guide side of the first embodiment.

FIG. 9 is a cross-sectional view of the second embodiment in a paperless state.

FIG. 10 is a cross-sectional view of a single sheet according to the second embodiment.

FIG. 11 is a cross-sectional view of a state in which two or more sheets of paper are used in the second embodiment.

FIG. 12A is a sectional view showing the vicinity of the contact point between the separation roller and the reverse rotation roller of the first embodiment, and FIG. 12B is a sectional view showing another embodiment using a needle clutch.

13A and 13B are schematic cross-sectional views showing a conventional sheet feeding device.

[Explanation of symbols]

1 reverse rotation roller 25 separation roller 26 feed roller 29 lower document guide 34a spring clutch C contact D most upstream position θ ₀ angle

Claims (2)

[Claims] 1. A separation roller having an outer peripheral surface in contact with a sheet, and a one-way clutch for driving the separation roller in a forward direction so as to feed the sheet in a predetermined direction. The reverse surface roller is disposed at a position where the surface projects from the sheet stacking table, and faces the separation roller, and rotates in the forward direction at a position downstream of the separation roller in the feeding direction. In the sheet feeding device provided with the feed roller, the peripheral speed of the feed roller is set to be higher than the peripheral speed of the separation roller, and the ratio of the peripheral speed of the separation roller to the peripheral speed of the reverse rotation roller is set to α is the outer peripheral surface of the protruding portion of the separation roller, and the region from the leading edge of the sheet waiting for separation to the most upstream position of the protruding portion in the feeding direction is an angle about the axis of the separating roller. Is θ ₀ and the non-drive transmission angle of the one-way clutch is θ _BK , θ _BK <(α + 1) θ ₀ . 2. The sheet feeding apparatus according to claim 1, wherein the one-way clutch is a spring clutch.