JPH06156785A - Paper feeding device - Google Patents

Abstract

PURPOSE:To spread the torque value set-enabled range of a torque limiter and prevent the bending of the top edge of a paper sheet by forming the relative limits related to the frictional coefficient, frictional force and the press contact force between a feeding roller, paper sheet roller, and a separating roller. CONSTITUTION:When a paper sheet 4 does not reach a separation part, a separating roller 2 is revolve in the normal direction by the revolution of a feeding roller 11, and facilitates the introduction of the paper sheet 4. When the paper sheet reaches the separation part, the separating roller 2 starts the fine reverse revolution. At this time, if the frictional coefficient between the feeding roller and the separating roller is represented by mu, each frictional coefficient between the feeding roller 1 and the paper sheet 4 and between the separating roller 2 and the paper sheet 4 is mu1, mu2, frictional coefficient between paper sheets is murho, torque value of a torque limiter installed in the separating roller 2 is Tr, radius of the separating roller is R, between- roller press contact force in the revolution in the normal direction of the feeding roller 1 in the case where no paper exists between both the rollers is (q), and the between-roller press contact force in the normal revolution of the feeding roller in the case where a paper exists between both the rollers is represented by Q, the following equations are to be satisfied: mu.q>Tr/R>mu2Q, mu>mu1>mu2>murho, q>Q.

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 applied to an image forming apparatus such as a copying machine, facsimile, printer or the like.

[0002]

2. Description of the Related Art As a method of separating stacked sheets of paper and feeding them one by one, a so-called friction pad paper feed using a separating pad and a paper feed roller is disclosed in Japanese Patent Laid-Open No. 63-212637. The method was widely adopted. However, in this method, since the front end of the paper is separated by the pad surface, the front end of the paper is easily damaged and there is a problem such as paper jam due to buckling of the front end. Further, since the paper feed roller is pressed against the flat pad to rotate, the pad is scraped along the diameter of the paper feed roller when used for a long time, and a U-shaped groove is generated. As a result, the leading edge of the paper easily enters the separating portion that is connected to the U-shaped groove, and the double feed jam of the paper frequently occurs.

Therefore, a friction roller paper feeding system as disclosed in JP-A-58-109337 has been considered.
However, with this method, when there is no paper between the paper feed roller and the friction roller, each roller is rotating in the opposite direction, so that the wear of the rollers progresses, and as a result, proper separation with time occurs. No pressure was obtained and a paper feed failure occurred.
Further, since the friction roller is rotated in the reverse direction when one sheet of paper enters the roller nip, it is disclosed in JP-A-63-21263.
Similar to Japanese Patent Laid-Open No. 7, the paper has buckled at the front end.

Therefore, a so-called FRR sheet feeding method, which is a method in which a torque limiter is interposed in a separation roller as disclosed in Japanese Patent Laid-Open No. 62-205934, has been considered.

In this system, the torque limiter operates when there is no paper between the upper forward rotation roller and the separation roller, so that the rotation roller follows the normal rotation roller. Therefore, the wear of the rollers is reduced, the paper is easily gripped by the roller nip, and the buckling of the leading edge of the paper does not occur.

When a normal sheet is sandwiched between nips, Ts / R> μp · Ns (where Ts: torque limiter torque value, R: separation roller radius, Ns: separation roller pressing force, μp: between normal sheet and separation roller). The friction coefficient) causes the Sabaki roller to start reverse rotation,
Return the double-fed sheets. Further, even if one ordinary sheet is sandwiched by the nip, the separation roller continues to rotate in the reverse direction.

Here, if one special sheet having a high friction coefficient is sandwiched between the nip, μt · Ns> Ts / R (however,
μt: The friction coefficient between the special sheet and the separation roller) causes the separation roller to rotate normally following the special sheet being fed. When a large number of special sheets are sandwiched by the nip, the sabaki roller is moved toward the sheet storage portion in order from the lowest sheet due to the relationship of Ts / R> μ ₀ · Ns (where μ ₀ : friction coefficient between sheets). Return to.

[0008]

However, the torque value Ts of the torque limiter in this system is μt.Ns.R.
Paper feed performance cannot be achieved unless the range is set to>Ts> μp · Ns · R. Substituting the specific numerical values disclosed in this publication, (720-150)
0) gf · cm>Ts> (450 to 720) gf · cm (however,
Ns = 300-400 gf, R = 1.5 cm, μp = 1.0
.About.1.2, .mu.t = 1.6 to 2.5), and cannot be set with the torque value of 500 to 600 gf.cm disclosed in this publication.

Further, regarding the friction coefficient (μt and μp) between the separation roller and the sheet, when the number of passing sheets increases, the roller surface deteriorates and the friction coefficient changes. Generally, the coefficient of friction tends to decrease due to the influence of paper dust and the like. Therefore, the difference between the friction coefficient μt between the special sheet and the separation roller and the friction coefficient μp between the normal sheet and the separation roller disappears.

As a result, it becomes more and more difficult to set the torque limiter torque value. Therefore, it becomes inevitable to use a high-precision limiter with less variation in torque value. Similarly, it is necessary to select a material for the Sabaki roller that has a small friction coefficient due to paper powder.

As described above, this method requires a high-performance torque limiter and a separation roller, and therefore has a drawback of high cost.

Incidentally, Japanese Utility Model Laid-Open No. 1-109023 and Japanese Unexamined Patent Publication No. 3-18532 are paper feeders of the type previously proposed by the applicant of the present invention, which serve both as a pick-up roller and a feed roller. force acting force Torukurimitsuta in reverse roller is Gyotsu in (herein symbol T _a), to use the acting force (T _a) as the paper return force causes the up-frictional force between the reverse roller and the paper Since it is indispensable, the reverse roller is conventionally made of rubber that generates a high frictional force such as μ rubber.

If a material having a high friction is used for the reverse roller, the leading edge of the sheet is caught by the reverse roller when the sheet enters the separating portion, and the leading edge is broken.

Particularly in the case of a large-diameter roller which also serves as a pick-up roller and a feed roller, the sheet feeding pressure P is not released at the sheet calling portion, so that the leading edge of the sheet buckles and breaks when the separation roller reverses or stops. Therefore, there is room for improvement in these technologies.

The present invention has been made on the basis of such a background, and it is an object of the present invention to provide a sheet feeding device capable of widening a torque value setting range of a torque limiter and preventing the leading edge of a sheet from being bent. It is intended.

[0016]

The above-mentioned object is to support a feed roller which is rotationally driven in a direction for feeding a sheet at a predetermined timing, a separation roller which presses the feed roller to separate the sheet, and an axially supporting the separation roller. In a paper feeding device in which a separation shaft and a torque limiter for transmitting a predetermined torque are interposed between the separation shaft and the separation roller, the coefficient of friction between the feed roller and the separation roller is μ, and the friction coefficient between the feed roller and the paper is Friction coefficient is μ ₁ , friction coefficient between separation roller and paper is μ ₂ , friction coefficient between paper is μp, torque value of torque limiter is Tr, radius of separation roller is R, between feed roller and separation roller If there is no paper in the feed roller and the feed roller rotates forward, There are sheets between the feedroll and cell Palais Chillon roller, when the contact force between the rollers when the feedroll rotates forward and the Q, μ · q> Tr /
This is achieved by the first means configured so as to satisfy the expressions R> μ ₂ · Q, μ> μ ₁ > μ ₂ > μp, q> Q.

Further, the above-mentioned object is achieved by the second means in the first means, which has a stopper member for preventing the rotation of the separation shaft.

Further, the above object is provided with a pressing means for pressing the stacked sheets against the feed roller and a driving means for driving the separation shaft in the sheet returning direction, and the sheet returning speed v of the separation roller is 0.05V. <V <0.
This is achieved by the third means for setting the range to be 30 V (V: paper feed speed of the feed roller).

[0019]

In the first means, the acting force (Tr / R) of the torque limiter is set to be smaller than the frictional force (μ · q) between the feed roller and the separation roller, so that when the feed roller rotates in the forward direction. When there is no sheet in the separating section, the separation roller rotates in the forward direction of the sheet, so that the leading edge of the sheet can enter the separating section without being damaged.

Further, the acting force of the torque limiter (Tr /
R) is the frictional force between the paper and the separation roller (μ ₂
Since it is set to be larger than Q), when there is a sheet in the separating portion, the forward rotation of the separation roller is stopped, so that the double feeding of the sheet can be prevented.

Further, since there is no paper between the feed roller and the separation roller and the pressure contact force q of the roller when the feed roller rotates in the forward direction is set to be larger than the separation pressure Q, the acting force (Tr) of the torque limiter (Tr / R) can be set in a large range.

Further, since the separation roller is made of a material having a low frictional force, it is possible to avoid the trouble such as the bending of the leading edge of the paper.

In the second means, the stopper member is
When the paper enters the separating portion, the rotation of the separation roller is stopped, so that the double feeding of the paper can be prevented. Further, since the stopper member stops the forward rotation of the separation roller without the reverse rotation drive source, a low-cost sheet feeding device can be achieved.

In the third means, since the returning speed of the separation roller is set to a low speed, good paper feeding performance can be obtained without causing breakage or the like at the leading edge of the paper during separation. You can

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the sheet feeding device according to the embodiment, FIG. 2 is a sectional view taken along line XX of FIG. 1, and FIG. 3 is a sectional view taken along line YY of FIG.

A large number of sheets 4 are stacked on the bottom plate 5 in the cassette 3, and the end portion of the sheet bundle is pressed against the feed roller 1 at a predetermined sheet feeding pressure P by a pressing means (not shown).

The feed roller 1 is rotated in the direction of the arrow in the drawing by the clutch 22 at a predetermined timing to convey the sheet 4 toward the grip roller 15. The hub portion of the feed roller 1 is provided with a one-way clutch 20 so that the feed roller 1 is rotated when the paper 4 is conveyed by the grip roller 15. Further, between the feed roller shaft 19 and the side plate 25, when there is no sheet 4 in the separating portion and the clutch 22 is inoperative, the reverse rotation of the feed roller 1 is prevented by the reverse rotation force of the separation roller 2 so as to prevent the reverse rotation. A one-way clutch 21 is provided.

A separation roller 2 is arranged in close proximity to the feed roller 1. The separation roller 2 includes a drive shaft 11 rotated by a drive source 23, a gear 10 fixed to the shaft 11, a separation gear 9 fixed to the separation shaft 8, and a torque limiter 24 provided on the shaft 8. A constant torque is applied in the sheet returning direction via the sheet.

As an example of the torque limiter 24, the coil spring 17 wound around the boss portion 18 fitted to the separation shaft 8 and the boss portion 16 fitted to the hub of the separation roller 2 is slid. In terms of surface, the one that utilizes the frictional force obtained when the coil is rotated in the loosening direction is adopted. Considering the stability of the torque value of the torque limiter 24, stainless steel or the like should be selected as the material of the boss portions 16 and 18, but in the present invention, the setting range of the torque value is wider than the conventional one as will be described later. , Choose a resin such as polyacetal, and use low-priced parts.

The right end of the separation shaft 8 is pivotally supported by the bearing 26 so as to be swingable in a certain range and rotatable about its own axis within a plane including the shaft and the feed roller shaft 19. There is. Furthermore, a separation axis 8
Is supported by a slide bearing 6 slidably fitted in a guide 7 which is fixed to the machine frame on the right side of the torque limiter 24 and which guides the separation shaft 8 in a plane including the feed roller shaft 19 and the separation shaft 8. ing. The lower surface of the bearing 6 is slidably pressed by the upper surface of one end of the pressure arm that is urged to rotate about the support shaft 13 by the pressure spring 14, so that the separation roller 2 becomes the feed roller 1. Pressed with a predetermined initial pressure.

The material of each roller is determined so as to satisfy μ> μ ₁ > μ ₂ > μp (1). Therefore, feed roller 1
Is made of rubber such as EPDM or nosolex, and the separation roller 2 is made of urethane foam.

The friction coefficient between each roller and the sheet 4 is μ ₁ = 1.6 to 2.0 for the feed roller 1 and μ ₂ = 0.8 to 1.0 for the separation roller 2. Feed roller 1
And the separation roller 2 have a friction coefficient of μ = 2.5 to
It is 3.0. The friction coefficient between the sheets is μp = 0.4 to 0.
7

FIGS. 4 and 5 are model diagrams when the feed roller 1 is rotating in the forward direction, but the paper 4 has not reached the separating portion. At this time, the separation roller 2 rotates forward together with the feed roller 1 as shown in the figure. This is to prevent damage to the front end of the paper 4 such as paper folding when the front end of the paper 4 enters the separation section.

Further, as conditions for the separation roller 2 to rotate around the feed roller 1, q is the inter-roller pressure contact force when the feed roller 1 rotates normally without the paper 4 in the separating portion, Tr is the transmission torque of the torque limiter 24, and the separation is When the radius of the chillon roller 2 is R, the torque value is set so as to satisfy the relational expression μ · q> Tr / R (2).

The inter-roller pressure contact force q at this time is expressed by the equation (3) of the moment around the axis of the separation shaft 8 in FIG. 4 and the equation (4) of the moment around the bearing (fulcrum) 26 in FIG. ).

[0037] _{Rz · P 1 = R · Tr} / R + Rb · Tb (3) L 1 · P 1 + L 3 · P 3 = L 2 · P 2 + L 4 · q (4) ( where, P _1: Se Palais Chillon gear tangential component force of the pressing force from the driving gear 10 acting on the tooth surface of 9, P _2: Separeshiyon shaft 8 and the own weight of the mounted member in this,
P ₃ : The force for pushing up the slide bearing 6 by the pressure arm 12, L ₁ : The distance from the fulcrum (bearing 26) to the point of action of P ₁ , L ₂ : The distance from the fulcrum (bearing 26) to the point of action of P _2. , L _3: distance from the fulcrum (bearing 26) to the point of action of P _3, L _4: distance from the fulcrum (bearing 26) to the point of application of q, Tb: the sliding resistance of the bearing 26, Rz: Separeshiyon Pitch circle radius of gear 9, Rb: radius of separation shaft 8) In the above equations (4) and (5), assuming Tb = 0, solving for q yields the following equation.

(L ₁ · Tr) / (L ₄ · Rz) + (L ₃ P ₃ −L ₂ P ₂ ) / L ₄ (5) FIGS. 6 and 7 show the forward rotation of the feed roller 1. FIG. 9 is a model diagram when the sheet 4 reaches the separation unit. At this time, the torque limiter 24 does not operate and the separation roller 2 starts reverse rotation in the paper returning direction as shown in the figure.
This is because the separation roller 2 slightly reverses to prevent the lower sheet from entering the separating section along with the upper sheet. However, if the reverse rotation speed v of the separation roller 2 is set too high, damage such as a paper break will occur at the leading end of the double-fed paper. Therefore, when various papers were passed through the experiment, when the paper conveyance speed of the feed roller 1 was V, the reverse rotation speed of the separation roller 2 was set in the range of 0.05V <v <0.30V (6). It was possible to obtain good paper feeding performance.

As a condition for the reverse rotation of the separation roller 2 as shown in the figure, the pressure contact force (separation pressure) between the rollers when the sheet 4 is present in the separating portion and the separation shaft 8 rotates in the reverse direction is Q. Then, the torque value is set so as to satisfy the relational expression Tr / R> μ ₂ · Q (7).

The inter-roller pressure contact force Q at this time is calculated by the equation (8) of the moment around the axis of the separation shaft 8 in FIG. 6 and the equation (9) of the moment around the fulcrum 26 in FIG. Calculated.

Μ ₂ · Q · R = P ₁ ′ · Rz (8) L ₁ · P ₁ ′ + L ₃ · P ₃ = L ₂ · P ₂ + L ₄ · Q (9)
[P ₁ ′: component force in the tangential direction of the pressing force from the drive gear 10 that acts on the tooth surface of the separation gear 9 (however, P ₁ ′)
≠ P ₁ , P ₁ ′ <P ₁ )] In the above equations (8) and (9),
Solving for Q gives the following equation.

Q = (Rz · L ₃ · P ₃ −Rz · L ₂ · P ₂ ) / (L ₄ · Rz−L ₁ · μ ₂ · R) (10) From the above equations (5) and (10) Calculated roller contact pressure Q
Comparing q with q, the surface pressure P ₁ of the gear 9 when the torque limiter 24 operates becomes larger than the surface pressure P ₁ ′ of the gear 9 when not operating (P ₁ ′ <P ₁ ), Therefore, FIG.
And if L ₁ , L ₂ , L ₃ , L ₄ , P ₂ , P ₃ in FIG. 7 are constant, the relationship of q> Q (11) is established.

From the equations (2) and (7), the acting force of the torque limiter 24 may be set within the range of μ · q> Tr / R> μ ₂ · Q (12). Further, the feed roller 1 and the separation roller 2 are deteriorated and the friction coefficient is lowered,
Even if the difference between μ and μ ₂ is reduced, the setting range is wider than before because of the relational expression (11).

Specifically, the torque limiter 24 (median value of torque 530 gfcm) when the separation pressure Q is 250 g
Try to calculate the setting range of. However, the value of each constant is assumed as follows.

(L ₁ = 50 mm, L ₂ = 120 mm, L ₃ = 1
35 mm, L ₄ = 170 mm, R = 12 mm, Rz = 7 mm, P ₂
= 70gf) Substituting each value into the equation (10) and obtaining the arm pressure P ₃ for obtaining the separation pressure Q250g, P ₃ = 234gf (however, P
To calculate ₃ , the friction coefficient μ ₂ is calculated as 0.9, but even if μ ₂ decreases over time, the separation pressure Q decreases, so the torque setting range tends to widen. .

By substituting this value into the equation (5) to obtain the pressure contact force q, q = 359 gf Therefore, by substituting these values into the equation (12), 898 gf> Tr / R> 225 gf The torque value setting range is greatly expanded.

In the above-mentioned apparatus, the separation roller 2 is provided with a reverse rotation driving force by the driving source 23, and this separates the leading edge of the multi-fed paper 4 to improve the separating performance. . However, since the drive source 23 is expensive, a method of making the drive shaft 11 non-rotatable by the stopper member 27 as shown in FIG. 8 is also conceivable. That is, when the paper 4 has not reached the separation portion, the separation roller 2 rotates forward along with the feed roller 1 to easily insert the paper 4, and when the paper 4 reaches the separation portion, the separation roller 2 Reference numeral 2 stops rotation to prevent double feeding of the sheets 4. This system is inferior to the above-mentioned system in the double feed prevention performance, but the latter system is adopted for the copying machine and the like in which cost is given the highest priority.

The conditional expression of this method is the same as that of the former method, and the description is omitted.

According to this embodiment, the pressing means can press the sheet bundle against the feed roller 1, so that the conventional pick-up roller dedicated to calling is unnecessary, the apparatus can be downsized, and the manufacturing cost can be reduced. It Further, since the drive source reversely rotates the separation roller 2 when the paper enters the separating portion, it is possible to reliably prevent the double feeding of the paper.

In the method described above, the rollers for picking up the sheets from the sheet bundle and the conveying rollers in the separating section are
Although the description has been made in the embodiment in which the individual large-diameter rollers are also used, the present system can also be adopted in the configuration with the pick-up roller 28 as shown in FIG. However, Pickup roller 2
Since it is necessary to add an up-and-down moving mechanism 8 and a height detecting means for detecting the height of the sheet bundle, the cost becomes high.
In the method described above, the separation pressure Q is set so as to satisfy the following conditions. 1) Single-Feeding Condition In the model of FIG. 10, when the conveying force is larger than the load force, the sheet is conveyed without stopping.

Μ ₁ · (P + Q)> μ ₂ · Q + μp · P ∴P> (μ ₂ −μ ₁ ) · Q / (μ ₁ −μp) (13) 2) Double feed prevention conditions In the model of FIG. , If the added force is greater than the added force from the paper above,
The lower sheet is stopped without double feeding.

Μp · (p + Q) <μ ₂ · Q + μp ′ · P ∴P <(μ ₂ −μp) · Q / Δμp (14) Therefore, the separation pressure Q and the supply pressure in the shaded area shown in FIG. Set the paper pressure P. (However, μ ₁ = 1.8, μ ₂ = 0.
The values of 9, μp = 0.55 and Δμp = μp−μp ′ = 0.2 were substituted. In particular, Δμp is the actual value of the variation of the friction coefficient within the sheet bundle.

Here, since the slope of equation (13) is negative, it is meaningless as a conditional equation, and P> 0.

[0054]

According to the invention of claim 1, the acting force (Tr / R) of the torque limiter is set to be smaller than the frictional force (μ · q) between the feed roller and the separation roller. If there is no paper in the separating portion when the paper rotates in the normal direction, the separation roller rotates in the paper feeding direction in the normal direction, so that the leading end of the paper can enter the separating portion without being damaged.

Further, the acting force of the torque limiter (Tr /
R) is the frictional force between the paper and the separation roller (μ ₂
Since it is set to be larger than Q), when there is a sheet in the separating portion, the forward rotation of the separation roller is stopped, so that the double feeding of the sheet can be prevented.

Further, since there is no paper between the feed roller and the separation roller and the pressure contact force q of the roller when the feed roller rotates in the forward direction is set to be larger than the separation pressure Q, the acting force of the torque limiter (Tr / R) can be set in a large range.

Further, since the separation roller is made of a material having a low frictional force, it is possible to avoid a trouble such as bending of the leading edge of the paper.

According to the second aspect of the present invention, the stopper member stops the rotation of the separation roller when the sheets enter the separating section, so that the double feeding of the sheets can be prevented. Further, since the stopper member stops the forward rotation of the separation roller without the reverse rotation drive source, a low-cost sheet feeding device can be achieved.

According to the third aspect of the invention, since the returning speed of the separation roller is set to a low speed, good paper feeding performance can be obtained without causing breakage or the like at the leading edge of the paper during separation. Can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

3 is a cross-sectional view taken along line YY of FIG.

FIG. 4 is a side view of the separation unit when the feed roller is rotating in the forward direction but the paper has not reached the separation unit.

5 is an explanatory diagram showing distances of respective parts for calculating inter-roller pressure contact force q in the state of FIG. 4. FIG.

FIG. 6 is a side view of the separation unit when the paper reaches the separation unit by the forward rotation of the feed roller.

FIG. 7 is an explanatory diagram showing distances of respective parts for calculating inter-roller pressure contact force Q in the state of FIG. 6;

FIG. 8 is a main part configuration diagram showing an example in which a stopper member is provided on a drive shaft.

FIG. 9 is a simplified configuration diagram showing an example in which a pick-up roller is provided.

FIG. 10 is a schematic diagram of a separation unit for explaining conditions for single-sheet feeding.

FIG. 11 is a schematic diagram of a separation unit for explaining conditions for preventing double feed.

FIG. 12 is a characteristic diagram showing a predetermined range of separation pressure Q and paper feed pressure P.

[Explanation of symbols]

 1 Feed roller 2 Separation roller 24 Torque limiter

Claims (3)

[Claims] 1. A feed roller rotatably driven in a direction for feeding a sheet at a predetermined timing, a separation roller that presses the feed roller to separate the sheet, a separation shaft that supports the separation roller, and the separation roller. In a paper feeding device in which a torque limiter for transmitting a predetermined torque is interposed between the shaft and the separation roller, the coefficient of friction between the feed roller and the separation roller is μ, the coefficient of friction between the feed roller and the paper is μ ₁ , and the separation is The friction coefficient between roller and paper is μ ₂ ,
The friction coefficient between the sheets is μp, the torque value of the torque limiter is Tr, the radius of the separation roller is R, and there is no sheet between the feed roller and the separation roller, and the pressure contact force between the rollers when the feed roller rotates forward is q. , If there is paper between the feed roller and the separation roller, and the pressure contact force between the rollers when the feed roller rotates in the normal direction is Q, μ · q> Tr / R> μ ₂ · Q μ> μ ₁ > μ _A sheet feeding device characterized by being configured so as to satisfy the respective formulas ₂ > μp q> Q. 2. The sheet feeding device according to claim 1, further comprising a stopper member that prevents rotation of the separation shaft. 3. A sheet returning speed v of the separation roller is set to 0.05 V <v <, and a pressing means for pressing the stacked sheets against a feed roller and a driving means for driving a separation shaft in a sheet returning direction. A paper feeding device characterized by being set to a range of 0.30 V (where V: paper feed speed of a feed roller).