JP2003237967A - Sheet feeding method, sheet feeder and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeding method that can expand a variable range of operating lines offering a target nip pressure without limitations in layout. <P>SOLUTION: An angle θ formed between a straight line connecting the shaft centers of a reverse driving gear shaft 4a and a reverse shaft 8 and a straight line connecting the shaft centers of the reverse shaft 8 and a feed shaft 6 is expanded to a range of 0 [rad] to π [rad]. The range of nip pressure PB is thus expanded. The nip pressure PB is formulated by the following equation: PB=ä[K/Cos(θ-π/2)+Tan(θ-π/2)]×TA+P0}/[1-K×k/Cos(θ-π/2)]. A suitable design condition obtained according to the equation enables a design capable of expanding the range of nip pressure limited by a layout of component elements of the sheet feeding method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying method and sheet conveying apparatus for sheets and OHP sheets used in copying machines, facsimiles, printers, etc., and stacked sheets such as banknotes and tickets. , An image forming apparatus. More specifically, the present invention relates to a sheet conveying method, a sheet conveying apparatus, and an image forming apparatus that separate and convey a large number of stacked sheets one by one.

[0002]

2. Description of the Related Art As one of sheet conveying methods of this type,
Ricoh / Technical / Report N
o. 12, December, 1984 (P44-4
8) "FRR paper feeding method" (written by Yasuaki Ishii) is known. Here, FRR means Feed & Reverse
It is an acronym for Roller. Further, as one of the sheet conveying devices of this type, a "sheet feeding device" in Japanese Patent Laid-Open No. 56-7847 has been proposed.

1 to 4 show the above-mentioned "FRR paper feed system".
2 shows a conventional sheet conveying device according to the above. This sheet conveying device includes a reverse roller 1, a torque limiter 2, a reverse driven gear 3, a reverse drive gear 4, a feed roller 5,
A feed shaft 6, a bearing 7, a reverse shaft 8, a fulcrum 9 and the like are provided. The reverse roller 1 is axially supported by the reverse shaft 8 via the torque limiter 2. The reverse driven gear 3 is pivotally supported by the reverse roller shaft 8. The reverse roller shaft 8 is rotatably supported by a bearing 7 and a fulcrum 9. The reverse drive gear 4 is rotatably supported by the reverse drive gear shaft 4a, and the reverse driven gear 3
Meshes with. The feed roller 5 has a feed shaft 6
Is supported by. Here, the reverse roller shaft 8 swings around a fulcrum 9 arranged on the right end side in FIG. 3, together with the reverse driven gear 3 and the bearing 7, and the reverse roller 1 axially supported on the left end side in FIG. , Is configured to swing in a substantially vertical direction. Further, the bearing 7 is applied with a pressing force P3 shown in FIG. 3 in a direction of pushing up the bearing 7 by the spring shown in FIG. The bearing 7 is pushed up by the pressing force P3, whereby the reverse roller 1 is brought into pressure contact with the feed roller 5, and a nip for transporting the sheet S is formed at a pressure contact portion of both rollers.

1 to 3, when a sheet S is fed by a feed roller (not shown), the feed roller 5 and the reverse drive gear 4 rotate at a predetermined timing. The rotation of the reverse drive gear 4 applies a gear pushing force to the reverse driven gear 3. As a result, the reverse roller 1, the reverse driven gear 3, the reverse shaft 8,
And, via the torque limiter 2, the fulcrum 9 rises about the swing center, and the reverse roller 1 with respect to the feed roller 5
The contact pressure of is increased. Here, the feed roller 5 is
The sheet in contact with the sheet is conveyed toward the downstream side in the sheet feeding direction, and the reverse roller 1 conveys the sheet in contact with the sheet toward the upstream side in the sheet feeding direction.

Further, the materials of the feed roller 5 and the reverse roller 1 and the contact pressure between the two rollers in the sheet conveying device are set so as to satisfy the sheet conveying conditions described below. That is, when only one sheet is fed into the nip, the sheet moves to the downstream side in the sheet feeding direction due to the frictional force acting between the feed roller 5 and the sheet due to the nip pressure and the rotation of the feed roller 5. Be transported. And this sheet and reverse roller 1
The frictional force acting between the reverse roller 1 and the reverse roller 1 that rotates via the torque limiter 2 overcomes the returning force that returns the sheet to the upstream side in the sheet feeding direction. As a result, the reverse roller 1 rotates together with the sheet conveyance direction opposite to the original rotation direction. Hereinafter, the above return force is referred to as "torque limiter return force".
Say. As a result, the fed sheet is conveyed to the downstream side in the sheet feeding direction without causing non-feeding. In contrast,
When a plurality of sheets are fed into the nip in an overlapping manner, the frictional force acting between the feed roller 5 and the sheet overcomes the frictional force between the overlapping sheets. As a result, the sheet in contact with the feed roller 5 is conveyed downstream in the sheet feeding direction without being fed.
On the other hand, for the sheet in contact with the reverse roller 1, the frictional force acting between the reverse roller 1 and the sheet overcomes the frictional force between the overlapped sheets, so that the torque limiter restoring force causes the sheet to move to the upstream side in the sheet feeding direction. Will be returned. As described above, the frictional force generated between the reverse roller 1 and the sheet S by the torque limiter returning force is set to be smaller than the frictional force between the feed roller 5 and the sheet S during the sheet conveyance. Further, the frictional force generated between the reverse roller 1 and the sheet S is set to be larger than the frictional force between a plurality of overlapping sheets.

The drive force of the reverse shaft 8 is given by the rotation of the reverse drive gear 4. This driving force is a force that balances the torque limiter return force and the return resistance, but since the reverse shaft 8 is swingable only in the Y axis direction, it is sufficient to consider the component force in the Y axis direction. is there. Therefore, the Y-axis direction component force P1 of the gear pushing-up force applied to the reverse driven gear 3 by the rotation of the reverse drive gear 4 is established by the following equation (1) established by the balance of forces centering on the reverse shaft 8 shown in FIG. It is represented by. P1 = (RS / RZ) TA + (RB / RZ) μB · PB (1) In the formula (1), RZ is the radius of the reverse driven gear 3,
RS is the radius of the reverse roller 1, RB is the radius of the reverse shaft 8 on which the reverse roller 1 is mounted, and μB is the reverse shaft 8.
The friction coefficient between the radius of the bearing 7 and the radius of the bearing 7. Further, PB is a pressing force between the feed roller 5 and the reverse roller 1 (hereinafter, this is referred to as a nip pressure), and TA is a torque limiter 2
The return force of the torque limiter 2 defined by the rotation torque Tr of

Further, the nip pressure PB is established by the following equation (2), which is established by the balance of forces centered on the fulcrum 9 shown in FIG.
It is represented by. PB = (L1 / L4) P1 + (L3.P3-L2.P2) / L4 (2) In formula (2), L1 is the distance from the fulcrum 9 to the reverse driven gear 3, and P2 is the reverse roller 1, The weight of each of the reverse shaft 8, the torque limiter 2, the bearing 7, and the reverse driven gear 3 is the total weight. Further, L2 is the distance from the fulcrum 9 to the total gravity center of gravity, P3 is the drag force received by the reverse shaft 8 from the bearing 7, L3 is the distance from the fulcrum 9 to the bearing 7, and L4 is the distance from the fulcrum 9 to the reverse roller 1. did.

Substituting equation (1) for P1 in equation (2) gives the following equation (3). PB = (L1 / L4) ・ {(RS / RZ) TA + (RB / RZ) μB ・ PB} + (L3 ・ P3-L2 ・ P2) / L4 ... (3)

In the equation (3), the return force TA of the torque limiter 2 is set to TA = Tr / RS, and (L1 / L4). (RS /
RZ) = K (first factor) and (RB / RS) μB = k (second factor). Also, (L3 / P3-L2 ・ P2)
When / L4 = P0 (initial pressure), the equation (3) is formulated by the following equation (4). PB = (K ・ TA + P0) / (1-K ・ k) (4)

FIG. 4 shows the nip pressure P in the above equation (4).
The graph which drew B as the operating line 12 is shown. In this graph, the horizontal axis represents the returning force TA of the torque limiter 2 and the vertical axis represents the nip pressure PB. Above "FRR paper feed method"
Then, the conditions for not causing double feeding of sheets and the conditions for not causing non-feeding are as shown in the following equations (5) and (6).
Given by (inequality). Double feed condition: PB <(1 / μP) ・ TA-3m ・ ・ ・ (5) Non-feed condition: PB ＞ (1 / μr) ・ TA + (μP / μr) ・ m ・ ・ ・ (6) In formulas (5) and (6), the weight of the sheet is m. Further, the coefficient of friction between sheets was set to μP, and the coefficient of friction between the sheets and the feed roller 1 was set to μr.

Therefore, each boundary line under each condition of the above equations (5) and (6), that is, the double feed boundary line 10 and the non-feed boundary line 11 in FIG.
(6) '. Double feed boundary line: PB = (1 / μP) ・ TA-3m ... (5) 'Non-feed boundary line: PB = (1 / μr) ・ TA + (μP / μr) ・ m ・ ・ ・ (6) '

That is, in FIG. 4, the multifeed boundary line 10
The area between the non-feeding boundary line 11 and the non-feeding boundary line 11 is an appropriate area 24 in which neither the double feeding nor the non-feeding of the sheet S occurs. Therefore, when designing the above-mentioned "FRR sheet feeding type" sheet conveying apparatus, the following is performed. First, the above-mentioned constants L1, L2, L3, L4, P2, R are set so that the operating line 12 obtained by the above equation (4) is located in the suitability region 24 of FIG.
B, RZ, RS are decided. Next, the return force TA of the torque limiter 2 is set. Then, the operating point 1 which is the value on the operating line 12 determined by the set point 13 of the returning force TA
The design is completed by setting 4 to the nip pressure PB. As described above, in the above-mentioned “FRR sheet feeding type” sheet conveying apparatus, the operation line 12 obtained by the above equation (4) is represented by
By locating the sheet S in the appropriate area 24, double feeding and non-feeding of the sheet S are prevented.

[0013]

However, in the conventional sheet conveying apparatus of this type, as described above, the range of change of the operation line 12 shown in FIG. Often becomes. The change of the operating line 12 referred to here means that when the operating line is calculated for each combination of each parameter while changing the value of each parameter in setting various conditions at the design stage, the change between the combinations This is the difference in operating line. For example, in this type of sheet conveying device, a very high coefficient of friction between sheets μ
The nip pressure PB may be set to a high value in advance in order to prevent the sheet from not being fed when the sheet having P is conveyed. Here, the distance L1 from the position of the fulcrum 9 to the position of the reverse driven gear 3 is, for example, a factor most effective in the inclination of the above formula (4). Therefore, it is assumed that the reverse driven gear 3 is set to have the longest distance in the layout so that the reverse driven gear 3 does not collide with other devices (for example, the casing or the cable). As described above, even if the distance L1 is set to the longest distance, in the conventional sheet conveying apparatus, as shown in FIG.
In most cases, the inclination of the operating line 12 does not become as large as expected, and it is likely to reach a ceiling. Therefore, in this type of conventional sheet conveying apparatus, the torque limiter returning force TA is unavoidably increased. That is, it is customary to set the value of the set point 13 in FIG. 4 to a large value and shift the operating point 14 determined by this value upward to increase the nip pressure PB.

However, as described above, when the torque limiter returning force TA is increased, the torque limiter torque Tr represented by TA × RS increases. When the torque limiter 2 having such a high torque limiter torque Tr is used, the cost of the sheet conveying device is increased. Further, in this case, a large transport load is applied to the reverse roller 1 due to the rotation torque of the torque limiter 2, and the life of the reverse roller 1 is shortened and the quality thereof is deteriorated. As described above, in this type of sheet conveying device, there is little merit even if the torque limiter returning force TA is increased. Therefore, this torque limiter return force TA is
It is desirable to keep the value as small as possible.

On the other hand, a sheet conveyed by such a sheet conveying apparatus may have an adhesive force between the overlapping sheets depending on the use environment. For example, in a low-humidity environment, the adhesion between the overlapping sheets increases due to the generation of static electricity. In a high humidity environment,
Due to the generation of water droplets, the adhesion between the overlapping sheets becomes high. When such an adhesion force is generated between the sheets, the frictional force between the sheets at the time of sheet conveyance becomes larger than the frictional force between the reverse roller 1 and the sheet due to the returning force of the torque limiter 2, and the weight of the sheets is increased. Sending may occur. That is, as described above, when the adhesive force between the sheets becomes high, the multi-feed boundary line 10 in FIG. 4 shifts to a position in which the double feed boundary line 10 is lowered in parallel. As a result, the actuation line 12 in FIG. 4 may be located outside the aptitude region 24, resulting in double feeding of sheets. As a method for avoiding such double feeding of sheets, generally, the distance L1 from the position of the fulcrum 9 to the position of the reverse driven gear 3 is reduced to lower the nip pressure PB, and the operating point 14 of FIG. Are located inside the aptitude region 24. However, in such a method, the distance L1 cannot be reduced so much due to layout restrictions.
In some cases, the nip pressure PB could not be reduced to the target value.

The present invention has been made in view of the above problems, and it is an object of the present invention to widen the range of change of the operating line for obtaining a target nip pressure without being restricted by layout. A sheet conveying method is provided. Further, a sheet conveying device using the sheet conveying method,
An object of the present invention is to provide an image forming apparatus equipped with the sheet conveying device. Note that the range of change in the operating line here refers to the range of changes in the operating line calculated for each combination of parameters while changing the value of each parameter when setting various conditions at the design stage. It means the range of difference of the operating line.

[0017]

In order to achieve the above object, the invention of claim 1 is the same as the feed roller that rotates in the sheet conveying direction to convey the sheet and the feed roller by the rotational torque of the torque limiter. In the case where there is a single sheet conveyed by the nip between the feed roller and the reverse roller, the reverse roller which is rotated in the direction and is provided with a reverse roller which is rotatable in the forward and reverse directions is brought into pressure contact.
By the frictional force between the sheet and the reverse roller,
The reverse roller is positively rotated in the direction in which the reverse roller rotates in accordance with the rotation force of the feed roller against the return force of the torque of the torque limiter. In a sheet conveying method in which a roller is reversely rotated by a returning force generated by the torque of the torque limiter, a radius of a reverse driven gear that rotates together with the reverse roller is RZ, a radius of the reverse roller is RS, and a reverse that pivotally supports the reverse roller. The radius of the shaft is RB, the friction coefficient between the reverse shaft and the bearing of the reverse shaft is μB, the distance from the fulcrum that is the fixed end of the reverse shaft to the reverse driven gear is L1, the reverse roller, the reverse shaft, Torque limiter,
The total self-weight of the bearing and the reverse driven gear is added to P2, the distance from the fulcrum to the center of gravity of the total self-weight is L2, the reaction force received by the reverse shaft from the bearing to P3, and the fulcrum to the bearing Distance to L
3, the distance from the fulcrum to the reverse roller is L
4. The rotation torque of the torque limiter is Tr, and can be defined by the above. The first factor K = (L1 / L4).
(RS / RZ), second factor k = (RB / RS) · μB,
And coefficient P0 = (L3 · P3−L2 · P2) / L4 and the return force TA = Tr / RS by the torque limiter,
A straight line connecting the axis of the reverse drive gear shaft that supports the reverse drive gear for driving the reverse roller and the reverse shaft, and the center of the axis of the reverse shaft and the feed shaft that supports the feed roller. When the angle formed by the straight line connecting the lines is θ [rad], the range of θ and the nip pressure PB generated between the feed roller and the reverse roller are 0 [rad] <θ <
π [rad], PB = {[K / Cos (θ−π / 2) +
Tan (θ−π / 2)] · TA + P0} / [1-K · k
/ Cos (θ−π / 2)]. In this sheet conveying method, an angle θ formed by a straight line connecting the center axes of the reverse drive gear shaft and the reverse shaft and a straight line connecting the center axes of the reverse shaft and the feed shaft is π / 2 [ra
No longer limited to d]. That is, the angle θ is expanded to the range from 0 [rad] to π [rad]. As a result, the range of the nip pressure PB is expanded. Therefore, the nip pressure PB generated between the feed roller and the reverse roller is calculated by the above equation, PB = {[K /
Cos (θ−π / 2) + Tan (θ−π / 2)] · TA
+ P0} / [1-K · k / Cos (θ−π / 2)]. Then, an appropriate design condition can be obtained based on this equation. As a result, it is possible to design the nip pressure range that can be expanded due to the layout restrictions of the components in the conventional sheet conveying methods. As described above, in this sheet conveying method, it is possible to widen the change range of the operation line indicating the nip pressure between the feed roller and the reverse roller without being restricted by the layout of the constituent elements. In other words, in this toner conveying method, even when the layout of the reverse driven gear cannot be moved, the range in which the operation line changes can be expanded. As a result, the design margin of the nip pressure is widened, and it becomes possible to design for improving the sheet conveying property and the sheet separating property. The details of the method of deriving the formula for the nip pressure PB will be described later. According to a second aspect of the present invention, a feed roller that rotates in the sheet conveying direction to convey the sheet, a reverse roller that can rotate normally and reversely, a pressurizing unit that presses and contacts the feed roller and the reverse roller, and the reverse roller. A torque limiter that applies a returning force to the roller in the same direction as the feed roller by a rotational torque is provided, and when the number of sheets conveyed by the nip between the feed roller and the reverse roller is one, The frictional force between the sheet and the reverse roller causes the reverse roller to positively rotate in the direction in which the reverse roller rotates along with the rotation of the feed roller against the returning force due to the rotational torque of the torque limiter. If there are multiple sheets conveyed by, the reverse roller causes the return force due to the rotation torque of the torque limiter. In a sheet conveying device configured to rotate in a more reverse direction, a radius of a reverse driven gear that rotates together with the reverse roller is RZ, a radius of the reverse roller is RS, a radius of a reverse shaft that pivotally supports the reverse roller is RB, and the reverse shaft is The friction coefficient between the bearing and the bearing of the reverse shaft is μB, the distance from the fulcrum that is the fixed end of the reverse shaft to the reverse driven gear is L1, the reverse roller, the reverse shaft, the torque limiter, the bearing, and the reverse driven gear. P2 is the total self weight of the respective self weights, L2 is the distance from the fulcrum to the center of gravity of the total self weight, P3 is the drag force from the bearing to the reverse shaft, L3 is the distance from the fulcrum to the bearing, and the fulcrum is To the reverse roller is L4, the torque of the torque limiter is Tr, and More definable, first factor K = (L1 /
L4) · (RS / RZ), second factor k = (RB / RS)
.Mu.B and coefficient P0 = (L3.P3-L2.P2) /
L4, return force by the torque limiter TA = Tr / R
S, a straight line that connects the reverse drive gear shaft that supports the reverse drive gear for driving the reverse roller and the reverse shaft, and a feed shaft that supports the reverse shaft and the feed roller. When the angle formed by the straight line connecting the axis centers of the above is θ [rad], the range of θ and the nip pressure PB generated between the feed roller and the reverse roller are given by the following equation:
d] <θ <π / 2 [rad], π / 2 [rad] <θ <
π [rad], PB = {[K / Cos (θ−π / 2) +
Tan (θ−π / 2)] · TA + P0} / [1-K · k
/ Cos ([theta]-[pi] / 2)] is set. According to a third aspect of the present invention, in the sheet conveying apparatus according to the second aspect, two sets of gear trains each including the reverse drive gear and the reverse driven gear are provided, and the fixed end of the reverse shaft of each of the gear trains. Distance from the fulcrum to the reverse driven gear
Are different from each other, and when one of the reverse drive gear or the reverse driven gear of the two sets of gear trains is engaged with the gear train of one set by the rotation of the gear train, the other set of gear trains is engaged. It is characterized in that it has a toothless portion and a toothed portion at one or a plurality of positions, which are formed so that the gear train of (1) is disengaged. According to a fourth aspect of the present invention, in the sheet conveying apparatus according to the third aspect, among the reverse driven gears of the gear trains of the respective sets, the reverse driven gear having a shorter distance L1 from the fulcrum is rotated by the toothless portion. When the time is PBLT, the nipping width at which the feed roller and the reverse roller contact each other is NI.
P and the rotation speed of the reverse roller are VR, the following equation, PBLT = NIP / VR, is established. According to a fifth aspect of the present invention, in the sheet conveying apparatus according to the fourth aspect, among the reverse driven gears of the gear trains of each set, the angle θ [rad] with respect to the reverse driven gear having a longer distance L1 from the fulcrum is: The following equation, π / 2 [r
ad] <θ <π [rad], and among the reverse driven gears of each set of gear trains, the angle θ [rad] with respect to the reverse driven gear whose distance L1 from the fulcrum is shorter is:
It is characterized by complying with the following equation, 0 [rad] <θ <π / 2 [rad]. According to a sixth aspect of the present invention, in the sheet conveying apparatus according to the second aspect, one reverse driven gear meshes with two reverse drive gears, and one of the reverse drive gear and the reverse driven gear rotates a gear train. At the time of driving, the tooth portions of the gear train of one set mesh with each other, so that the tooth portions of the gear train of the other set are disengaged from each other. It is characterized in that all the drive transmission tooth portions provided on the reverse drive gear are configured to be rotationally driven by meshing of idler gears. According to a seventh aspect of the invention, in the sheet conveying apparatus according to the fifth aspect, the distance L1 from the fulcrum of the gear having the angle θ of π / 2 [rad] <θ <π [rad] is 0 [rad. ] <Θ <π / 2 [rad] The angle of the gear θ is set to be larger than the distance L1 from the fulcrum. Claims 2 to 7
In the sheet conveying apparatus of No. 2, the angle θ is π / 2.
Not limited to [rad], 0 [rad] <θ <π / 2
The range is [rad] and π / 2 [rad] <θ <π [rad]. Further, the nip pressure PB generated between the feed roller and the reverse roller is expressed by the above equation, PB =
{[K / Cos (θ−π / 2) + Tan (θ−π /
2)] · TA + P0} / [1-K · k / Cos (θ−π
/ 2)], is formulated. This enables a design in which the range of the nip pressure restricted by the layout of the components in the sheet conveying method is expanded. In other words, in this sheet conveying device, it is possible to widen the change range of the operating line for obtaining the target nip pressure without being restricted by the layout of its constituent elements.
According to an eighth aspect of the present invention, a sheet stacking body for stacking and stacking a plurality of sheets, a sheet feeding unit for feeding the stacked sheets on the sheet stacking unit, and a sheet feeding unit for feeding the sheets. An image forming apparatus comprising: a sheet conveying unit that conveys a sheet while separating the sheets one by one; and an image forming unit that forms an image on the sheet conveyed by the sheet conveying unit. 3, 4, 5, 6 or 7
The present invention is characterized by using the sheet conveying device of. In this image forming apparatus, since the sheet conveying device is used, it is possible to design with a high degree of freedom in layout.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments in which the present invention is applied to a sheet conveying device will be described below. As described above, this sheet conveying device includes the reverse roller 1, the torque limiter 2, the reverse driven gear 3, the reverse drive gear 4,
A feed roller 5, a feed shaft 6, a bearing 7, a reverse shaft 8 and a fulcrum 9 are provided. In this sheet conveying device, as shown in FIGS. 1 to 3, the rotation of the reverse shaft 8 is transmitted to the torque limiter 2 by the engagement between the shaft (not shown) of the torque limiter 2 and the shaft. There is. Further, the rotational torque of the torque limiter 2 is transmitted to the reverse roller 1 by engaging the convex portion 17a fixed to the reverse roller 1 by the ring 18 and the concave portion 17b of the torque limiter 2. ing.

However, in the sheet conveying device having such a structure, in order to increase the torque limiter returning force TA, the torque limiter 2 having a high torque limiter torque Tr is used.
Must be used, resulting in an increase in the cost of the sheet conveying device. Therefore, it is desirable to keep the torque limiter returning force TA as small as possible. Also,
As a method of avoiding the double feeding of the sheets that are in close contact with each other, generally, the distance L1 from the position of the fulcrum 9 to the position of the reverse driven gear 3 is reduced to lower the nip pressure PB, and the operating point 14 of FIG. It is located inside the aptitude region 24. However, in such a method, the distance L1 cannot be reduced so much due to layout restrictions, and therefore the nip pressure PB cannot be lowered to a target value.

The sheet conveying method and apparatus according to the present embodiment will be described with reference to FIGS. In addition,
In the following description, regarding components having functions equivalent to those of the above-described conventional sheet conveying device,
The same symbols as the above-mentioned symbols are given, and the detailed description thereof is omitted.

(Embodiment 1) FIG. 5 to FIG. 13 show an example configuration of a toner carrying device according to the present embodiment. In FIG. 5, a straight line connecting the center of the feed shaft 6 and the center of the reverse shaft 8 and a line connecting the center of the reverse shaft 8 and the center of the reverse drive gear shaft 4a of the reverse drive gear 4 are formed. Let the angle be θ. In the sheet conveying apparatus according to the present embodiment, this angle θ is π / shown in FIG.
It is not limited to 2 [rad], and it is from 0 [rad] to π [ra
extended to the range up to d]. Then, the nip pressure PB derived at this time is formulated to be a design condition. That is,
In the toner conveying device according to the present embodiment, the angle θ is set to the angle that satisfies the following expression (7). 0 [rad] <θ <π [rad] (7) Further, the nip pressure PB is formulated by the following equation (8). PB = {[K / Cos (θ−π / 2) + Tan (θ−π / 2)] TA + P0} / [1−K · k / Cos (θ−π / 2)] ... (8)

The above formula (8) is a formula formulated with reference to FIGS. 5 to 8. The method of deriving this equation (8) will be described below. FIG. 5 shows the force applied around the reverse shaft 8. Further, FIG. 6 shows the forces decomposed into the X and Y axis components in FIG. Here, a reaction force T between the reverse drive gear 4 and the reverse driven gear 3, which is not defined in the conventional sheet conveying apparatus, is considered. First, in FIG. 5, the following equation (9) is derived from the balance of the rotational moment about the reverse shaft 8. P1 = (RS / RZ) · TA + (RB / RZ) · μB · PB ... (9) Also, pay attention to FIG. 6, and from FIG. 7, the moment of the Y axis (vertical direction) around the fulcrum 9 From the balance of
0) is led. L1 [P1 · Cos (θ−π / 2) + T · Sin (θ−π / 2)] + L3 · P3 = L2 · P2 + L4 · PB ... (10)

On the other hand, as shown in FIG.
The following equation (11) is derived from the balance of the moments of the forces on the X axis (horizontal direction). L1 [−P1 · Sin (θ−π / 2) + T · Cos (θ−π / 2)] = L4 · TA (11) In order to eliminate the drag force T from the formula (11), (1
1) is transformed into the following equation (11) ′. T = P1 * Tan ((theta)-(pi) / 2) + (L4 / L1) * TA / Cos ((theta)-(pi) / 2) ... (11) 'And the said Formula (9), (11)' is used as a formula. The above equation (8) is derived by substituting into (10) and replacing from the above equation (3).

Here, the coefficient of the torque limiter restoring force TA of the equation (8), [K / Cos (θ−π / 2) + Tan (θ
−π / 2)] / [1-K · k / Cos (θ−π / 2)]
Changes depending on the angle θ. The coefficient of TA of the torque limiter returning force TA of the conventional device when the angle θ = π / 2 is K / (1−K · k). Compared with this coefficient, the slope decreases in the range of 0 [rad] <θ <π / 2 [rad], and the slope increases in the range of π / 2 [rad] <θ <π [rad] (FIG. 10). reference). Here, as an example, the case of each parameter shown in the following Table 1 (design parameter table) is used.

[Table 1]

For example, the angle θ is set to π / 2 [rad]
When <θ <π [rad], the operating line of the nip pressure PB is the operating line 16 in FIG. 9. This operating line 1
6 is an operation line 12 of the conventional sheet conveying device shown in FIG.
The slope is higher than that of. As a result, the nip pressure PB of the conventional sheet conveying device is the operating point 14 on the operating line 12 with respect to the set point 13, whereas in this sheet conveying device, the operating point 15 is higher than the operating point 14. Become.
However, the angle θ is π [rad] <θ <2π [ra
In the range of d], the inclination becomes significantly large. For this reason, the sheet conveying apparatus with the angle θ in this range is not suitable for practical use because the nip pressure PB changes greatly in consideration of deterioration over time, for example, an angle change due to RS change due to wear of the reverse roller 1. Therefore, the angle θ of the sheet conveying device
The range of 0 is 0 [rad] <shown in the above formula (7).
The condition of θ <π [rad] is suitable.

As described above, for example, θ = 110 °, θ
In the case of the sheet conveying device in the case of = 70 °, the conventional θ = π /
The inclinations of the operation lines are 1.5 times and 0.6 times, respectively, as compared with the sheet conveying device of 2 [rad] (= 90 °). From this, layout restrictions, for example, the reverse driven gear 3
Even if the change in the inclination of the operating line cannot be ensured due to the limitation of the distance L1 from the fulcrum 9, the range in which the inclination of the operating line changes can be increased by adopting the configuration in which the angle θ is changed. Therefore, in this sheet conveying device, the nip pressure PB
Since the design margin is increased, it becomes possible to configure the sheet relatively freely so as to improve the sheet conveying performance regardless of the layout restrictions.

(Embodiment 2) FIG. 12 and FIG. 13 show the structure of an example of a toner conveying device according to this embodiment. This sheet conveying device, as shown in FIGS.
Reverse drive gear 1 in which two drive gears are integrally formed
Eight. The reverse drive gear 18 is arranged so that each drive gear meshes with the two reverse driven gears 3 and 3 '. Thereby, each drive gear of the reverse drive gear 18 and the reverse driven gear 3,
3'and two sets of gear trains are configured. Here, the two reverse driven gears 3 and 3 ′ are arranged with respect to the reverse drive gear 18 so that the angle θ described above satisfies the condition of π / 2 [rad] <θ <π [rad]. There is. Further, the distance from the fulcrum 9, which is the fixed end of the reverse shaft, to each of the reverse driven gears 3 and 3'of the gear trains of each set is different from each other as L1a> L1b. Further, as shown in FIG. 13, the reverse drive gear 18 has
The two drive gears include a toothless portion 22 and 22 'and a toothed portion 2
3 and 23 'are formed respectively. This missing tooth part 2
2, 22 'and the toothed portions 23, 23' are formed on the peripheral surface of each drive gear of the reverse drive gear 18 so as to have mutually different phases. For example, when the reverse driven gear 3 is meshed with the toothed portion 23 of the drive gear of one set due to the rotation of each gear train, the reverse gear and the toothed portion 23 'of the drive gear of the other set are reversed. It is formed so as to be disengaged from the driven gear 3 '.

With this structure, when the reverse drive gear 18 rotates in FIG. 12, the drive gears of the reverse drive gear 18 are different from the reverse driven gears 3 and 3'having different distances L1. The tooth portions 23, 23 'are alternately meshed. As a result, the nip pressure PB between the feed roller 5 and the reverse roller 1 is increased / decreased in a predetermined cycle. That is, as shown in FIG. 12, the reverse driven gear 3 having a long distance L1a from the fulcrum 9 is the reverse drive gear 1
In the state of meshing with the toothed portion 23 of the No. 8 drive gear, the nip pressure PB increases. On the other hand, when the reverse driven gear 3 ′ having a short distance L1b from the fulcrum 9 meshes with the toothed portion 23 ′ of the drive gear of the reverse drive gear 18, the nip pressure PB becomes low.

By the way, for example, when an extremely high adhesion force is exerted between the sheets due to static electricity or water droplets, if this adhesion force is Q, the equations (5) 'and (6)' are respectively given by the following (5) ) ″, (6) ″. Double feed boundary line when adhesion force works: PB = (1 / μP) TA-3m-2Q / μP (5) ″ Non-feed boundary line when adhesion force works: PB = (1 / μr ) ・ TA + (μP / μr) ・ m + Q / μr ・ ・ ・ (6) ″

Therefore, the configuration shown in Table 1 above and θ
= 120 °, L1 = 95 mm, and L1 = 43 mm, an experiment was performed to measure the maximum conveyance force and the maximum separation force of the sheets when the adhesion force Q acts between the sheets. However, the maximum carrying force was obtained by attaching and fixing the force sensor to one sheet and measuring the maximum fixing force of the force sensor at the start of the sheet carrying operation.
On the other hand, the maximum separation force is to add a droplet between two sheets,
It was obtained by measuring the maximum value of the adhesive force that can be separated by imposing the pseudo adhesive force.

As a result of the measurement by the above experiment, the maximum carrying force is L1 = 95 mm and L1 = under the condition of θ = 120 °.
Substituting 43 mm into the above equation (8), the difference between the value of the high nip pressure PBa and the value of the low nip pressure PBb is approximately one-third and the value obtained by adding the low nip pressure PBb to the value. , Μr. That is, the value obtained by dividing the maximum carrying force by μr is used as the actual carrying nip pressure PBc.
Then, the following equation (12) is established. PBc = PBb + 1/3 (PBa−PBb) (12)

The maximum separating force is approximately (μP /
2)-(TA / μP-3m-PBb). Therefore, the following equation (13) holds. Q = (μP / 2) · (TA / μP-3m-PBb) ... 13 From this formula (13), let the nip pressure when the maximum separating force is obtained be the actual separating nip pressure PBd, then the following formula is obtained. (14) is established. PBd = PBb = TA / μP-3m-2Q / μP (14)

As is apparent from these equations (12) and (14), in the sheet conveying apparatus according to the present embodiment, the value of the nip pressure PB is different between the sheet conveying and the sheet separating. Here, the actual transport nip pressure PBc and the actual separation nip pressure P
Since the difference from Bd is a positive value, it is understood that the margin of the double feed boundary line when the adhesive force Q acts between the sheets increases by this difference. As described above, in the sheet conveying apparatus according to the present embodiment, the margin of the double feed boundary line is increased by the above difference as compared with the conventional apparatus, so that even when the adhesive force Q acts between the sheets, It is possible to prevent double feeding of sheets.

(Third Embodiment) The sheet conveying apparatus according to the present embodiment is the same as the sheet conveying apparatus of the second embodiment, except that the reverse shaft 8 of the reverse driven gears 3 and 3'of the two sets of gear trains is fixed. Distance from fulcrum 9 which is the end (L1
b) Shorter part of reverse driven gear 3 ', toothless portion 22'
Let PBLT be the rotation time by, and NIP be the nip width at which the feed roller 5 and the reverse roller 1 contact each other, and VR be the rotation speed of the reverse roller 1.
5), PBLT = NIP / VR (15)

In this sheet conveying device, the rotation time PBLT was changed by 4 types, and the same experiment as in the case of the sheet conveying device of the second embodiment was conducted. This experimental result is
The results are shown in Table 2 below.

[Table 2]

As is clear from the results of this experiment (Table 2), in this sheet conveying apparatus, the actual conveying nip PBc has a toothless portion of the reverse driven gear 3'of which the distance L1b from the fulcrum 9 is shorter. Rotation time PB by 22 '
It decreases with increasing LT. Further, the actual separation nip PBd was almost saturated under the condition of the above expression (15). As a result, the difference between the actual transport nip PBc and the actual separation nip PBd becomes the largest under the condition of Expression (15). That is, this expression (15) is the most advantageous condition in sheet conveyance when the adhesive force Q acts between the sheets. Therefore, in the sheet conveying apparatus according to the present embodiment, the sheet is conveyed under the condition that the double-feed margin when the adhesive force Q acts between the sheets is most increased.

(Embodiment 4) The sheet conveying apparatus according to the present embodiment is configured such that each reverse driven gear 3 of each set of gear trains is
Of 3 ′, the angle θ [rad] with respect to the reverse driven gear 3 having the longer distance (L1a) from the fulcrum 9 is calculated according to the following formula (16) and the distance (L1b) from the fulcrum 9 is shorter. Angle θ [rad] with respect to reverse driven gear 3 '
Is configured to comply with the following equation (17). π /
2 [rad] <θ <π [rad] ... (16) 0 [rad] <θ <π / 2 [rad] ... (17)

FIG. 1 shows an example of the structure of this sheet conveying apparatus.
4 and FIGS. 15 (a) and 15 (b). In this sheet conveying device, the reverse driven gears 3 and 3'of the gear trains of the respective sets are meshed with the independent reverse drive gears 18 and 18 'which are independent of each other. Further, as shown in FIG. 15A, the reverse driven gear 3 and the reverse drive gear 1 are
8 is the angle θ = θ1, and the reverse driven gear 3 ′ and the reverse drive gear 18 ′ are in the positional relationship of the angle θ = θ2. Furthermore, each reverse drive gear 1
8 and 18 'are provided with drive-transmitting all-tooth portions 19 having teeth all around. Each of these reverse drive gears 18,
18 'is rotationally driven in synchronization by an idler gear 20. That is, in FIG. 15, one of the reverse drive gears 18 and 18 ′ is connected to the main rotary drive system and driven, so that the other reverse drive gear is also rotationally driven via the idler gear 20. Has become.

As a result, the nip pressure when the reverse driven gear 3 rotates and the nip pressure when the reverse driven gear 3'rotates become different. Then, the difference between these nip pressures, that is, PBLT = shown in Table 2 above.
Actual transport nip PBc and actual separation nip P during NIP / VR
The difference from Bd is 0.5 × (PBa−PBb), which is the maximum. As a result, the above equation (1
The value of the high nip pressure PBa determined by 6) is higher than the nip pressure PB at the angle θ = π / 2 [rad] in the conventional sheet conveying apparatus. The value of the low nip pressure PBb determined by the above equation (17) is similarly lower than the nip pressure PB at the angle θ = π / 2 [rad] in the conventional sheet conveying apparatus. Therefore, in this sheet conveying device, the nip pressure is guaranteed to be higher than that of the sheet conveying device of the third embodiment due to the difference of 0.5 × (PBa−PBb), and the adhesive force Q The double feed allowance at the time of working increases, and more stable sheet conveyance can be realized.

(Fifth Embodiment) An example of a sheet conveying apparatus according to the present embodiment is shown in FIGS. This sheet conveying device has two independent reverse drive gears 18 and 18 'similar to the sheet and conveying device of the fourth embodiment, and an idler gear meshed with all the drive transmission tooth portions 19 thereof. It is adapted to be rotationally driven by 20 in synchronization. However, in this sheet conveying device, unlike the sheet and the conveying device of the fourth embodiment, only one reverse driven gear 3 meshes with each reverse drive gear 18, 18 '. Thereby, the fourth embodiment
It is possible to realize the same operation as that of the sheet feeding device and the conveying device with a space-saving configuration using one reverse driven gear 3. (Sixth Embodiment) The sheet conveying apparatus according to the present embodiment is the same as the sheet conveying apparatus according to the fourth embodiment except that the angle θ is π /
The distance L1a from the fulcrum 9 of the reverse driven gear 3 according to the above equation (16) of 2 [rad] <θ <π [rad] is the above when the angle θ is 0 [rad] <θ <π / 2 [rad]. It is set to be larger than the distance L1b from the fulcrum 9 of the reverse driven gear 3'according to the expression (17). This allows
In this sheet conveying apparatus, the difference of 0.5 × (PBa−PBb) described in the fourth embodiment is always a positive value. Further, this difference of 0.5 × (PBa−PBb) ensures that the nip pressure is higher than that in the case of the conventional sheet conveying apparatus having the angle θ = π / 2 [rad]. The double-feeding margin when the adhesion force Q works increases, and more stable sheet conveyance can be realized.

(Other Embodiment 1) In the sheet conveying and mounting according to this embodiment, the angle θ is set to 0 [rad] <θ <π / 2 [rad] (18). is there. In this sheet conveying apparatus, from the above equations (4) and (8), [K / Cos (θ−π / 2) + T
an (θ−π / 2)] / [1-K · k / Cos (θ−π
/ 2)] / (1-K · k) reduces the slope of the operating line. For example, in a high-humidity environment, when a high adhesion force between the sheets works, if the adhesion force between the sheets is Q, the double feed boundary line 10 shown in FIG. (5) ″ (not shown). Double feed boundary line when adhesion force Q works: PB = (1 / μP) · TA-3m−2Q / μP ... (5) ″ At this time, layout When L1 cannot be shortened due to the restriction of, for example, the limit of L1 of the reverse driven gear 3,
The angle θ is set within the range of Expression (18) without shortening 1. As a result, the slope is [K / Cos (θ−π / 2) + Tan
(Θ-π / 2)] / [1-K · k / Cos (θ-π /
2)] / (1-K · k) times smaller. As a result, the nip pressure PB is lowered, and the nip pressure PB below the double feed boundary line where the adhesive force represented by the formula (5) acts is realized.
Sheets can be conveyed without double feeding.

(Other Embodiment 2) In the sheet conveying and mounting according to the present embodiment, the angle θ is set as π / 2 [rad] <θ <π [rad] (19). is there. In this sheet conveying apparatus, from the above equations (4) and (8), [K / Cos (θ−π / 2) + T
an (θ−π / 2)] / [1-K · k / Cos (θ−π
/ 2)] / (1-K · k). Therefore, in the conveyance of a sheet having a high friction coefficient, the inter-sheet friction coefficient μP is large, so that the non-feed boundary line 11 as shown in FIG. 4 rises in parallel under the equation (6) ′. At this time, if L1 cannot be increased due to a layout restriction, for example, the limit of L1 of the reverse driven gear 3, the angle θ is set within the range of Expression (19) without increasing L1. As a result, the slope becomes [K / Cos (θ−π / 2) +
Tan (θ−π / 2)] / [1-K · k / Cos (θ−
π / 2)] / (1-K · k) times. As a result, the nip pressure PB is increased, and even if the non-feed boundary line 11 rises in parallel in FIG.
B is realized, and the sheet can be conveyed while preventing non-feeding.

(Other Embodiment 3) In the sheet conveying and mounting according to the present embodiment, the torque limiter returning force TA used in the sheet conveying method at the angle θ = π / 2 [rad].
Is defined as TA90, the torque limiter restoring force TA shown in the following equation (20) is adopted. TA = {[1-K · k / Cos (θ−π / 2)] · (K · TA90 + P0) / (1−K · k) −P0} / [K / Cos (θ−π / 2) + Tan ( θ−π / 2)] (20) In the torque limiter restoring force TA according to the equation (20), by substituting the equation (20) into the equation (8), the following equation (21) is obtained.
Is guided. PB = (K · TA90 + P0) / (1−K · k) (21) This formula (21) is the conventional sheet conveying method when TA90 is adopted, that is, when θ = π / 2 [rad]. This is the same value as the sheet conveyance method of. That is, while the nip pressure PB is the same value, at the same time, from equations (19) and (20), T
A <TA90 is established. This is shown in Figure 1
It is 1. The conventional torque limiter return force TA90 is the set point 13. A set point 17, which has the same value as the operating point 14 on the operating line 12 at the set point 13 and is determined by the operating line 16 in the other embodiment 2, is the torque limiter returning force TA in the third embodiment. From the above, while keeping the nip pressure PB at the same value as the conventional value, TA <TA90, and therefore the torque limiter torque T determined by Tr = TA · RS.
r is reduced as compared with the conventional one. As a result, the performance of the reverse roller 1 can be maintained and the cost can be reduced by reducing the torque, and the sheet can be conveyed with the same performance as the conventional one.

FIG. 18 shows a copying machine as an example of an image forming apparatus equipped with the sheet conveying device 39 according to the above embodiment. This copying machine includes a document reading unit (image scanner) 101, a writing unit 107, and an image forming unit 11.
2. The sheet feeder 119 and the like. The document reading unit 101 includes a light source 102, a mirror 103, and an imaging lens 1.
04, CCD105 and the like as an image sensor. An automatic document feeder (ARDF) 106 is installed on the contact glass of the document reading unit 101. The document reading unit 101 forms an image of the document on the contact glass on the CCD 105 via the light source 102, the mirror 103, and the imaging lens 104, reads it in pixel units, and converts it into a digitized image signal. This image signal is sent to the writing unit 107 or stored in a pixel memory (not shown). The writing unit 107 includes a laser diode 108 as a light source, a rotating polygon mirror 109 for scanning, a polygon motor 110, and a scanning optical system 111 such as an fθ lens. This writing unit 107
Laser light is scanned according to the image signal read by the document reading unit 101, and an image is written on the photoconductor through the mirror. The image forming unit 112 includes a photosensitive drum 113 as an image carrier, a charging device 114, and a developing device 11.
5, a transfer device 116 using a transfer conveyance belt, a cleaning device 117, a fixing device 118, and the like. The photoconductor drum is uniformly charged by the charging device 114 and then irradiated with laser light from the writing section 1 and 7 to form an electrostatic latent image. This electrostatic latent image is developed by the developing device 115 to form a toner image as a visible image. On the other hand, a sheet serving as a transfer material is fed from the paper feed unit 119, and the sheet conveying device 39 causes the photosensitive drum 113 and the transfer device 1 to move.
16 is conveyed to the transfer position which faces. Then, the transfer device 116 electrostatically transfers the toner image formed on the photosensitive drum 113 to the sheet. Then, the sheet is sent to the fixing device 118, and the image is obtained by fixing the toner on the sheet. On the other hand, the residual toner on the photosensitive drum 101 is removed by the cleaning device 117. Further, in this copying machine, a duplex unit 120 is installed between the image forming unit 112 and the paper feeding unit 119. The double-sided unit 120 makes it possible to form an image on both sides of a sheet by reversing the sheet printed on one side and re-feeding the sheet.

As described above, in the sheet conveying method and the sheet conveying apparatus to which the present invention is applied, the design margin of the nip pressure is widened, so that the sheet can be conveyed and separated easily. In particular, in the sheet conveying device of the second embodiment, the nip pressure PB is high when the reverse driven gear 3 having a long distance L1a from the fulcrum 9 meshes with the toothed portion 23 of the drive gear of the reverse drive gear 18. On the other hand, the reverse driven gear 3 ′ having a short distance L1b from the fulcrum 9 is the toothed portion 2 of the drive gear of the reverse drive gear 18.
The nip pressure PB becomes low in the state of being meshed with 3 '.
As a result, the margin of the double feed boundary line is increased by the above difference as compared with the conventional one, and even when the adhesive force Q acts between the sheets, the transportability between the sheets and the separation performance are improved, It will be possible to prevent double feeding. In addition, the third embodiment
In the sheet conveying apparatus of, the actual conveying nip PBc
However, the reverse driven gear 3 ′ whose distance L1b from the fulcrum 9 is shorter decreases as the rotation time PBLT by the toothless portion 22 ′ increases. Then, the actual separation nip PBd
However, it is almost saturated under the condition of the above formula (15). As a result,
The difference between the actual transport nip PBc and the actual separation nip PBd is
Under the condition of the formula (15), it becomes the largest, and under the condition that the double feed allowance when the adhesive force Q acts between the sheets is the largest,
Sheets will be conveyed. As a result, the sheet separating property is improved by a half of the change in the nip pressure, which is higher than that of the conventional sheet conveying device, and the adhesive force Q between the sheets is increased.
Even in the case where the work occurs, the conveyance property between the sheets and the separation performance are further improved, and the double feeding of the sheets can be prevented. Further, in the sheet conveying apparatus of the fourth embodiment, the nip pressure is the difference 0.5 × (PBa−PBb),
A higher value is guaranteed than in the case of the sheet conveying apparatus according to the third embodiment. As a result, the double-feed margin when the adhesive force Q works increases, and more stable sheet conveyance can be realized. Also, since the angle θ is different between the two gear trains, the angle θ in the conventional sheet conveying device is π /
This is an angle condition that advantageously raises or lowers the nip pressure in comparison with the nip pressure at 2 [rad]. As a result, the amount of change in the nip pressure is further increased, and the sheet separation performance is further improved. Further, in the sheet conveying device of the fifth embodiment, only one reverse driven gear 3 meshes with each reverse drive gear 18, 18 '. As a result, the same operation as that of the seam and the transport device of the fourth embodiment can be realized with a space-saving configuration using one reverse driven gear 3. As a result, it becomes possible to avoid layout restrictions in the arrangement of the reverse driven gear 3, so that the design is easy, the number of parts is reduced, and the cost is reduced. Furthermore, in the sheet conveying apparatus of the sixth embodiment, the difference of 0.5 × (PBa−PB described in the fourth embodiment is used.
b) is always a positive value. In addition, this difference 0.5 × (P
Ba−PBb) causes the nip pressure to change according to the angle θ = π /
A higher value is guaranteed as compared to the case of the conventional sheet conveying apparatus of 2 [rad]. As a result, the double-feed margin when the adhesive force Q works increases, and more stable sheet conveyance can be realized. Further, the positions of the two sets of gear trains from the fulcrums 9 serve as an advantageous arrangement condition for increasing the change in the nip pressure, so that the change in the nip pressure is increased and the sheet separating performance is further improved. In the image forming apparatus to which the present invention is applied, since the sheet conveying device 39 as described above is used, it is possible to design with a high degree of freedom.

[0046]

According to the present invention, even if the disposition of the reverse driven gear is fixed, the range of change of the operating line showing the nip pressure between the feed roller and the reverse roller is expanded, and the design margin of the nip pressure is expanded. . As a result, there is an excellent effect that it is possible to design to improve the sheet conveying property and the sheet separating property as compared with the conventional sheet conveying method.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a conventional sheet conveying device.

FIG. 2 is a schematic cross-sectional view for explaining the balance of forces of each component in the sheet conveying apparatus.

FIG. 3 is a schematic cross-sectional view for describing a force balance in the axial direction of each component of the sheet conveying apparatus.

FIG. 4 is an operation diagram of the sheet conveying apparatus.

FIG. 5 is a diagram illustrating a sheet conveying device according to an embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view for explaining the balance of forces in the cross-sectional direction.

FIG. 6 is a component diagram of force in FIG.

FIG. 7 is a diagram illustrating a sheet conveying apparatus according to an embodiment of the present invention.
FIG. 6 is a schematic cross-sectional view for explaining a force balance in the longitudinal direction (Y-axis direction).

FIG. 8 is a diagram illustrating a sheet conveying device according to an embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view for explaining the balance of forces in the longitudinal direction (X-axis direction).

FIG. 9 is an operation diagram of the sheet conveying apparatus according to the embodiment of the present invention.

FIG. 10 is a diagram showing an inclination of an operation line in the sheet conveying device according to the embodiment of the present invention.

FIG. 11 is an operation diagram in the case of a low torque limiter returning force in the sheet conveying device according to the embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view for explaining force balance in the longitudinal direction (Y-axis direction) of the sheet conveying device including two pairs of gear trains according to the embodiment of the present invention.

FIG. 13 is a perspective view showing an example of a configuration of a reverse drive gear in the sheet conveying device according to the embodiment of the present invention.

FIG. 14 is a schematic cross-sectional view for explaining the balance of forces in the longitudinal direction (Y-axis direction) of a sheet conveying apparatus that includes two pairs of gear trains and that has different angles θ according to the embodiment of the present invention.

FIG. 15A is a perspective view showing an example of the configuration of another reverse drive gear in the sheet conveying apparatus according to the embodiment of the present invention. FIG. 3B is a side view showing the configuration of the reverse drive gear.

FIG. 16 shows the balance of forces in the longitudinal direction (Y-axis direction) of a sheet conveying apparatus having two reverse drive gears and one reverse driven gear according to the embodiment of the present invention and having different angles θ. The schematic sectional drawing for explaining.

FIG. 17A is a perspective view showing an example of the configuration of still another reverse drive gear in the sheet conveying apparatus according to the embodiment of the present invention. FIG. 3B is a side view showing the configuration of the reverse drive gear.

FIG. 18 is a schematic configuration diagram showing an image forming apparatus equipped with a sheet conveying device according to an embodiment of the present invention.

[Explanation of symbols]

1 reverse roller 2 torque limiter 3 reverse driven gear 3'reverse driven gear 4 reverse drive gear 4a reverse drive gear shaft 5 feed roller 6 feed shaft 7 bearing 8 reverse shaft 9 fulcrum 10 double feed boundary line 11 non-feed boundary line 12 FRR operation Line 13 Set point 14 Operating point 15 Operating point 16 FRR operating line 17 Set point 18 Reverse tooth drive gear 18 'Partial tooth reverse drive gear 19 All tooth portions for drive transmission 20 Idler gear 21 Seat 22 Partial tooth portion 23 Tooth portion 24 Aptitude Area 25 Sheet conveying device P1 Gear pushing force P2 Own weight P3 Bearing force PB Nip pressure TA Torque limiter returning force Tr Torque limiter torque T Drag angle θ Feed shaft-reverse shaft-reverse drive Gear angle θ1 Feed shaft-reverse shaft-reverse drive Angle between gears θ2 Feed axis-reverse Angle between shaft and reverse drive gear μB Reverse shaft-bearing friction coefficient RB Reverse shaft radius RZ Reverse driven gear radius RS Reverse roller radius L1 Reverse driven gear-fulcrum distance L1a Reverse driven gear-fulcrum distance L1b Reverse driven gear- Distance between fulcrums L2 Distance between center of gravity-fulcrum L3 Distance between bearings-fulcrum L4 Distance between reverse roller-fulcrum

Claims (8)

[Claims] 1. A feed roller that rotates in a sheet conveying direction to convey a sheet, and a reverse roller that can rotate in the normal direction and a reverse roller that is given a restoring force that rotates in the same direction as the feed roller by a torque of a torque limiter. When there is one sheet that is brought into pressure contact and conveyed by the nip between the feed roller and the reverse roller, the reverse roller is driven by the frictional force due to the frictional force between the sheet and the reverse roller. When the number of sheets conveyed by the nip is positive, the reverse roller rotates the reverse rotation of the torque limiter against the return force of the rotation torque of the feed roller. In the sheet conveying method in which the sheet is rotated in the reverse direction by the returning force due to the torque, the reverse slave rotating together with the reverse roller is used. The radius of the gear is RZ, the radius of the reverse roller is RS, the radius of the reverse shaft that supports the reverse roller is RB, the friction coefficient between the reverse shaft and the bearing of the reverse shaft is μB, and the radius of the reverse shaft is μB. The distance from the fulcrum that is the fixed end to the reverse driven gear is L1, the reverse roller, the reverse shaft, the torque limiter, the bearing,
And the total self weight of the reverse driven gears is P2, the distance from the fulcrum to the center of gravity of the total self weight is L2, and the drag force received by the reverse shaft from the bearing is P
3, the distance from the fulcrum to the bearing is L3, the distance from the fulcrum to the reverse roller is L4, the rotational torque of the torque limiter is Tr, and the first factor K = (L1 / L4) can be defined as above. ) ・ (RS / R
Z), the second factor k = (RB / RS) · μB, and the coefficient P
0 = (L3 · P3−L2 · P2) / L4, the return force TA = Tr / RS by the torque limiter, and the reverse drive gear shaft supporting the reverse drive gear for driving the reverse roller and the reverse drive. When the angle formed by the straight line connecting the shaft center with the shaft and the straight line connecting the shaft centers of the reverse shaft and the feed shaft supporting the feed roller is θ [rad], the range of the θ is: And the nip pressure PB generated between the feed roller and the reverse roller is expressed by the following equation: 0 [rad] <θ <π [ra
d], PB = {[K / Cos (θ−π / 2) + Tan
(Θ-π / 2)] TA + P0} / [1-Kk / Co
s ([theta]-[pi] / 2)]). 2. A feed roller that rotates in a sheet conveying direction to convey a sheet, a reverse roller that can rotate normally and reversely, a pressing unit that presses and contacts the feed roller and the reverse roller, and the reverse roller. On the other hand, a torque limiter that applies a return torque that rotates in the same direction as the feed roller by a rotational torque is provided, and when the number of sheets conveyed by the nip between the feed roller and the reverse roller is one, Due to the frictional force between the sheet and the reverse roller, the reverse roller is positively rotated in the direction in which the reverse roller rotates along with the rotation of the feed roller against the return force of the torque of the torque limiter, and is conveyed by the nip. If there are multiple sheets,
In a sheet conveying device configured to reversely rotate the reverse roller by a returning force generated by the torque of the torque limiter, a radius of a reverse driven gear that rotates together with the reverse roller is RZ, and a radius of the reverse roller is Rz.
S, the radius of the reverse shaft that supports the reverse roller is R
B, the friction coefficient between the reverse shaft and the bearing of the reverse shaft is μB, the distance from the fulcrum that is the fixed end of the reverse shaft to the reverse driven gear is L1, the reverse roller,
The total self weight of the reverse shaft, the torque limiter, the bearing, and the reverse driven gear is P2, the distance from the fulcrum to the center of gravity of the total self weight is L2, and the reaction force received by the reverse shaft from the bearing is P3. The distance from the fulcrum to the bearing is L3, the distance from the fulcrum to the reverse roller is L4, the rotational torque of the torque limiter is Tr, and the first factor K = (L1 / L4). RS / RZ), second factor k
= (RB / RS) μB and coefficient P0 = (L3 · P3
-L2 · P2) / L4, and the return force TA = Tr / RS by the torque limiter, and the center of the reverse drive gear shaft that pivotally supports the reverse drive gear for driving the reverse roller and the reverse shaft. The angle formed by the connecting straight line and the straight line connecting the axis of the reverse shaft and the feed shaft that supports the feed roller is θ [r
ad], the range of θ and the nip pressure PB generated between the feed roller and the reverse roller are expressed by the following equations: 0 [rad] <θ <π / 2 [rad], π / 2
[Rad] <θ <π [rad], PB = {[K / Cos
(Θ−π / 2) + Tan (θ−π / 2)] · TA + P
0} / [1-K · k / Cos (θ−π / 2)], the sheet conveying apparatus is set to a value formulated. 3. The sheet conveying device according to claim 2, further comprising two sets of gear trains each comprising the reverse drive gear and the reverse driven gear, wherein each set of gear trains is a fixed end of the reverse shaft. The distance L1 from the fulcrum to the reverse driven gear is different from each other, and one of the two sets of the reverse driven gear or the reverse driven gear is meshed with the gear train of one set by the rotation of the gear train. A sheet conveying device having one or more toothless portions and toothed portions formed so that the meshing of the other set of gear trains is disengaged when the gear train is in the open state. 4. The sheet conveying apparatus according to claim 3, wherein, among the reverse driven gears of the gear trains of each set, the reverse driven gear whose distance L1 from the fulcrum is shorter is the rotation time by the toothless portion. When using PBLT, the nip width at which the feed roller and the reverse roller contact each other is NI.
P, where VR is the rotational speed of the reverse roller, the following equation holds: PBLT = NIP / VR 5. The sheet conveying apparatus according to claim 4, wherein among the reverse driven gears of the gear trains of each set, an angle θ with respect to the reverse driven gear having a longer distance L1 from the fulcrum.
[Rad] is the following equation, π / 2 [rad] <θ <π [r
ad], and among the reverse driven gears of each set of gear trains, the angle θ [rad] with respect to the reverse driven gear whose distance L1 from the fulcrum is shorter is expressed by the following equation: 0 [ra]
d] <θ <π / 2 [rad]. 6. The sheet conveying apparatus according to claim 2, wherein one reverse driven gear meshes with two reverse driving gears, and one of the reverse driving gear or the reverse driven gear is driven when the gear train is rotationally driven. , One of the sets of gear trains has a toothed portion which is disengaged from the teeth of the other set of gear trains, and has one or more toothless portions, and the two reverse drives described above. A sheet conveying device characterized in that all drive transmission tooth portions provided on a gear are rotationally driven by meshing of idler gears. 7. The sheet conveying apparatus according to claim 5, wherein the distance L1 of the gear having the angle θ of π / 2 [rad] <θ <π [rad] from the fulcrum is 0 [rad].
A sheet conveying device, wherein a gear having an angle θ of <θ <π / 2 [rad] is set to be larger than a distance L1 from the fulcrum. 8. A sheet stacking body for stacking and stacking a plurality of sheets, a sheet feeding means for feeding the stacked sheets on the sheet stacking body, and a sheet fed by the sheet feeding means. An image forming apparatus having a sheet conveying unit that conveys the sheets while separating them one by one, and an image forming unit that forms an image on the sheet conveyed by the sheet conveying unit. An image forming apparatus, wherein 4, 5, 6, or 7 sheet conveying devices are used.