JPH10109787A - Sheet transferring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To position a tip of a sheet accurately by a nip of a low-cost resist roller without affected by stiffness of the sheet. SOLUTION: Sheet transmitted from a carrier part 14 to resist roller 21a, 21b is passed at an image forming part 2 side by normal rotation action of the resist roller 21a, 21b and the sheet is turned back until its tip reaches a nip part of the resist roller 21a, 21b by reverse action of the resist roller 21a, 21b and stopped at a constant position and the sheet is carried to the image forming part 2 by normal rotation action of next resist roller 21a, 21b. Thereby, position of the tip of the sheet can be accurately positioned by the nip part of the resist roller 21a, 21b when the weak sheet is used. Used amount of expensive metal material is reduced by forming an outer periphery part of the resist roller 21a, 21b with bending and flexible elastic material and production cost can be reduced by reducing processing accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a copying machine,
The present invention relates to a sheet conveying device used for an image forming apparatus such as a printer and a facsimile.

[0002]

2. Description of the Related Art When a sheet is conveyed to an image forming apparatus, the sheet is fed until the leading end of the sheet comes into contact with a nip portion of a pair of registration rollers and bends in order to supply the sheet in synchronization with an image forming process. A sheet is conveyed to an image forming unit by rotating a registration roller at a predetermined timing.

[0003]

When the paper is conveyed toward the nip of the registration roller to be stopped, since the outer periphery of the registration roller is formed of a material having a high coefficient of friction, the paper is resisted from the outer peripheral surface of the registration roller. Receive.
For this reason, in the case of a sheet having a weak stiffness, the sheet may not stay at the nip of the registration roller but may stay. In order to prevent such a situation, it is necessary to adjust the position of the guide plate for guiding the sheet to the nip of the registration roller. Alternatively, it is necessary to adopt a structure in which the paper is guided to the nip portion of the registration roller by a guide made of a polyester film or the like that elastically bends in order to reduce the resistance applied to the weak paper. In any case, the manufacturing cost of the paper feed passage increases.
On the other hand, in the case of a sheet having a strong stiffness, a thrust generated when the sheet is bent may pass through the nip portion of the registration roller. As a result, it is very difficult to position the leading edge of the sheet depending on the type of sheet.

[0004]

According to the first aspect of the present invention,
A paper feed path connecting between the paper feed unit and the image forming unit, and a pair of registration rollers disposed near the image forming unit in the paper feed passage and driven by a forward / reverse rotatable motor,
A transport unit disposed upstream of the registration roller in the paper feed path and driven by a motor to transfer a sheet to the registration roller, and a tip of the sheet delivered from the transport unit during paper feeding to the registration roller Motor control means for controlling the operation of the motor so as to return the leading end of the sheet to the nip of the registration roller by a reverse rotation operation of the registration roller immediately after passing through the image forming unit side by the normal rotation operation, The outer periphery of the registration roller is formed of an elastic material that can flex. Therefore, the paper delivered to the registration roller by the transport unit passes through the nip of the registration roller by the normal rotation of the registration roller, and the leading end is returned to the nip of the registration roller by the reverse rotation of the registration roller, and is bent. Then, the sheet is stopped at a certain position, and is conveyed to the image forming section by the next normal rotation operation of the registration roller. Further, since the outer periphery of the resist roller is formed of an elastic material, it is possible to reduce the diameter of the metal material forming the core, and even if the processing accuracy of the outer periphery of the core is reduced, There is no effect on paper transport performance. The elastic material of the outer peripheral portion of the registration roller includes a synthetic resin having elasticity or natural rubber.

According to a second aspect of the present invention, in the first aspect of the invention, the pair of registration rollers have different elastic materials from each other. Therefore, in the nip portion of the registration roller, the registration roller having a lower hardness of the elastic material is deformed into a concave shape. Thus, when the registration roller is rotated in the reverse direction and the sheet is returned, the sheet is sandwiched by the registration roller that is deformed in a fixed relationship, and the slack direction of the sheet is constant.

According to a third aspect of the present invention, in the first aspect of the present invention, the pair of registration rollers differ from each other in the thickness of the elastic material at the outer peripheral portion. Therefore, at the nip portion of the registration roller, the registration roller having a thick elastic material is deformed into a concave shape. Thus, when the registration roller is rotated in the reverse direction and the sheet is returned, the sheet is sandwiched by the registration roller that is deformed in a fixed relationship, and the slack direction of the sheet is constant.

[0007]

FIG. 1 shows a first embodiment of the present invention.
A description will be given with reference to FIG. In FIG. 1, reference numeral 1 denotes an apparatus main body, and a photoreceptor 3 constituting a main part of an electrophotographic image forming section 2 is rotatably provided in the apparatus main body 1. A plurality of paper feed units 4 are provided below the apparatus main body 1 so as to be vertically arranged. These paper feed units 4
Is composed of a paper feed cassette 5, a paper feed roller 7 for sequentially feeding the paper lifted by the bottom plate 6 of the paper feed cassette 5 from the topmost one, and a separation unit 8 arranged downstream of the paper feed roller 7. The separation unit 8 includes a transport roller 9 and a reverse roller 10 that are driven counterclockwise with respect to each other. In this case, the reverse roller 10 rotates clockwise due to friction with the sheet that is pulled out when one sheet is pulled out between the transport roller 9 and the reverse roller 10. In the known separation, the papers are slipped with each other so that only the uppermost paper is passed through, and the lower paper is pushed back in a direction opposite to the paper feeding direction by rotating counterclockwise. Structure.

The paper feed section 4 and the image forming section 2 are connected by a paper feed path 11. This paper feed passage 11
Has a plurality of branch paths 12 each leading to the paper feeding section 4, and the lower end is opened to enable bottom-pass paper feeding. Branch 12 in paper feed path 11
The transporting units 13 and 14 are arranged at the branch point of. These transport units 13 and 14 include transport rollers 15 and 16 which are rotating bodies, and press contact rollers 17 and 18 which are rotary bodies elastically contacted with these transport rollers 15 and 16.
19 and 20. A pair of registration rollers 21 located at the end on the image forming unit 2 side
a, 21b, a paper detector 22 located near the downstream side of the transport unit 13, a paper detector 23 located near the downstream side of the transport unit 14, and a resist located near the upstream side of the registration rollers 21a, 21b. A detector 24 is arranged.

Next, with reference to FIG. 2, a description will be given of a drive mechanism 25 for driving the transport units 13, 14 and the registration rollers 21a. The shaft 2 of the transport rollers 15 and 16 of the transport units 13 and 14
Pulleys 28 and 29 are fitted to the ends of the shafts 6 and 27, respectively.
A pulley 31 having a gear 30 is rotatably fitted to a support shaft (not shown) provided on the upper part of the pulley 7.
8, 29 and 31 are endless timing belts 32
Is wound. 33 is a tension pulley for applying tension to the timing belt 32. A gear 35 is fixedly fitted to the end of the shaft 34 of the lower registration roller 21a. Reference numeral 36 denotes a forward / reverse rotatable motor. To this motor 36, a gear 37 meshed with the gear 30 of the pulley 31 and the gear 35 of the registration roller 21a is directly connected.

When the motor 36 is normally rotated in the direction indicated by the solid line arrow, the driving mechanism 25
a and the transport rollers 15 and 16 are normally rotated in the direction of the solid arrow, and the paper is transported toward the image forming unit 2. Motor 3
When the roller 6 is rotated in the direction of the dotted arrow, only the registration roller 21a is rotated in the direction of the dotted arrow, but the pulleys 28 and 29 are provided with one-way clutches (not shown) so that the rotational force is not transmitted to the transport rollers 15 and 16. Zu) is built-in.

In the present embodiment, the paper feed roller 7 and the separation unit 8 of the paper feed unit 4 are driven by the drive mechanism 25 in response to a paper feed signal.
It is driven by another driving mechanism (not shown) different from the above. Of course, the paper feed roller 7
Alternatively, the separation unit 8 may be driven.

Here, as shown in FIG. 4, a pair of registration rollers 21a, 21b are made of a metal roller body 38a,
38b, and elastic members 39a, 39b covering the surfaces of the roller bodies 38a, 38b. In this case, the elastic members 39a and 39b include an elastic synthetic resin or natural rubber.

Here, a pair of registration rollers 21a, 21
b is elastically deformed at the nip portion since the outer peripheral portion is formed by the elastic members 38a and 38b, but the elastic member 39 of one of the registered registration rollers 21a or 21b is determined.
The hardness of the elastic members 39a and 39b at the outer peripheral portions is changed so that a or 39b is deformed into a concave shape. Alternatively, even if the hardness is the same, the thicker the thickness is, the easier the deformation is, so the thickness is changed. By any of these methods, in this example:
The elastic member 39a of the lower registration roller 21a is configured to be easily deformed into a concave shape.

Next, referring to FIG. 5, the structure of a motor control means for controlling the operation of the motor 36 will be described.
Although not shown, the motor control means monitors the state of a detection signal and a sheet feed signal from the registration detector 24.
When, and a motor driving circuit for driving the period specified in the direction specified motor 36 is controlled in this CPU, the time t ₁ which has received the paper feed signal, by normal rotation motor 36 transporting Rollers 15, 16 and registration rollers 21a,
21b is rotated forward and resist detector 24 is to the motor 36 to the time to T ₂ inversion after T ₁ has elapsed and from the time t ₂ when turned ON time is stopped, preset time t
When the number reaches ₃ , the motor 36 is rotated forward again. Note that the trailing edge of the paper is
Is passed, the motor 36 is stopped as in the conventional case.

In such a configuration, when the paper feed cassette 5 is selected according to the size of the paper and a paper feed signal is output, the paper feed roller 7 and the separation unit 8 are driven, and the paper is sent to the paper feed path 11. It is sent out and heads to the transport roller 16. Since the motor 36 is driven in the forward direction by the sheet feed signal, and the transport roller 16 and the registration rollers 21a and 21b also rotate forward, as shown in FIG.
1a and 21b. During this time, since the leading end of the sheet S is detected by the registration detection unit 24, the period from the detection time point t ₂ T ₁ is the resist rollers 21a, 21b is driven in the normal direction by the motor 36, the sheet S resist It passes through the nip of the rollers 21a and 21b.

[0016] When the motor 36 after T ₁ elapses is reversed by the action of the one-way clutch, a registration roller 21
Since only the rollers a and 21b are rotated in reverse, and the transport rollers 15 and 16 are kept in a stopped state, the leading end of the sheet S is returned to the nip portion of the registration rollers 21a and 21b as shown in FIG. It bends in a curved shape. Since the thrust is generated by the action of the paper S trying to return from the bent state to the original state, the paper S returns to the position away from the nip portion of the registration rollers 21a and 21b during the reverse rotation of the registration rollers 21a and 21b. Not done. Motor 36 rotates forward again after T ₂ elapses in the time, the registration rollers 21a, in order to forward the 21b and the conveying roller 15, the sheet S is conveyed toward the image forming unit 2.

As described above, after the sheet S is once fed until it passes through the nip portion of the registration rollers 21a and 21b, the leading end is returned to the nip portion of the registration rollers 21a and 21b by the reverse rotation of the registration rollers 21a and 21b. Therefore, even when the paper S having a weak stiffness is used, the position of the leading end of the paper S can be accurately positioned.

Since the transport rollers 15 and 16 are stopped when the registration rollers 21a and 21b rotate in the reverse direction, the paper S is held between the transport roller 16 and the pressure roller 20 when the registration rollers 21a and 21b rotate in the reverse direction. Thereby, the sheet S can be effectively bent. This can be applied to a case where the transport roller 16 is driven by a dedicated motor.

Further, the transport rollers 1 of the transport units 13 and 14
5 and 16 are connected via a one-way clutch to a forward / reverse rotatable motor 36 for driving the registration rollers 21a and 21b.
a, 21b and transport rollers 15, 16 driven in one direction
Can be driven by a common motor 36, and the power of the motor 36 is controlled by the registration rollers 21a, 21b.
Since an electromagnetic clutch is not required for transmitting the sheet S to the transfer rollers 15 and 16, the sheet S can be transported accurately.

Further, since the outer peripheral portions of the registration rollers 21a and 21b are formed of the elastic members 39a and 39b, the diameter of the metal material forming the cores 38a and 38b can be reduced. Accordingly, the amount of the metal material that is more effective than the elastic members 39a and 39b can be reduced, and the cost can be reduced.

When the entirety of the registration rollers 21 and 21b is made of a metal material, the paper S cannot be conveyed unless the accuracy of the distance between the axes and the outer diameter is improved. On the other hand, in the present embodiment, the registration rollers 21a,
Since the outer peripheral portion of the outer member 21b has elastic members 39a and 39b that bend elastically, the conveying performance of the sheet S is not adversely affected even if the distance between the shafts or the outer diameter is reduced. That is, the processing accuracy of the outer peripheral surfaces of the cores 38a and 38b can be reduced. Therefore, the cost can be reduced also in this respect.

Further, as described above, the elastic members 39a,
Since the elastic material 39a of the lower registration roller 21a is easily deformed into a concave shape by changing the hardness or thickness of the registration roller 39b, the registration rollers 21a and 21b are rotated in reverse as shown in FIG. In this case, the registration roller 21a deforms into a concave shape near the edge of the sheet S.
And a resist roller 21b that maintains the convex state, and curves in a direction to wind around the outer periphery of the resist roller 21b following the outer periphery of the upper resist roller 21b that maintains the convex state. In other words, the slack direction of the end of the sheet S when returned can be always fixed.

Generally, as shown in FIG. 4, guide plates 40 and 41 may be opposed to the paper feed path 11 so as to reduce the interval between the registration rollers 21a and 21b toward the nip portion. In some cases, the inclination of the guide plates 40 and 41 with respect to the entering direction of the paper S may be different. In the example shown in FIG. 4, the guide plate 41 is inclined with respect to the direction in which the sheet S enters. In such a case, the registration rollers 21a, 21a
If the slack direction of the paper S returned by reversing 1b is not constant and loosens toward the guide plate 40, the paper S may be pressed against the guide plate 40, bend or bend, and develop into a jam.

However, as described above, since the returned sheet S is always constant, for example, to the guide plate 41 side, the sheet S can be loosened between the guide plates 40 and 41 with a margin. Thereby, it is possible to prevent the sheet S from being bent or squashed and the occurrence of a jam.

Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the previous embodiment are denoted by the same reference numerals and description thereof is omitted. The motor control unit of this example is the same as the motor control unit of the previous embodiment except that the reverse rotation operation of the registration rollers 21a and 21b is continued until the start of the next forward rotation operation. Specifically, at time t ₁ when the sheet feed signal is received, the motor 36 is rotated forward to rotate the transport rollers 15 and 16 and the registration rollers 21 a and 21 b.
At the time t when the registration detector 24 is turned ON.
Although reversing the motor 36 in the _two time after T ₁ has elapsed, the period of this reversal is configured to continue until the rotated forward the motor 36 again reaches the point t ₃ when set in advance.

In such a configuration, when a paper feed signal is output, the paper feed roller 7 and the separation unit 8 are driven, and the paper is sent out to the paper feed path 11 and travels toward the transport roller 16.
The motor 36 is driven in the normal rotation direction by the paper feed signal, and the transport roller 16 and the registration rollers 21a and 21b also rotate forward, so that the sheet S is delivered to the registration rollers 21a and 21b as shown in FIG. . During this time, although the leading end of the sheet S is detected by the registration detection unit 24, period T ₁ from the detection time point t ₂ the resist roller 21a, 21
Since the sheet b is driven in the normal rotation direction by the motor 36, the sheet S passes through the nip portion between the registration rollers 21a and 21b.

[0027] When the motor 36 after T ₁ elapses is reversed, the registration rollers 21a, 21b only is reversed, since the conveying rollers 15, 16 is maintained in a stopped state, as shown in FIG. 3 (b), the sheet S The tip is a registration roller 21
It returns to the nip portion of a and 21b and bends in a curved shape. At this time, the registration rollers 21a, 21b continues to reversed throughout the period until t ₃ when driven to rotate normally again. Therefore, the sheet S generates a thrust by the action of returning to the original state from the bent state. The thrust is stronger as the sheet S is stiffer, but the registration rollers 21a and 21b resist the sheet S against the thrust. As a result, the leading end of the paper S does not penetrate through the nip portions of the registration rollers 21a and 21b even when the stiff paper S is used.

The transport units 13 and 14 include transport rollers 15 and 16 and pressing rollers 17, 18, 19,
Although the description has been made with reference to FIG. 20, a transport unit using a belt as a rotating body may be used.

[0029]

According to the first aspect of the present invention, a pair of registration rollers driven by a forward / reverse rotatable motor, and a transport unit driven by the motor and delivering a sheet to the registration rollers are provided in a paper feeding path. Immediately after passing the leading edge of the sheet delivered from the transport unit at the time of paper feeding to the image forming unit side by the forward rotation operation of the registration roller, the leading edge of the sheet is rotated by the reverse rotation operation of the registration roller. Since the motor control means for controlling the operation of the motor so as to return to the nip is provided, the sheet delivered to the registration roller by the transport unit is passed through the nip portion of the registration roller by the normal rotation of the registration roller, and the sheet is Due to the reverse rotation of the registration roller, the tip is returned until it reaches the nip of the registration roller, bent and stopped at a certain position. The forward operation of the controller can carry the paper to the image forming unit. Therefore, even when a sheet having a weak stiffness is used, the position of the leading end of the sheet can be accurately positioned. Along with this, it is not necessary to provide a flexible guide in the paper feed passage to reduce the resistance applied to the paper having a weak stiffness, or to strictly adjust the guide plate of the paper feed passage. Manufacturing cost can be reduced. In addition, since the outer periphery of the registration roller is formed of an elastic material, the diameter of the expensive metal material forming the core can be reduced to reduce the amount of the metal used, and furthermore, the use of the core can be reduced. Even if the processing accuracy of the outer peripheral surface is reduced, the transporting performance of the sheet is not affected, so that the manufacturing cost of the registration roller can be reduced.

According to the second aspect of the invention, since the pair of registration rollers have different hardnesses of the elastic members, the registration rollers having the lower hardness of the elastic members are concavely deformed at the nip portion of the registration rollers. Thus, when the registration roller is rotated in the reverse direction and the sheet is returned, the sheet is sandwiched by the registration roller that is deformed in a fixed relationship, and the slack direction of the sheet is constant. Therefore, the guide plates are opposed to each other so that the facing interval becomes narrower toward the nip portion of the registration roller, and even when one of the guide plates is substantially parallel to the paper entering direction, the guide plate tilts the sheet. It can be relaxed on the side with margin,
It is possible to prevent the paper from being bent, squeezed, or jammed due to the slack portion of the paper being pressed against the guide plate.

According to the third aspect of the present invention, the pair of registration rollers differ from each other in the thickness of the elastic material at the outer peripheral portion. Therefore, at the nip portion of the registration roller, the registration roller having a thick elastic material is deformed into a concave shape. This allows
When the sheet is returned by reversing the registration roller, the slack direction of the sheet becomes constant. Therefore, the same effect as the configuration according to claim 2 can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing a first embodiment of the present invention.

FIG. 2 is a perspective view of a driving mechanism.

FIG. 3 is a vertical cross-sectional front view showing a paper conveying process.

FIG. 4 is an enlarged front view showing a configuration of a registration roller.

FIG. 5 is a time chart showing the operation of the motor.

FIG. 6 is a time chart illustrating an operation of a motor according to a second embodiment of the present invention.

[Explanation of symbols]

 2 Image forming unit 4 Paper feed unit 11 Paper feed path 13, 14 Transport unit 15-20 Rotating body 21a, 21b Registration roller 36 Motor 39a, 39b Elastic material

Claims (3)

[Claims] 1. A pair of a paper feed passage connecting between a paper feed unit and an image forming unit, and a pair of paper feed passages disposed near the image forming unit in the paper feed passage and driven by a forward / reverse rotatable motor. A registration roller, a conveyance unit disposed upstream of the registration roller in the paper feed path and driven by a motor to transfer a sheet to the registration roller, and a leading end of the sheet delivered from the conveyance unit during paper feeding Motor control means for controlling the operation of the motor so that the leading end of the sheet is returned to the nip of the registration roller by the reverse rotation operation of the registration roller immediately after passing through the image forming section side by the normal rotation operation of the registration roller. Wherein the registration roller is formed of an elastic material whose outer peripheral portion is bendable. 2. The sheet conveying device according to claim 1, wherein the pair of registration rollers have different elastic materials from each other in hardness. 3. The sheet conveying apparatus according to claim 1, wherein the pair of registration rollers have different thicknesses of the elastic material at the outer peripheral portion.