JP2000159358A - Feeder and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feeder and an image forming device, in which troubles such as double feed are prevented even in the case of diversified sheets and the durability of rollers and the like is significantly enhanced. SOLUTION: In a typical arrangement of a feeder and an image forming device, the feeder has a sheet storage means for stacking sheets, a feed means for feeding the sheets stacked, and a separating conveying means for separating from one another the sheets fed by the feed means, the separating conveying means comprising a feed roller 26 for feeding the sheets and a retard roller 27 cooperating with the feed roller 26 to separate the sheets by imparting a driving force toward the sheet storage means. A hard rugged face 26a is formed on the surface of the feed roller 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device in an image forming apparatus such as a printer, a copying machine, and a facsimile for forming an image on a sheet.

[0002]

2. Description of the Related Art A conventional feeding device will be described with reference to FIG. The feeding device 100 feeds a sheet S to an image forming unit (not shown). As shown in the figure, a plurality of sheets S are stacked and stored in the sheet storage means 101,
The pickup roller 102 serving as a feeding means is pressed against the uppermost sheet S and is driven to rotate, whereby pickup feeding is performed. The picked-up sheet is guided by a sheet guide 103 and sent to a nip between a feed roller 104 and a retard roller 105, which are separating and conveying means.

The feed roller 104 is driven to rotate in the transport direction as shown by an arrow a in the figure. On the other hand, retard roller 105
While being pressed against the feed roller 104 by a pressing means (not shown), a rotational driving force is applied in a direction opposite to the transport direction as shown by an arrow b. A drive shaft of the retard roller 105 is provided with a torque limiter (not shown).
It is configured to run idle when a predetermined or more driving load is applied.

Therefore, when the feed roller 104 and the retard roller 105 are in contact with each other directly or via only one sheet, the driving force given by the feed roller 104 is large, so that the torque limiter reduces the driving force. After cutting, the retard roller 105 is driven by the feed roller 104. However, when a plurality of sheets S are picked up by the pickup roller 102, the frictional resistance between the sheets is relatively low, so that the torque limiter transmits the driving force, and the retard roller 105 is driven to rotate in the direction of arrow b. I do.

As a result, only one sheet S abutting on the feed roller 104 is conveyed, and the other multi-fed sheets are pushed back to the sheet storage means 101. One sheet S is pulled out by a sheet guide 106 into a pair of pull-out rollers 10.
7 and further conveyed to the downstream image forming unit.

Next, a theoretical expression that satisfies the conditions for feeding and separating the sheet S in the feeding apparatus 100 having the above structure is as follows: N> T / rμBP + (μAPP−μAP) W / μBP (1) N <T / rμBPP -2μAPP W / μBPP (2) N <T / rμCP (3) where μAP: friction coefficient between pickup roller 102 and sheet S μBP: friction coefficient between feed roller 104 and sheet S μCP: retard roller 105 Of friction between sheet S and sheet S μAPP: coefficient of friction between sheets S in pickup roller 102 μBPP: coefficient of friction between sheets S in nip between feed roller 104 and retard roller 105 N: pressure of retard roller 105 T: idling torque of torque limiter r: radius of retard roller 105 W: pressure of pickup roller 102 Equation (1) is the feed condition, Equation (2) is the separation condition,
(3) is an equation for satisfying the rotation condition of the retard roller 105, respectively.

If the same sheet is used in the above equation, the frictional force of the pressing portion of each roller does not vary so much. Therefore, if μAPP ≒ μBPP = μPP, the above equations (1) and (2) ) Is N> T / rμBP + (μPP−μAP) W / μBP (4) N <T / rμPP-2W (5) FIG. 7 is a graph showing the relations of the above equations (3), (4) and (5) using the pressure of the retard roller 105 and the idling torque T of the torque limiter as parameters. In the figure, a hatched portion indicates a feeding area.

That is, in order to enlarge the feeding area of the hatched portion, it is necessary to increase the coefficient of friction between each roller and the sheet.
It is necessary to reduce the pressing force W of the pickup roller 102, and the feeding conditions are set in the direction of increasing both the pressing force N of the retard roller 105 and the idling torque T of the torque limiter (upper right direction in the figure). It can be seen that the feed area becomes wider when set. However, if the idling torque T of the torque limiter is increased more than necessary, the load in driving the roller increases, so that the upper limit (the upper right limit in the figure) of the appropriate feeding region is also limited to some extent.

[0009]

On the other hand, with the recent increase in speed of image forming apparatuses and diversification of sheets, it has become difficult to set an almighty feeding area.
That is, it is difficult to set both the sheet feeder and the retard roller in order to prevent double feed of various sheets beforehand and to ensure sufficient durability. Specifically, to prevent double feed, the idling torque T of the torque limiter is used.
May be increased or the pressure N of the retard roller 105 may be reduced, but this will reduce the durability of the feed roller 104 and the retard roller 105.

Here, factors that determine the durability of the feed roller 104 and the retard roller 105 will be described.
Conventionally, the feed roller 104 is generally formed of a synthetic rubber such as EPDM or silicon, and the retard roller 105 is generally formed of a similar synthetic rubber or a sponge material such as urethane or silicon. The surface of these rollers is provided with a polishing grain provided in a polishing process, and the polishing grain is an important factor in determining the durability of the roller during actual feeding and conveyance.

Specifically, paper dust is generated from the conveyed sheet during the actual feeding operation. However, since the paper dust escapes to the grooves (valleys) of the polished eyes, the roller surface and the sheet surface are removed. Can reliably contact with each other, and a desired frictional conveyance force can be obtained. However, if the polishing line is worn and disappears due to durability, there is no place for paper dust to escape, and a layer of paper dust is formed between the roller and the sheet. In such a situation, slip jam occurs frequently. Usually, such a state is defined as the durable life of the roller.

That is, in order to improve the durability life of the roller, it is only necessary to improve the abrasion resistance of the rubber material and take measures to prevent the polishing streaks from disappearing. It is impossible to improve performance over time, and it remains a long-term issue.

In view of the above problems, it is an object of the present invention to provide a feeding apparatus and an image forming apparatus which do not cause troubles such as double feeding even for diversified sheets and which have remarkably improved the durability of rollers. Is to provide.

[0014]

A typical configuration of a feeding apparatus and an image forming apparatus according to the present invention for solving the above-mentioned problems includes a sheet storing means for stacking sheets, and a sheet feeding means for feeding the stacked sheets. A feeding device for feeding the sheet, and a separating / conveying device for separating the sheets fed by the feeding device into sheets one by one, wherein the separating / conveying device feeds the sheet. A feed roller for feeding the sheet, and a retard roller for separating the sheet in cooperation with the feed roller by applying a driving force toward the sheet storage means, forming a hard uneven surface on the surface of the feed roller. It is characterized by having done.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of a feeder and an image forming apparatus according to the present invention will be described with reference to the drawings. 1 is an overall configuration diagram of an image forming apparatus according to the present embodiment, FIG. 2 is a partially enlarged view illustrating driving of a feeding device, FIG. 3 is an enlarged cross-sectional view of a feed roller and a retard roller, and FIG. It is a partial enlarged view of a retard roller.

An image forming apparatus 1 shown in FIG. 1 is a so-called electrophotographic copying machine, and has a feeding device 2 for supplying a sheet S to the image forming apparatus 1. First, the outline of the image forming apparatus 1 will be described, and then the feeding apparatus 2 will be described.

(Image Forming Apparatus) The image forming apparatus 1 has a document reading device 3 for reading an image on a document at an upper portion, an image forming portion 4 at a substantially central portion, and a sheet feeding portion for supplying a plurality of types of sheets below. Five. The document reading device 3 reads an image of a document placed on a platen glass 6 by an optical unit 7 and irradiates an image carrier 9 with a light beam to form an electrostatic latent image. An automatic document feeder 8 for feeding and pressing a document is provided on the platen glass 6.

The image carrier 9 of the image forming section 4 is a primary charging device.
After the electrostatic latent image is uniformly charged by 10 and an electrostatic latent image is formed by the optical unit 7, the electrostatic latent image is visualized by a developing unit 11, and the formed toner image is conveyed by a transfer unit 12. Is transferred to the sheet S. The toner remaining on the image carrier 9 after the transfer of the toner image is removed by the cleaning device 13, and the next image formation is performed.

A plurality of cassettes 14 for stacking sheets S are arranged in the sheet feeding section 5 at the lower portion of the apparatus, and the sheets S are separated and fed one by one from these cassettes 14 and a feeding device 2 described later. You. The fed sheet S is the image carrier 9
The skew is corrected by temporarily stopping and forming a loop by the pair of registration rollers 15 on the upstream side, and the image carrier 9 is fixed.
The conveyance is started again in synchronization with the above. The sheet on which the toner image has been transferred by the transfer unit 12 is conveyed to the fixing unit 17 by the conveying unit 16, and the toner image is fixed by applying heat and pressure to form an image.

The sheet S on which the image has been fixed is discharged to the discharge stacking tray 19 outside the apparatus by the discharge means 18 or is sent to the re-conveying path 21 by the flapper 20 on the upstream side of the conveying means 16. Here, in the case of multiplex recording, the recording paper is advanced to the re-feeding path 23 as it is, and in the case of double-sided recording, the traveling direction is reversed in the reversing path 22 and the recording paper is again supplied to the image forming section 4 from the re-feeding path 23. After the sheet is fed and the image is formed again, the sheet is discharged out of the apparatus.

(Feeding Device) Next, the feeding device 2 will be described. As shown in FIG. 1, a plurality of sheets S are stacked on a loading table (not shown) provided inside the sheet storage means 24 of the feeding device 2, and a feeding means is provided on the uppermost surface of the loaded sheets. The pickup roller 25 is configured to abut and press. A drive source (not shown) is connected to the pickup roller, and transmits a conveyance driving force to the uppermost surface of the sheet by a frictional force.

The sheet P sent out by the pick-up roller 25 is fed to the image forming section 4 in the main body of the image forming apparatus 1 by a separate conveying means including a feed roller 26 and a retard roller 27. As shown in FIG. 2, the feed roller 26 and the retard roller 27
Driven by 28.

In the drive transmission device 28, the feed roller 26
, A retard shaft 30 that supports the retard roller 27, and a retard drive shaft 31 that is connected to the feed roller shaft 29 are disposed substantially parallel to each other. The retard shaft 30 is supported by a swingable support member (not shown), and can be separated from and connected to the feed roller shaft 29 while keeping the feed roller shaft 29 horizontal. A coupling 32 and a torque limiter 33 are provided between the retard shaft 30 and the retard drive shaft 31.
This coupling 32 is for transmitting the drive from the retard drive shaft 31 to the retard shaft 30 even if the retard roller 27 is displaced.

An electromagnetic clutch 34 is attached to an end of the feed roller shaft 29, and a driving force is transmitted from a main driving unit of the image forming apparatus 1 via a driving input belt 35. A retard drive belt 36 is also stretched between the feed roller shaft 29 and the retard drive shaft 31, and the retard roller 27 is also configured to rotate by the driving force from the main drive unit.

That is, the rotational driving force transmitted from the main driving means via the drive input belt 35 is provided to the armature portion of the electromagnetic clutch 34 by controlling the ON / OFF of the electromagnetic clutch 34 in accordance with the feeding timing. The feed roller shaft 29 rotates, and the feed roller 26 rotates in the sheet conveying direction. Further, the retard drive belt 31 and the retard shaft are driven by the retard drive belt 36.
When a driving force is input to 30, the retard roller 27 transmits the driving force in a direction opposite to the sheet conveying direction.

Here, the retard roller 27 is a feed roller.
26, or when pressure is applied via only one sheet, the frictional force exceeds the idling torque of the torque limiter, and the connection is cut off. To follow. When a plurality of sheets S are fed, since the frictional force between the sheets is smaller than the frictional force between the retard roller 27 and the sheet S,
The torque limiter 33 does not run idle, and the retard roller 27 rotates in the direction opposite to the transport direction. As a result, only the uppermost sheet S among the plurality of fed sheets S, that is, the uppermost sheet S, is fed, and separated from the other sheets to prevent double feeding.

FIG. 3 is an enlarged view of the feed roller 26 and the retard roller 27. The feed roller 26 is made of a metal material such as iron or stainless steel, and has a plurality of projections 26a on its surface. The projection 26a is formed by cutting and raising a surface material, and has a wedge-like tip at a height of about 20 to 100 μm. The retard roller 27 is made of a synthetic rubber such as silicon or a sponge material such as urethane or silicon, similarly to a general roller.

Then, when the sheet S is nipped by the feed roller 26 and the retard roller 27, the sheet S is conveyed while being mechanically engaged with the sheet S as shown in FIG. Therefore, it is clearly configured to convey by frictional force as in the related art, and even if paper dust is generated and interposed, slippage occurs between the feed roller 26 and the sheet S. Therefore, a stable transport speed can be secured. Further, with respect to the change with time due to durability, since the projection 26a itself is a metal material, the projection 26a is completely free from wear in the range of the life cycle of a normal image forming apparatus.

As described above, the life of the retard roller is determined by the wear of the polished eyes provided on the outer peripheral surface and the clogging by the paper dust as described above using the conventional example. However, according to the present embodiment, since the protrusion 26a of the feed roller 26 is in press contact with the outer peripheral surface of the retard roller 27 in the paper tube at the time of normal feeding, the protrusion 26a Retard roller 27
Mechanically engages with the outer peripheral surface of the

Further, since the driving of the retard roller 27 is normally input in the direction opposite to the conveying direction via a load system such as a torque limiter 33, the outer peripheral surface of the retard roller 27 is
Thus, the motor rotates while receiving a load in the circumferential direction at all times. Then, the paper dust adhering to the outer peripheral surface of the retard roller 27 is removed by the rubbing effect of the projection 26a, and a concave portion due to the projection 26a is continuously formed on the outer peripheral surface of the retard roller 27. The outer peripheral surface of the retard roller can always be maintained in a refreshed state without the portions disappearing.

The projections 26a can be formed in a processing step in which the outer peripheral surface of the feed roller 26 made of a metal material is only cut and raised by cutting, so that it is necessary to provide a new material. And can be provided at a low material cost.

(Second Embodiment) Next, a second embodiment of the feeding apparatus and the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 5 is a view for explaining the feed roller and the retard roller according to the present embodiment. The same reference numerals are given to the same parts as those in the first embodiment, and the description will be omitted.

In FIG. 5, the surface layer of the feed roller 37 is coated with a ceramic layer 38, and this ceramic layer 38 is composed of alumina powder 38a and an adhesive 38b. The alumina powder 38a has a wedge-shaped pointed tip, and is integrated with the outer peripheral surface of the feed roller 37 by an adhesive 38b to form a projection.

With this configuration, even if the material of the feed roller 37 is a synthetic rubber such as EPDM or silicon, or a molding material, the protrusion can be provided on the outer peripheral surface. Instead, the same effects as those of the first embodiment can be obtained.

Further, in the present embodiment, even if the roller shape has a complicated three-dimensional shape, it is only necessary to coat the base material once the shape is determined. Is a highly versatile means that can be used.

[0036]

As described above, according to the feeding apparatus and the image forming apparatus according to the present invention, it is possible to greatly improve the conveying performance and to increase the durability of the feed roller and the retard roller extremely. It can be set and maintenance-free.

Further, such a configuration can be achieved only by replacing the feed roller and the retard roller, which can be easily attached to and detached from the conventional feeding device. However, it is easy to respond individually, and is very versatile. Therefore, even when there is a user who uses a variety of sheets more than expected, it is possible to provide a feeding device capable of promptly responding.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a partially enlarged view illustrating driving of a feeding device.

FIG. 3 is an enlarged sectional view of a feed roller and a retard roller.

FIG. 4 is a partially enlarged view of a feed roller and a retard roller.

FIG. 5 is a diagram illustrating a feed roller and a retard roller according to a second embodiment.

FIG. 6 is a diagram illustrating a conventional feeding device.

FIG. 7 is a graph in which the pressing force of the retard roller 105 and the idling torque T of the torque limiter are used as parameters.

[Explanation of symbols]

 S: Sheet 1: Image forming apparatus 2: Feeding device 3: Document reading device 4: Image forming unit 5: Sheet feeding unit 6: Platen glass 7: Optical means 8: Automatic document feeding device 9: Image carrier 10 … Primary charging device 11… Developing device 12… Transfer device 13… Cleaning device 14… Cassette 15… Registration roller pair 16… Transport device 17… Fixing device 18… Discharge device 19… Discharge stack tray 20… Flapper 21… Re-convey path 22 ... reversing path 23 ... re-conveying path 24 ... sheet storage device 25 ... pickup roller 26 ... feed roller 26a ... projection 27 ... retard roller 28 ... drive transmission device 29 ... feed roller shaft 30 ... retard shaft 31 ... retard drive shaft 32 ... cup Ring 33: Torque limiter 34: Electromagnetic clutch 34a: Pulley 35: Drive input belt 36: Retard drive belt 37: Feed roller 38: Ceramic Layer 38a ... alumina powder 38b ... adhesive

Claims (6)

[Claims] 1. A sheet storage means for stacking sheets, a feeding means for feeding the stacked sheets, and a separation conveyance for separating the sheets fed by the feeding means one by one. And a feeding device having a feeding roller for feeding a sheet, and a driving force applied to the sheet storage device to cooperate with the feed roller to feed the sheet. A feeding device comprising: a retard roller for separating; and a hard uneven surface formed on a surface of the feed roller. 2. The hard uneven surface is a plurality of projections formed by cutting and raising the metal material on the outer peripheral surface of the feed roller made of a metal material. The feeding device according to 1. 3. The feeding device according to claim 2, wherein the projection formed on the surface of the feed roller has a height of 20 to 100 μm. 4. The feeding device according to claim 1, wherein the hard uneven surface is a ceramic layer formed on an outer peripheral surface of the feed roller with alumina powder and an adhesive. 5. The feeding device according to claim 1, wherein the retard roller is made of a synthetic rubber such as EPDM or silicone, or a sponge material such as urethane or silicone. Feeder. 6. An image forming apparatus, comprising: the sheet feeding apparatus according to claim 1; and an image forming unit that forms an image on a sheet fed from the sheet feeding apparatus. .