JP2000264454A - Paper supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a roller by providing a roller with an annular surface layer part made of an elastic material, forming the surface layer part with an annular first and second parts axially arranged, and making an outer diameter of the roller of the first part larger than that of the roller of the second part. SOLUTION: A pick-up roller is formed by a frictional member 2 comprising two large diameter parts 2-a and a small diameter part 2-b formed therebetween, and a core member 3 having a mounting part 3-a and a flange part 3-b of the frictional member 2. At the start of use, two large diameter parts 2-a of the frictional member 2 are contacted with a sheet material to feed the sheet material. When the frictional coefficient is decreased due to the change of the surface condition of the large diameter part 2-a caused by consumption, the feeding force is impaired, the slippage is generated between the large diameter parts 2-a and the sheet material, the large diameter parts 2-a are shaven by the sheet material, which reduces the outer diameter, so that the small diameter part 2-b makes contact with the sheet material. Since the surface condition of the small diameter part 2-b is not deteriorated, the sheet material can be fed without slippage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device used in an image forming apparatus for forming an image on a sheet material, for example.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus, there is an image forming apparatus as shown in FIG. The image forming apparatus includes a sheet feeding deck 102 in which a large amount of sheet materials S 'are stacked and stored on one side of the image forming apparatus main body 101, and a predetermined amount of sheet materials S' in a lower portion of the image forming apparatus main body 101.
Are provided with a plurality of paper cassettes 103 and 105 in which are stacked and stored. Then, a sheet feeding deck 102 as a sheet feeding unit for feeding the sheet material S ′, and each sheet feeding cassette 10
The installation sites 3 and 105 are respectively provided with sheet feeding devices 106, 107 and 109 of the retard separation type.

A paper feeding deck 102, a paper feeding cassette 103,
The sheet material S ′ in the sheet feeding unit 105 includes
When the sheet is fed by 107 and 109, the sheet is first sent to a registration roller pair 110 which stops rotating and enters, where the skew state is corrected.

Next, the photosensitive drum 111 and the transfer charger 112 are rotated by a registration roller 110 which rotates at a timing with a latent image formed on the photosensitive drum 111.
And the toner image on the photosensitive drum 111 is transferred here (image formation). Thereafter, the sheet material S '
Is a fixing device (fixing roller pair) 11 by a transport belt 113.
5, the fixing process is performed to fix the transferred toner image on the sheet surface.

The present image forming apparatus has a duplex copying mode for performing duplex copying on the sheet material S 'and a multiplex copying mode for performing multiple copying. In the normal copying mode, the sheet material S' after the fixing process is used. The paper is discharged onto a paper discharge tray 119 outside the apparatus by the inner paper discharge roller pair 117.

In the case of the double-sided copy mode and the multiple copy mode, the pair of internal discharge rollers 116 or the pair of switchback rollers 127 temporarily move the image onto the intermediate tray 121 via the re-feeding path 120 and the double-sided conveying path 126. It is loaded and stored. Then, the sheet material S 'stored on the intermediate tray 121 is conveyed again to the registration roller pair 110 for image formation by the re-feeding device 130, and thereafter discharged out of the apparatus through the same process as for one-sided copying.

FIG. 15 shows a conventional sheet feeding device 201. This sheet feeding device 201 supplies the sheet material 202 to the image forming apparatus shown in FIG. As shown in FIG.
Reference numeral 01 denotes a pickup roller 205 that feeds the uppermost sheet material 202 one by one from a sheet material storage device 203 in which a plurality of sheet materials are stacked and stored on a loading table (not shown). A feed roller 206 that conveys the sheet material 202 fed from the material storage device 203 into the main body of the image forming apparatus (in the direction of the arrow b in the drawing), and is disposed opposite to the feed roller 206 and fed from the sheet material storage device 203. When there are a plurality of sheet materials, a retard roller 207 for rotating in the direction opposite to the rotation direction of the feed roller 206 to separate the sheet material 202 into a single sheet material, and a conveyance roller arranged in front of the image forming apparatus main body. And a roller pair 209. Further, the pickup roller 205 and the feed roller 206
Sheet passage area 2 between the sheet and the retard roller 207
A guide 211 is disposed on the feed roller 20.
6, a guide 212 is arranged between the retard roller 207 and the conveying roller pair 209 and between the conveying roller pair 209 and the image forming apparatus main body, and the sheet material 202 is guided and conveyed, respectively. The PS detects the arrival of the sheet material 202 fed by the pickup roller 205 to the conveyance roller pair 209 by a sheet material detection unit including a light emitting element and a light receiving element disposed immediately before the conveyance roller pair 209. The feed roller 206 and the retard roller 207 are driven by a drive transmission device 213 shown in FIG.

As shown in FIG. 16, a drive transmission device 213 is connected to a feed roller shaft 215 on which a feed roller 206 is supported, a retard roller shaft 216 for supporting a retard roller 207, and the retard roller shaft 216. The retard roller drive shaft 217 is provided substantially in parallel. The retard roller shaft 216 is supported by a swingable support member (not shown), and is capable of coming into contact with and separating from the feed roller shaft 215 in parallel. Further, a coupling 219 and a torque limiter 220 are disposed between the retard roller shaft 216 and the retard roller drive shaft 217. Further, at an end of the feed roller shaft 215, there is provided an electromagnetic clutch 222 for transmitting a driving force transmitted from a main driving unit (not shown) of the image forming apparatus main body via the drive input belt 221 to the feed roller shaft 215. I have. Between the feed roller shaft 215 and the retard roller drive shaft 217, a retard drive belt 223 that transmits the rotational driving force transmitted to the feed roller shaft 215 to the retard roller drive shaft 217 is wound. The coupling 219 is for transmitting the drive from the retard roller driving shaft 217 to the retard roller shaft 216 even when the retard roller 207 is displaced.

The driving of the feed roller 206 and the retard roller 207 by the drive transmission device 213 will be described. A rotational driving force provided from a main driving unit (not shown) of the image forming apparatus main body is transmitted to a drive input belt 221 and is controlled to be ON-OFF in accordance with a sheet feeding timing. Is input to Here, the feed roller shaft 215, the retard roller drive shaft 217, and the retard roller shaft 216 that rotate integrally with the rotor portion of the electromagnetic clutch 222.
Are connected by the retard drive belt 223, the feed roller shaft 215 and the retard roller shaft 216
The retard roller drive shaft 217 rotates in the same direction, and the feed roller 206 and the retard roller 207 are rotationally driven in synchronization with the sheet feeding timing ON. By the drive transmission means 213, the sheet 202 is fed in the sheet feeding direction (FIG. 1).
5, when the sheets are fed one by one in the direction of arrow b shown in FIG.
The retard roller 207 causes the torque limiter 22 to rotate due to friction between the feed roller 206 and the sheet material 202.
0 runs idle and rotates in the direction opposite to the drive rotation direction of the retard roller drive shaft 217.

When a plurality of sheet materials 202 are fed, the frictional force between the plurality of sheet materials 202 is smaller than the frictional force between the retard roller 207 and the sheet materials 202. The torque limiter 220 does not idle and the retard roller 207 rotates in the same direction as the rotation driving direction of the retard roller drive shaft 217. As a result, the sheet material 202 on the feed roller 206 side, that is, the uppermost sheet material 202 and the other sheet materials 202 in the plurality of fed sheet materials 202 are separated, and the sheet material 2 is transferred into the image forming apparatus main body.
02 is prevented. Next, a theoretical formula that satisfies the conditions for feeding and separating the sheet material 202 by the sheet feeding device 201 having the above configuration will be described.

N> T / r · μBP + (μAPP−μAP) W / μBP (1) N <T / r · μBPP-2 μAPPW / μBPP (2) N <T / r · μCP (3) Here, μAP: Coefficient of friction between pickup roller 205 and sheet material 202 μBP: Coefficient of friction between feed roller 206 and sheet material 202 μCP: Coefficient of friction between retard roller 207 and sheet material 202 μAPP: Under pressure of pickup roller 205 Coefficient of friction between the sheet materials 202 of the sheet: the feed roller 206 and the retard roller 20
The frictional coefficient between the sheet material 202 in the nip portion with No. 7 N: the pressing force of the retard roller 207 T: the idling torque of the torque limiter 220 r: the radius of the retard roller 207 W: the pressing force of the pickup roller 205

The above equation (1) satisfies the sheet feeding condition, (2) satisfies the separation condition, and (3) satisfies the retard roller rotation condition. If the same sheet material is used in the above equation, the friction coefficient of each roller pressing portion does not vary so much. Therefore, when μAPP ≒ μABP = μPP, (1) and (2) become (4) ( 5)

N> T / r · μBP + (μPP−μAP) W / μBP (4) N <T / r · μPP-2W (5) In the above equations (3), (4) and (5) Relationship between retard roller 20
7 and the idling torque T of the torque limiter 220
FIG. 17 is a graph obtained by using as a parameter.

In FIG. 1, a hatched portion is a feeding area.
That is, in order to enlarge the shaded area, it is necessary to increase the friction coefficient between each roller and the sheet material or to decrease the pressing force of the pickup roller 205.
Pressure N of retard roller 207 and torque limiter 2
It can be understood that the feeding area becomes wider when the sheet feeding conditions are set under the condition of increasing both the idling torques T of 20 (upper right direction in the figure). However, the torque limiter 22
If the idling torque T of 0 is excessively increased, the load torque in roller driving increases, so that the upper limit (the upper right limit in the figure) of the appropriate feeding region is also restricted to some extent.

[0015]

However, with the recent increase in speed of image forming apparatuses and diversification of sheet materials, it has become difficult to set an almighty feeding area. In other words, it is possible to reliably feed the sheet materials stacked and stored for various sheet materials, prevent double feeding beforehand, and achieve a system that can sufficiently ensure the durability of the pickup, feed, and retard roller. It is becoming difficult to do. In other words, when the function is prioritized, the durability is likely to be sacrificed.

Here, a conventional pickup roller is shown in FIG.
8 and 19. The pickup roller 205 includes a friction member 300 made of an elastic material such as rubber and a core member 301 for attaching the friction member 300.

When the pickup roller 205 repeatedly feeds the sheet material 202, the surface state of the friction member 300 changes, so that the above-mentioned friction coefficient μAP is reduced and the outer diameter is worn. As a result, a slip occurs between the sheet material 202 and the speed at which the sheet material 202 is fed is reduced, and if the speed is large, the sheet material 202 can be fed to a predetermined position within a predetermined time. The device judges that a paper jam has occurred, issues a warning display, and stops operation.
At this time, even if the user removes the clogged sheet material, the same state occurs when the next sheet material is fed, and the service person is called for repair.

Accordingly, the present invention has been made in view of the above circumstances, and provides a paper feeder in which the conveying force does not decrease even if the outer diameter and the friction coefficient change due to the durability of the friction member of the roller for feeding the sheet material, and the jam is less likely to be jammed. The purpose is to do.

[0019]

According to a first aspect of the present invention, there is provided a paper feeder having at least one roller, through which a sheet material can be freely conveyed. In the apparatus, the roller has an annular surface portion formed of an elastic material, and the surface portion has first and second portions formed in an annular shape in an axially aligned form,
The outer diameter of the roller at the first portion is equal to the second diameter of the second portion.
Wherein the outer diameter of the roller is larger than the outer diameter of the roller at the portion.

The invention according to claim 2 of the present invention is characterized in that:
Of the first portion and the second portion, one portion is arranged at a plurality of portions in a form arranged in the axial direction, and the other portion is sandwiched between the one portion adjacent in the axial direction. Are arranged in a vertical shape.

The invention according to claim 3 of the present invention provides
The roller has a core member, and a cylindrical surface member inserted and fitted on the outer peripheral side of the core member so as to form the surface layer, and the outer diameter of the core member is uniform in the axial direction. Wherein the thickness of the surface member at the first portion is greater than the thickness of the surface member at the second portion.

The invention according to claim 4 of the present invention is characterized in that:
The roller has a core member, and a cylindrical surface member inserted and fitted on the outer peripheral side of the core member so as to form the surface portion. The outer diameter of the core member is the first diameter. It changes in the axial direction so as to correspond to the portion and the second portion, and the thickness of the surface layer member is uniform in the axial direction.

The invention according to claim 5 of the present invention is as follows.
The first portion and the second portion are axially adjacent to each other so as to form a step-shaped boundary portion.

The invention according to claim 6 of the present invention is characterized in that:
The first portion and the second portion are formed so as to be continuous in the axial direction.

The invention according to claim 7 of the present invention is as follows:
The roller is a pickup roller, a feed roller, or a retard roller.

[Operation] In the paper feeder configured as described above, the surface layer (friction member) of the roller that conveys the sheet material
As the outer diameter changes due to durability, the portion of the surface layer that comes into contact with the sheet material moves from the first portion to the second portion. As a result, the sheet material can be stably fed without lowering the conveying force of the roller, and the durability is improved.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> FIGS.
FIG. 1 is a view showing the configuration of the embodiment of the present invention, wherein 1 is a pickup roller, 2 is a friction member, and 3 is a core member, which comprises a mounting portion 3-a of the friction member 2 and a flange portion 3-b. The friction member 2 includes two large-diameter portions 2-a and a small-diameter portion 2-b therebetween. Also, the inner diameter of the friction member 2 is slightly smaller than the outer diameter of the mounting portion 3-a of the core member 3 so as not to slip between the core member 3 and the core member 3.

At the start of use, the two large-diameter portions 2-a of the friction member 2 come into contact with the sheet material 202, so that the sheet material 20
Convey 2. When the surface state of the large-diameter portion 2-a changes due to durability and the friction coefficient decreases, the conveying force decreases, and the large-diameter portion 2-a changes.
a slip occurs between the sheet material 202 and the sheet material 202. By slipping, the large-diameter portion 2-a is shaved by the sheet material 202 to reduce the outer diameter, and the small-diameter portion 2-b comes into contact with the sheet material 202. Since the small-diameter portion 2-b does not deteriorate in surface condition, the reduced conveying force can be compensated for and the sheet material 202 can be conveyed without slipping.

The friction member has a diameter of about 20 mm and a hardness of 25 °.
In the case of using a rubber of a degree, the surface is worn and the radius is reduced to 0.
If the diameter is reduced by about 2 mm, a conveyance failure is likely to occur. Therefore, it is appropriate to set the level difference between the large-diameter portion 2-a and the small-diameter portion 2-b to 0.2 mm or less. Usually, the roller is polished to make the surface have a predetermined coefficient of friction.

Further, the sheet is fed by the pickup roller 205 due to slippage generated before the outer diameter of the large diameter portion 2-a of the friction member 2 decreases and the small diameter portion 2-b comes into contact with the sheet material 202. There is a possibility that the time until the detection means PS disposed immediately before the conveyance roller pair 209 from the start until the detection of the sheet material 202 becomes long, and the apparatus main body may determine that the paper jam has occurred. Can be avoided by making variable. However, it is necessary to transmit the driving force of the sheet feeding device 201 from a driving unit that can change the driving speed independently of a main driving unit (not shown) of the image forming apparatus main body, such as a step motor. A method of changing the driving speed at the time of feeding the next sheet material according to the detected time according to the flowchart of FIG. 13 will be described.

Here, Ts is the elapsed time from the start of sheet feeding to the time when the detecting means PS detects the sheet material 202;
2, T3 are the first, second, and third elapsed times, and T1 <
It is assumed that T2 <T3. V is the driving speed of the sheet feeding device 201 (the driving speed of a step motor (not shown)), V1 and V2.
Are the first and second drive speeds, and V1 <V2.

The initial setting of the speed V is the first speed V1, and when no slip occurs between the friction member 2 and the sheet material 202, the elapsed time Ts is determined when various conditions fluctuate.
It changes from the minimum T1 to the maximum T2. The elapsed time T
3 shows that the small-diameter portion 2-b of the friction member 2
It is set to a value that is slightly larger than the maximum value of the elapsed time Ts until the slip is eliminated by contacting the contact 2.

First, in step S10, the elapsed time Ts is equal to T1.
It is determined whether it is within the range of ≦ Ts ≦ T2. If Yes, it is determined that there is no problem in the drive speed, and the drive speed changing process ends. If No, the process moves to step S11. In step S11, it is determined whether the elapsed time Ts is in the range of T2 <Ts ≦ T3. If Yes, a slip has occurred between the friction member 2 and the sheet material 202, but it is determined that the slip is not large enough to cause a jam, and the process proceeds to step S14. In step S14, the driving speed V becomes the first driving speed V
It is determined whether it is 1. If Yes, step S15
Then, the drive speed V is changed to the second drive speed V2, and the process is terminated. If No, the drive speed V is equal to the second drive speed V
The process is determined to be 2, and the process is terminated as it is. Step S1
In the case of No in Step 1, the process proceeds to Step S12. In step S12, it is determined whether the elapsed time Ts is smaller than the first elapsed time T1. If No, the elapsed time Ts is determined to be longer than the third elapsed time T3, and the process shifts to step S13 to end the process as a jam. If Yes, it is determined that no slip has occurred between the friction member 2 and the sheet material 202, and the process shifts to step S16. In step S16, it is determined whether the driving speed V is the second driving speed V2.
If Yes, the process proceeds to step S17, where the drive speed V is changed to the first drive speed V1, and the process ends. If No, the drive speed V is determined to be the first drive speed V1, and the process is terminated.

To summarize the above processing, a slip occurs in the large diameter portion 2-a and the speed increases when the slip occurs, and the small diameter portion 2-b
When the slippage disappears due to contact, the speed returns to the initial speed. Thereafter, if a slip occurs at the small warp portion 2-b and becomes unacceptably large, the jam is processed.

<Second Embodiment> FIGS. 3 and 4 show the structure of a second embodiment, in which 10 is a pickup roller,
Reference numeral 11 denotes a friction member, and reference numeral 3 denotes a core member similar to that of the first embodiment. The friction member 11 includes a large-diameter portion 11-a at the center, a first small-diameter portion 11-b outside thereof, and a second small-diameter portion 11-c outside thereof.

In this configuration, the central large-diameter portion 11-a initially comes into contact with the sheet material 202 due to durability.
When the outer diameter of a decreases, the first small-diameter portion 11-b comes into contact with the sheet material 202 when the outer diameter of the first small-diameter portion 11-b further decreases. As a result, the conveying force is maintained. In this case, the driving speed changing process similar to that of the first embodiment is effective.

<Third Embodiment> FIGS. 5 and 6 show the structure of a third embodiment, in which 20 is a pickup roller,
21 is a friction member, and 3 is a core member similar to that of the first embodiment. The friction member 21 has a central large-diameter portion 21-a and a large-diameter portion 21-a.
It has a reduced diameter portion 21-b whose outer diameter continuously decreases from -a to both ends.

In this configuration, the large-diameter portion 21-a of the friction member 21 is initially in contact with the sheet material 202, but as the outer diameter of the large-diameter portion 21-a decreases due to durability, the reduced-diameter portion 21-a gradually decreases. Since the contacting portion b spreads toward both ends, the conveying force can be maintained without causing a slip between the friction member 21 and the sheet material 202.

The reduced diameter portion 21-b may be formed when the surface of the friction member 21 is polished as in the first embodiment. Further, since the reduced diameter portion 21-b gradually contacts as the outer diameter of the large diameter portion 21-a decreases, the difference between the outer diameters of the reduced diameter portion 21-b is the axial length of the reduced diameter portion 21-b. May be set in accordance with.

In this embodiment, the friction member 21 and the sheet material 2
Since the slip is not generated during the period 02, the drive speed change processing as described in the first and second embodiments is not required.

<Fourth Embodiment> FIGS. 7 and 8 show the structure of a fourth embodiment, in which 30 is a pickup roller,
Reference numeral 31 denotes a friction member, and reference numeral 3 denotes a core member similar to that of the first embodiment. Contrary to the third embodiment, the friction member 31 has large-diameter portions 31-a at both ends and a reduced-diameter portion 3-b whose outer diameter continuously decreases from the large-diameter portion 31-a to the center. I have.

In this configuration, at first, the large-diameter portion 31-a of the friction member 21 is in contact with the sheet member 202, but as the outer diameter of the large-diameter portion 31-a decreases due to durability, the reduced-diameter portion 31-a gradually decreases. Since the contacting portion b spreads toward the center, the conveying force can be maintained without causing a slip between the friction member 31 and the sheet member 202.

<Fifth Embodiment> FIGS. 9 and 10 show the structure of a fifth embodiment, in which 40 is a pickup roller, 41 is a friction member, 42 is a core member and a friction member 41 is shown.
Large diameter portion 42-a and reduced diameter portion 42-b for attaching
And a flange portion 42-c. The reduced-diameter portion 42-b of the core member 42 extends from the central large-diameter portion 42-a to the flange portion 4-a.
The shape is such that the outer diameter continuously decreases toward 2-c. Here, the friction member 41 has a cylindrical shape but a core member 42.
In this case, the outer shape becomes the same as that of the friction member of the third embodiment, and the same effect as that of the third embodiment can be obtained.
The shape of the core member 42 can be made by ordinary resin molding,
Since the friction member 41 does not require any special outer shape processing, it is advantageous in terms of cost.

<Sixth Embodiment> FIGS. 11 and 12 are views showing the structure of a sixth embodiment, wherein 50 is a pickup roller, 51 is a friction member, 52 is a core member, and a friction member 51 is provided.
Large-diameter portion 52-a and a reduced diameter portion 51-b for mounting
And a flange portion 52-c. Contrary to the sixth embodiment, the reduced diameter portion 52-b of the core member 52 has a shape in which the outer diameter continuously decreases from the large diameter portion 52-a adjacent to the flange portions 52-c at both ends to the center portion. Has become. Although the friction member 51 has a cylindrical shape, the outer shape is the same as that of the friction member according to the fourth embodiment when the friction member 51 is attached to the core member 52, and the same effect as that of the fourth embodiment can be obtained.

Although the above embodiment has been described with respect to the pickup roller, it goes without saying that the same effect can be obtained with the feed roller and the retard roller.

[0046]

As described above, the present invention (claim 1)
According to the first aspect, the sheet material and the roller contact at first only via the first portion, and when the friction coefficient changes due to durability and slip occurs between the first portion and the sheet material, the first portion is contacted with the roller. Is scraped by the sheet material so that the second portion is in contact with the sheet material. Thus, the sheet can be suitably conveyed at the second portion. In other words, a paper feeding device is provided in which the life of the rollers is significantly longer than that of the related art, the conveyance force is not reduced as much as possible, and the paper is hardly jammed.

Further, one of the first and second parts is arranged at a plurality of positions so as to be arranged in the axial direction, and the other part is provided between the one part adjacent in the axial direction. If they are arranged in a form sandwiched between (claim 2),
Since the contact of the sheet material with the entire roller is made even, the skew of the sheet material is prevented, which is convenient.

Further, the roller has a core member and a cylindrical surface member inserted and fitted on the outer peripheral side of the core member so as to form the surface layer portion. In the case where the thickness is uniform in the axial direction and the thickness of the surface layer member at the first portion is larger than the thickness of the surface layer member at the second portion (claim 3). As the core member side, a conventional one can be adopted as it is, so that the versatility is high. Conversely, the outer diameter of the core member changes in the axial direction corresponding to the first and second portions, and the thickness of the surface member is uniform in the axial direction. In this case (claim 4), the shape of the surface layer member is simple and the processing is simplified.

In the case where the first portion and the second portion are adjacent to each other in the axial direction so as to form a step-like boundary portion (claim 5), the contact area with the sheet material is increased. It is convenient because it can be taken. Further, in the case where the first portion and the second portion are formed so as to be continuous in the axial direction (claim 6).
Is advantageous because the slip time can be shortened.

When the roller is a pickup roller, a feed roller, or a retard roller (claim 7), the durability of the pickup roller, the feed roller, or the retard roller is advantageously improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment.

FIG. 2 is a diagram showing a first embodiment.

FIG. 3 is a diagram showing a second embodiment.

FIG. 4 is a diagram showing a second embodiment.

FIG. 5 is a diagram showing a third embodiment.

FIG. 6 is a diagram showing a third embodiment.

FIG. 7 is a diagram showing a fourth embodiment.

FIG. 8 is a diagram showing a fourth embodiment.

FIG. 9 is a diagram showing a fifth embodiment.

FIG. 10 is a diagram showing a fifth embodiment.

FIG. 11 is a diagram showing a sixth embodiment.

FIG. 12 is a diagram showing a sixth embodiment.

FIG. 13 is a flowchart of a driving speed changing process.

FIG. 14 is a diagram illustrating a conventional example of an image forming apparatus.

FIG. 15 is a diagram illustrating a conventional example of a sheet feeding device.

FIG. 16 is a diagram showing a conventional example of a drive transmission device.

FIG. 17 is a diagram showing a relationship between a retard roller pressing force and a torque limiter idling torque.

FIG. 18 is a view showing a conventional pickup roller.

FIG. 19 is a view showing a conventional pickup roller.

[Explanation of symbols]

1, 10, 20, 30, 40, 50 Pickup roller 2, 11, 21, 31, 41, 61 Friction member 3, 42, 62 Core member 201 Paper feeder 202 Sheet material 205 Pickup roller 206 Feed roller 207 Retard roller

Claims (7)

[Claims] 1. A sheet feeding device having one or more rollers and capable of conveying a sheet material via the rollers, wherein the rollers have an annular surface portion formed of an elastic material, The surface layer portion has first and second portions formed in an annular shape and arranged in the axial direction, and the outer diameter of the roller at the first portion is the second diameter.
A sheet feeding device, wherein the outer diameter of the roller is larger than the outer diameter of the roller at the portion. 2. The method according to claim 1, wherein the first part and the second part are
One part is arranged at a plurality of places in a form arranged in the axial direction, and the other part is arranged so as to be sandwiched between the one parts adjacent in the axial direction. The paper feeding device according to claim 1. 3. The roller has a core member, and a cylindrical surface member inserted and fitted on the outer peripheral side of the core member so as to form the surface layer portion. The thickness of the surface member at the first portion is greater than the thickness of the surface member at the second portion, the thickness being uniform in the axial direction. 2. The paper feeding device according to 1. 4. The roller has a core member, and a cylindrical surface member inserted and fitted on an outer peripheral side of the core member so as to form the surface layer portion. The thickness of the surface member is uniform in the axial direction, and changes in the axial direction so as to correspond to the first portion and the second portion. Paper feeder. 5. The sheet feeding device according to claim 1, wherein the first portion and the second portion are adjacent to each other in an axial direction so as to form a step-shaped boundary portion. 6. The sheet feeding device according to claim 1, wherein the first portion and the second portion are formed so as to be continuous in an axial direction. 7. The sheet feeding device according to claim 1, wherein the roller is a pickup roller, a feed roller, or a retard roller.