JP3510074B2 - Developing unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrophotography.
Printers, facsimile machines, and copiers
Related to a developing device used in an image forming apparatus such as
You. [0002] 2. Description of the Related Art Generally, image formation using electrophotographic technology
The apparatus includes a photosensitive member having a photosensitive layer on an outer peripheral surface, and the photosensitive member.
Charging means for uniformly charging the outer peripheral surface of the device, and the charging means
By selectively exposing the outer peripheral surface uniformly charged by
Exposure means for forming an electrostatic latent image, and
Visible by applying toner as a developer to the formed electrostatic latent image
Developing means for forming an image (toner image) and the developing means
A transfer for transferring the developed toner image to a transfer medium such as paper.
Shooting means. [0003] Conventional developing means include toner
And a case rotatably supported by a shaft.
Supported by the developing roller and the case so as to be rotatable around a shaft.
The toner by pressing against the developing roller.
A supply roller made of an elastic body that supplies the surface of the developing roller
Provided on the side of the developing roller and the supply roller.
To prevent toner from leaking out of the case from the shaft.
There is known a device provided with a sealing member for stopping. [0004] The conventional developing device described above.
Now, press-contact of the supply roller made of elastic material with the developing roller
Part is concave, and the end of the supply roller
Projecting in such a way that this projection bites into the seal member.
And the driving torque of the supply roller increases as a result.
There was a problem that would. The present invention seeks to solve the above problems.
The purpose is to reduce the driving torque of the supply roller.
An object of the present invention is to provide a developing device capable of reducing the number of developing devices. [0006] [MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
2. The case according to claim 1, wherein the toner is stored in the case.
And a developing roller rotatably supported by a shaft in this case
And a developing roller rotatably supported on the case by a shaft.
By pressing the toner on the surface of the developing roller.
A supply roller made of an elastic material to be supplied, and a developing roller
Is provided on the side of the feed roller and the supply roller.
A sealing member for preventing toner from leaking out of the case;
And an end face of the developing roller and a supply roller.
Roller and the roller end face are approximately the same in the axial direction of these rollers.
And the supply roller has its elasticity.
As a result, the pressure contact portion with the developing roller is depressed.
Roller, and a corner of the supply roller is chamfered.
It is characterized by having. [0007] According to the first aspect of the present invention, there is provided a developing device comprising:
Since the corner of the corner is chamfered, the supply
The pressure contact part of the roller with the developing roller becomes concave
Also its side protrudes outward from the side of the supply roller
It will not be. Therefore, the projection is sealed as in the prior art.
There is no longer any digging into the parts
Dynamic torque is reduced. [0009] Embodiments of the present invention will be described below.
This will be described with reference to the drawings. <First Embodiment> FIG. 1 shows a first embodiment of the present invention.
Example of an image forming apparatus using a first embodiment of a developing device
FIG. First, an outline of the image forming apparatus will be described.
And then the development unit and this unit
The developing device incorporated in the printer will be described in detail. [0012] This image forming apparatus includes yellow, cyan,
Using a magenta and black toner developer
Is a device that can form a full-color image. In FIG. 1, reference numeral 50 denotes a case of the apparatus main body.
The case 50 includes an exposure unit 60 and a paper feeding device.
Unit 70, photoconductor unit 100, developing unit 200,
Intermediate transfer unit 300, fixing unit 400, and
A control unit 80 for controlling the entire apparatus is provided.
Have been killed. The photoconductor unit 100 includes a photoconductor 110
And contact the outer peripheral surface of the photoconductor 110 to make the outer peripheral surface uniform.
A charging roller 120 as charging means for charging the toner;
And a leaning means 130. The developing unit 200 includes, as a developing unit,
Developing unit 210Y for yellow, developing unit 210 for cyan
C, developing unit 210M for magenta, developing unit for black
210K. Each of these developing units 210Y, 21
0C, 210M, 210K have yellow inside
-, Cyan, magenta, and black toner
You. Further, the developing rollers 211Y, 211C, 2
11M, 211K, one of the developing units
Only the developing roller can come into contact with the photoconductor 110.
ing. The intermediate transfer unit 300 includes a driving roller 3
10, primary transfer roller 320, wrinkle removing roller 330
, Tension roller 340 and backup roller 3
50 and an endless middle stretched around these rollers
The transfer belt 360 and the intermediate transfer belt 360
Cleaning means 370 that can be separated from and contacted with the cleaning means. The secondary transfer to the backup roller 350
The rollers 380 are arranged to face each other. This secondary transfer row
The arm 380 is pivotally supported by a support shaft 381.
382, the arm 382 is rotatably supported.
By swinging by the operation of the cam 383, the intermediate transfer belt
It comes into contact with and separates from the tilt 360. The driving roller 310 has a gear (FIG.
(Not shown) is fixed, and this gear
Gear 100 (not shown).
Therefore, the photosensitive drum 110 is driven to rotate at substantially the same peripheral speed,
Therefore, the intermediate transfer belt 360 is substantially the same as the photoconductor 110.
It is designed to be circulated at a peripheral speed of. When the intermediate transfer belt 360 is driven to circulate,
Between the primary transfer roller 320 and the photoconductor 110.
The toner image on the photoconductor 110 is transferred to the intermediate transfer belt 36.
0 and transferred onto the intermediate transfer belt 360
The toner image is supplied between the secondary transfer roller 380 and the toner image.
The image is transferred to a recording medium S such as paper. The recording medium S is fed
Supplied from the device 70. The paper feeding device 70 has a plurality of recording media S stacked thereon.
A tray 71 placed in a layer state and a pickup roller
72 and the recording medium S placed on the tray 71
A hopper 73 for urging toward the up-roller 72;
Make sure that one sheet of paper is fed by the backup roller 72
And a separation roller pair 74 that separates each roller. The recording medium S fed by the paper feeding device 70
Are a first conveying roller pair 91, a first paper sensor 91S,
2 transport roller pair 92, 2nd paper sensor 92S, gatero
The second transfer portion, ie, the intermediate transfer bell,
Is supplied between the transfer roller 360 and the secondary transfer roller 380.
After that, the fixing unit 400, the first discharge roller pair 94,
The paper is discharged onto the case 50 via the two paper discharge roller pairs 95. The fixing unit 400 includes a fixing unit having a heat source.
Roller 410 and pressure roller 42 pressed against it
0. The operation of the entire image forming apparatus as described above is as follows.
It is as follows. (I) A host computer (not shown)
-Print command signal (image type) from a personal computer, etc.
Is input to the control unit 80, the photosensitive member 1
10, the developing roller of the developing unit 200, and the middle
The transfer belt 360 is driven to rotate. (Ii) The outer peripheral surface of the photoconductor 110 is charged low.
The toner is uniformly charged by the rubber 120. (Iii) of the uniformly charged photoreceptor 110
On the outer peripheral surface, the first color (for example,
(Yellow) Selective exposure L according to image information
As a result, an electrostatic latent image for yellow is formed. (Iv) The first color (example)
Developing roller 211 of developing device 210Y for yellow)
Only Y contacts, thereby developing the electrostatic latent image.
The toner image of the first color (for example, yellow) is
10 is formed. (V) Toner formed on photoreceptor 110
The image is transferred to the primary transfer portion, that is, the photosensitive member 110 and the primary transfer portion.
Roller 320 on the intermediate transfer belt 360.
Will be copied. At this time, cleaning means 370 and 2
Next transfer roller 380 is separated from intermediate transfer belt 360
are doing. (Vi) Toe remaining on photoconductor 110
After the toner is removed by the cleaning means 130,
Due to the neutralization light L 'from the neutralization means (see 61 in FIG. 2)
The photoconductor 110 is discharged. (Vii) Operations of (ii) to (vi) above
Is repeated as necessary. That is, the above print command
According to the content of the signal, the second color, the third color, the fourth color,
Is repeated according to the content of the print command signal.
The images are superimposed on the intermediate transfer belt 360 to form
Is done. (Viii) Paper feeder at predetermined timing
70, the recording medium S is supplied.
2 Immediately before or after reaching the transfer section (in short,
At a desired position on the recording medium S, the intermediate transfer belt 360
(When the toner image is transferred)
380 is pressed against the intermediate transfer belt 360 and the intermediate transfer belt 360 is pressed.
Toner image on default 360 (basically full color image)
Is transferred onto the recording medium S. Cleaning means
370 contacts the intermediate transfer belt 360, and after the secondary transfer,
The toner remaining on the intermediate transfer belt 360 is removed.
You. (Ix) The recording medium S is in the fixing unit 400
, The toner image is fixed on the recording medium S.
After that, the recording medium S passes through the discharge roller pairs 94 and 95, and
It is discharged onto the case 50. The outline of the image forming apparatus has been described above.
However, next, details of the developing unit 200 and the developing device will be described.
explain about. The developing unit 200 has a structure as shown in FIG.
A substantially inverted "L" -shaped frame 220;
The above four developments which are detachably incorporated into the 220
Unit 210 (Y, C, M, K). As shown in FIG. 1, the developing unit 200
The frame 220 is moved in the direction of the arrow a1 (counter
Clockwise) and can rotate clockwise.
When moved, it is locked in the position shown in FIG. The cover 54 of the case 50 is also hinged.
It is configured to be openable in the direction of arrow a by 54a.
Therefore, in FIG. 1, 54 b indicates an end of the cover 54.
), By opening this cover 54,
The developing device 210 is not rotated by rotating the frame 220.
To be attached to and detached from the frame 220 in a substantially horizontal direction.
Can be. Further, the cover 54 and the developing unit 200
Open in the directions of arrows a and a1, and
The socket 100 can be attached and detached. FIG. 2 shows four developing units 210 (Y, C,
M, K), an enlarged view of the photoconductor 110 and its surroundings.
FIG. 3 is an enlarged view of the developing unit 210M. Also,
FIG. 4 is a partially omitted IV-IV sectional view in FIG. 3, and FIG.
FIG. 5 is a partially-enlarged VV enlarged sectional view in FIG. 3. Four developing units 210 (Y, C, M, K)
Has a slightly different shape, but the basic structure is
Since they are the same, the magenta developing device 210M is representative.
First, referring mainly to FIG.
The configuration will be described. The developing device 210 includes a case 230 and this case.
The toner T stored in the base 230 and the toner T
A developing roller 211 for supplying the surface of the optical body 110;
Supply roller 24 that supplies toner T to developing roller 211
0 and the toner T toward the supply roller 240
Three transfer fins 251, 252, 253 for transferring;
The toner is pressed against the developing roller 211 and is
And a regulating blade 260 for regulating the amount. The case 230 is a case body (lower case).
231 and a lid 232. The developing roller 211 is, as shown in FIG.
The shaft 212 is connected to the casing via bearing members 232 and 232.
Rotatably supported by the side walls 231a of the main body 231.
Is held. A developing roller 211 is attached to one end of the shaft 212.
A gear 213 for rotating and driving is fixed.
Power from a drive source (not shown) is transmitted to the gear 213
Transmission gear 214 is meshed. Also, the shaft 21
Rollers 215 are rotatably provided at both ends of
You. The roller 215 serves as a developing roller as described later.
When the roller 211 contacts the photoconductor 110, the
To contact flanges (not shown) provided at both ends
Therefore, the position of the developing roller 211 with respect to the photoconductor 110
Is regulated. The supply roller 240 is, as shown in FIG.
The shaft 241 is connected to bearing members 242 and 242 (see FIG. 5).
(Only one is shown) through the side wall 23 of the case main body 231.
1a and 231a rotatably supported. Shaft 241
A gear for rotating the supply roller 240 at one end
243 is fixed, and this gear 243 is not shown.
A transmission gear (not shown) for transmitting power from a
Are engaged. The transfer fins 251, 252, 253 (FIG. 3)
Is basically the same, and the supply
Like the roller 240, the side walls 231a, 231 of the case body 231
A shaft 254 rotatably supported by the shaft 31a;
4 and an end of the arm 255
Flexible thin (sheet-shaped) fin fixed to the end
And fixed to the shaft 254 outside the case 231
Gears or ratchets
It is driven to rotate in the direction of the arrow in FIG.
Swelling. The transfer fins 251, 252, 2
The rotation speed of 53 is 1/20 of the rotation speed of the supply roller 240.
It is about 1/50. The case body 231 has a substantially semi-cylindrical
And a rotating transfer filter 233 is provided.
The fin 256 of the toner is located on the wall surface 233 a of the toner storage portion 233.
In the wedge-shaped space 233b formed by sliding contact with
So that the toner T is transferred
ing. That is, the toner T is transferred to the transfer fins 253.
→ 252 → 251 → Supply roller 240
Supplied to the controller 211. The regulating blade 260 is provided at the tip of the support plate 261.
It is fixed to the end 261a. The support plate 261 is
The bent rear end 261b is fixed to the case main body 231.
The three hook portions 262b of the base plate 262 (see FIG. 4)
), This support is the center
And swingable. And the support plate 261 is
The middle part 261c and the front part 262a of the base plate 262
At least two (three in the figure) provided between
The regulating blade 260 is developed by the tension spring 263.
It is urged so as to press against the roller 211. The developing device 210 as described above is
Sea urchin (see FIGS. 1 and 2), 210Y for yellow,
210C for cyan, 210M for magenta,
4 frames for black 210K, frame 22
0 is detachably attached. In FIG. 2, 222 (Y, C, M, K)
Is the receiving of each developing unit 210 (Y, C, M, K)
It is a board. The receiving plate 222 has a pair of side plates (not shown).
This side plate is formed integrally as shown in FIG.
The receiving plate 222 is supported by a shaft 223 projecting from the outer surface of the
It is swingably attached to the frame 220.
A tension spring 224 is provided between the side plate and the frame 220.
The receiving plate 222 is provided by the spring 224.
Is the clockwise direction in FIG. 6, that is, the current fixed to the receiving plate.
The developing roller 211 of the imager 210 is
It is biased in the pressing direction, but at least one side
A cam pin 225 is provided on the plate.
For the cam 22 provided on the frame 220.
6 is restricted by its contact with
I have. The cam 226 is driven by driving means (not shown).
It is driven to rotate, and the position shown by a solid line in FIG.
Is in the position, the developing roller is biased by the spring 224.
Roller 211 is pressed against the photoconductor 110, and is indicated by a virtual line in FIG.
When it is in the position shown, the receiving plate 222 and the developing device 2
10 is swung counterclockwise to sense the developing roller 211.
It is separated from the light body 110. This cam structure is used for all receiving plates 222
(Y, C, M, K).
By controlling the rotation of the cam,
Only one of the developing rollers 211 is
Contact. The shaft 223 and the cam pin 225
May be provided on the case body 231 of the developing device 210.
Wear. In FIG. 2, reference numeral 180 denotes the photosensitive unit 1.
00, and the subframe 180
The charging roller 120 and the cleaning means 130
It has been incorporated. The cleaning means 130 includes a photosensitive member 110
To remove the toner remaining on the outer peripheral surface of the
-Brush 131, and also remains on the outer peripheral surface of photoconductor 110
Cleaner blade 1 that scrapes off adhered toner
32 and the fur brush 131 or the cleaner
Raised or scraped by raid 132
Toner transfer tray as a transport means for transporting the used toner
Liu 133 is provided. At the lower part of the sub-frame 180, the toner
A collection chamber 182 is formed, and the toner collection chamber 182 is formed.
Inside the fur brush 131, the cleaner blade 13
2, and the toner conveying screw 133 is disposed.
You. The fur brush 131 is mounted on the sub frame 18.
0 is fixed to a shaft 131a passing through the side plate of
1a is driven by driving means (not shown).
2 is driven to rotate in the direction of the arrow in FIG. The cleaner blade 132 is attached to the mounting plate 132.
a attached to the sub-frame 180 by a
The leading end (lower end) contacts the outer peripheral surface of the photoconductor 110 and
-It is designed to scrape off. The toner conveying screw 133 is not shown.
2 in the direction of the arrow in FIG.
-The toner collected in the collection chamber 182 is regarded as waste toner.
To a waste toner box (not shown). Further, in this embodiment, various devices are used.
Has been or can be done, so
This will be described. <Regarding the Arrangement of the Developing Unit 210> FIG.
As described above, as a toner supply unit to the developing roller 211,
The rotation center of the supply roller 240 and the supply roller 240 are scratched.
As a means to transfer toner by frying or scraping
Line S connecting the center of rotation of all the transfer fins 251 and the horizontal
When the angle between the line H and the line H is θ,
All of the arranged developing devices 210 (in this case, Y, C,
M and K), θ is -20 ° <θ <75 ° The developing device 210 is arranged so as to fall within the range. What
Note that θ is + in the clockwise direction with respect to the horizontal line H.
It is. When θ is −20 ° or less, the transfer fin 2
Poor transfer of toner from 51 to supply roller 240
On the contrary, θ is 75 ° or more
And the toner is transferred too much toward the supply roller 240,
This is because toner may be in a powder state.
You. The powder state means that the developing roller 211 and the supply roller 24
0 and the space formed by the regulating blade 260
Phenomenon that the space pressure is increased by toner
Say. Once in the powder state, the developing blade is
The amount of toner on the printer cannot be
The toner overflows from the section. If θ is within the above range, the supply roller 24
0 is properly supplied with toner, and thus the developing roller
Since the toner is also supplied to the 211 properly, a single photosensitive
Arranging a plurality of developing devices 210 around the body 110
High-speed image format with short idle time
Is possible. The diameter of the photoconductor 110 is φ80.
It should be in the range of 90 mm. The range of θ is more preferably -12 ゜ <θ <56 ゜ Range. <Regarding the transfer fins 251, 252 and 253,
As described above, the toner in the case body 231 is
The fins 256 of the rotating transfer fins are
3 is formed by sliding contact with the wall surface 233a
It is transported while being held in the space 233b,
The fins 256 are formed into a flexible thin plate (sheet).
Since the fins 256 are configured,
3 is removed from the wall surface 233a.
The toner that has been transported so as to be embraced by 3b
It can be played by the restoring force due to the elasticity of the fins 256
And the discharge power is the fin 25
6 depends on the rigidity (elasticity). Then, (1) Fins 25 of transfer fins 251, 252, 253
The rigidity of No. 6 is as follows. That is, the angle θ becomes small.
The developing device 210 (for example, the developing device 210
For K), the transfer fins 251, 252, 253
The rigidity (restoring force by elasticity) of the pin 256 is relatively strong.
And On the contrary, a state in which the angle θ increases.
To the developing device 210 (for example, the developing device 210Y)
The fins 2 of the transfer fins 251, 252, 253
The rigidity (restoring force due to elasticity) of 56 is relatively weak
You. With this configuration, the toner
Can be further optimized. In particular, the toner is transferred to the supply roller 240.
The fin 256 of the transfer fin 251 is described above.
It is desirable to have a configuration. (2) Transfer fins 251, 252, 253
Can be obtained by making the rotation phases different from each other.
Thus, the rotational load is equalized. Specifically, n toner transfer means are connected in series.
(N = 3 in this case), the transfer fields of the n transfer means
By shifting the angle of the fins by 360 ° / n,
6 is in contact with the wall surface 233a and the sliding contact length is rotated.
251 252 253
This makes it possible to equalize the rotational load. (3) The fin 256 slides on the wall surface 233a.
Of the fin 256 gradually starts
By making the shape of the wall surface 233a such that
Thus, the rotational torque can be reduced. (4) The fin 256 is outside the wall surface 233a.
The fins 256 gradually release
When the shape of the wall surface 233a is such that
Because the amount of delivery (release intensity or release) is reduced,
Developing device 210 (for example, the current
To prevent excessive transfer of toner in the imager 210Y),
The powder phenomenon can be prevented. <Developing Roller 211 and Developing Unit 210
Regarding the swing support structure> The developing roller 211 has a diameter of φ15.
SUS of up to 25 mm (more preferably, about φ18 mm)
Or made of AL material, the surface of which is blasted or
Provide a roughness suitable for carrying the toner by chemical polishing, etc.
Was. The developing roller 211 is provided as shown in FIG.
Rotate with respect to the photoconductor 110 as described above.
Is 1.5 to 2.5 times the peripheral speed of the photoconductor 110.
Times (more preferably about twice). As a result, the developing device 210
Since the force F1 acts, the force F1 acts in the biting direction.
In order not to use, the swing center O3 of the developing device 210
(The shaft 223) and the rotation center O1 of the photoconductor 110
Center line O2 of the developing roller 211,
Is located on the side of the action direction of the force F1.
The image roller 211 is moved away from the force F1 in the direction of action.
Was completed. <Regarding the Supply Roller 240> (1) The supply roller 240 is made of a porous elastic material (for example,
(A foam member such as urethane), and the surface bears toner.
And rub it against the developing roller 211
It was configured to supply. Here, the supply roller 240 has a lower half
Degree is buried in toner (the upper half is exposed from the toner surface)
To supply the toner to the developing roller 211.
Desirable for feeding. Further, the peripheral speed of the supply roller 240 is
50% to 80% of the peripheral speed of the
(Preferably about 60-70%)
While ensuring toner supply to the roller 211,
Can be prevented from deteriorating. (2) As described above, the developing roller 211
Shaft 212, supply roller 240 shaft 241 and transfer
Each shaft 254 of the fins 251, 252, 253 is a case
The main body 231 is rotatably supported by the side wall 231a.
And at least one end thereof penetrates the side wall 231a.
Therefore, this part is used to prevent toner leakage.
It is necessary to provide a sealing member. On the other hand, the supply roller 240 is made of a porous elastic material.
As shown in FIG. 3, the developing roller
The press contact portion 240a with the 211 is in a recessed state. This state
The state is schematically shown in FIGS. 7 (a) and 7 (b). As can be seen from this figure, the supply roller 24
0 is the portion depressed by the press contact portion 240a.
As shown in (b), the end protrudes to the side.
The protrusion is indicated by 240b. The projecting portion 240b is a sealing member
Acts to bite into the SE, resulting in the supply roller 2
This leads to an increase in the drive torque of the forty. Therefore, in this embodiment, FIG.
So that the corner 244 of the supply roller 240 is chamfered.
It is. The chamfer (244) is straight as shown in the figure.
Or rounded (with R)
No. With the above configuration, the above
The feeding roller 2 can prevent
40 can be reduced. Further, the bite occurs as described above.
As shown in FIG. 7 (b),
A gap C is formed between the developing member 211 and the end surface of the developing roller 211.
And the toner enters the gap C to deteriorate the sealing property.
And the end of the developing roller 211 is stained with toner.
Problem arises. However, according to this embodiment,
Such a problem can be prevented beforehand. You
That is, while improving the sealing property, the developing roller 2
11 can be prevented from being stained with toner. <Regarding the Sealing Member> As described above,
The shaft 212 of the image roller 211 and the shaft 24 of the supply roller 240
1 and each axis 2 of the transfer fins 251, 252, 253
54 is rotatable on the side wall 231a of the case body 231
At least one end of which is supported by a side wall 231a.
This part prevents toner leakage.
It is necessary to provide a sealing member for stopping. In this embodiment, as shown in FIG.
As described above, the sealing member 270 is
1 and a raised material 272 are bonded together, and mainly
The sealing pressure is obtained by the foam material 271,
272 provides a sealing effect. FIG. 5B is a view taken in the direction of arrow b in FIG.
And the roller end (in this case, the end of the supply roller 240)
Schematically shows the state of the raised material 272 between the foam material 271
FIG. As can be seen from this figure, the raised material 272
The brushed 273 is disconnected as the rollers rotate.
It has a spiral shape, which is a labyrinth seal. Therefore, leakage of toner is reliably prevented.
It will be. In addition, the raised 273 follows the rotation of the roller.
In this state, the rotational torque of the roller is also reduced. The seal member 270 is shown in FIG.
Not on the axis of the transfer fins 251, 252, 253
It is provided in the same manner. In FIG. 5A, reference numeral 274 denotes fluorine.
It is a sheet-like lubricating material made of a low friction material. <Regarding Driving Structure of Developing Roller 211>
As shown in FIG. 4, the shaft 212 of the developing roller 211 is
Side wall of case main body 231 via receiving members 232 and 232
231a, supported by 231a, fixed to one end
Transmission gear 214 for power transmission
Are engaged. The roller 2 is provided at both ends of the shaft 212.
The roller 215 is provided rotatably.
Indicates that the developing roller 211 is a photosensitive member as shown in FIG.
When pressed against 110, it is provided at both ends of photoconductor 110.
(Not shown) (or the image forming area of the photoconductor)
Contact with the photoconductor 110 by contact with the
The position of the developing roller 211 is regulated.
You. Therefore, the developing roller 211 is
10, when pressed against rollers 215 and 215
The case main body 231 and the shaft
And a lateral load acts via the bearing members 232 and 232,
The shaft 212 may be bent. Here, suppose that no measures are taken.
Then, the shaft 212 bends, and the transmission with the gear 213 occurs.
There is a possibility that the meshing state with the transmission gear 214 may become unstable.
is there. Therefore, in this embodiment, FIG.
As described above, reference is made to the gear 213 and the transmission gear 214 respectively.
Surfaces 213a and 214a are provided, and these reference surfaces are brought into contact with each other.
Meshing of the gear 213 with the transmission gear 214
To stabilize the condition. <Others> (1) For the developing device 210, the shape or color
By making it different, the mounting position can be clarified.
Wear. (2) When taking out the developing device 210,
So that the developing unit pops up a certain amount in the extension direction
And can be easily taken out. (3) The operator operates the developing device 210 with one hand.
To make it thin enough to be easily grasped, and to facilitate the attachment and detachment operation. <Second Embodiment> FIG. 8 shows a second embodiment of the present invention.
Main components of image forming apparatus using second embodiment of developing device
It is a schematic diagram which shows a part. The second embodiment is different from the first embodiment described above.
The difference from the embodiment is that the black developing device 210
K 'and the other points remain the same. The developing device 21 for black of this embodiment
0K 'is formed to be slightly larger, and the toner capacity is increased.
Comb. The transfer fins are 251 ', 253'
There are two. Generally, among the four color toners, the black toner
Is expected to consume the most
As in the embodiment, the size of the black developing device 210K 'is increased.
It is desirable to do. [0104] Hereinafter, more specific examples will be described.
You. The following description is based on the toner and the developing roller 21.
1, the supply roller 240 and the regulating blade 260
We are going to explain the specific configuration.
To clarify or understand the significance of the concrete structure of
First, the toner and the above components
Transfer characteristics, transferability, developing roller filmin
Phenomenon, regulating blade filming phenomenon, development efficiency,
Properties, fogging, durability, hysteresis, image unevenness,
And concentration difference between the front and rear ends
The effect of each of the above components on the phenomenon
Both are hopper containers that are considered important in constructing the developing unit.
It also mentions the quantity and the shelf life, then finally,
A description will be given of how the above specific configuration is made. The basic structure of the toner of this embodiment is as follows.
Synthetic pigments, CCA (charge control agent) and wax
It binds with grease and gives its surface mainly durability.
External additive with relatively large particle size
And a relatively small particle size external additive.
ing. Hereinafter, the development characteristics and the like will be sequentially described.
You. <Transportability> The transportability referred to here is the transfer property.
Of toner to supply roller 240 by toner 251 and the like
It is. If the transportability is too high, the supply roller 240
And excessive toner is supplied to the developing roller 211, and
In other words, the toner on the developing roller 211 can be regulated.
And the toner overflows out of the developing unit 210.
U. Conversely, if the transportability is poor, the supply roller 240
And the amount of toner supplied to the developing roller 211 is insufficient.
A desired image is not formed. The transportability depends on the fluidity of the toner.
It is. In particular, when the particle size is too small to affect the fluidity of the toner.
When the amount of the additive is 1.0% or more, good transportability is not obtained.
However, if it exceeds 3.0%, the transportability will be too high.
U. A. D (loose apparent density)
Desirably, it is 0.30 g / cc or more. <Supplyability> The supplyability referred to here is the supply low.
Roller 240 to the developing roller 211.
You. If the supply property is poor, the cycle of the supply roller 240
Causes image omission. The supply property is determined by the properties of the toner and the supply roller 24.
0 and the configuration of the developing roller 211. The amount of the external additive having a small particle diameter is not more than 1.0%.
Above to improve liquidity and supply
Can be done. When the amount of the pigment is 15% or less, C
By setting the amount of CA to 3% or less, the rise of charging can be reduced.
And supply properties can be improved. The supply roller 240 and the developing roller 211
The biting depth (the depth of the recess of the supply roller 240) is 0.1
mm or more, the toner
Is sufficiently rubbed, and the triboelectric charge of the toner is improved.
The supply is improved. Further, the surface roughness of the developing roller 211 is defined as R
Improve mechanical transfer force by setting z5μm or more
And good supply properties can be obtained. These can be used alone to improve supplyability.
But can be more effectively combined
The supply property can be improved. On the other hand, if the supply property is too high, the developing roller
The supply of toner to the roller 211 becomes excessive, and the developing roller 21
Regulations to optimize the amount of toner above 1
It became difficult and the toner overflowed out of the developing unit 210
I will. In particular, the amount of the small particle size external additive of the toner exceeds 3.0%.
In this case, the fluidity of the toner becomes too good and the supply
It will stick too much. The amount of development (actually,
0.80 mg / cm^TwoBelow,
Conveyance amount (toner on developing roller 211 used for development)
Amount) is 0.60 mg / cm^TwoThe charge amount is -8
It is desirable that the concentration be not more than μC / g. <Developing Roller Filming Phenomenon> This phenomenon
Is a phenomenon in which the toner is fused to the surface of the developing roller 211.
You. When filming of the developing roller occurs, the
A considerable part of the image is missing or shading occurs. The development roller filming is particularly effective for toner.
It depends on availability. If the supply of toner is poor, the developing roller 21
1 has an extremely small amount of toner.
The toner of the portion is regulated blade 260 and developing roller 21
1 causes excessive stress, which
This causes a developing roller filming phenomenon. Therefore, in order to improve the toner supply property,
In addition, the amount of CCA is 3% or less, the amount of pigment is 15% or less,
The amount of the external additive having a particle size of 1.5% or more. These are
But it is effective, but even better by combining
It becomes. <Regulatory Blade Filming Phenomenon>
The phenomenon is a phenomenon in which the toner fuses to the regulating blade 260.
You. When this phenomenon occurs, the image of a substantial part
The image is missing (white stripes). This phenomenon is caused by toner supply property and regulation fluctuation.
Depending on the state of the contact portion of the blade 260 with the developing roller 211.
It depends. If the supply of toner is poor, the developing roller 21
1 has an extremely small amount of toner.
The toner of the portion is regulated blade 260 and developing roller 21
1 causes excessive stress, which
This causes a regulating blade filming phenomenon. Therefore, in order to improve the toner supply property,
In addition, the amount of CCA is 3% or less, the amount of pigment is 15% or less,
The amount of the external additive having a particle size of 1.5% or more. In addition, Tg (Ga
(Transition point) is 55 ° C or more, and Tm (melting temperature) is 11
When the temperature is 0 ° C. or more, the abrasion resistance of the toner is improved.
Thus, the filming phenomenon can be suppressed. Furthermore, the regulating blade 260 is
Abutment R on the blade 211 (in the regulating blade 260)
The radius of curvature of the contact portion with the developing roller 211 (half of the arc-shaped portion)
(Diameter)) is 100 μm or more and the contact angle (regulation blade 26
0 is a developing roller 2 passing through a point where the developing roller 211 abuts.
Angle α formed between the tangent to 11 and the regulating blade 260
(See FIG. 6)) is set to 50 ° or more, so that
Formed at the contact portion between the roller 211 and the regulating blade 260.
Of the space defined by the regulating blade 260
The toner on the image roller 211 returns to the supply roller 240 side.
It can be of any size. The size of this space
If the size is too small, toner may clog
Will cause trouble. Although these are effective alone, they can be used in combination.
It gets even better by letting it go. <Developing efficiency> Developing by developing roller 211
Of the amount of toner transported to the position,
This is the ratio of the amount of toner used for development. That is, the development efficiency is Development amount / (conveyance amount x peripheral speed of developing roller with respect to photoconductor)
Ratio) x 100 (%) It is. In order to improve the development efficiency, CCA
Amount is 0.5% or more, and the development amount is 0.80 mg / cm^Two
And the transport amount is 0.35 mg / cm^TwoAbove
Is desirable. <Sealability> The sealability referred to here is the
Toner provided on end face and lower face of roller 211
Seal (the bottom seal is shown at 275 in FIG. 3)
) Of the toner. [0138] Toner leakage causes image defects in the image area.
Connected, in-flight contamination even outside of image area
Will occur. The sealability is affected by the fluidity of the toner.
Is done. When the fluidity of the toner is extremely high, the developing roller 2
The toner easily leaks from the gap between the toner seal 11 and the toner seal. Therefore, a small influence on the fluidity of the toner is obtained.
It is desirable that the amount of the external additive having a particle size be 3.0% or less. Further, A.I. D is 0.40 g / cc
It is desirable. <Fogging Phenomenon> This phenomenon is caused by
This is a phenomenon in which the toner adheres to the regular white area). In the case of the reversal developing method using negatively charged toner,
As an example, the potential of the photoconductor is about -50 V in the image area.
, Set to about -600V in the non-image area, and
Voltage is set to about -300V. For this reason, usually, the negatively charged toner is charged in the non-image area.
Although it does not adhere to
If there is positively charged toner on the
I will wear it. Also, there is a toner having a low charge amount.
And the restraining force on the developing roller (static
(Adsorption force by electric force, etc.) is weak.
It may adhere to the photoreceptor. Therefore, the charging polarity of the toner is made uniform,
The toner charge amount (a small amount for negatively charged toner).
To reduce the fogging phenomenon
Can be. In order to increase the charge amount of the toner,
Reduces feed rate and charges regulating blades, developing rollers, etc.
Increases the chance of contact between the applied member and the toner
You. The transport amount is 0.60 mg / cm.^TwoLess than
It is desirable that the charge amount be −8 μC / g or less.
No. The supply roller must be at the same potential as the developing roller.
Is desirable. <Durability> The durability mentioned here refers to image formation.
Is the degree of deterioration of the image due to overlapping. The deterioration of the image is caused by the deterioration of the toner itself and the toner.
Filming and wear of the regulating blade 260 etc.
Occurs. The toner has a small particle diameter attached to its surface.
External additives are buried in the resin and
And transferability deteriorate. Therefore, the amount of the small particle size external additive of the toner is set to 1.
5% or more, and the amount of the large particle size external additive is 0.5% or more.
It is desirable to control the burial of small particle size external additives by
New The type of large particle size external additive is silicone oil.
However, the particle size is desirably about 40 nm. When the amount of CCA and the amount of pigment are large,
Lumming is likely to occur and the durability deteriorates.
It is desirable that the pigment content be 3% or less and the pigment amount be 15% or less. <Historical phenomenon> This phenomenon is caused by the previously formed image.
Phenomenon that the image pattern affects the image formed later
It is. The hysteresis phenomenon is that the rise of toner charge is
Occurs when bad. The rise of electrification depends on the CCA of the toner.
And the amount of external additives. When the amount of CCA is 0.5% or more, the charge
Rises better. The effect of the CCA is that the coverage of the external additive is low.
In this case, the base particles kneaded with CCA are directly connected to the charging member.
It is easy to come into contact because it is easy to contact. When a large amount of small particle size external additive is attached,
Although the coverage rate increases and the effect of CCA becomes difficult to appear
When using a large particle size external additive, the same weight ratio
Has a lower coverage than the small particle size additive.
The effect becomes easy to come out. On the other hand, if the amount of the external additive is small, the supply property is reduced.
Will be done. Therefore, the amount of the large particle size external additive should be 1.5% or less.
5% or less, and the amount of the small particle size external additive is 1.5% or less.
In addition, it is desirable to set it to 3% or less. [0160] The type of large particle size is treated with silicone oil.
HMDS (Hexane)
Methyl disilazane) and external addition of large particle size
The particle size of the additive is about 40 nm, and the particle size of the small external additive is 14 nm.
It is desirable to set it to about nm. The amount of charge of the toner is determined by the difference between the leading and trailing edges.
(Described later) should be 15 μC / g or less.
desirable. <Image unevenness phenomenon> This phenomenon is caused by a uniform image.
The phenomenon that the image becomes non-uniform while trying to form
It is. This phenomenon is caused by the development roller, the supply roller, etc.
Occurs depending on the rotation period of the rotating body. If the rotation of the rotating body is large, image unevenness is likely to occur.
Therefore, the developing roller must be
The run-out is 30 μm or less.
It is desirable that the runout relative to the center of rotation be 150 μm or less.
Good. Further, the pipe used as the developing roller
The roughness of the underlayer before adjusting the surface roughness is Rmax1 μm
If it exceeds, make the surface roughness uniform in the subsequent processing
Is difficult, and image unevenness is likely to occur. Accordingly
Therefore, the roughness of the base of the pipe is Rmax1 μm or less.
It is desirable to do. [0166] Further, the rotation axis of the developing roller
If the material is weak, the amount of deflection due to external force during rotation increases.
Therefore, it is desirable that the material of the shaft is iron. <Difference in Leading Edge Density> This phenomenon is caused by
When the image is formed, the darkness between the leading edge of the image and the other trailing edge
This is a phenomenon in which the degree (developing amount) is different. This phenomenon is caused by the fact that the front end portion and the other rear end portion
The amount of toner charge and the amount of conveyance on the developing roller corresponding to
The result is that the amount of development at the top and
It is caused by putting away. This phenomenon is caused by the fact that the toner at the leading end and the trailing end
0.15mg / cm^TwoWithin, and the difference in charge amount
Can be suppressed by setting the value within 15 μC / g.
it can. Further, the difference in the development amount was 0.15 mg / cm.^TwoWithin
Can be suppressed. Developing roller
Has a linear velocity of 300 mm / s or more and a regulated load of 50 g / cm.
In order to reduce the difference in the amount of toner transport,
It is necessary to abut the edge of the board. Regulator blade is ridgeline
If the contact surface includes the front and rear surfaces of the
Would. To prevent contact with the regulating blade screen,
The tangent angle should be 50 ° or more and 85 ° or less. The amount of CCA in the toner is 0.5% or less.
Desirably above. <Hopper Capacity> A predetermined number of images are formed.
This is the capacity of the toner in the developing device case required for the above. High density toner (toner containing a large amount of pigment)
By using, the desired image density can be obtained even with a small amount of toner.
Can be secured. Therefore, high density toner
The hopper can be used while ensuring image density
The capacity can be reduced, and the developing unit 210 is compact.
It becomes possible to be. It is desirable that the amount of the pigment be 5% or more. <Storability> The equipment such as transport environment and storage environment
This is the degree of deterioration of the above-mentioned various characteristics in the non-operation state. This deterioration is caused by the fact that the toner hardens in the developing device.
Caused by so-called blocking. To make the Tg of the toner 55 ° C. or more
Therefore, blocking can be prevented. The development characteristics and the like have been mainly described above.
However, based on the above situation, the final
Roller 211, supply roller 240, and regulating blade
260, how the specific configuration was
This is described below. <Regarding Toner> As described above, the toner
Combines pigment, CCA (charge control agent) and wax
It is bound with synthetic resin and gives its surface mainly durability.
Large-diameter external additive to provide fluidity mainly
By attaching a relatively small diameter external additive to
It is constituted. In this example, these components or
The characteristics were as follows. (1) Synthetic resin Synthetic resin is used with polyester to improve the fixability.
did. (2) Pigment The amount of the pigment was 5% or more and 15% or less. As described above, while securing the image density,
Reduce the capacity of the hopper and make the developing unit 210 compact.
That's because. When the amount of the pigment is 5% or less, the color
Over 15% because the saturation of the image is reduced
If this is not possible, supply will be reduced, and
This is because lading filming is likely to occur. (3) CCA The amount of CCA was 0.5% or more and 3% or less. The reason is as described above. When the amount of CCA exceeds 3%, the transcription
This is because the property is reduced. (4) Wax The amount of wax was 0.5% or more. The reason for this is that the releasability of the toner from the fixing roller is
It is to improve. Also, a recording medium such as toner paper
This is also to increase the fixing strength to the toner. (5) External additives having a relatively large diameter The large-diameter external additive is silicone oil, and its particle size is 40
nm and the amount should be 0.5% or more and 5% or less.
Was. The reason is as described above. (6) External additives having relatively small diameter The external additive of small diameter is HMDS and its particle size is about 14nm
And the amount was 1.0% or more and 3% or less. The reason is as described above. When the addition amount is 3% or more, the fixing property is improved.
Is reduced. In order to improve transferability, addition of
It is desirable that the amount be 1.5% or more. (7) Particle size The particle size of the toner was 6 μm or more and 9 μm or less. When the thickness is 6 μm or less, the cleaning property is low.
This is because the cost is high. On the other hand, when the thickness is 9 μm or more, the resolution is reduced.
This is because that. The particle size distribution of the toner used this time is shown in FIG.
It was shown to. The particle size distribution of this toner is
The measurement was performed using an intermodel TA-II. Apa
-Character diameter is 100μm, electrolyte is ISOTON-II
Was used. In the table shown in FIG. 9A, the number is shown in the right column.
The left column shows the volume, the lower row shows the measurement results, and the upper row shows this
The calculated values calculated based on the measurement results are shown. In addition,
"Volume" means that the measured toner particles are spheres
It is the volume when it is regarded as. In the graphs shown in FIGS. 9B and 9C,
The bar graph shows the count data, and the line graph shows the cumulative data
Is shown. In the table shown in FIG.
The meanings of the items shown are as follows. DIF N: The most basic data,
Number data (toner number data) input from I / O
) Is displayed for each channel. DIF%: The above number data (DIF
N) is shown in% for each channel. CUM N: The above number data (DIF
N) is accumulated and displayed. CUM%: The above DIF% is accumulated and displayed.
It is shown. The meaning of the item indicating the calculated value in the upper row is as follows.
It is as follows. 25.4 μ ↑: of 25.4 μm or more
It shows the cumulative% value. 6.35 μ ↓: for those of 6.35 μm or less
It shows the cumulative% value. KURTOSIS: Represents the kurtosis (sharpness) of the distribution
It is something. SKEWNESS: Represents the skewness of the distribution
You. Average: The arithmetic average particle diameter is indicated.
You. 25%: when the cumulative% reaches 25%,
This is the value of the particle diameter (see the graphs in FIGS. 9B and 9C). 50%: The value of the particle size when the cumulative% reaches 50%
(See graphs in FIGS. 9B and 9C) 75%: The value of particle size when the cumulative% reaches 75%
(See graphs in FIGS. 9B and 9C) CV%: Coefficient of variation (%). SDμ: Standard deviation (μm). (8) A. D A. D is 0.30 g / cc or more and 0.40 g / cc or less
And The reason is as described above. [0216] In this range, good transferability is obtained.
Because it is obtained. [0217] It should be noted that the content should be 0.40 g / cc or less.
This also improves the cleaning performance. (9) Coverage of external additives The coverage of the external additive is 100% or more, that is, the toner particles
It is possible to cover almost the entire surface of the child with the external additive (projected area conversion).
More than the possible amount was added. (10) Tg Tg was 55 ° C. or higher. The reason is as described above. (11) Tm Tm was set to 110 ° C. or more and 130 ° C. or less. The reason is as described above. When the temperature is 130 ° C. or more, the fixing property is poor.
It is because it decreases. (12) Molecular weight distribution The molecular weight distribution (MW / MN) was set to 100 or more. If it is less than 100, the fixability is lowered.
It is. (13) Development amount The development amount is 0.40 mg / cm^Two0.80 mg /
cm^TwoThe difference between the leading and trailing edges is 0.15 mg / cm^TwoWithin
did. The reason is as described above. In addition, 0.40 mg / cm^TwoIs below
And 0.80 mg on the contrary.
/ Cm^TwoThis is because transferability is reduced if the above is satisfied. (14) Transport amount The transport amount is 0.35mg / cm^TwoAs described above, 0.60 mg /
cm^TwoThe difference between the leading and trailing edges is 0.15 mg / cm^TwoWithin
did. The reason is as described above. (15) Charge amount The charge amount should be -35μC / g or more and -8μC / g or less.
Was. The reason for setting -8 μC / g or less is as described above.
It is. When the density is -35 μC / g or less, the transfer
This is because the property is reduced. <Regarding the developing roller> (1) The shaft material was iron and the diameter was 5 mm. (2) End face of flange (end face of developing roller)
The surface roughness of (Side) is Rmax 0.5 μm or less.
Was. This is for improving the sealing performance. (3) Corners of developing roller (cylindrical face and end face)
(The corner with (side)) is chamfered with R, and the R is
0.1 mm or more. The photoconductor 110 should not be damaged at the corners.
That's because. (4) The surface roughness is Rz 5 μm or more,
It was 10 μm or less. When Rz is 5 μm or less, toner supply property
Is decreased, and conversely, Rz is 10 μm or more.
This is because the resolution of the image decreases. (5) The deflection was 30 μm or less. The reason is as described above. When the runout is 30 μm or more, the toner
This is because the supply of energy is also reduced. (6) The outer diameter tolerance is about ± 0.02 mm.
Was. In order to secure the supply property,
This is to prevent unevenness. <Regarding the Supply Roller> (1) The shaft material was iron and the diameter was 5 mm. This is to prevent image unevenness. (2) The run-out was set to 150 μm or less. This is to prevent image unevenness. (3) The outer diameter tolerance is about ± 0.15 mm.
Was. The purpose of this is to secure supply capability.
This is to prevent unevenness. (4) The hardness is 40 ° or more and 70 ° or less.
Was. If it is less than 40 °, the supply property is reduced, and
This is because if the value is ゜ or more, the driving torque increases. (5) The open cell rate was 30 to 80%. This is to ensure supply. (6) The polishing direction is (rotation direction of supply roller)
To) forward direction. [0257] This is in order to ensure supplyability. (7) The peripheral speed ratio with respect to the developing roller 211 is
About 50% to 80%, more preferably 60 to 70%,
Physically, it was about 64%. If it is less than 50%, the toner on the developing roller
If supply is no longer ensured and it is 80% or more,
Will deteriorate the drive torque and increase the driving torque.
It is. (8) Depth of penetration (contact with developing roller)
The amount of dent in the part) is 0.1 mm or more and 0.4 mm or less
And When the thickness is 0.1 mm or less, the developing roller
Insufficient rubbing of toner, 0.4 mm or more
This is because the driving torque increases. (9) The potential was the same as that of the developing roller. This is to prevent fogging and history. <Restriction blade> (1) The contact R with the developing roller 211 is 30 μm or less
The upper limit is 150 μm or less. When the thickness is 30 μm or more, necessary toner
This is to prevent the feeding amount from being ensured.
The reason for this is to reduce the difference between the front and rear end densities. (2) The contact angle with the developing roller 211 is 5
0 ° or more and 85 ° or less. The difference of 50 ° or more means that the difference between the front and rear end densities is small.
85% or less for the purpose of cutting
This is to prevent filming. (3) Straightness was set to 30 μm or less. Image unevenness (occurs in the entire image, especially in the width direction)
This is for reducing density unevenness). (4) The surface roughness is set to Rz 15 μm or less.
Was. Stripes (thin streaky image unevenness,
In particular, there is a possibility that an image is missing in a line parallel to the paper transport direction.
This is to reduce The embodiments and examples of the present invention have been described above.
Although the present invention has been described, the present invention is not limited to the above embodiment or embodiment.
The present invention is not limited to the examples, but falls within the scope of the present invention.
Can be appropriately modified. [0273] 【The invention's effect】Of the present inventionAccording to the developing device, the supply roller
Drive torque is reduced. [0274]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an example of an image forming apparatus using a developing device according to a first embodiment of the present invention. FIG. 2 is an enlarged view of four developing units 210, a photoreceptor 110, and the periphery thereof. FIG. 3 is an enlarged view of a developing unit 210M. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3; 5 (a) is an enlarged cross-sectional view taken along line VV in FIG. 3, and FIG. 5 (b) is a view taken in the direction of arrow b in FIG. FIG. 6 is an operation explanatory view. FIG. 7 is an operation explanatory view. FIG. 8 is a schematic diagram showing a main part of an image forming apparatus using a developing device according to a second embodiment of the present invention. 9A and 9B are diagrams illustrating the particle size distribution of the toner, in which FIG. 9A is a table illustrating the particle size distribution, and FIGS. [Description of Signs] T Toner 210 Developing device 211 Developing roller 211 212 Axis 230 Case 240 Supply roller 241 Axis 244 Corner 270 Seal member SE Seal member

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Yamada 3-5-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (56) References JP-A-8-185040 (JP, A) 4-1559 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 15/08

Claims (1)

(57) [Claim 1] A case accommodating toner, a developing roller rotatably supported by a shaft in the case, and a developing roller rotatably supported by the case with a shaft. A supply roller made of an elastic body that supplies the toner to the surface of the developing roller by being pressed against the developing roller; Wherein the end face of the developing roller and the end face of the supply roller are arranged at substantially the same position in the axial direction of the rollers, and the supply roller is provided with the developing roller by its elasticity. A roller whose pressing portion is in a concave state, and wherein a corner of the supply roller is chamfered.