JP3323694B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image formed on an image carrier by an electrophotographic system or an electrostatic recording system into a visible image, and more particularly to a one-component developing apparatus. The present invention relates to a developing device that can obtain a high-quality image using a developer.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer of an electrophotographic system or an electrostatic recording system, a developing device using a non-magnetic one-component or magnetic one-component developer (hereinafter referred to as toner). Is often used. FIG. 8 shows an example of a one-component developing system developing device used in an electrophotographic image forming apparatus.

As shown in FIG. 1, the developing device includes a developing chamber 102 having an opening 103 at a portion facing the photosensitive drum 101, and a toner container 114 for storing toner inside the developing chamber 102 at the back of the developing chamber 102. Is arranged. Further, a partition wall 115 for partitioning between the developing chamber 102 and the toner container 114 is provided. A conductive developer carrier (hereinafter, referred to as a developing sleeve) 110 is rotatably arranged in the developing chamber 102 such that a part thereof is exposed to the opening 103, and a developing sleeve 110 is rotated in a direction indicated by an arrow in a developing operation. And transports the toner toward the photosensitive drum 101 while carrying the toner.

The developing sleeve 110 is held at a distance of 50 to 500 μm from the photosensitive drum 101, and has a developing area for supplying the toner carried on the developing sleeve 110 toward the photosensitive drum 101. Further, the developing chamber 102 is supplied from the toner container 114 to the conveying means 11.
A supply roller 112 for supplying the toner conveyed by 1 to the developing sleeve 110 is accommodated.

A developing bias voltage obtained by superimposing a DC voltage and an AC voltage is applied from a bias power supply 106 to the developing sleeve 110 during a developing operation.

[0006] Above the developing sleeve 110, a blade 113 for regulating the layer thickness of the toner carried on the developing sleeve 110 is arranged. The blade 113 is attached to the developing chamber 102. Further, below the developing sleeve 110, a blowing prevention sheet 1 for preventing toner from blowing out from the lower part of the developing chamber 102 to the outside.
08 is provided.

During the developing operation, the conveying means 111 conveys the toner toward the supply roller 112 over the partition wall 115, and the toner is supplied to the supply roller 112 which rotates in the direction of the arrow shown in the figure.
Is applied to the developing sleeve 110. In particular, in the case of a non-magnetic toner containing no magnetic material, the developing sleeve 1
Since it is difficult to supply the toner due to the magnetic restraining force to the roller 10, when a non-magnetic toner is used, it is necessary to provide the supply roller 112 shown in FIG. The developing sleeve 110 is rotated in a direction indicated by an arrow in the drawing, and the toner carried on the developing sleeve 110 is regulated to a predetermined layer thickness by a blade 113 and then sent to the developing area facing the photosensitive drum 101. . In this developing area, an electric field is formed by a developing bias supplied from the bias power supply 106 to the developing sleeve 110, and the electric field causes toner to move from the developing sleeve 110 to a portion where an electrostatic latent image on the photosensitive drum 101 is formed. And electrostatic latent images are visualized.

Here, conventionally, in order to form a high-resolution and high-quality image, a method of improving the particle diameter and fluidity of the toner has been used. In particular, a method of improving the fluidity of the toner is widely used as a simple method that can improve the fluidity only by changing the formulation of the toner external additive without changing the formulation of the classified toner product.

[0009]

However, the present inventors have found new facts through experiments and studies in the developing device. To improve the line image reproducibility and the isolated dot reproducibility, toner with excellent toner fluidity was used, but when the amount of toner in the developing device was reduced due to repeated image formation, the toner Despite the presence of the toner, a non-uniform density portion (hereinafter, referred to as white void) appeared on the image.

This is because, as shown in FIG. 9, when the amount of toner in the toner container decreases and the toner gets over the partition wall 115 and is transported into the developing chamber, the toner in the developing chamber is supplied to the supply roller 112 and the sleeve 110. As a result, the blade 113 is biased toward the blade 113 side. This state is more conspicuous as the amount of toner in the toner container is smaller. If the toner fluidity of the toner used is better, the unevenness of the toner is reduced.
16 tends to be low. At this time, blade 1
If the leading end position of the blade 13 is located above the sleeve, the toner 116 does not easily reach the leading end of the blade, and a sufficient amount of toner cannot enter the contact portion between the blade and the sleeve. A missing image appears.

Accordingly, it is an object of the present invention to provide a uniform image, particularly an image having improved uniformity in the latter half of use of the developing device.

[0012]

According to the present invention, there is provided a developer accommodating chamber for accommodating a developer, and a developer accommodating chamber separated from the developer accommodating chamber by a partition wall. , A developer carrying member that carries the developer in the developing chamber and transports the developer to the developing area, a supply roll that supplies the developer to the developer carrying member, and a supply roll that is supplied by the supply roll. and the developing device having a regulating member, a for regulating the developer layer thickness on the developer carrying member, and satisfies the L × tanθ ≦ h ≦ (r + d-L) × tanθ, and 1 ≦ h development apparatus.

R (mm): radius of the supply roll d (mm): minimum gap between the supply roll and the partition wall L (mm): horizontal distance between the regulation position of the regulating member and the center of the supply roll h (mm): supply Distance between the supply position by the roll and the regulation position by the regulation member θ (°): angle of repose of developer According to the present invention, the regulation portion by the regulation member is buried in the developer even during non-development. Stable regulation of the layer thickness and provision of a tribo can be performed immediately after the start of the formation, and white spots at the leading end of the image can be generated without requiring long idling.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of the developing device according to the present invention. FIG. 9 is an enlarged cross-sectional view around a developing sleeve and a supply roller, and a detailed description of the same members as in the example illustrated in FIG. 8 is omitted.

In this embodiment, a non-magnetic one-component toner is used. The repose angle θt of the toner used in the present embodiment is 20 ° to 45 ° based on actual use.

Here, the angle of repose, which is the toner fluidity index in the present invention, was measured by the following method using a conventionally known powder tester (PT-E type manufactured by Hosokawa Micron Corporation). The measurement environment is 23 ° C. and 60% RH.

(1) A funnel and a sieve (appropriate one of 100 mesh (mesh size: 150 μm) -400 mesh (mesh size: 38 μm)) are set on the shaking table, and a table for measuring the angle of repose is set under the funnel. .

(2) After allowing the toner to stand in the measurement environment for 12 hours, an appropriate amount (about 50 g) is gently put on a sieve.

(3) A voltage is gradually applied to the vibration system and the voltage value is set so that toner does not accumulate in the funnel.

(4) When toner starts to spill from around the table for providing the angle of repose, the applied voltage is reduced, the amplitude is reduced, and the outflow of toner is reduced.

(5) When the angle of repose becomes constant, the vibration is stopped and the outflow of toner is stopped.

(6) The protractor stand is set, and the protractor is moved so that the linear portion of the protractor is parallel to the ridge line of the deposited toner, and the scale is read.

Thus, the angle of repose of the developer can be measured.

In FIG. 1, 116a, 116b, 11
6c schematically shows the state of the ridge line of the toner in the developing chamber when the developing device is operated according to the use condition of the developing device. When the developing device is operated, the toner is biased toward the sleeve side with the rotation of the toner supply roller 112 and the sleeve 110, and the toner 116c is in a position where the toner amount in the toner container is slightly lower than the partition wall 115. This is schematically shown. The toner 116a is in a state in which the amount of toner in the toner container is considerably reduced, and is near the life of the developing device. Here, except for an extreme case where the toner runs out and the life is short as in the state of the toner 116a, the toner 11a is usually used.
There is an average at the position of 6b. Therefore, in order to stably form a toner coat on the sleeve with the developing blade during image formation and prevent toner supply failure, the developing blade 11
By arranging the three leading end positions below the toner ridge line 116c, preferably below the toner ridge line 116b, toner can be supplied to the developing blade 113, and stable toner coat formation is achieved. In FIG. 1, the radius of the toner supply roller 112 is r, the minimum gap between the toner supply roller 112 and the partition wall 115 is d, and the horizontal distance from the rotation center of the toner supply roller 112 to the contact portion of the developing blade 113 with the sleeve 110 is L. When the vertical distance from the downstream side of the nip portion between the toner supply roller 112 and the sleeve 110 in the sleeve rotation direction to the distal end position of the developing blade 113 is h, the developing blade 11
In order to make the leading end position buried in the developing chamber toner, the toner ridge line 116c is
0 is the highest at the outer peripheral portion, and the toner ridgeline 116
It suffices if c intersects the elastic blade at the position of h or more.

The length of the bottom side of the toner ridge line 116c is L + r
+ D, the height of the toner ridge line 116c is (L + r
+ D) × tan (θt).

For this reason, h ≦ (L + r + d) × tan (θ
By satisfying t), the blade tip can be buried with toner.

In addition, the toner near the life of the developing device may be deteriorated due to repeated image formation, and may cause problems such as a density increase and fog. Therefore, it is desirable that the blade tip position is disposed above the toner ridge line 116a, and L × tan (θt)
≤h is preferred.

As described above, L × tan (θt)
By arranging the tip of the developing blade at a position that satisfies ≦ h ≦ (L + r + d) × tan (θt), the tip of the blade is always buried in the toner, and a uniform and stable toner coat can be formed, and a blank white image is generated. Is prevented.
Although the non-magnetic one-component toner has been described in the present embodiment, the same means is effective when a magnetic one-component toner is used. Normally, when a magnetic one-component toner is used, since a magnet is provided inside the sleeve, it is easier to form a state in which the blade tip is buried in the toner. Therefore, according to this embodiment, a more stable toner coat can be formed. .

The toner container 11 shown in FIG.
In the developing device 4 above the developing chamber, a line A extrapolated from the wall 115 separating the toner container and the developing chamber and a line B extrapolated from above the toner supply roller 112
It is sufficient to set the leading end position of the developing blade 113 so as to satisfy the above-mentioned relational expression, where d is the closest distance between the toner supply roller 112 and the point lowered in the vertical direction from the intersection with the developing blade 113.

(Second Embodiment) FIG. 3 shows a second embodiment of the developing device according to the present invention. FIG. 4 is an enlarged cross-sectional view of the vicinity of a developing sleeve and a supply roller, and a detailed description of a portion described in the related art is omitted.

In this embodiment, a study was conducted using a non-magnetic one-component toner. The repose angle θt of the toner used in the present embodiment is 20 ° to 45 ° based on actual use.

In FIG. 3, 117a, 117b and 11
FIG. 7C schematically shows the state of the ridge line of the toner in the developing chamber when the developing device is stopped according to the use state of the developing device. Referring to FIG. 4, when the developing device is operated, the toner in the developing chamber is biased toward the sleeve side with the rotation of the sleeve and the toner supply roller (toner ridge line 116 in FIG. 4). Since the rotation of the sleeve and the toner supply roller is stopped, a part of the toner in the developing chamber collapses so as to return to the toner container side, and a toner ridge line 117 having a vertex near the uppermost point of the toner supply roller is formed. If the leading end of the developing blade is located above the toner ridge line 117 in such a toner state, the amount of toner taken in at the beginning of the next image formation is reduced, and as a result, white dropout occurs at the upper end of the image. There is a risk of doing so. Therefore, in order to stably form the toner coat on the sleeve with the developing blade at the start of operation of the developing device and to prevent toner supply failure, the leading end position of the developing blade 113 is positioned below the toner ridge 117c, preferably the toner ridge. 117
By disposing the toner at a position lower than b, toner can be supplied to the developing blade 113, and stable toner coat formation is achieved. In FIG. 3, the radius of the toner supply roller 112 is r, the minimum gap between the toner supply roller 112 and the partition wall 115 is d, and the horizontal distance from the rotation center of the toner supply roller 112 to the contact portion of the developing blade 113 with the sleeve 110 is L. the vertical distance from the nip portion the sleeve rotation direction downstream side position of the toner supply roller 112 and the sleeve 110 to the developing blade 113 tip position is taken as h, h ≦ ((r + d-L) / (r + d)) ×
((R + d) × tan (θt)) = (r + d−L) × t
By satisfying the relationship an (θt), a stable toner coat can be formed even at the start of operation of the developing device, and white dropout can be prevented. If the tip of the blade is too close to the toner supply roller, the toner at the tip of the blade receives a very strong force during the image forming operation, causing toner deterioration and fogging. There is a risk that formation will be hindered. Thus, the present inventors have studied and found that h ≧ 1 (m
m) is desirable. When h <1, not only the above problem occurs but also the toner supply roller may bite into the tip of the blade depending on the accuracy of the outer diameter of the toner supply roller. Therefore, it is desirable that the blade tip position h is in the range of 1 ≦ h ≦ (r + d−L) × tan (θt).

As described above, 1 ≦ h ≦ (r + d−
By arranging the tip of the developing blade at a position satisfying (L) × tan (θt), the tip of the blade is always buried in the toner even when the developing device is stopped, so that a stable toner coat can be formed from the start of image formation. The occurrence of a white missing image at the image tip is prevented.

(Third Embodiment) FIGS. 5, 6, and 7 show an embodiment of a cartridge and an image forming apparatus according to the present invention. Portions described in the related art, such as the periphery of the developing sleeve and the supply roller, are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 5 shows a case where the developing device according to the present invention is a cartridge detachably mountable to the main assembly. As shown in FIG. 5, the developing device is in the form of a cartridge 119 enclosed in a cartridge cover 118, and the state in which the toner in the toner container 114 is exhausted is defined as the life of the cartridge. By replacing the developing device with a new cartridge, image formation can be performed again. This eliminates the hassle of toner supply and the like. As shown in FIG. 6, the cartridge 119 has a form that can be attached to and detached from the main unit 121 through a cartridge insertion port 120 provided in the main unit 121.

Next, a detailed description of the image forming apparatus in this embodiment and the image forming process will be described with reference to FIG. The image forming apparatus shown in FIG. 7 is a device capable of forming a color image by containing toners of different colors in the cartridge 119, respectively. In this type of color image forming apparatus, a process of transferring a recording image formed by charging, exposing, and developing on an image carrier onto a recording sheet is repeated a plurality of times to form a multi-color superimposed image on the recording sheet. There is a method of obtaining a color image. FIG. 7 is a cross-sectional view of the color image forming apparatus according to the present embodiment. As shown in the figure, the entirety of the apparatus includes a photosensitive drum 101 serving as an image carrier and a roller charger 12.
2. Further, on the left side of the photosensitive drum, a plurality of cartridges 119a, 119b, 119c, and 119d are made detachable from a rotatable support 123, and when supported by the support 123, around a support rotation axis. Each cartridge 119a, 119b, 119c, 119
d developing opening surfaces 124a, 124b, 124c, 12
4d is set. Also, the cartridge 119
A, 119b, 119c, and 119d contain magenta toner, cyan toner, yellow toner, and black toner, respectively. The cartridge inner sleeve 110 rotates at a peripheral speed of 1.75 times the peripheral speed of the photosensitive drum 101. Further, the cartridges 119a, 119b, 119c, and 119d stored in the support member 123 have developing opening surfaces 124a, 124b, and 124c as shown in FIG.
124d is always driven to oppose the photosensitive drum surface. One means of the driving method is described in detail in JP-A-50-93437.

On the right side, a transfer drum 125 having a function of holding a transfer material (not shown) and transferring an image on the photosensitive drum 101 to the transfer material (not shown) is arranged. With the above configuration, the photosensitive drum 101 is driven by a driving unit (not shown) at a peripheral speed of 100 mm / sec in a direction indicated by an arrow. The photosensitive drum 101 has a diameter of 40.
mm on an outer circumferential surface of an aluminum cylinder.
Although the photoconductor made of C) is applied, the photoconductor may be A-Si, CdS, Se, or the like.

Next, a laser diode and a high-speed motor which constitute an exposure position are provided above the apparatus main body.
A rotating polygon mirror, an optical unit 126 including a lens, and a folding mirror 127 are disposed. The charging roller 122 has a DC voltage of -700 V and a Vpp (peak to peak) 180 at an AC frequency of 1000 Hz.
An AC voltage of 0 V is superimposed and uniformly charged to about -700 V. When the image information signal is input to the optical unit 126, the laser beam emitted from the laser diode is irradiated on the photosensitive drum 101 through the light 128, and the irradiated position of the photosensitive drum 101 is approximately -100V. become. When the photosensitive drum 101 further moves in the direction of the arrow, the process cartridges 119a, 119b, 119c, 11
Visualized by 9d.

Next, the transfer process will be described in detail. Detailed drum 1
25, an elastic layer 127 having a thickness of 5 mm is wound around a metal cylinder 126 having a diameter of 155 mm, and
A configuration in which PVdF128 of 00 μm was wound was used, and urethane foam was used for the elastic layer. And the transfer drum 1
Reference numeral 25 denotes a driving unit (not shown) which is driven in a direction indicated by an arrow at a peripheral speed of 100 mm / sec which is the same as that of the photosensitive drum 101. The transfer material fed from the transfer material cassette 129 by a pickup roller (not shown) is held at the leading end of the transfer material by a gripper 130, and then electrostatically attracted to a transfer drum by a suction roller 131 to which a voltage is applied. The toner image on the photosensitive drum 101 is transferred onto a transfer material (not shown) attracted to the transfer drum by a voltage applied to the transfer drum 125 from a power supply (not shown). The above process is performed for magenta, cyan, yellow,
By performing black, a plurality of color toner images are formed on the transfer material. After the final color transfer step, the transfer material is peeled off from the transfer drum 125 by the separation claw 132, and the transfer material is fused and fixed by a conventionally known overheating and pressure fixing device 133 to obtain a color image.

The transfer residual toner on the photosensitive drum 101 is cleaned by a cleaning device 1 such as a well-known fur brush or blade means.
Cleaned by. Further, the photosensitive drum 101 is neutralized by the neutralization device and is initialized. Here, in the case of this embodiment, the charging roller 1 is used for charging the photosensitive drum 101.
In the case where the photosensitive drum 101 is neutralized, the alternating voltage to be applied is kept as it is, and the DC voltage is reduced to approximately 0 V to eliminate the static electricity. Further, it is preferable that the toner on the transfer drum 125 is also cleaned by a transfer drum cleaning device 135 such as a fur brush or a web as necessary. Further, the transfer drum is neutralized by a voltage applied from a power supply (not shown) to the neutralization roller 136, and is initialized.

In the above-described color image forming apparatus, if an image defect such as white drop occurs even in one color even though toner is present in the cartridge, the color balance is disturbed and the image quality is remarkably deteriorated. Further, there is a possibility that other colors of toner may be unnecessarily consumed. Therefore, not only a monochrome image forming apparatus but also a color image forming apparatus require higher quality assurance. Therefore, in the cartridge of the present embodiment, the relationship between the toner repose angle and the blade tip position is described below, so that the four color cartridges can form stable images.

In a color image forming apparatus requiring high gradation and high resolution, it is necessary to improve the fluidity of toner. In this embodiment, the toner repose angle θt is from 24 ° to 30 °.
Was used. The reason that the angle of repose θt differs for each color is
This is because pigments, charge control agents, and the like contained in the classified toner products are slightly different. The radius of the toner supply roller 112 is 8 m
m, the minimum gap between the toner supply roller 112 and the partition wall 115 is 1 mm, and the vertical distance from the rotation center of the toner supply roller 112 to the nip portion of the sleeve 110 of the developing blade 113 downstream from the rotation direction of the sleeve 110 to the tip of the developing blade 113. Was set to 2.1 mm. As a result, the tip of the developing blade 113 can always be kept buried in the toner in the developing chamber, stable toner coat formation can be achieved, and image defects such as white spots can be prevented. still,
The toner remaining amount in the toner container 114 (not shown) is used to determine the remaining amount of toner in the process cartridge, and a warning is displayed to urge the user to replace the cartridge. Was.

As described above, even in the color image forming apparatus using the cartridge of the present embodiment, it was possible to prevent white blank images and to achieve adaptation to the color image forming apparatus. In the present embodiment, the process cartridge including the developing device has been described.
A similar effect can be obtained even in a form included with the photosensitive drum and the like. Needless to say, the same effect can be obtained even with a single-color image forming apparatus.

[0045]

As described above, it is possible to provide a uniform image without a density increase by adapting the toner angle of repose and the position of the developing blade to the relational expression of the present invention.
Furthermore, not only the miniaturization of the apparatus and the maintenance-free operation can be achieved, but also the present invention can be applied to a color image forming apparatus, thereby providing high quality and high quality color images.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the first embodiment of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a state of toner when the developing device is operating and when it is stopped.

FIG. 5 is a diagram illustrating a process cartridge according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating a state in which a process cartridge is mounted on a main body device.

FIG. 7 is a diagram illustrating an image forming apparatus according to a third embodiment of the present invention.

FIG. 8 is a sectional view of a developing device.

FIG. 9 is a diagram illustrating a state of toner in a developing device.

[Explanation of symbols]

 Reference Signs List 101 photosensitive drum 102 developing chamber 110 developing sleeve 112 supply roller 113 blade 115 partition wall 116 toner

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsuya Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hiroshi Sasame 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Takaaki Tsuruya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akihiko Uchiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Yoichiro Maebashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Haruo Fujii 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-6-19296 (JP, A) JP-A-2-76745 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/08

Claims (6)

(57) [Claims] An image forming apparatus includes: a developer accommodating chamber for accommodating a developer; a developing chamber to which a developer is supplied from the developer accommodating chamber partitioned by the developer accommodating chamber and a partition; A developer carrier that carries and conveys the developer to the developing area, a supply roll that supplies the developer to the developer carrier, and a regulation that regulates the thickness of the developer layer on the developer carrier that is supplied by the supply roll in the developing device having a member, a developing device and satisfies the L × tanθ ≦ h ≦ (r + d-L) × tanθ, and 1 ≦ h. r (mm): radius of the supply roll d (mm): minimum gap between the supply roll and the partition wall L (mm): horizontal distance between the regulation position of the regulating member and the center of the supply roll h (mm): supply by the supply roll Distance between the position and the restriction position by the restriction member θ (°): angle of repose of the developer 2. The developing device according to claim 1, wherein said developer is a one-component non-magnetic toner. 3. The developing device according to claim 1, wherein said regulating member has an elastic blade which is urged toward the developer carrier and frictionally charges the developer to a predetermined polarity. Wherein said supply roll is pressed against a developer carrying member, one of the developing apparatus of claims 1 to 3, characterized in that also performs scraping the developer carrying member of a developing agent. 5. The developing device according to claim 1 , wherein the developing device is a single-use type that is replaced by a new one when the developer in the developer chamber runs out. 6. The developing device according to claim 1, wherein the angle of repose of the developer is 20 to 45 °.