JP2003131490A - Developer carrying means, developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent image free from an image defect such as irregular image density by stably driving and rotating a belt even in the case of realizing the speed-up of the device by improving toner supplying/peeling ability. SOLUTION: In a toner carrying means 14 carrying toner by a toner carrying belt 15 stretched and laid on a plurality of rollers and supplying the toner while making the belt 15 abut on a developing roller 11, a roller abutting on the roller 11 out of a plurality of rollers is set as a 1st laying roller 16 and a roller positioned on an upstream side in the moving direction of the belt 15 with respect to the roller 16 is set as a 2nd laying roller 17, then, an angle θformed by a line linking the center of the roller 11 and that of the roller 16 with a line linking the roller 16 and the roller 17 satisfies relation 10 deg.<θ<110 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer transport means for transporting and supplying a developer, a developing device having the developer transport means, and an image forming apparatus having the developing device.

[0002]

2. Description of the Related Art Conventionally, a non-magnetic one-component developing device has been used as a developing device represented by a simple color developing method. The non-magnetic one-component developing device can basically have a configuration similar to that of the magnetic one-component developing method.

That is, the non-magnetic one-component developing device has a developing container containing a toner which is an insulating one-component developer, and a developing roller as a developer carrying member carrying the toner. Here, the toner is a non-magnetic toner containing a pigment of any one of yellow, magenta, cyan and black.

In the developing container, there are a toner first stirring member and a toner second stirring member, which are plate-shaped or screw-shaped in various shapes, and are rotated. It is conveyed in the direction of the developing roller.

A regulating blade formed of an elastic material such as urethane rubber is in contact with the developing roller as a toner amount regulating member, and regulates the toner on the developing roller to form a toner thin layer, It defines the amount of toner conveyed to the developing area. The toner conveyed to the developing area adheres to the latent image formed on the photosensitive drum as an image carrier in the image forming apparatus, and undergoes a developing process for visualizing the latent image as a toner image.

In the non-magnetic one-component developing method, since it is impossible to supply the toner by the magnetic force, the developing roller is in contact with the peeling / supplying roller for removing and supplying the urethane sponge. Is common. The peeling / supply roller rotates in the counter direction at the nip portion with the developing roller to supply the toner onto the developing roller, and at the same time, the developing roller on the developing roller that has not been developed even after passing through the developing area. The toner is being stripped.

On the other hand, Japanese Unexamined Patent Publication No. 11-190932 discloses a developing device having a belt-like developer conveying means instead of the stripping / supplying roller. That is, as shown in FIG. 7, the belt-shaped developer conveying means 71 stretched by a plurality of rollers 72 and 73 is used in place of the stripping / supplying roller, so that the developer supplying path A and the developing agent are supplied. The agent stripping path B is formed and the toner is stripped / supplied onto the developing roller 74 as a developer carrying member, and at the same time, the toner stripped from the developing roller 74 is developed by the developer conveying means 71. It is configured to prevent toner deterioration that is caused when the toner that has been conveyed further away than 74 and is peeled off stays near the developing roller 74.

[0008]

However, in the developing device having the above-mentioned belt-shaped developer conveying means, for example, when the speed of the device is to be increased, the toner supply / peelability is high. Was an issue.

That is, in the developing device having the above-mentioned belt-shaped developer conveying means 71, the toner supplying / peeling ability by the developer conveying means 71 depends on the material and surface property of the belt, or the developing roller and the belt. The desired toner supply / peelability required for the apparatus is obtained by adjusting these conditions, such as the peripheral speed ratio.

In order to increase the speed of the apparatus, it is necessary to set the rotation speed of the developing roller 74 faster as the speed of the apparatus increases. In this case, the relative contact area of the developing roller 74 with the belt is Get smaller. For this reason, if the moving speed of the belt in the counter direction is not increased, toner supply may be insufficient, and defects such as uneven density may occur due to image defects.

On the other hand, the moving speed of the belt is also increased at the same time,
If an attempt is made to secure the contact area of the developing roller with respect to the belt per unit area, the peripheral speed ratio becomes considerably large. For this reason, the rotational drive is not stable, image defects such as density unevenness may occur, and deterioration of the belt or the like due to rubbing may cause a problem such that desired durability cannot be obtained. .

Therefore, an object of the present invention is to improve the toner supply / peelability and to perform a stable rotational drive of the belt even when the speed of the apparatus is increased, and it is possible to obtain a good image without image defects such as uneven image density. To get the image.

[0013]

A typical constitution of the present invention for achieving the above object is to convey a developer by a belt member stretched over a plurality of rollers, and to convey the developer to the belt member. In the developer transporting means that supplies the developer by bringing it into contact with a carrier, a roller of the plurality of rollers that comes into contact with the developer carrier is a first tension roller, and When the roller located on the upstream side in the moving direction of the belt member is the second tension roller, a line connecting the center of the developer carrying member and the center of the first tension roller, and the first tension roller, An angle θ formed by a line connecting to the second stretching roller satisfies the relation of 10 ° <θ <110 °.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a schematic explanatory view of an image forming apparatus, FIG. 2 is an explanatory view of a developing device of the first embodiment, and FIG. 4 is an enlarged view of FIG. 4, and FIG. 4 is a view showing the results of the accelerated durability test of the developing device. In the description, first, a schematic description of the image forming apparatus will be given, and then a detailed description of the developing apparatus as a developing unit will be given.

(Image Forming Apparatus) The image forming apparatus shown in FIG. 1 uses an intermediate transfer belt 6 as an intermediate transfer member,
The developing device 2 (2a, 2b, 2c, 2d) for each color, the laser scanner 5 (5a, 5b, 5c) as an exposing unit,
5d), the photosensitive drum 1 (1a, 1 as an image bearing member
b, 1c, 1d), charging roller 3 (3a, 3b, 3c,
3d), cleaning means 4 (4a, 4b, 4c, 4
d).

The photosensitive drums 1 of the respective colors are uniformly driven by the charging roller 3 while being rotationally driven in the direction of arrow d1 at a predetermined peripheral speed, and modulated in accordance with the digital image signal scanned by the laser scanner 5. An electrostatic latent image of each color component is formed by receiving the generated laser beam via the imaging exposure optical system. Subsequently, the developing device 2 is used to develop the electrostatic latent image with toner as a developer of each color (yellow, magenta, cyan, black) to obtain a visible image for each color component.

The intermediate transfer belt 6 is rotationally driven in the direction of arrow d2 at the same peripheral speed as the photosensitive drum 1. The visible image of each color is transferred (primary transfer) from the photosensitive drum 1 to the intermediate transfer belt 6 by applying a primary transfer bias supplied from a power source S (Sa, Sb, Sc, Sd). On the intermediate transfer belt 6, a toner image in which all colors are superimposed is obtained.

The toner image formed on the intermediate transfer belt 6 is collectively transferred (secondary transfer) onto the transfer material P conveyed at the nip portion with the secondary transfer roller 7 rotating in the direction of arrow d3. . The transfer material P to which the toner image is secondarily transferred is conveyed to the fixing device 8, and the toner image is fixed by heat and pressure in the fixing nip portion N between the fixing roller and the pressure roller.

(Developing Device) The developing device 2 in this embodiment is a non-magnetic one-component developing device to which the present invention is applied. The developing device 2 will be described in detail below. In FIG. 2, toner T is yellow produced by a pulverization method,
It is a negatively chargeable non-magnetic toner containing a pigment of each color of magenta, cyan and black. The developing device 2 includes a toner storage container 10 for storing the toner T, a developing roller 11 as a developer carrying member, a toner amount regulating member 13, and a toner transporting means 14 as a developer transporting means.

The developing roller 11 made of aluminum and having a diameter of 16φ is made of a conductive material by a gap regulating member (not shown).
A constant distance from the photosensitive drum 1 (not shown) (300 μ in this example)
(gap of m) and is rotated in the counterclockwise direction indicated by the arrow.

Toner amount regulating member made of silicone resin
13 is heat-welded to a phosphor bronze plate having a thickness of 150 μm, which is a supporting member, and is brought into contact with the developing roller 11 in a counter direction (opposite direction at the contact surface) with respect to the rotation direction at a linear pressure of 30 g / cm. , The toner on the developing roller 11 is regulated to form the toner thin layer 12, and the amount of toner to be conveyed to the developing area (a position facing the drum) is regulated, and at the same time, an appropriate charge (-
20 μC / g).

The toner conveyed to the developing area is transferred from the developing roller 11 to the photosensitive drum 1 by the developing electric field generated by the developing bias applied between the developing roller 11 and the photosensitive drum 1.
It flies upward, adheres to the latent image on the photoconductor drum 1, and visualizes the latent image as a toner image. As the developing bias, a DC voltage of -500 V and an AC voltage of 2000 Hz and 2 kVpp are superimposed and used.

The toner conveying means 14 includes a toner conveying belt 15 as a belt member, a belt driving roller 16 as a first tension roller, and a tension roller as a second tension roller.
The toner T is conveyed toward the developing roller 11, and the toner is supplied to and stripped from the developing roller 11. In this embodiment, a tube-shaped belt member having an outer diameter of 30 mm, a width of 240 mm, and a thickness of 300 μm, which is made of an elastic member such as urethane elastomer, is used as the toner conveying belt 15.

Belt drive roller 16 and tension roller
17 is made of φ5 mm SUS and has an outer diameter φ
It has a structure in which an elastic layer of NBR, EPDM, urethane rubber, CR or the like is formed so as to be 8 mm, and the shafts are positioned so as to stretch and stretch the belt circumference by 5%,
Bearing in parallel with the longitudinal direction of the developing roller 11,
It is arranged. Belt drive roller 16 is 20 g / cm
The developing roller 11 is brought into contact with the developing roller 11 by the contact pressure, and is rotationally driven in the counter direction as shown by an arrow a with a peripheral speed difference of 78% with respect to the developing roller 11 by a drive gear (not shown). .

As a result, the toner carrying belt 15 and the tension roller 17 are driven to rotate, and the toner is carried through the toner supply path A and supplied to the sliding portion between the developing roller 11 and the toner carrying belt 15. At the rubbing portion, the toner conveyed on the toner conveying belt 15 is frictionally charged and applied (supplied) to the developing roller 11 by the image force of the toner itself. At the same time, the toner that has not been used for development in the developing area is peeled off from the developing roller 11 by the sliding friction between the developing roller 11 and the toner conveying belt 15,
The toner is conveyed along the toner stripping path B formed by 15.
In this way, after reaching the rear of the developing container in the opposite direction to the developing roller 11 in the developing device 2, the toner supply path A
As shown in FIG.
The toner circulation shown by the middle broken line is formed.

Further, in this embodiment, the developing roller 11 is made to invade and come into contact with the toner carrying belt 15 so that the contact area between the toner carrying belt 15 and the developing roller 11 becomes larger.

That is, as shown in FIG.
The angle θ formed by the line connecting the centers of 11 and the belt driving roller 16 and the line connecting the centers of the belt driving roller 16 and the tension roller 17 is set to 75 ° (acute angle). Also,
The developing roller 11 is configured such that the intrusion amount d at the developing roller portion is 2 mm with respect to the belt conveying surface on the upstream side of toner conveying.

With this structure, the contact portion between the toner conveying belt 15 and the developing roller 11 is a belt driving roller.
It is possible to form a portion that is backed up and abutted by 16 and a portion that is abutted by the tension of the toner conveying belt 15, and the toner conveying belt 15 and the developing roller 11 can be formed.
It is possible to increase the contact area of. For this reason,
In particular, the relative contact area of the developing roller 11 with the toner conveying belt 15 can be secured without increasing the peripheral speed ratio.

Therefore, even when the speed of the apparatus is increased, it is possible to obtain a sufficient toner supply / peeling ability without increasing the peripheral speed ratio, and a good image without image defects such as density unevenness can be obtained. It becomes possible to obtain.

Further, by forming a portion backed up by the belt driving roller 16 and abutting and a portion abutting by the tension of the toner carrying belt 15, the contact of the toner carrying belt 15 with the developing roller 11 can be improved.
Ability to make light contact on the upstream side (portion where toner supply force is required) and strong contact on the downstream side (portion where toner stripping force is required). Is improved.

If θ exceeds 110 °, a large contact area cannot be obtained, sufficient toner supply / peeling ability cannot be obtained, and when speeding up, uneven density or the like occurs. Problems due to defective images occur.
If θ is 10 ° or less, the amount of intrusion becomes too large depending on the conditions such as the roller diameter, and the toner conveying belt 15
The tension and the rotation torque of the are increased, and desired durability cannot be obtained.

FIG. 4 shows the results of the accelerated durability test of the developing device 2 of this embodiment. As Comparative Example 1, θ is 1
An example of the case of 50 ° is also shown. Here, as a condition of the accelerated durability test, condition 1: normal speed (process speed 9
0 mm / s, reference), Condition 2: When speeding up (process speed 150 mm / s), two conditions,
The developing device 2 was subjected to idle rotation durability (200 h), and the output image was evaluated.

As shown in FIG. 4, in Comparative Example 1, at the normal speed, there was no density unevenness even after the rotation durability.
A good image was obtained. However, when the speed is increased, the toner supply / peeling ability is insufficient, and image defects such as uneven density occur. On the other hand, the developing device 2 of this embodiment
In the case of using No. 2, good images without image defects such as density unevenness were obtained even after the rotation endurance in both Condition 1 and Condition 2.

(Second Embodiment) A second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 5 is an illustration of the developing device of the second embodiment. The same components as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.
The developing device of the present embodiment uses a toner conveying means 24 instead of the toner conveying means 14 of the developing device 2 of the first embodiment.

As shown in FIG. 5, the toner conveying means 24 of this embodiment is a belt driving roller as a first tension roller.
The toner transport belt 25 is stretched by three rollers, namely, a driven roller 27, a tension roller 28 as a second tension roller, and the tension roller 28 supports the belt by lifting it. . As a result, the contact area between the developing roller 11 and the toner conveying belt 25 can be widened, and the developing roller 11 and the toner amount regulating member can be widened.
13. Since a toner pool can be formed between the toner transporting means 24 and the toner transporting means 24, it is possible to more reliably supply and strip the toner to and from the developing roller 11. The toner carrying belt 25 is made of an elastic material such as urethane elastomer and has an outer diameter of 38 mm, a width of 240 mm, and a thickness of 3 mm.
A tube-shaped belt of 00 μm is used.

The belt driving roller 26, the driven roller 27, and the tension roller 28 are made of SUS having a diameter of 6 mm, and have NBR and EPD with an outer diameter of 12 mm on the outer circumference.
It has a structure in which an elastic layer such as M, urethane rubber, and CR is formed, is positioned so as to stretch and stretch the belt circumference by 10%, and is arranged by bearing in parallel with the longitudinal direction of the developing roller. There is.

The belt driving roller 26 is brought into contact with the developing roller 11 with a contact pressure of 20 g / cm, and a driving gear (not shown) has a peripheral speed difference of 73% with respect to the developing roller 11 in the drawing. As indicated by the arrow, it is driven to rotate in the counter direction.

Also in the present embodiment, the developing roller
The contact area of the toner transport belt 25 and the developing roller 11 is further increased by making the toner transport belt 11 intrude into contact with the toner transport belt 25. That is, the angle θ formed by the line connecting the centers of the developing roller 11 and the belt driving roller 26 and the line connecting the centers of the belt driving roller 26 and the tension roller 28.
Is arranged so as to be 70 °, and the intrusion amount d at the developing roller portion is 3 mm with respect to the belt conveyance surface on the upstream side of toner conveyance.

With this structure, the contact portion between the toner conveying belt 25 and the developing roller 11 is a belt driving roller.
It is possible to form a portion which is backed up and abutted by 26 and a portion which is abutted by the tension of the toner conveying belt 25, and the toner conveying belt 25 and the developing roller 11 can be formed.
It is possible to increase the contact area of. For this reason,
In particular, the relative contact area of the developing roller 11 with the toner conveying belt 25 can be secured without increasing the peripheral speed ratio.

Therefore, even when the speed of the apparatus is increased, it is possible to obtain a sufficient toner supply / peeling ability without increasing the peripheral speed ratio, and it is possible to obtain a good image without image defects such as density unevenness. It becomes possible to obtain. In the present embodiment as well, as a result of performing the accelerated durability test as in the first embodiment, a good image without image defects such as density unevenness was obtained even after the rotation durability.

(Third Embodiment) A third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 6 is an explanatory diagram of the developing device according to the third embodiment. The same components as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.
The developing device 2 of the present embodiment has a configuration in which the developing device of the first embodiment is tilted by 90 degrees and is a so-called developer assembly type developing device in which the toner conveying direction is the vertical direction.

In the toner conveying means 34 of this embodiment, as the toner conveying belt 35, an elastic member such as urethane elastomer is used as a base layer, and a cell-like void such as a sponge formed by foaming urethane / EPDM is formed on the surface layer. The two-layered structure in which the member having the above is formed is used. By using such a belt, the toner is retained in the cell-shaped voids,
The toner can be transported in the direction of gravity. The structure of the toner conveying belt may be used in the first and second embodiments.

By using the vertical developing device 2 as in the present embodiment, the width of the developing device 2 can be shortened and the device can be downsized even when image forming units of a plurality of colors are arranged as an image forming device. Is possible.

Also in this embodiment, the developing roller 11 is made to invade and come into contact with the toner carrying belt 35 so that the contact area between the toner carrying belt 35 and the developing roller 11 becomes larger. That is, the developing roller 11 and the first
The angle θ formed by the line connecting the center of the belt driving roller 36 as the stretching roller and the center of the belt driving roller 36 and the center of the tension roller 37 as the second stretching roller is 75 °.
Is arranged so that the intrusion amount d at the developing roller portion is 2 mm with respect to the belt conveyance surface on the upstream side of toner conveyance.

With such a configuration, the contact portion between the toner conveying belt 35 and the developing roller 11 is divided into a portion backed up by the belt driving roller 36 and abutting, and a portion abutting by the tension of the toner conveying belt 35. Can be formed, toner transport belt 35 and developing roller
It is possible to increase the contact area with 11. Therefore, the relative contact area of the developing roller 11 with the toner transport belt 35 can be secured without increasing the peripheral speed ratio.

Therefore, even when the speed of the apparatus is increased, it is possible to obtain a sufficient toner supply / peeling ability without increasing the peripheral speed ratio, and a good image without image defects such as density unevenness can be obtained. It becomes possible to obtain.

Further, as the toner conveying belt 35, a two-layered member having an elastic member such as urethane elastomer as a base layer and a member having cell-like voids such as sponge formed by foaming urethane and EPDM on the surface layer is formed. The belt driving roller 36 and the developing roller 11
Due to the change in the cell diameter due to the extension of the toner conveying belt 35 in the part, the effect of supplying / peeling the toner becomes larger.

Also in this embodiment, as a result of performing the accelerated durability test in the same manner as in the first embodiment, a good image without image defects such as density unevenness was obtained even after the rotation durability.

(Other Embodiments) In the above-mentioned embodiments, a four-color printer is exemplified as the image forming apparatus, but the present invention is not limited to this, and the present invention may be applied to a copying machine or a facsimile machine. .

[0050]

As described above, in the present invention, the line connecting the center of the developer carrying member and the center of the first tension roller,
Since the angle θ formed by the line connecting the first tension roller and the second tension roller satisfies the relationship of 10 ° <θ <110 °, the contact area of the developer carrier with the belt member is increased. Since it can be ensured, the supply / peeling ability of the developer can be improved without particularly increasing the peripheral speed ratio. Therefore, even when the speed of the apparatus is increased, the supply of the developer does not become insufficient, and a good image without image defects such as uneven image density can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an image forming apparatus.

FIG. 2 is an explanatory diagram of the developing device according to the first embodiment.

FIG. 3 is an enlarged view around a developer carrier.

FIG. 4 is a diagram showing a result of an accelerated durability test of a developing device.

FIG. 5 is an explanatory diagram of a developing device according to a second embodiment.

FIG. 6 is an explanatory diagram of a developing device according to a third embodiment.

FIG. 7 is an explanatory diagram of a conventional developing device.

[Explanation of symbols]

A ... Toner supply path B ... Toner stripping path P ... Transfer material S ... Power supply T ... Toner d ... Intrusion amount 1 ... Photosensitive drum 2 ... Developer 3 ... Charging roller 4 ... Cleaning means 5 ... Laser scanner 6 ... Intermediate transfer belt 7 ... Secondary transfer roller 8 ... Fixing device 10… Toner container 11… Developing roller 12 ... Toner thin layer 13 Toner amount control member 14 ... Toner transporting means 15 Toner transport belt 16… Belt drive roller 17… Tension roller 24 ... Toner transporting means 25… Toner transport belt 26… Belt drive roller 27 ... driven roller 28… Tension roller 34 ... Toner transporting means 35 ... Toner transport belt 36… Belt drive roller 37… Tension roller

Claims (5)

[Claims] 1. A developer transport means for transporting a developer by a belt member stretched between a plurality of rollers, and bringing the belt member into contact with a developer carrier to supply the developer. Of the rollers, the roller abutting on the developer carrying member is a first tension roller, and the roller located upstream of the first tension roller in the moving direction of the belt member is a second tension roller, An angle θ formed by a line connecting the center of the developer carrier and the center of the first tension roller and a line connecting the first tension roller and the second tension roller is 10 ° <θ. <110 °, a developer conveying means characterized by satisfying the relation of <110 °. 2. The developer carrying means according to claim 1, wherein the belt member is composed of an elastic member having a cell-shaped void. 3. The developer carrying means according to claim 1, wherein the belt member is carried in a vertical direction. 4. A developer container for accommodating a developer, a developer carrier for supplying the developer onto the image carrier, and a developer transport means for transporting the developer onto the developer carrier. A developing device having: a developing device characterized in that the developer carrying means has any one of the features of claims 1 to 3. 5. An image forming apparatus comprising: an image bearing member; and a developing unit for supplying a developer onto the image bearing member to form a toner image, wherein the developing unit is the developing unit according to claim 4. An image forming apparatus characterized in that there is.