JP3358643B2 - Developing device and image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus and a developing apparatus using a one-component toner.

[0002]

2. Description of the Related Art In general, in an electrophotographic image forming apparatus, if a one-component toner can be used as a developer, the size of the developing apparatus and the size of the entire apparatus can be reduced, and maintenance is basically required. It is known that it has an advantage that it is unnecessary. On the other hand, the reliability is low and it is difficult to uniformly charge the toner.
Further, there is a problem that toner charged to a polarity opposite to a desired charging polarity is generated, and the oppositely charged toner adheres to a background portion of the recording paper, thereby causing background staining.

[0003] As a means for solving this problem,
Conventionally, there is a technique described in Japanese Patent Application Laid-Open No. 61-34557, in which a charged one-component high-resistance toner is transported by a first toner transport unit, and the toner is transferred onto a second toner transport unit. A technique is disclosed in which the toner is transferred and adhered by an electric force, and the toner is transported to the image carrier by the second toner transport unit.

Japanese Patent Application Laid-Open No. 61-34557 discloses the first
A roller member is applied as the toner conveying means, a belt member is applied as the second toner conveying means, and a drum member is applied as the image carrier, and the second toner conveying means is provided between the first toner conveying means and the image carrier. A configuration is disclosed in which means are disposed in contact with respective surfaces. Further, recently, it has been considered that the image carrier and the first toner conveying means are formed of a hard material, and the second toner conveying means is formed of a roller body made of a soft material, thereby achieving further miniaturization. I have.

[0005]

Incidentally, it is necessary to form a toner layer with uniformly charged toner on a toner carrier (corresponding to the first toner conveying means and the second toner conveying means) of the developing device. However, in order to perform uniform charging, the toner amount cannot be increased too much. Also, if the linear velocity ratio between the toner carrier and the image carrier is increased in order to increase the amount of toner supplied to the image carrier, the return force at the contact point becomes too large, or the friction of the toner with the image carrier is increased. Problems such as soiling due to charging or the like are likely to occur.

[0006] Even when the toner is frictionally charged by bringing the blade-shaped toner amount regulating member into contact with the toner carrier, or when the toner is charged by charge injection, the amount of uniformly charged toner (the amount of toner on the toner carrier) is reduced. Since there is a limit to the amount of toner per unit area), even if the toner is uniformly charged, the amount of toner on the first toner conveying means and the amount of toner required on the image carrier are not always the same. Absent.
If the limit is exceeded, the proportion of toner charged to the opposite polarity may increase.

Therefore, at present, it is necessary to design the balance between "the amount of toner on the toner carrier" and "the linear velocity ratio between the toner carrier and the image carrier". A good image was not always formed.

The same can be said for a so-called two-stage developing system, such as the technique described in Japanese Patent Application Laid-Open No. 61-34557, in which a toner having a desired thickness is provided to the second toner conveying means. There is a predetermined linear velocity difference between the first toner conveying means and the second toner conveying means for forming a layer,
In addition, there is often a slight difference in the linear velocity between the second toner conveying means and the image carrier, so that a contact portion between the two is subjected to stress due to the difference in the linear velocity. In particular, the first
In the case of a system in which the and the second toner conveying means come into contact with each other and rotate in the opposite direction (counter) at the contact point,
The stress applied to the contact portion is large.

In the case where the image carrier and the first toner conveying means are made of a hard material and the second toner conveying means is made of a roller made of a soft material, as shown in FIG. Toner adhesion area W on conveyance roller 50
The stress applied to the second toner transport roller 51 is large at the boundary between the first toner transport region 51 and the non-toner-attached region W2. In particular, the second
When the toner conveying roller 51 is coated, the hardness of the coating layer 52 is often higher than that of the base roller, so that the toner adhering area W1 and the non-toner adhering area W2 of the first toner conveying roller 50 Cracks are likely to occur in the coating layer 52 on the second toner transport roller 51 that contacts the boundary portion. Further, the second toner conveying roller 51
At the end of the base roller 53, the amount of deformation of the base roller 53 is large, so that the coating layer 52 cannot completely follow the deformation of the base roller 53, and the end of the coating layer 52 tends to peel or crack. When the second toner conveying roller contacts and rotates in the opposite direction (counter) at the contact point, the degree is likely to be severe.

Further, if the edge of the second toner conveying roller is square, stress concentrates on the edge, and the edge tends to be deformed, and peeling and cracking are easily generated from the end.

Further, when the first and second toner conveying rollers are pressed against each other, the shaft is bent, so that the bite amount at the end portion becomes larger than at the center portion. Therefore, if the bite amount at the central portion is adjusted to a standard value, the bite amount at the end portion becomes more than necessary, and the stress increases by that amount, so that peeling and cracking tend to occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to prevent chipping of an end portion of a second toner conveying roller and peeling of a coating layer, and to prevent occurrence of an abnormal image due to the chipping. It is an object of the present invention to provide a developing device and an image forming apparatus that realize the above.

[0013]

To SUMMARY OF THE INVENTION To achieve the above object, the present invention includes a first toner conveying roller, the first toner
ー Along with thinning the one-component toner on the transport roller
The one-component toner on the first toner transport roller is transferred and adhered to the doctor blade to be frictionally charged, and the first toner transport roller and the image carrier are brought into contact with each other. A developing device provided with a second toner conveying roller for developing an electrostatic latent image;
The width of the contact portion between the toner transport roller and the first toner transport roller is within a range narrower than the width of the toner-attached portion on the first toner transport roller.

Further, characterized in that chamfered end of the previous SL second conveying roller.

Further, prior Symbol second conveying roller, wherein the diameter of the central portion is larger than the diameter of the end portions.

Further, the image forming apparatus is provided with an image carrier for carrying an electrophotographic electrostatic latent image on a surface thereof, and a developing device having the above-described configuration for supplying a one-component toner to the image carrier. It is characterized by the following.

[0017]

According to the above construction, the width of the contact portion between the second toner transport roller and the first toner transport roller is within a range narrower than the width of the toner adhering portion on the first toner transport roller. The second toner conveying roller does not contact the boundary between the toner adhering area and the non-toner adhering area on the toner conveying roller.

Further, since the end of the second toner conveying roller is chamfered, distortion at the end can be reduced.

Since the center of the second toner conveying roller is larger than the both ends, the second toner conveying roller and the first toner conveying roller are separated from each other.
When the second toner transport roller is brought into contact with the toner transport roller, the bite amount at the center and the end of the second toner transport roller becomes more uniform.

Further, by applying the developing device, it is possible to prevent the reversely charged toner from adhering to the image carrier and to prevent the coating layer of the second toner transport roller from cracking or peeling off, which has an adverse effect on the image. Can be prevented.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a structural view showing a basic structure of an embodiment of an image forming apparatus according to the present invention, wherein 1 is a drum-shaped photosensitive member as an image carrier, and 2 is a charger for charging the surface of the photosensitive member 1. 3, an optical writing unit for exposing the charged photoreceptor 1 to form an electrostatic latent image, and 4, transferring and transferring a one-component toner to the electrostatic latent image to visualize the electrostatic latent image. 1 shows a developing device to be used. 5 is a developing roller which is a first toner conveying roller, 6 is an intermediate roller which is a second toner conveying roller,
Reference numeral 7 denotes a replenishing agitator that agitates the toner and sends the toner to the developing roller 5. Reference numeral 8 denotes a doctor blade that comes into contact with the developing roller 5 at a constant pressure, and these members are provided in the developing device 4. The configuration of the first to third embodiments of the developing device described later is applied to the developing device 4.

Further, 9 is a transfer unit for transferring a toner image onto recording paper, 10 is a cleaning unit for removing residual toner on the photoreceptor 1, and 11 is a device for removing charges on the photoreceptor 1 to remove the photoreceptor 1. 4 shows a static elimination lamp to be returned to an initial state. The developing roller 5 is formed of a hard roller body and a rubber layer covering the roller body. The intermediate roller 6 is formed of a soft member such as rubber. Form a dielectric coating layer (described later).

Next, the developing process will be described.

At the time of development, the developing roller 5 and the intermediate roller 6 rotate counterclockwise in the drawing, and the photosensitive member 1 rotates clockwise. Then, first, by the rotation of the replenishment agitator 7, the toner is carried right below the developing roller 5. The carried toner is a one-component developing magnetic toner and has magnetic powder, so that the toner is attracted to the surface of the magnetized developing roller 5 and is carried. Thereafter, the toner on the surface of the developing roller 5 is thinned by the doctor blade 8 made of metal and is triboelectrically charged to have a negative charge.

Further, since the surface potential of the intermediate roller 6 is higher than the surface potential of the developing roller 5, the toner on the surface of the developing roller 5 which is negatively charged is removed at the contact portion between the intermediate roller 6 and the developing roller 5. 6 is transferred. Furthermore, in the photoconductor 1, the portion charged by the charger 2 is lower than the surface potential of the intermediate roller 6, and the portion of the electrostatic latent image formed by the optical writing unit 3 is the surface of the intermediate roller 6. It is higher than the potential. Therefore, the toner on the surface of the intermediate roller 6 is selectively transferred and attached only to the portion of the electrostatic latent image, and a toner image is formed on the surface of the photoconductor 1. Even if the positively charged toner exists on the surface of the developing roller 5, the positively charged toner may not transfer to the intermediate roller 6 because the surface potential of the intermediate roller 6 is higher than the surface potential of the developing roller 5. Absent.

Then, the toner image formed on the photoreceptor 1 is transferred to a recording sheet by a transfer unit 9 and, after being thermally fixed, the recording sheet is discharged outside.

FIG. 2 is a plan view showing a main part of the first embodiment of the developing device of the present invention. FIG. 3 is a side view of FIG. 3 shows a toner seal that has been used. The toner seal 12 is in sliding contact with both ends of the developing roller 5 when the developing roller 5 rotates, thereby restricting the movement of the toner carried by the developing roller 5 in the axial direction, thereby preventing toner leakage.

In FIG. 2, W indicates the width of the toner adhering area in the axial direction of the developing roller 5, and L indicates the axial width of the intermediate roller 6. At this time, there is a relation of W> L between the width W and the width L, and a non-contact portion h is provided between both ends of the toner adherable area and both ends of the intermediate roller 6.
There is. In FIG. 3, d indicates the amount of biting of the intermediate roller 6 into the developing roller 5.

A running test was performed on the first embodiment of the developing device having the above-mentioned configuration using a 10% image area ratio chart under the following setting conditions.

First, as the developing roller 5, a hard roller having a diameter of 16.0 mm and a width W of 270.0 mm was used. The intermediate roller 6 has a diameter of 20.0 mm, a width L of 268.0 mm, and a hardness (JIS A) of 7 mm.
An elastic roller whose surface was coated with fluorine at 0 ° was used, and the non-contact portion h was 1.0 mm. Further, the photoconductor 1
A 30.0 mm diameter aluminum tube was used.

The linear velocity of the developing roller 5 is 228 mm / sec.
The linear speed of the intermediate roller 6 is 74 mm / sec in the counter direction at the contact portion with the developing roller 5, and the linear speed of the photosensitive member 1 is 68 mm in the forward direction with the intermediate roller 6 at the contact portion with the intermediate roller 6.
/ sec, and the bite amount d was 0.35 mm.

For comparison, a developing roller having a width W of 275.0 mm and an intermediate roller having a width L of 275.0 mm were prepared.
The test was also performed without the non-contact portion h.

As a result, when the non-contact portion h was not provided, cracks A were generated in the coating layer when the number of sheets was about 4,000 as shown in FIGS. 4 (a) and 4 (b). On the other hand, when the non-contact portion h was provided, cracks occurred when about 20,000 sheets were formed.

As described above, according to the first embodiment, the life of the intermediate roller 6 is increased about five times.

FIG. 5 is a structural view of an intermediate roller according to a second embodiment of the developing device, FIG. 6 is an enlarged view of a main part of FIG. 5, and 16 indicates an intermediate roller according to the second embodiment. As shown in FIGS. 5 and 6, in the second embodiment, both ends of the intermediate roller according to the developing device of the first embodiment are chamfered C (chamfer surface 5.0 mm). As shown in FIG. 6, the chamfer angle θ is 0 <θ <
It is set in the range of 90 °.

A test was carried out on the second embodiment of the developing device thus constructed under the same conditions as the test in the first embodiment. As a result, about 27,000 sheets were cracked.

FIG. 7A is an explanatory view showing the pattern of the toner layer at the end when the chamfer is not applied, and FIG. 7B is an explanatory view showing the pattern of the toner layer at the end when the chamfer is applied. It is. As shown in FIG. 7, a pattern with a pitch of 0.3 mm was formed in both cases, but when no chamfer was applied, a flow pattern of about 1.0 mm was formed between 3.0 mm from the end, 2.0mm from the edge if chamfered
It can be seen that a fine flow pattern is formed between them, and the pattern of the toner layer when no chamfering is performed is distorted compared to the case where chamfering is performed. That is, when the chamfering is not performed, when the intermediate roller 16 comes into contact with the developing roller 5, the stress concentrates on the end portion and the end portion is deformed. On the other hand, when the chamfering is performed, the end portion is deformed. Since such stress is dispersed, the amount of deformation at the end is reduced. As a result, it is considered that the chamfering reduced the stress applied to the coating layer and suppressed the occurrence of cracks.

According to the second embodiment of the developing device, a straight chamfer C is formed at the end, but a curved chamfer may be used.

FIG. 8 is a structural view showing an intermediate roller of a third embodiment of the developing device, and FIG. 9 is an enlarged sectional view of a main part of FIG. As shown in FIG. 8, the intermediate roller 26 of the third embodiment has a so-called spindle shape in which the diameter at the center is larger than the diameter at both ends, and has a diameter of 20.0 mm at both ends. It is designed as 20.2mm in diameter. Also, as shown in FIG. 9, the intermediate roller 26 includes a rotating shaft 26a having a diameter of 10.0 mm,
A cylindrical base soft roll 26b attached to the rotating shaft 26a, an intermediate layer 26c composed of an electrode layer that covers the soft roll 26b and has a spindle shape, and a coating layer 26d formed on the surface of the intermediate layer 26c Consists of

A test was conducted on the third embodiment of the developing device thus constructed under the same conditions as those in the first embodiment of the developing device described above. As a result, cracks began to form in about 30,000 sheets.

By the way, in the third embodiment, the developing roller 5
Is designed to have a diameter of 14.0 mm, so that the rotating shaft 26a of the intermediate roller 26 is easier to bend.
Then, when the intermediate roller 26 was simulated and pressed against a test metal flat plate with a load of 700 gf on one side, the contact portion was observed.
As shown in Figure 10.

FIG. 10 (a) is an observation of a contact portion between a metal flat plate and a cylindrical intermediate roller having a diameter of 20.0 mm.
(b) shows a metal plate and the intermediate roller 26 of the third embodiment of the developing device.
This is a result of observing a contact portion with the substrate. As shown in FIG. 10 (a), at the contact portion of the cylindrical intermediate roller, the center is about 2.0 mm, and the end is about 5.0 mm to 5.5 mm, and the difference is 2.0 mm.
mm to 3.5 mm. The range of the distortion is about 40.0 mm on one side. On the other hand, in the contact portion of the intermediate roller according to the third embodiment of the developing device, the central portion is approximately 2.5 mm, and the end portion is approximately 3.0 mm.
3.5 mm, and the difference is 0.5 mm to 1.0 mm. The range of the distortion is about 30.0 mm on one side.

As described above, it has been found that the degree and range of deformation of the intermediate roller are reduced by forming the spindle shape as in the third embodiment. Therefore, the third of the developing device
According to the embodiment, it is considered that the occurrence of cracks was suppressed because the contact between the developing roller and the intermediate roller became more uniform.

In the third embodiment of the developing device, the intermediate layer
Although the spindle shape is obtained by changing the thickness of 26c, the spindle shape may be obtained by changing the thickness of the soft roll 26b and the coating layer 26d in some cases. Further, the first to third embodiments of the developing device exemplify only one or only a combination of the two.
If the first to third embodiments of the developing device are performed at the same time, it is considered that the effect is further improved.

[0046]

Effect of the Invention] According to the present invention according to claim 1-4, wherein configured as described, by preventing peeling and chipping at both ends of the second conveying roller, abnormal The occurrence of an image and the occurrence of a developing bias defect can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a basic configuration of an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a plan view showing a configuration of a main part of the first embodiment of the developing device.

FIG. 3 is a side view of FIG. 2;

FIG. 4 is an explanatory diagram illustrating peeling that has occurred at both ends of a developing roller.

FIG. 5 is a configuration diagram of an intermediate roller according to a second embodiment of the developing device.

FIG. 6 is an enlarged view of a main part of FIG. 5;

FIG. 7 is an explanatory diagram illustrating a pattern of a toner layer at an end of a developing roller.

FIG. 8 is a configuration diagram illustrating an intermediate roller according to a third embodiment of the developing device.

FIG. 9 is an enlarged sectional view of a main part of FIG. 8;

FIG. 10 is an explanatory view showing a contact portion between a test metal flat plate and a cylindrical intermediate roller.

FIG. 11 is an explanatory diagram including a partial cross section showing a boundary between a toner-attached region and a non-toner-attached region in the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Charger, 3 ... Optical writing unit, 4 ... Developing device, 5 ... Developing roller, 6, 16, 26
... Intermediate roller, 7 ... Replenishment agitator, 8 ... Doctor blade, 9 ... Transfer unit, 10 ... Cleaning unit, 11
... static elimination lamp, 12 ... toner seal, 26a ... rotating shaft,
26b… Soft roll, 26c… Intermediate layer, 26d… Coating layer.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Iwao Matsumae 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Yoshiro Tanaka 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Hiroshi Hosokawa 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Inside the Ricoh Co., Ltd. (72) Unjigi Jiro 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Hiroshi Saito 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Eiji Takenaka Company, 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Inside Ricoh (72) Inventor Tetsuo Yamanaka 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Inside Ricoh (72) Eisai Murakami 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Inside the Ko (72) Inventor Satoru Komatsubara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-6-175477 (JP, A) JP-A-2-37378 (JP) JP-A-4-336561 (JP, A) JP-A-2-136256 (JP, U) JP-A-2-89454 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB (Name) G03G 15/08

Claims (4)

(57) [Claims] A first toner conveying roller and a first toner
ー Along with thinning the one-component toner on the transport roller
The one-component toner on the first toner transport roller is transferred and adhered to the doctor blade to be frictionally charged, and the first toner transport roller and the image carrier are brought into contact with each other. A developing device provided with a second toner conveying roller for developing an electrostatic latent image;
A developing device, wherein a width of a contact portion between the toner transport roller and the first toner transport roller is within a range smaller than a width of a toner adhering portion on the first toner transport roller. 2. A pre-Symbol developing apparatus according to claim 1, characterized in that chamfered end of the second conveying roller. 3. A pre-Symbol second conveying roller is also claim 1 diameter of the central portion being greater than the diameter of the end portions
Is a developing device according to 2 . 4. An image carrier having an electrophotographic electrostatic latent image on a surface thereof, and a developing device according to claim 1, 2 or 3 for supplying a one-component toner to the image carrier. An image forming apparatus characterized in that: