JP2002014527A - Developing device in image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image without any fogging or toner scattering by preventing any stagnation or excessive feeding of developer by reliably carrying out scooping-up of the developer from the lower side to the upper side in a developer agitating and carrying means that are installed in two places, the top and the bottom. SOLUTION: In a developing device that is a rotating body provided with an even number of magnetic poles and a developer scooping-up means arranged in a direction of a periphery, a relationship between a magnetic force A (10-4T) of each pole of the developer scooping-up means and circumferential speed B (mm/sec) is 72,000<=A.B<=300,000. The developing device is installed in an image forming device.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an image forming apparatus such as a copying machine and a printer.

2. Description of the Related Art In a developing apparatus which performs development by supplying a developer consisting of two components, a toner and a carrier, to an electrostatic latent image carrier, the toner and the carrier are stirred by stirring the toner and the carrier in a developing housing. There is known a developer agitating means for mixing and friction-charging and conveying in a predetermined direction. 2. Description of the Related Art In recent years, there has been a high demand for space saving in image forming apparatuses. In particular, in a four-tandem color copier and a color printer using a plurality of developing apparatuses, it is essential to reduce the size of the developing apparatuses. Japanese Patent Application Laid-Open No.
No. 142942 discloses a developer supply means for supplying a developer to an electrostatic latent image carrier, and a first stirring and conveying means provided near the developer supply means for stirring and conveying the developer in a first direction. Means, a second stirring and conveying means provided below the first stirring means for stirring and conveying the developer in a second direction opposite to the first direction, and coaxial with the developing supply means. And a feeding unit that is driven in accordance with the driving of the developing supply unit and sends the developer conveyed by the second stirring and conveying unit to the first stirring unit. A second rotating sleeve different from the first rotating sleeve and having a magnetic pole for attracting the developer by a magnetic force; and rotating the developer conveyed by the second stirring and conveying means to rotate the second rotating sleeve. Feed to the first stirring and conveying means What is stage it is disclosed.

However, even the developing device disclosed in the above publication is not sufficient in terms of stagnation of the developer and downsizing of the device. In particular, the magnetic strength of the magnetic poles provided in the second rotating sleeve that pumps and supplies the developer from the lower second stirring / conveying means to the upper first stirring / conveying means depends on the developer conveyance. The contribution is large and has a large effect on image quality. The present invention relates to a developing device of a vertical stirring / transporting means having a first stirring / transporting means and a second stirring / transporting means above and below. An object of the present invention is to obtain a stable and high-quality developed image by pumping a developer without stagnation and oversupply.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a developing sleeve which rotates while bearing a developer, facing a latent electrostatic image bearing member, and a vicinity of the developing sleeve. A first stirring / conveying means provided for stirring and conveying the developer; and a developer provided at a lower end of the first stirring / conveying means in a conveying direction of the developer provided below the first stirring / conveying means. A second agitating means for receiving the developer, agitating and conveying the developer, and supplying the developer to the developing sleeve; and a second agitating means provided substantially at the center in the height direction of the first agitating means and the second agitating means. In the developing device having the developer pumping means for receiving the developer at the downstream portion in the developer conveyance direction and supplying the developer to the first stirring means, the developer pumping means has an even number of magnetic poles provided in the circumferential direction. Rotating body, on top of developer Relationship of the magnetic force A of each pole (10 ^-4 T) and the peripheral speed B (mm / sec) of the means, 72000 ≦ A ·
B ≦ 300,000 (claim 1). The magnetic force A of each pole of the developer pumping means
(10 ⁻⁴ T) ^satisfies 500 ≦ A ≦ 1200 (Claim 2) Further, since the developer pumping means is a rotating body having a magnetic pole and a sleeve is not provided around the rotating body, The length in the width direction can be reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The developing device according to the present embodiment will be described taking a developing device using Carlson electrophotography as an example. Since the entire configuration is already well-known, the developing device according to the present invention is illustrated in FIG. Exposure means, cleaning means, etc. are not shown. FIG. 1 shows a developing device according to an embodiment of the present invention, and is a view of the developing device as viewed from above. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a sectional view taken along line BB in FIG. The developing device 30 includes the developing housing 1
The developing sleeve 14 is provided at the leftmost portion in FIG.
6 are arranged. The developing sleeve is made of a non-magnetic material such as aluminum, and has a magnet material 150 disposed therein. Next, the developer stirring / conveying means is composed of a first stirring / conveying means 68 and a second stirring / conveying means 70 provided immediately below the first stirring / conveying means 68. The stirring and conveying means has spiral blades formed in the axial direction of the rotation shaft, and conveys the developer in a predetermined direction while stirring. In particular, the second stirring and conveying means is disposed in the developing housing so as to face the developing sleeve, and supplies the developer over the entire area of the developing sleeve in such a manner that the developer is attracted by the magnetic force of the developing sleeve. Next, the developer pumping means 82 will be described. As shown in FIG. 3, the developer pumping means 82 is located substantially at the center in the vertical direction of the first stirring / transporting means and the second stirring / transporting means, and to the right of the first stirring / transporting means and the second stirring / transporting means. It is arranged. The developer pumping roller 86 is made of a magnetic material. N poles and S poles are alternately arranged in the circumferential direction, and a total of eight poles are magnetized over the entire area in the axial direction. The length of the pumping roller is 15 to 50 mm, preferably 20 to 30 mm. The feature of the present invention is that, in order to prevent the developer stress caused by the developer remaining or lacking on the agitating / conveying means and the developing sleeve, the magnetic force A of each pole of the developer pumping means is firstly determined. And the peripheral speed B are set so that 72000 ≦ A · B. Table 1 shows the relationship between the relational expression, image fogging, toner scattering outside the apparatus, image density, and the like. The experiment was confirmed by using a tandem type color printer and printing up to 1000 sheets of A4 size PPC paper at a rate of 26 sheets / min.
The developer used at this time uses polyester as a binder, contains a colorant and other additives, and has toner particles having a center particle size of 8.5 μm and a core material having a center particle size of 8.5 μm as a magnetic material.
A carrier using 0 μm ferrite particles was adjusted at a toner concentration of 4% by weight. The length of the pumping roller was 27 mm.

[Table 1] In the table, “developer blowing” refers to a state in which the developer overflows from the weak magnetic portion at the end of the developing sleeve to the outside of the developing device. In this experiment, since the amount of developer pumped by the developer pumping means was insufficient, the developer was retained on the developer pumping means side of the second stirring and conveying means, and the magnetic force of the end of the developing sleeve on the developer pumping means side was increased. Some of the developer overflowed from weak areas. Further, "image fogging" is a defect in which insufficiently charged toner adheres to a non-image portion, and "toner scattering" refers to a state in which the toner adheres to a conveyance path other than an image. In this experiment, there was a case where the toner was not sufficiently stirred due to the stagnation of the developer, resulting in insufficient charging. Since the image density is maintained at a higher level, there is no problem with the image density itself, but the image portion is more prominently raised than the non-image portion, resulting in poor overall image quality. Further, if the toner is used more than necessary, the amount of consumed toner increases, which leads to a problem that the user is not economical. "Toner aggregation" means that when the stress on the developer increases due to the stagnation of the developer, the fluidity of the toner deteriorates,
This causes the toner to clump. From the results shown in Table 1, by setting the magnetic force A and the peripheral velocity B of each pole as described above, pumping is performed without stagnation,
It can be understood that there is no fogging due to the stagnation of the developer in the first stirring / transporting means and the developing sleeve, and an image having a high image density is obtained. Note that the value of the toner blowing from the developing sleeve and the aggregation of the toner in the first stirring and conveying means can be reduced to 69000 ≦ A · B. However, the above-described evaluation cannot be performed as a whole due to image fogging and toner scattering. is there. As the second feature of the present invention,
The relationship between the magnetic force A and the peripheral speed B of each pole of the developer pumping means is set so as to satisfy 300,000 ≧ A · B. Table 2 shows the relationship between the relational expression and the fog in the image, the scattering of the toner outside the apparatus, the image density, and the like. The experiment was performed as described above.

[Table 2] In this experiment, since the pumping amount is large, the developer does not stay in the second stirring and conveying means, and the developer does not blow out. With respect to image fogging and toner scattering, the deterioration of the developer is promoted by reducing the amount of the developer in the second stirring and conveying means. As a result, the toner was not sufficiently charged, and image fogging and toner scattering occurred. The image density cannot be maintained because the supply amount of the developer to the developing sleeve is insufficient. Regarding toner aggregation, the pumped-up developer stayed in the first stirring / conveying unit, and the stress on the toner was increased, resulting in an aggregation state.
Therefore, the magnetic force A and the peripheral velocity B of each pole are set to 300000 ≧ A ·
By setting B, the developer is conveyed without excessive pumping, that is, without shortage of the developer in the first stirring / conveying means and the developing sleeve. Therefore, the pumping means and the second stirring / conveying means are used. The image density can be maintained without causing aggregation of the toner in the means. No fog or toner scattering due to deterioration of the toner is observed. From these experiments, the magnetic force A
72000 ≦ A · B ≦ 300,000
However, when focusing only on the magnetic force, 400 ≦ A
An effective value is obtained when ≦ 1600 (10 ⁻⁴ T). Also,
It is desirable to control the speed or set the magnetic force distribution so as not to apply an excessive stress to the developer that causes deterioration of the developer at the time of pumping. Therefore, considering the condition that the peripheral speed of the developer pumping roller is not increased and the magnetic force is not increased, the value of the magnetic force A is 500 ≦ A
≦ 1200 (10 ⁻⁴ T) is preferred.

As described above, according to the present invention, the developer is pumped up from the downstream in the transport direction of the second stirring and transporting means without staying and oversupplying by the developer pumping means and sent to the first stirring and transporting means. This makes it possible to obtain a high-quality developed image without fogging and toner scattering and stably maintaining an appropriate image density. Further, the developer pumping means is a rotating body having a magnetic pole, and the length in the width direction can be reduced because a sleeve is not provided around the rotating body.

[Brief description of the drawings]

FIG. 1 is an overall view of a developing device.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a sectional view taken along line BB in FIG. 1;

[Explanation of symbols]

 28: electrostatic latent image carrier 30: developing device 68: first stirring / conveying means 70: second stirring / conveying means 82: developer scavenging means 86: developer scavenging roller 144: developing housing 146: developing sleeve 150: Magnet material

Claims (2)

[Claims] A developing sleeve that is opposed to the electrostatic latent image carrier and carries the developer and rotates; a first stirring and conveying means provided near the developing sleeve for stirring and conveying the developer;
A second developer, which is provided below the first stirring and conveying means, receives the developer at the downstream end of the first stirring and conveying means in the conveying direction of the developer, stirs and transports the developer, and supplies the developer to the developing sleeve. A stirrer, and a developer that is provided at a substantially central portion in the height direction of the first stirrer and the second stirrer and receives the developer at a downstream portion in the developer conveyance direction by the second stirrer; in the developing device having a developer pumping means for supplying the stirring means, means scooping developer is a rotating body having an even number of magnetic poles provided in the circumferential direction, developer pumping force a of each pole means (10 ^{- 4} T) and peripheral speed B (mm
/ Sec) is 72000 ≦ AB × 30000
A developing device in the image forming apparatus, wherein 2. A magnetic force A of each pole of said developer pumping means.
The developing device according to claim 1, wherein (10 ⁻⁴ T) ^satisfies 500 ≦ A ≦ 1200.