JPH0887173A - Developing device - Google Patents

Abstract

PURPOSE: To improve the durability with respect to the secular change by relaxing a range limit of the gap amount between a developing roller and a doctor blade in the direction for reducing the gap amount. CONSTITUTION: The effective range of the gap position of the doctor blade 64 with respect to the developing roller surface is defined by the angle θ toward 1 second developer transporting electrode S1 from a first developer transporting electrode N2 based on the tangent direction magnetic flux density on the developing roller surface. In the concrete, the gap position is set on the position shifting in the range from the first developer transporting electrode N2 toward the second developer transporting electrode S1 from 3.5 deg. to 21 deg.. The range is equivalent to the extent between the position nearest to the first developer transporting electrode N2 where the minimum magnetic flux density in the developing roller tangent direction is 80 Gs and the position capable of transporting the developer of minimum necessary when the gap amount is set at 0.4mm. Thus, the range limit of the gap amount can be relaxed particularly in the direction for reducing the gap amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an electronic copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, a developing device used in an electronic copying machine or the like has a developing roller inside, and a layer of a developer having a uniform thickness (hereinafter referred to as a developing layer) is attached to the surface of the developing roller. After being formed, the developer is conveyed and supplied to the electrostatic latent image held on the surface of the photosensitive drum to develop the electrostatic latent image. The doctor blade is for uniformly forming a developing layer having a uniform thickness on the surface of the developing roller, and is formed by a gap (gap) provided between its tip and the surface of the developing roller (rotating sleeve). A developing layer having a thickness corresponding to the gap is formed on the surface of the developing roller by adhesion.

Usually, the gap amount is 0.4 mm to 0.5.
It has been proved by experiments that the thickness is mm, and if it is smaller than this value, the developer is insufficiently conveyed, and if it is larger, the developer is easily scattered during the conveyance. However, when considering the changes over time, it is necessary to secure the required margins for the upper limit value and the lower limit value of the gap amount, respectively, and the range that can be actually set as the gap amount is limited to a narrower range. . In addition, it is difficult at present to secure a sufficient margin because the range of the allowable gap amount itself is small.

[0004]

As described above, in the conventional developing device, the gap amount between the surface of the developing roller and the tip of the doctor blade is taken into consideration in consideration of the developer carrying ability and the scattering property during the carrying of the developer. It is set within a narrow range of 0.4 mm to 0.5 mm, and it is difficult to provide sufficient durability against aging, etc. as it is.

The present invention is intended to solve such a problem, and can limit the range of the gap amount between the surface of the developing roller and the tip of the doctor blade, particularly in the direction of reducing the amount of the gap. Accordingly, it is an object of the present invention to provide a developing device capable of improving durability against aging and the like.

[0006]

In order to achieve the above-mentioned object, the developing device of the first invention is a cylindrical magnet having a plurality of developer carrying poles and one developer peeling pole, and this cylindrical magnet. A rotor is rotatably arranged on the outer circumference of the magnet, and a magnetic field formed between the developer transport poles adjacent to each other causes a developer to adhere to the surface of the developer and transport the developer. A gap is provided between the surface of the rotor and the rotor. In a developing device having a developer layer forming member arranged to form a developer layer having a uniform thickness on the peripheral surface of the rotating body, the developer layer forming member rotates with respect to the developer peeling pole. The developer transport between the first developer transport pole adjacent to the predetermined rotation direction of the body and the second developer transport pole adjacent to the first developer transport pole in the predetermined rotation direction of the rotary body. The minimum magnetic flux density in the tangential direction of the rotor between the poles is the surface of the developer on the rotor. Shows a value that can satisfy adhere transport, is characterized in that formed by arranged with a gap position.

In order to achieve the above-mentioned object, the developing device of the second invention satisfies the range of 0.25 mm to 0.4 mm between the developer layer forming member and the surface of the rotating body, and
The developer layer forming member is adjacent to the developer peeling pole in the predetermined rotation direction of the rotating body, and is adjacent to the first developer transport pole in the predetermined rotation direction of the rotating body. The minimum magnetic flux density in the tangential direction of the rotating body between the developer conveying poles and the second developing agent conveying pole is such that the gap amount of the developer adhered to the surface of the rotating body is 0.25 mm to 0. It is characterized in that it is arranged with a gap at a position showing a value that can be satisfied under the condition of 0.4 mm.

In order to achieve the above-mentioned object, the developing device of the third invention is such that the developer layer forming member is located adjacent to the developer peeling pole in the predetermined rotation direction of the rotating body from the first developer carrying pole. It is characterized in that it is arranged with a gap provided at a position displaced by 3.5 ° to 21 ° in the predetermined rotation direction of the rotating body.

In order to achieve the above-mentioned object, the developing device of the fourth invention satisfies the range of the gap between the developer layer forming member and the surface of the rotary member of 0.25 mm to 0.4 mm, and
The developer layer forming member is located at a position displaced by 3.5 ° to 21 ° in the predetermined rotation direction of the rotating body from the first developer conveying pole adjacent to the developer peeling pole in the predetermined rotation direction of the rotating body. The feature is that they are arranged with a gap.

[0010]

That is, according to the present invention, the insufficient conveyance of the developer, which may be caused by reducing the gap between the developer layer forming member and the surface of the rotating body, can be considered as the magnetic flux density in the tangential direction of the rotating body between the developer conveying poles. Of 0.25 mm to 0.4 m, which is sufficient to prevent the scattering of the developer during conveyance by the above-mentioned gap amount.
It can be set in the range of m.

Further, the position of the gap where the minimum magnetic flux density in the tangential direction of the rotating body between the developer conveying poles satisfies the surface adhering and conveying of the developer on the rotating body is the first developer. This corresponds to a position in the range displaced by 3.5 ° to 21 ° in the predetermined rotation direction of the rotating body from the transport electrode, and in this range, the gap amount between the developer layer forming member and the surface of the rotating body is 0.25 mm to 0. 4m
It can be set in the range of m.

[0012]

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

FIG. 1 is a view showing the arrangement of a copying machine which is an image forming apparatus equipped with a developing device according to an embodiment of the present invention.

As shown in FIG. 1, this copying machine has a document table (transparent glass) 2 for placing a document on the upper surface of its main body.
1 is fixed. Below the document table 21, a lamp 22 that illuminates the document D, a reflecting plate 24 that condenses the illumination light generated from the lamp 22 onto the document D, and a second carriage 30 that reflects the reflected light from the document D to be described later. A first mirror 26 that reflects the light toward the front side, a first carriage 28 that is movable in parallel with the mounting table 21 by a pulse motor (not shown) via a toothed belt (not shown), etc. A second mirror 32 and a third mirror 34 for reflecting the reflected light from the document D reflected by the carriage 28 toward a photosensitive drum 40 described later, and a toothed belt (not shown) for driving the first carriage 28 are provided. Is driven by the first carriage 28 via
The second carriage 30 that is moved at a speed of 1/2 with respect to the first carriage 28 is arranged.

Further, the reflected light from the second carriage 30 is provided with a condensing property in the plane below the first carriage 28 and including the optical axis of the light reflected by the second carriage 30. At the same time, the moving lens itself forms an image of the reflected light at a predetermined magnification, and the reflected light is folded back toward a photosensitive drum 40, which will be described later.
A fourth mirror 38 that is movable along the optical axis by a driving mechanism (not shown) in order to form an image at a desired position on the photoconductor drum 40 and to correct the fluctuation of the focal length due to the movement of the imaging lens 36. Are arranged. still,
It goes without saying that the reflected light is a character or a figure written on the document D, that is, image information on the document D.

Under the image forming lens 36, that is, near the center of the copying machine, the light guided by the fourth mirror 38 is imaged to form a charge distribution pattern, that is, an electrostatic latent image. The drum 40 is arranged. Around the photoconductor drum 40, a charging device 42 for charging the photoconductor drum 40 with a predetermined electric charge and an electrostatic latent image formed on the photoconductor drum 40 are visualized by using toner. A developing device 44 and an AC voltage applying device 46a for separating the paper P from the photoconductor drum 40 are integrally provided, and a toner image formed on the photoconductor drum 40 is transferred from a paper feeding / discharging unit described later. A transfer device 46 for transferring the material, that is, the copy paper P, and a cleaning device 48 for removing the distribution of electric charges on the photosensitive drum 40 to return the charged state of the photosensitive drum 40 to the initial state and scraping off the residual toner in order. It is arranged. Needless to say, since the latent image formed on the photosensitive drum 40 is converted into a toner image via the developing device 44, the image information contained in the document D is copied as a toner image, and the paper image is printed. Is output on P.

On the right side of the copying machine, the photosensitive drum 40 is provided.
Material to be transferred, such as copy paper P, postcard, OH
Paper cassettes 50a and 50b for supplying P sheets and the like are inserted.

Left side of the copying machine, that is, the photosensitive drum 4
At a position corresponding to the downstream in the rotational direction at 0, an ejection tray 52a is arranged on which the image (toner image) formed on the photosensitive drum 40 is transferred and the fixed copied sheet P is stocked. . Inside the copier,
Between the photoconductor drum 40 and the paper cassettes 50a and 50b, the paper P from the paper cassettes 50a and 50b is further provided.
The first and second paper feed rollers 51a for pulling out one by one,
51b and a pair of conveying rollers 53a and 53b, respectively.
And feed paths 54a and 54b for feeding the paper P toward the photoconductor drum 40, the inclination of the paper P is corrected, and the leading end of the image formed on the photoconductor drum 40 and the leading end of the paper P. And a pair of timing rollers 5 for feeding the paper P at the same speed as the rotation speed of the photosensitive drum 40.
5 and 5 are arranged.

In addition, the copying machine includes a photosensitive drum 40.
A conveyance device 56 that conveys the sheet P on which the toner image formed thereon is electrostatically adhered and the toner is electrostatically attached, and a fixing device that melts and fixes the toner that is transferred to the sheet P. The device 58 and the paper P on which the toner image is fixed
Has a pair of discharge rollers 52 for discharging the sheet to the outside of the apparatus.

FIG. 2 is a diagram showing a detailed structure of the developing device 44.

In the figure, reference numeral 61 is a developing roller.
The developing roller 61 includes a cylindrical magnet 62 having a total of five poles, for example, a plurality of four developer carrying poles N2, S1, N1, S2 and one developer peeling pole N3, and an outer periphery of the magnet 62. A rotating sleeve 63 arranged coaxially with the magnet 62 and rotatable in the direction of the arrow.
It consists of and. A doctor blade 64 is a developer layer forming member for uniformly forming a developer layer having a uniform thickness on the peripheral surface of the rotary sleeve 63 of the developing roller 61. A predetermined gap is provided between the tip of the doctor blade 64 and the peripheral surface of the rotary sleeve 63. Further, 65 and 65 are mixers for stirring the developer in the developing device 44, and 66 is a sensor for detecting the toner specific concentration in the developing device 44.

In the developing device 44 having the above structure, the doctor blade 64 is the first roller on the developing roller 61.
N2 which is a developer carrying pole and S1 which is a second developer carrying pole
Are arranged so that the above gap is provided at a position between and. The gap position of the doctor blade 64 is in a range displaced from the position of the first developer carrying pole N2 by 3.5 ° to 21 ° toward the second developer carrying pole S1, and within this range, Developing roller 6
By setting the gap position with respect to 1, it becomes possible to relax the range limitation of the gap amount, particularly in the direction of decreasing the gap amount. The reason will be described below.

FIG. 3 is a diagram showing the relationship between the gap amount and the toner scattering level. As described above, in order to suppress toner scattering to an allowable level, it is necessary to set the gap amount to 0.5 mm or less. However, the gap amount is one of the factors that greatly influences the amount of developer conveyed by the developing roller, and if the gap amount is made too small, defective conveyance of the developer may occur.

Therefore, in the present embodiment, attention is paid to the fact that the magnetic flux density in the tangential direction on the surface of the developing roller at the above-mentioned gap position is another factor that influences the amount of developer conveyed,
Based on the magnetic flux density in the tangential direction on the surface of the developing roller, the effective range of the gap position is defined by the angle θ from the first developer carrying pole N2 to the second developer carrying pole S1.

Specifically, since the required minimum value of the magnetic flux density in the tangential direction of the developing roller capable of adhering the developer to the developing roller 61 is 80 gauss in this embodiment,
The effective range of the gap position is a position where the minimum magnetic flux density in the tangential direction of the developing roller from the first developer carrying pole N2 is 80 gauss (from the position of the first developer carrying pole N2 to the second developer). From the position rotated by 3.5 ° toward the transport pole S1), as shown in the fourth position, the minimum required developer transport is possible when the gap amount is set to 0.4 mm (first developer transport pole N2). From the position of the second developer carrying pole S
It is up to the position rotated by 21 ° toward 1). In addition, the mark ◯ in FIG. 4 is a point at which it has been confirmed by experiments that the developer transportability on the developing roller is good. Here, the reason that the minimum necessary developer transport position was selected when the gap amount was set to 0.4 mm was because the margin of 1 mm was secured against aging.

FIG. 5 is a diagram showing the effective range of the gap position on the magnetic flux density distribution on the surface of the developing roller. Here, the range from to is the range of the gap position of the doctor blade in the conventional example, and the range from to is the range of the gap position of the doctor blade in the present embodiment (from the first developer carrying pole N2 to the second developer). Transport pole S1
From 3.5 ° to 21 °). In this magnetic flux density distribution curve, the magnitude of the gradient indicates the magnitude of the magnetic flux density in the tangential direction of the developing roller, and the gradient of the magnetic flux density distribution curve in the range from to of this embodiment is from that of the conventional example. It can be seen that the magnetic flux density in the tangential direction of the developing roller is higher than the inclination of the magnetic flux density distribution curve in the range. Therefore, if the gap position is selected within the range up to this point, the insufficient conveyance of the developer due to the small gap amount can be effectively compensated for by the magnitude of the magnetic flux density, and further, the gap amount can be reduced, whereby the toner scattering can be prevented. The level can be within the allowable range.

[0027]

As described above, according to the developing device of the present invention, it is possible to prevent the developer from being insufficiently conveyed due to the small gap between the developer layer forming member and the surface of the rotary member. It can be compensated by the magnitude of the magnetic flux density in the tangential direction of the rotor between the poles, and the gap amount can be set within a range of 0.25 mm to 0.4 mm, which is sufficient to prevent scattering of the developer during conveyance. As a result, the range limitation of the gap amount can be relaxed, especially in the direction of decreasing the gap amount, and thus durability against aging etc. can be improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a copying machine that is an image forming apparatus including a developing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed configuration of a developing device in the image forming apparatus of FIG.

FIG. 3 is a diagram showing a relationship between a gap amount between a doctor blade and a developing roller and a toner scattering level.

FIG. 4 is a diagram showing a range limitation of a gap position in the present embodiment.

FIG. 5 is a diagram showing an effective range of a gap position in the present embodiment on a magnetic flux density distribution on the surface of the developing roller.

[Explanation of symbols]

61 ... Developing roller, N2 ... First developer carrying pole, S1 ... Second developer carrying pole, N3 ... Developer peeling pole, 62 ... Magnet, 63 ... Rotating sleeve, 64 ... Doctor blade.

Claims (4)

[Claims] 1. A cylindrical magnet having a plurality of developer carrying poles and one developer peeling pole, and rotatably arranged on the outer periphery of the cylindrical magnet and formed between the developer carrying poles adjacent to each other. The rotating body that conveys the developer by adhering to the surface by the generated magnetic field and the surface of the rotating body are arranged with a gap therebetween, and a developer layer having a uniform thickness is formed on the peripheral surface of the rotating body. In a developing device having a developer layer forming member for carrying out the above, the developer layer forming member and a first developer carrying pole which is adjacent to the developer peeling pole in a predetermined rotation direction of the rotating body, The minimum magnetic flux density in the tangential direction of the rotor between the developer transporting poles and the second developer transporting pole adjacent to the first developer transporting pole in the predetermined rotation direction of the rotor is the above-mentioned. Shows a value that can satisfy the required developer transport on the rotating body. A developing device, wherein the developing device is disposed at a position where the gap is provided. 2. A cylindrical magnet having a plurality of developer carrying poles and one developer peeling pole, and rotatably arranged around the outer circumference of the cylindrical magnet, and formed between the developer carrying poles adjacent to each other. The rotating body that conveys the developer by adhering to the surface by the generated magnetic field and the surface of the rotating body are arranged with a gap therebetween, and a developer layer having a uniform thickness is formed on the peripheral surface of the rotating body. In a developing device having a developer layer forming member for achieving the above, a gap amount between the developer layer forming member and the surface of the rotating body satisfies a range of 0.25 mm to 0.4 mm, and
The developer layer forming member includes a first developer transport pole adjacent to the developer peeling pole in a predetermined rotation direction of the rotary body, and a predetermined developer transport pole of the rotary body with respect to the first developer transport pole. Between the second developer transport poles adjacent in the rotation direction,
The minimum magnetic flux density in the tangential direction of the rotating body between the developer conveying poles can satisfy the required developer conveying on the rotating body under the condition that the gap amount is 0.25 mm to 0.4 mm. A developing device, wherein the developing device is arranged at a position showing such a value with the gap provided. 3. A cylindrical magnet having a plurality of developer carrying poles and one developer peeling pole, and rotatably arranged around the outer circumference of the cylindrical magnet and formed between the developer carrying poles adjacent to each other. The rotating body that conveys the developer by adhering to the surface by the generated magnetic field and the surface of the rotating body are arranged with a gap therebetween, and a developer layer having a uniform thickness is formed on the peripheral surface of the rotating body. In the developing device having a developer layer forming member for performing the rotation, the developer layer forming member is rotated from a first developer carrying pole adjacent to the developer peeling pole in a predetermined rotation direction of the rotating body. 3.5 ° to 21 in the prescribed rotation direction of the body
A developing device, wherein the developing device is arranged so as to be provided with the above-mentioned gap at a position in a shifted range. 4. A cylindrical magnet having a plurality of developer carrying poles and one developer peeling pole, and rotatably arranged around the outer circumference of the cylindrical magnet and formed between the developer carrying poles adjacent to each other. The rotating body that conveys the developer by adhering to the surface by the generated magnetic field and the surface of the rotating body are arranged with a gap therebetween, and a developer layer having a uniform thickness is formed on the peripheral surface of the rotating body. In a developing device having a developer layer forming member for achieving the above, a gap amount between the developer layer forming member and the surface of the rotating body satisfies a range of 0.25 mm to 0.4 mm, and
The developer layer forming member is displaced from the first developer carrying pole adjacent to the developer separation pole in the predetermined rotation direction of the rotating body by 3.5 ° to 21 ° in the predetermined rotation direction of the rotating body. A developing device, wherein the developing device is arranged at the position of the range with the gap.