JPH0792626B2 - Development device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to improvement of a developing device applied to, for example, electrophotography and electrostatic recording.

[Conventional technology]

With the recent widespread use of copying technology, small-sized and low-cost popular machines have been attracting attention in place of conventional large-scale copiers. A technique for improving the developing device used in such a popular machine is disclosed in, for example, JP-A-55
-18656, the contents of which will be described below with reference to FIG. In the figure, 1 is an image forming body that rotates at a peripheral speed of 100 mm / sec in the direction of an arrow, and has a photosensitive layer such as ZnO, cds, and Se, and 2 is a peripheral surface in the same direction as the image forming body 1. And a small diameter developing sleeve of 30mmφ that rotates at the same speed,
3 is a fixed magnet drum in the sleeve, and N and S alternate 8
It has a magnetic pole. In this developing device, a one-component developer made of magnetic toner is used as the developer, and the flow of the developer carried on the surface of the developing sleeve 2 is a bristling regulating member provided on one magnetic pole on the upstream side of the developing area. 70 μm by 4
Is cut into thin developer layers. When this thin developer layer reaches the developing area, it is subjected to the action of a high frequency voltage from the power source 5 to cause the magnetic toner to fly from the developer layer toward the image forming body 1 to cause a static toner on the image forming body 1. The image is developed.

[Problems to be solved by the invention]

In the developing device, since the developing sleeve 2 has a small diameter of 30 mmφ, advantages such as contributing to downsizing of the developing device and the entire copying machine can be recognized, but this is not always satisfactory. For example, although the magnet drum 3 has a small diameter, N and S magnetic poles are densely arranged, so that the workability is poor and the cost is rather high. There is.

In recent years, in the copying machine industry, it has been desired to develop a more popular, more compact, low-cost, and easy-to-use machine.

[Means for solving problems]

The present invention has been proposed based on the above circumstances, and an object of the present invention is to provide an improved developing device that is incorporated in a copying machine or the like and contributes to downsizing and cost reduction of the copying machine or the like. . Still another object of the present invention is to provide a developing device capable of forming a high-density copy image with excellent transportability of the developer to the developing area even though the developing sleeve has a small diameter in which a small number of magnetic poles are arranged. is there.

In a developing device having a fixed magnet body, a developing sleeve of a small diameter that rotates an outer circumference of the fixed magnet body to form a developer flow, and a spike-up restricting member arranged close to the developing sleeve surface, The diameter of the developing sleeve is 25 mm or less and 9 mm or more, and the fixed magnet body conveys the developer on the main magnetic pole for developing the electrostatic image on the image forming body and on the upstream side of the developer flow. A magnetic pole having a lower magnetic field strength than the main magnetic pole, and a second magnetic pole having a lower magnetic field strength than the main magnetic pole downstream of the developer flow for transporting the developer. The magnetic poles are arranged in a three-pole magnetic pole array, and the first and second magnetic poles are arranged with respect to a straight line passing through the rotation center of the developing sleeve and the position where the bristling regulating member faces the developing sleeve surface. Arrange the magnetic poles of the magnet body so that they are on the side opposite to the main pole, and The heading regulation member is located at a position facing the surface of the developing sleeve between the main magnetic pole and a horizontal axis extending to the side opposite to the image forming body including the rotation center of the developing sleeve, A = (∂H _θ ) / (∂
This is achieved by a developing device characterized by being arranged at a position where the rate of change A of the magnetic field strength indicated by θ) is -4 or more and +10 or less (Gauss / degree).

[In the formula, H _θ represents the strength (gauss) of the magnetic field in the tangential direction at an arbitrary point on the surface of the developing sleeve, and Θ represents the rotation angle (degree) of the developing sleeve in the developing direction. ]

[Operation] The feature of the present invention is that the developing sleeve has a small diameter of 25 mm or less and 9 mm or more, and the magnet body is a magnet body with three fixed poles, which makes the developing apparatus compact and cost far beyond the prior art. I have achieved it.

Furthermore, the problem that the developer transportability is deteriorated due to the reduction in the diameter of the developing sleeve and the decrease in the number of magnetic poles of the magnet drum is described. This is because, after paying attention to the close relationship with the installation position of the regulation member, repeated researches have been made to solve the problem, and it has been possible to form a high density image by obtaining good developer transportability.

Hereinafter, experimental examples by the present inventors regarding the transportability of the developer will be described with reference to FIGS. 1 to 5. FIG. 1 is a cross-sectional view of a main part of a developing device for explaining the present experiment, FIG. 2 is a cross-sectional view of the main part for explaining the structure of a magnet body of the developing device of FIG. 1, and FIG. 3 is a developing sleeve. FIG. 5 is a cross-sectional view of the main part of the developing device for explaining the strength of the magnetic field on the surface, FIG. 4 is a graph showing the strength of the magnetic field in the tangential direction and the normal direction of each point on the surface of the developing sleeve, and FIG. [Fig. 4] is an enlarged graph of the region where the spike-up restraining member is provided in the graph of Fig. 4.

In FIG. 1, reference numeral 1 is an organic photoreceptor for positive charging described in Example 1 of Japanese Patent Application No. 59-171741, 0 is a two-component developer described below, and 2 is a surface roughened by sandblasting. The developing sleeve 3 made of aluminum with a diameter t ₀ of 20 mm is a fixed magnet body, and the main magnetic pole 7 has a magnetic field strength of N pole of 750 gauss, and the magnetic field strength of S pole has a magnetic field strength of 400 gauss. 8 and the second conveying magnetic pole 9 are integrally formed with a plastic drum 10. Reference numeral 4 is a bristling regulating member for the developer conveyed from the casing 6 of the developing device to the developing area, 5 is a bias power source, and 11 is a rotating shaft of the developing sleeve 2. Further, both the first carrier magnetic pole 8 and the second carrier magnetic pole 9 are main magnetic poles 7.
Are arranged at positions rotated by 140 ° in opposite directions from each other, and the gap d2 in the developing area 12 between the photoconductor 1 and the developing sleeve 2 is 0.6 mm. The gap d1 is 0.5 mm.

The detailed structure of the magnet body is shown in FIG. 2. Each of the magnetic poles 7, 8 and 9 is made of an anisotropic sintered magnet, and the surface of each magnetic pole facing the inner surface of the developing sleeve 2 is an arc-shaped curved surface ( It does not have to be a curved surface). The width (t ₁ , t ₃ , t ₅ ), thickness (t ₂ , t ₄ , t ₆ ) of each magnetic pole in FIG. 2 and the gap between the inner surface of the sleeve 2 (t ₇ , t ₈ , t ₉ ), Sleeve thickness (t
₁₀ ) etc. are as follows.

t ₁ = 8 mm, t ₃ and t ₅ = 6 mm, t ₂ = 4 mm, t ₄ and t ₆ = 3 mm,
t ₇ , t ₈ and t ₉ = 0.5 mm, t ₁₀ = 1.0 mm Next, the two-component developer used in this experimental example is as follows.

(Structure of developer) Toner: 7% by weight of carbon black dispersed in styrene-acrylic resin and 0.4% by weight of hydrophobic silica
Externally added negatively charged toner having an average particle diameter of 12 μm.

Carrier: A carrier with an average particle size of 70 μm, which is obtained by coating ferrite particles with a diameter of 70 μm with styrene acrylic resin.

Developer: A mixture of 95% by weight of the carrier and 5% by weight of the toner.

In the developing device having the above-described structure, the developing sleeve 2 is rotated in the direction of the arrow at a speed of 200 rpm, and the peripheral speed of the photosensitive member 1 is reduced to 1/3 of the peripheral speed of the developing sleeve. Image formation is performed by rotating in the same direction as.
In the present experimental example, the position of the spike-up restraining member 4 from the horizontal axis PO (shown as 0 degree) in FIG. 1 to the main magnetic pole 7 has six different rotation angles Θ (P1, P2, P3, P4, P5, P6), and the transportability of the developer was compared and examined in relation to the rate of change of the magnetic field strength on the surface of the developing sleeve 2.

Here, as shown in FIG. 3, the strength of the magnetic field 13 on the position P at an arbitrary rotation angle Θ from the horizontal axis PO of the developing sleeve 2 is the modulus ▲ ▼ of the magnetic field in the tangential direction of the point P. It is decomposed into the magnetic field strength ▲ ▼ in the line direction. The strengths ▲ ▼ and ▲ ▼ of the decomposed magnetic fields were measured on the entire circumference of the developing sleeve 2 based on the following measuring method, and the results are shown in the graph of FIG.

(Measurement method of magnetic field strength) Gauss meter (Gauss meter 325 manufactured by Yokogawa Hokushin Electric Co., Ltd. is installed at a place where the normal line of the measuring point extends from the developing sleeve surface by 2 to 3 mm.
1) Set the probe (Probe 3251-01 manufactured by the same company) and measure. The Gauss unit is the emu unit of the magnetic flux density, and the unit of the magnetic field strength should be expressed in Oersted. However, since the absolute values in the air are almost the same, in the present invention, the Gauss unit is used for the explanation. To do.

In the graph of FIG. 4, the horizontal axis represents the rotation angle Θ in the developing direction when the position of the horizontal axis PO is 0 degrees, and the vertical axis is the N pole (main magnetic pole) above the center line of O Gauss. And the lower side represents the magnetic field strength of the S pole (first and second carrier magnetic poles). The dashed-dotted line graph is the magnetic field strength in the normal direction ▲ ▼, and the solid line is the tangential field strength ▲.
Represents ▼.

In the present experimental example, paying attention to the graph of the magnetic field strength ▲ ▼ in the tangential direction in FIG. 4, the strength of the magnetic field in the tangential direction at the position P of the rotation angle Θ where the spike control member 4 is arranged.
The change rate A of ▼ is determined from the graph. The rate of change A is obtained from the differential coefficient ∂Hθ / ∂Θ with respect to the rotation angle Θ of the magnetic field strength ▲ ▼ at the point P, which is measured as the tangent slope A drawn at the point P in the graph of ▲ ▼. To be done.

In order to facilitate work, the horizontal axis PO (0
Fifth) to the center position of the N pole (180 degrees)
The graph in the figure was used. That is, the arrangement positions P1 to P6 of the above-mentioned 6 points of the spikelet restraining member 4 are taken on the graph of ▼ in FIG. 5, and the inclinations A1 to A6 of the tangent lines drawn at these respective positions are shown on the graph. The measurement was carried out, and the results are shown in Table 1.

Next, the following experiment was conducted on how a change in the position of the spike-height restricting member 4 of the developing device affects the transportability of the developer. That is, a uniform electrostatic charge of +600 V is applied on the photoconductor 1 and then a solid black document having a density of 1.0 is subjected to image exposure to form a solid latent image, which is formed by the developing device set under the above conditions. , While developing the spike control member 4 at the positions P1 to P6 in Table 1 to form six types of toner images,
The densities of the obtained toner images were compared. The data at that time are shown in Table 2.

The value of the slope A of the tangent line is the graph ▲ ▼ in FIG.
When the tangent line at each point of P1 to P6 is right downward, it is positive, and when it is left downward, it is negative.

As a result of the above, the position where the spike-height restricting member 4 is disposed has a significant effect on the transportability of the developer and thus on the image density, and the change rate A of the magnetic field strength in the tangential direction is -4 or more. It was decided that it should be placed in a position that should be +10 or less.

The image-forming body used in the present invention is provided with an intermediate layer on a substrate such as metal or conductive plastic, if necessary, on which Zn, Al, Sb, Cd, Mo and Hg oxides and iodides are formed. ，
Some have a photosensitive layer in which a photoconductive substance such as sulfide or selenide is dispersed in a binder resin, or a photosensitive layer in which Se, Si or an alloy of Se and Te, Sb, Bi, etc. is deposited or an organic photosensitive layer. .

Examples of the photoreceptor having the organic photosensitive layer include a charge generation layer in which an organic photoconductive substance such as a perylene derivative, chlordian blue, methylsqualilium, a bisazo pigment, and a polycyclic pigment is dispersed in a resin as necessary, and an oxadiazole. There is a positively-charged or negatively-charged composite photoreceptor including a charge transport layer in which a derivative, a pyrazoline derivative, a polyarylalkane-based aromatic amino compound, polyvinylcarbazole, or the like is dissolved or dispersed in a resin as necessary.

Next, the developer of the present invention is not particularly limited, but for example, a one-component developer described in JP-A-59-42565 or Japanese Patent Application No. 58-9
It may be a two-component developer described in 7973 specification. The developing method is, for example, a non-contact developing method described in JP-A-57-139761, JP-A-59-181362 or Japanese Patent Application No. 58-184381, or a conventional magnetic method. A brush development method may be used. However, in the present invention, it is preferable to use a two-component developer excellent in developability and to use a magnetic brush developing method having a simple structure and low cost.

A sectional view of a developing device applicable to the present invention is shown in FIG. 6, and the same contents as those in FIG. 1 are designated by the same reference numerals. 14 in the figure
Is a support plate for fixing the developer spike-up restraining member 4, 15 is a toner hopper, 16 is a replenishing lid for replenishing the toner in the hopper,
Reference numeral 17 denotes a stirring means for mixing the developers in the casing 6 with each other and the replenishment toner, and a circular blade, a plate blade, an elliptical blade, or a combination blade thereof is used, and is arranged close to the developing sleeve 2. Reference numeral 18 is a mountain-shaped projection that guides the developer after development in the direction of the stirring means, and 19 is a roller that replenishes the toner in the toner hopper 15 into the casing 6 in a fixed amount. In the developing device shown in FIG. 6, the two-component developer is preferably used as the developer, and the developing sleeve 2 has a diameter of 25 mm or less and a small diameter of 9 mm or more, and 100 to 500 rpm in the arrow direction.
Is rotated at the speed of. Magnet 3 in developing sleeve 2
Is fixed, and a developing main magnetic pole (N) and two developer carrying magnetic poles (S) are arranged. In FIG. 6, two carrying magnetic poles 8 and 9 are provided outside the main magnetic pole 7. An example of the arrangement is shown. In the figure, the magnetic field strength of the main magnetic pole 7 is 750 ± 50 gauss, and the magnetic field strength of the carrier magnetic poles 8 and 9 is 400 gauss or more. Further, the interval between the main magnetic pole 7 and each of the transport magnetic poles is such that the rotation angle Θ is in the range of 30 degrees to 180 degrees. The position of the developer regulating member is between the horizontal axis PO and the main pole 7 (rotation angle 180
Degree), preferably between the horizontal axis PO and the rotation angle of 160 degrees, and A ≧ −4, preferably A ≧ 4, obtained from the above experimental example.
-2 is satisfied. Next, the gap d1 between the spike-up restraining member 4 and the developing sleeve 2 is 0.1 to 1.2 mm, and the gap d2 between the developing sleeve 2 and the photoconductor 1 is 0.1 to 2.0 mm.
The gap d3 between the stirring blade 17 (and the developing sleeve 2) and the casing 6 is 0.1 to 5 mm.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but the embodiments of the present invention are not limited thereto.

(Embodiment 1) FIG. 7 is a sectional view of a copying machine for explaining this embodiment, and the same contents as those of the sixth embodiment are designated by the same reference numerals. In the figure, 20 is a charger, 21
Is a platen glass, 22 is a document, 23 is a converging optical transmitter, 24 is a light source, 25 is a developing device, 26 is a pre-transfer exposure device, 27 is a transfer device,
28 is a separator, 29 is a heat roller fixing device, 30 is a static eliminator before cleaning, 31 is a cleaning device, and 32 is a cleaning blade in the device.

As the photoconductor 1, the positively chargeable organic photoconductor used in the above experimental example is used. The photoconductor 1 has a diameter of 50 mmφ and is rotated at a peripheral speed of 60 mm / sec in the direction of the arrow.
20 gives a uniform charge of + 600V. Next, the charged surface is subjected to image exposure L obtained by focusing the reflected light obtained by optically scanning the original 22 on the original table 21 with the light source 24 and forming an electrostatic image. This electrostatic image is developed by a developing device 25 similar to that shown in FIG. 6 which is low in cost and compact in size, and a toner image is formed. Here, the developing device 25 has the following configuration. The developing sleeve 2 is made of aluminum whose surface is sandblasted to a roughness of # 30.
The sleeve is a small-diameter sleeve of 20 mmφ, and the gap d1 with the photosensitive member 1 in the developing area 12 is 0.51 mm, and the sleeve is rotated in the arrow direction at a speed of 250 rpm. The magnet drum 3 is fixed, and the main pole 7
(N) magnetic field strength is 800 gauss, carrier poles 8 and 9
The strength of the magnetic field of (S) is 500 gauss, and the main pole 7
The rotation angle between the carrier magnetic poles 8 and 9 is 140 degrees. The panning restriction member 4 has a rotation angle Θ with respect to the horizontal axis PO.
Is placed at a position of 60 degrees, and the gap d2 with the developing sleeve 2 is
It is set to 0.60 mm.

The stirring means 17 is rotated at 200 rpm in the same direction as the developing sleeve 2 with an elliptical blade having a diameter of 30 mm, and the developer D (other replenishment toner T) in the casing is stirred and mixed in the horizontal and vertical directions to achieve uniform development. The developer is supplied to the developing sleeve 2. The toner T in the toner popper 15 is copied per copy by the replenishing roller 19.
A fixed amount of 15 to 45 mg is replenished, and the developer D in the casing is agitated and mixed by the agitating means 17. The gap d3 between the stirring means and the casing 6 is 2.6 mm.
Further, in the present device 25, the developer flow after development is the chevron protrusion 28
And is smoothly conveyed to the agitating means 17, so that the agitating and mixing of the developer is promoted. In this embodiment, the two-component developer D in the experimental example is used, and the toner image obtained by developing with the developing device 25 containing the developer D is easily exposed by the exposure device 26 and transferred. After the transfer, the transfer device 27 transfers the transfer paper P onto the transfer paper P, and the transfer paper P is separated by the separator 28.
Is heated and fixed by. The photoconductor 1 after the transfer is the static eliminator 30
Then, the blade 32 of the cleaning device 31 removes the charge and prepares for the next image formation. According to the above-described embodiments, the developing device 25 is extremely low cost and compact, so that the photosensitive member 1, and hence the entire copying machine is small and
It was possible to reduce the cost, and when the copying machine was used to repeat the copying a number of times, it was possible to obtain a high-quality copied image with high density.

(Embodiment 2) The same arrangement as that of Embodiment 1 was repeated and copying was carried out by changing the arrangement position of the spike-height restricting member shown in FIG. 6 to a position where the rotation angle Θ was 90 degrees. Similar to the above case, a good quality copy image was obtained even in the repeated copying a number of times.

〔The invention's effect〕

As described above, according to the developing device of the present invention, the cost and the size of the device are lower than those of the conventional ones, and it is possible to reduce the cost and the size of a copying machine equipped with such a developing device and to achieve high density. Thus, an effect such as obtaining a high quality copied image can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part of a developing device for explaining an experimental example of the present invention, FIG. 2 is a cross-sectional view of an essential part of a developing device shown in FIG. FIG. 5 is a cross-sectional view of the main part of the developing device for explaining the strength of the magnetic field on the sleeve surface. FIG. 4 is a graph showing the strength of the magnetic field in the tangential direction and the normal direction of each point on the developing sleeve surface. 4 is a partially enlarged graph of the graph of FIG. 4, FIG. 6 is a sectional view of a developing device suitable for the present invention, and FIG. 7 is a sectional view of a copying machine for explaining an embodiment.
FIG. 8 is a sectional view of a main part of a conventional developing device. 1 ... Photoconductor, 2 ... Development sleeve 3 ... Magnet body, 4 ... Spike restraint member 6 ... Casing, 7,8,9 ... Magnetic pole 12 ... Development area, 13 ... Magnetic field 15 ... Toner hopper, 17 ... stirring means 19 ... toner replenishing roller 20 ... charger, 22 ... original 23 ... converging optical transmitter, 25 ... developing device 26 ... pre-transfer exposure device, 27 ... transfer device 28 …… Separator, 29 …… Fixer 30 …… Pre-cleaning static eliminator 31 …… Cleaning device 32 …… Blade, T …… Toner D …… Developer, P …… Transfer paper

Claims (1)

[Claims] 1. A fixed magnet body, a developing sleeve having a small diameter for rotating the outer periphery of the fixed magnet body to form a developer flow, and a spike-up restraining member arranged close to the developing sleeve surface. In the developing device, the diameter of the developing sleeve is 25 mm or less, 9 mm or more, the fixed magnet body, the main magnetic pole for developing the electrostatic image on the image forming body, and the upstream side of the developer flow. A first magnetic pole having a weaker magnetic field strength than the main magnetic pole for carrying the developer, and a magnetic field strength stronger than the main magnetic pole for carrying the developer on the downstream side of the developer flow. A three-pole magnetic pole array having a weak second magnetic pole, and the spike-up restraining member with respect to a straight line passing through the position facing the developing sleeve surface and the rotation center of the developing sleeve,
The magnetic poles of the magnet body are arranged so that the first and second magnetic poles are on the opposite side of the main magnetic pole, and the spike-up restraining member is opposite to the image forming body including the rotation center of the developing sleeve. The rate of change in the strength of the magnetic field _represented by the formula A = (∂Hθ) / (∂θ) at the position facing the developing sleeve surface between the main magnetic pole and the horizontal axis extending toward the side. A is -4 or more +10 or less (Gauss /
The developing device is characterized in that it is arranged at a position of (degree). In the equation, H _θ represents the strength (gauss) of the magnetic field in the tangential direction at an arbitrary point on the surface of the developing sleeve, and θ represents the rotation angle (degree) of the developing sleeve in the developing direction.