JPH0251178A - Developing device - Google Patents

Abstract

PURPOSE:To stably supply toner having a nearly fixed grain diameter for development from a developing device by housing the toner having a larger grain diameter in a supplying part housing the toner, where a toner carrier contacts than that in a replenishing part. CONSTITUTION:The smaller grain diameter the toner has among the toner in the supplying part 11, the higher probability that it is held on the surface of a toner supplying roller 4 is made. Then, the larger grain diameter the toner has, the higher probability that it is scraped off from the surface of the toner supplying roller 4 by a regulating blade 9 is made. On the other hand, since only the toner corresponding to a consumption quantity is replenished by the replenishing part 12 and the toner is not inversely replenished from the supplying part 11, the distribution of the grain diameter when it is supplied is maintained. Then, the toner having the distribution of some grain diameter is housed in the replenishing part 12, on the other hand, the toner having the distribution of the larger grain diameter than the above-mentioned is housed in the supplying part 11. Thus, the toner having the distribution of some approximate grain diameter is supplied for the development from the beginning and the toner finally supplied for the development can be stabilized in a state that it is made to nearly coincide with the distribution of the grain diameter in the replenishing part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device used in an image forming apparatus using an electrophotographic copying process.

(Prior Art and its Problems) Conventionally, a developing device shown in FIG. 1 has been provided for copying machines, printers, and the like.

In this developing device (1), a toner hopper (2) that accommodates toner has a housing (3) inside a toner supply roller (4), and a regulating member (5) that presses against the lower part of the toner supply roller (4). and a holding member (7) rotatably provided on the support shaft (6), and a holding member (7) attached to the holding member (7) and pressed against the upper outer peripheral surface of the toner supply roller (4) by a spring (8). By partitioning with the regulating blade (9), it is formed behind them (on the right side in FIG. 1). The toner hopper (2) is a partition wall (10) extending upward from the bottom of the housing (3), and includes a supply section (11) and a replenishment section (12) located behind the toner supply roller (4). The supply section (11) and the supply section (12) are divided into a regulating blade (9) and a partition wall (10).
), and a stirring member (14) is provided in the rear supply section (12).

A magnet body (15) having a plurality of magnetic poles arranged on the outer periphery is fixedly housed in the front part of the developing device (1), and a developing sleeve (16) can be driven to rotate around the magnet body (15). It is a provision. Further, around the developing sleeve (16), a magnetic carrier or a developer mixed with the toner is held in the form of a magnetic brush by the magnetic poles of the magnet (15). Furthermore, the developing sleeve (16) faces the toner supply roller (4) with a supply gap (Dss), and the electrostatic latent image carrier is transferred through an opening (17) formed in the front part of the housing (3). A photosensitive drum (1
00) and are opposed to each other with a development gap (Db).

In addition, the toner supply roller (4) and the developing sleeve (16)
A recovery bias (■SS) and a developing bias (vb) are applied from power supplies (18) and (19), respectively.

In the developing device (1) having the above configuration, a supply section (11)
The toner is held in the four minute parts formed on the surface of the toner supply roller (4) based on the rotation of the toner supply roller (4).
It is transported in the direction a), and the excess material is scraped off with the tip of the regulating blade (9).

The toner held on the surface of the toner supply roller (4) and passed through the contact part of the regulation blade (9) is transferred to the developing sleeve (
The developing sleeve (16) is conveyed to the supply area (X), which is the part facing the developing sleeve (16), and is rotated here in the direction of the arrow (b).
) and the electrostatic force based on the potential difference between the developing bias (vb) and the developing sleeve (16).

The toner supplied to the surface of the developing sleeve (16) is transported along with the carrier or developer in the direction of arrow (b),
The stirring section (21) is regulated by the first regulating member (20).
), the supplied toner is mixed and agitated with a carrier or a developer, imparted with an electric charge, and prepared as a new developer together with the carrier.

The developer prepared here passes through the opposing portion of the second regulating member (22) based on the rotation of the developing sleeve (16), and passes between the developing sleeve (16) and the photoreceptor drum (1,00). It is transported to the developing area (Y), which is the opposing part, and
) Toner is electrostatically supplied to the electrostatic latent image on the surface of the photoreceptor drum, which is sequentially sent from the direction of the photoreceptor drum, and the image is visualized. Note that the amount of developer conveyed to the development area (Y) is controlled by a second regulating member (2
2) and the developing sleeve (16).
b).

The developer that has consumed toner in the development area (Y) is then transferred to the supply area (X) based on the rotation of the development sleeve (16).
There, the toner is supplied and the amount consumed by development is replenished.

Furthermore, in the supply area (X), in addition to the toner supply operation, at the same time, based on the bias difference (Vss Vb), the toner concentration on the developing sleeve, that is, the weight concentration of the toner with respect to the carrier is maintained constant. Toner concentration control is performed, and when the toner concentration on the developing sleeve exceeds a certain reference value, excess toner is transferred to the toner supply roller (
4) will be collected.

The toner collected by the toner supply roller (4) is held on the surface of the toner supply roller (4), passes through the contact portion of the regulating member (5), and is collected by the supply section (11).

By repeating the above operations, the supply unit (11)
When the amount of toner decreases, new toner is replenished into the supply section (11) from the supply section (12) through the opening (13) based on the rotation of the stirring member (14).

Incidentally, the particle size of toner produced by a pulverization method or a classification method generally has a Gaussian distribution, as shown in FIG. 2 (a-1). That is, the toner contained in the toner hopper (2) contains large particle size toner and small particle size toner mixed in a certain ratio.

On the other hand, in the developing device (1), among the toners held on the surface of the toner supply roller (4) in the supply section (11), toner with a small particle size has a higher probability of contributing to development. The reason for this is that there is a high probability that small particle size toner is retained in the minute recesses on the surface of the toner supply roller (4), and that among the toner particles held on the toner supply roller (4), large particle size toner is This is because the probability of being scraped off by the regulating blade (9) is high.

Therefore, when the developing device (1) is started by filling an empty toner hopper (2) with toner, small particle diameter toner is initially supplied to the developing sleeve (16).

However, as mentioned above, since the toner in the supply section (11) is consumed starting from the small particle size, the average particle diameter there gradually increases, and the toner particle diameter in the supply section (11) increases. (1
The increase in diameter stops when the average particle size of the toner replenished from 2) becomes the same as the average particle size at the time of injection, and from then on, the toner with the average particle size at the time of injection regularly contributes to development. Ru.

Furthermore, when a small particle size toner and a large particle size toner are mixed with a carrier, the small particle size toner is charged to a higher potential.

Furthermore, the development in the development area (Y) is based on the potential difference between the charging potential of the electrostatic latent image formed on the photoreceptor drum (100) and the developing bias (vb), which is a lower potential than that. This is done by supplying enough charged toner to the electrostatic latent image to fill the area, so when a large particle size toner and a small particle size toner with a higher potential are supplied to an electrostatic latent image at a constant potential, In this case, the number of toner particles adhering per unit area is larger for large particle diameter toner and smaller for small particle diameter toner. In other words, the density of an image created with a large particle size toner is high (the density of an image created with a small particle size toner is thinner).

Therefore, when new toner is put into the developing device (1) and development is started, the density of the image created is initially low, and the density is insufficient until the particle size of the toner used for development stabilizes. The problem was that images were created.

(Means for Solving the Problems) The present invention has been made to solve the above problems,
To explain with reference to FIG. 1, the conventional developing device (1
), the toner hopper (2) is connected to a toner carrier (
4) a supply section (11) located on the side; and the supply section (11)
and a supply section (12) connected through an opening (13), and the supply section (11) stores toner having a larger particle size than the supply section (12).

(Example) As shown in FIG. 1, a regulation blade (9) is pressed against a toner supply roller (4) which is a toner carrier, and a toner thin layer is applied to the surface of the toner supply roller (4) based on the rotation of the toner supply roller (4). The change in toner particle size in the developing device (1) that forms the layer will be explained.

[Step 1] (Refer to Fig. 2) Both the replenishing part (12) and the supply part (11) of the toner hopper as shown in Fig. 2 (a-
When the developing operation is started with toner having the particle size distribution of 1), there is a high probability that among the toner in the supply section (11), the toner supply roller (4) has a small particle diameter to be retained on the surface. , Also, large particle size toner regulating blade (
9), there is a high probability that the toner will be scraped off the surface of the toner supply roller (4).
1), and particles with smaller diameters pass through the tip of the regulating blade (9) and are supplied to the developer. In addition, D in the figure.

means average particle size.

Here, the particle size of the toner and the probability of passing through the tip of the regulating blade (9) [passing probability]: E(d) are determined by the experiment.
It was confirmed that there was a hyperbolic relationship shown in the center of Figure (b-1).

Therefore, as shown in FIG. 2(b-1), the toner having the particle size distribution (i) is passed from the supply section (1) containing the toner to the developing sleeve (16) through the tip of the regulating blade (9).
) The toner supplied to the particle size distribution (i) has a probability of passing:
The particle size distribution (ii) is obtained by multiplying E(d), and the smaller the particle size, the more it contributes to development.

In addition, as shown in FIG. 2 (c-1), the supply section (11
), the toner with particle size distribution (ii) is consumed from the toner with particle size distribution (i), while the toner with particle size distribution (1) is replenished in the same amount as the consumed amount. The toner average particle size increases from (i) to (iii).

On the other hand, as shown in FIG. 2 (a-1), the supply section (12)
In this case, only the amount of toner corresponding to the consumption amount is consumed, and the toner is not replenished from the supply section (11), so that the particle size distribution (i) at the time of input is maintained.

[5tep2] (See Figure 3) When further development is performed, as shown in Figure 3 (b-2), the toner of particle size distribution (iii) passes through probability: E (d).
As a result, the particle size distribution of the toner supplied to the developer becomes the state shown in (iv), and the particle size distribution (i) in the initial state shown in FIG.
i) The diameter is larger than that of i).

On the other hand, the toner particle size in the supply section (11) is as shown in Fig. 3 (C-2
), the toner with the particle size distribution (iv) is consumed for development from the toner with the particle size distribution (iii), while the toner with the particle size distribution (i) is consumed from the replenishing section (12). By replenishing the same amount, the toner moves from (mountain) to (v
) to further increase the diameter. Note that the toner in the supply section is
As shown in Figure (a-2), the distribution state of (1) is maintained.

[Step 3] (Refer to Figure 4) As the state of Step 2 further progresses, as shown in Figure 4 (b = 3), the probability that the toner with distribution (V) will pass through development is E(d).
The toner having a particle size distribution (vi) is supplied to the developer. As the particle size of the toner in the supply section increases, this toner particle size distribution (1) gradually approaches the particle size distribution (1) at the time of feeding.

On the other hand, in the supply section (11), the toner with the distribution of (V) is
The toner with the distribution vl) is consumed, and the toner with the distribution () is replenished. As mentioned above, when the particle size of the consumed toner approaches (1), the toner particle size of the consumed and replenished toner particles becomes almost balanced, and the toner in the replenishment section is supplied as is for development. Supply section (11)
The particle size at (vii) is stable.

Therefore, from now on, the average particle size (i
) is stably supplied to the developing device, and the toner particle size in the supply section (11) stably maintains the state of (■).

The above phenomenon was confirmed experimentally. Note that the conditions for the experiment were set as follows.

a. Toner supply roller <4) ・Diameter: 20mm ・Rotation speed: 200rpm ・Recovery bias (Vss): DC-400V
AC700V rms ・AC frequency...3 Q Q Hz・Surface roughness...40μm b, Developing sleeve (16) ・Diameter...24.5mm ・Rotation speed...・・・200 rpm・Developing bias (VB)・・・DC-200VC gear knob・Developing gear knob (Ds)・・・0.6mm・Sugar high regulation gap (Db)・・・・・・・0.45mm・Supply gap (Dss)・・・0. 8mmd, regulation blade (18) ・Material: Stainless steel ・Thickness: t=100μm ・Pressure 1 & force: 0, kg/mm 1 Toner: Average particle size when charged... As a result of the 14 μm experiment, as shown in FIG. The average particle size of the toner sampled at [Measurement point D)] was small at the beginning of development, about 11.5 μm, but it showed a tendency to gradually increase in size, and after the number of copies was about 500, it gradually stabilized and the number of copies increased. At the point of 2,000 sheets, it stabilized at approximately 136 μm.

The average particle size of the toner sampled on the surface of the toner supply roller (4) [measurement point (C)] was initially 12 μm, but it showed almost the same tendency as the average particle size on the photoreceptor drum (100). , the final number of copies is 2. At the time of OO0 sheets, the particle size stabilized to match the average particle size of the input.

The diameter of the toner at supply section (11) C measuring point (B)] gradually increases from the start of copying, and when 500 copies have been made, the diameter of the toner becomes approximately 16 mm.
The size increased to μm and remained that state thereafter.

The toner particle size of the replenishing section (12) Cal1 point (A)] maintained an average particle size of 14 μm from beginning to end without any fluctuation.

From the above explanation and experiments, it is clear that the supply section (11) and the supply section (12)
), if toner with a larger particle size is stored, that is,
The supply section (12) stores toner having a particle size distribution (i), while the supply section (11) contains toner having a larger particle size distribution (vii).
), the toner with a particle size distribution approximating (1) will be supplied to the developer from the beginning, and the toner finally supplied to the developer will be in the replenishment section (12). It can be estimated that the particle size distribution is stable in a state that substantially matches particle size distribution (1).

Next, one supply section (12) with an average particle diameter of 14 μm is added to the supply section (12).
1) contains toner with an average particle size of 16 μm and performs continuous copying, and the supply section (12) (measurement point (A)) and the supply section (1
1) I: measurement point (B)], the surface of the toner supply roller (4) [measurement point (C)], and the surface of the photoreceptor drum (100) [measurement point (D)], for each predetermined number of sheets. The toner was sampled and its average particle size was measured.

As a result, as shown in FIG. 6, the average particle diameter of the toner at measurement point (A) of the replenishing section (12) remained 14 μm throughout.

Further, the average particle size of the toner at measurement point (B) of the supply section (11) increased slightly from the time of feeding, and stabilized at an average particle size of 16.2 μm. Further, a measurement point (D) on the surface of the photoreceptor drum (100), a measurement point (C) on the surface of the toner supply roller (4)
) is 14 μm from beginning to end and 13.4 to 13.5 μm, respectively.
The condition is maintained, and during development, the average particle size (16.2 μm), which is almost the same as the average particle size (16 μm) stored in the supply section (12), is used for development.
The toner (m) was stably supplied throughout.

(2) Second Embodiment The developing device shown in FIG. 25) and its tip extends upward to form a partition wall (28), and the partition wall (28) connects the toner hopper (29) with the supply unit (30). (31). The replenishment section (31) also includes two stirring members (32) and (33).
) are provided, and the toner in the supply section is replenished to the supply section (30) while being stirred. In addition, (34) is a magnet body, and (35) is a developing sleeve.

In the developing device of this embodiment as well, as in the previous embodiment, if the supply section (30) is loaded with toner having a larger diameter than the supply section (31), the developing device will be loaded in the supply section (31) from the beginning. Toner having approximately the same average particle size as the stored toner is supplied to the developer, and an image with a desired density can be stably obtained.

(3) Embodiment 3.4 In the first and second embodiments, the 2nd embodiment consists of toner and carrier.
Although the developing device using component developers has been shown, the eighth
, 9, the present invention can also be applied to a developing device using a -component developer.

The developing device (40) shown in FIG. 8 includes a toner hopper (41
) is rotatably installed in the lower opening of the metal developing roller (
A regulating blade (43) and a regulating member (4
4) and extend the bottom of the housing (45) to a position facing the regulating blade (43) to form the partition wall (46).
By forming the toner hopper (41), the interior of the toner hopper (41) is divided into a supply section (47) and a replenishment section (48) located behind the developing roller (42). ). Note that a bias voltage is applied to the developing roller (42) from a power source (50).

On the other hand, the developing device (51) shown in FIG.
), and the distal end of the regulating member (55) is extended upward to form a partition wall (56), and the partition wall (56) supplies the inside of the toner hopper (52) with the supply section (57). Part (5
8), and the supply section (58) is provided with two stirring members (59) and (60).

In the developing devices (40) and (51) having the above configuration,
Supply section (47), (57) and supply section (48), (58)
When toner having the same average particle size distribution is added to both, as shown in FIG. However, the average particle size of the toner in the supply section [measurement point (F)] gradually increases, and when the number of copies is 500, it is approximately 15.5 μm, and 1
,000 sheets or more, it stabilized at about 15.7 μm.

In addition, toner having an average particle diameter of about 12.3 μm is initially supplied to measuring points (G) of the developing rollers (42) and (53) and measuring point (H) of the photoreceptor drum (100), and then gradually increases in diameter. When the number of copies is 500, it is about 15.8 μm, and when 1,000 copies are made, it is about 16 μm.

Therefore, the developing device (40) containing new toner, (
51), several hundred images with insufficient image density will be created from the start of driving.

On the other hand, when the supply parts (48) and (58) are loaded with toner having an average particle size of 14 μm, and the supply parts (47) and (57) are loaded with toner having an average particle size of 16 μm, as shown in FIG. The average particle size of the toner in the supply sections (47) and (57) remains approximately 15.7 μm throughout. In addition, the supply department (48
), (58) maintains an average particle size of 14 μm.

Also, the surface of the photoreceptor drum (100) [measurement point (H)] and the surface of the developing rollers (42) and (53) [measurement point (G)]
The average particle size of the toner maintained at approximately 14 μm from beginning to end, and images with appropriate density were obtained from the beginning of copying.

(2) Fifth Embodiment The developing device (60) shown in FIG. 12 has almost the same configuration as the developing device shown in FIG. In addition, a contact portion (63) with a semicircular cross section is provided at the tip of the elastic blade (62), and this developing device (60) also has a supply portion (65) separated by a partition wall (64).
) is loaded with toner having a larger particle size than the replenishing section (66), an image of the desired density can be stably obtained from the beginning of development.

(2) Sixth Embodiment The developing device (70) shown in FIG.
two rollers (71) rotatably arranged at the front of the
A toner carrying belt (73) made of a thin metal film or a polyester film is wound around the housing (72).
The blade (75) provided at the top of the toner carrying belt (74) is pressed against the toner carrying belt (73), and the regulating member (76) provided at the bottom of the housing is connected to the rear roller (72) via the toner carrying belt (73). In this developing device, the supply section (78) accommodates toner having a larger diameter than the supply section (79). By doing so, toner having a desired particle size can be stably supplied to the developer from the beginning of the development.

■, Other Embodiments In the above embodiments, the supply section and the replenishment section were assumed to be in constant communication via the opening.
Like the developing device disclosed in the specification of 2-292464, a shutter is provided that can appropriately cut off the communication between the supply section and the replenishment section, so that when the developing device is attached to and detached from the image forming apparatus, the connection between the supply section and the replenishment section is removed. By preventing the toner from mixing with the replenishing section, it is possible to reliably supply toner of approximately constant particle size to the developing device from beginning to end.

(Effects of the Invention) As is clear from the above description, in the developing device according to the present invention, the supply section that accommodates toner that is in contact with the toner carrier is configured to accommodate toner having a larger particle diameter than the supply section. Therefore, toner having a substantially constant particle size is stably supplied from the developing device to the developing device.

Therefore, an image of constant image quality can be obtained from the initial stage of development and maintained over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the developing device, FIGS. 2 to 4 are explanatory diagrams explaining changes in particle size in each part of the developing device,
Figure 6 shows the relationship between the number of copies and the average toner particle diameter.
The figure corresponds to a conventional developing device, FIG. 6 corresponds to a developing device according to the present invention, FIG. 7 is a sectional view of the developing device of the second embodiment, and FIG.
, 9 are cross-sectional views of the developing device of the 3rd and 4th embodiments, and 10th.
Figure 11 is a diagram showing the relationship between the number of copies and toner average particle size in the developing device shown in Figures 8 and 9, and Figures 12 and 13 are diagrams showing the relationship between the number of copies and the average particle size of toner in the developing device shown in Figures 8 and 9.
．． FIG. 5 is a sectional view of a developing device according to a fifth embodiment. 1... Developing device, 2... Toner hopper, 3...
...Housing, 4.Toner supply roller, 5.
...Regulation member, 9 ...Regulation blade, 10...
Partition wall, 11... Supply section, 12... Replenishment section, 13... Opening, 16... Developing sleeve, 100... Photosensitive drum. Patent Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Blue and White 葆 Haka 1 person Fig. d Fig. d d d Fig. d Fig. ■ Fig.

Claims (1)

[Claims] (1) A toner layer thickness regulating member is brought into contact with a toner carrier that is in contact with the toner contained in a toner hopper, and the toner layer thickness regulating member regulates the toner held on the surface of the toner carrier based on movement of the toner carrier. In a developing device for forming a thin layer of toner, the toner hopper is divided into a supply section located on the side of the toner carrier and a supply section connected to the supply section through an opening, and the toner hopper is supplied to the supply section. A developing device characterized in that it accommodates toner having a larger particle diameter than that of the developing device.