JPH02203365A - Developing device - Google Patents

Abstract

PURPOSE:To reduce the occurrence of toner fusing on a toner supplying roll by predicting the used amount of the toner prior to the development and controlling the speed of revolution of the toner supplying roll based on this predicted value. CONSTITUTION:The used amount of the toner is predicted prior to the development and the speed of revolution of the toner supplying roll 75 is controlled based on this predicted value. The toner is supplied to a magnetic brush roll 41 from the toner supplying roll 75 only when toner concentration in an anxilliary developer agitating chamber 36 is a prescribed reference toner concentration or below. When the concentration of the toner included in the developer carried from the anxilliary developer agitating chamber 36 is the reference toner concentration or above, excess toner is conversely recovered into the toner supplying roll 75. At that time, the speed of revolution of the toner supplying roll 75 is controlled based on the used amount of the toner predicted by an adequate means. Thereby, the toner fusing on the toner supplying roll 75 is prevented and the toner concentration can be highly precisely controlled for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a developing device that uses a two-component developer consisting of toner and carrier.

(Prior Art) Conventionally, a thin layer of toner is formed on a toner supply roller by a toner thin layer forming member, and the toner formed on this thin layer is scraped off with a magnetic brush. A developing device is known that includes toner supply means configured to maintain a constant toner concentration on a magnetic brush roller by applying a voltage to each of the rollers. and,
In this device, the toner supply roller and the magnetic brush roller are connected to the same drive source and are configured to rotate at a constant speed in synchronization with each other.

<Problems to be Solved by the Invention> As described above, in the conventional apparatus, the toner supply roller always rotates at a constant rotational speed when the magnetic brush roller is rotating.

During this time, a thin layer of toner continues to be formed on the circumferential surface of the toner supply roller by the toner thin layer forming member, so toner fusion tends to occur, and as a result of this toner fusion, toner density fluctuations occur and image deterioration occurs. was there.

The present invention has been made to address the above-mentioned conventional problems, and an object thereof is to provide a developing device that can reduce the occurrence of toner fusing to a toner supply roller.

(Means for Solving the Problems) In order to solve the above-mentioned conventional problems, a first invention scrapes off the toner on the toner supply roller with a magnetic brush, and applies voltage to each of the toner supply roller and the magnetic brush roller. In a developing device equipped with a toner supply means configured to maintain a constant toner concentration on a magnetic brush roller by applying a voltage, a means for predicting the amount of toner used prior to development is provided, and a means for predicting the amount of toner used is provided based on this predicted value. The rotation speed of the toner supply roller is made controllable.

Further, in the second invention, the means for predicting the amount of toner used is configured to predict from the B/W ratio of the original, the original size, and the copying magnification.

Furthermore, in a third aspect of the invention, the rotation speed is controlled by on-off control.

(Function) By forming as described above, toner fusion on the surface of the toner supply roller is reduced.

In other words, by not rotating the toner supply roller at a constant rotation speed, the degree of toner fusion can be reduced.
In addition, by appropriately stopping the supply roller while the magnetic plan roller is rotating, (1) the thin layer of toner on the surface of the toner supply roller is thoroughly scraped off with a magnetic brush roller, thereby preventing the occurrence of toner fusion, and (2) While the toner supply roller is stopped, the toner thin layer forming member does not form a thin toner layer, so that the occurrence of toner fusion can be reduced.

(Example) Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a copying machine to which a developing device (1) according to the first invention is applied, and its main body generally includes a photoreceptor section (101), two image exposure sections (102), a paper feed section (103), and a conveyance section. (104
), a paper discharge section (105), a paper refeed section (106), and an operation section (not shown).

Among these, the details of the developing device side of the photoreceptor section (101) are shown in the second section.
It is shown in Figs.

This part is a photosensitive drum (10
At the point where toner is supplied to the electrostatic latent image formed on the photoreceptor layer (100a) provided on the outer circumferential surface of the photoreceptor layer (100a) and visualized as a toner image, the developer (2) and the toner cartridge (50).

The developing tank (3) of the developing device (2) has a side plate (4), (4X-
(not shown), a bottom casing (5), and upper casings (6), (7), and (8). are provided with openings (9) and (10), respectively.

The developing section (1) faces the front opening (9) of the developing tank (3).
1) has magnet bodies (12) and (13) fixed in a non-rotating state on the top and bottom, and a plurality of magnetic poles are arranged on the outer periphery of these magnet bodies (12) and (13), and In the magnet body (12) all magnetic poles (Sl, ~ + S 4, N1
．． ~． N4) are arranged alternately with S and N, especially in the rear region with a small spacing between the magnetic poles, while the lower magnet body (1
In 3), two S poles (S?-S e) are adjacent to each other only in the rear region, and in other regions, the S and N magnetic poles are alternately arranged.

The cylindrical developing sleeves (14) and (15) are attached to the magnet body (1
2) and (13), and fit them loosely to the outside of the arrows (b).
) and (C) directions at the same speed, and the tip of the height regulating plate (18) supported by the upper casing (7) is at a predetermined position on the upper outer periphery of the upper developing sleeve (14). They are opposed to each other with a height regulation gap (D b ,). Also, developing sleeves (14), (15)
Developing biases (Vbl) and (Vb2) are applied by power supplies (16) and (17), respectively.

The holder (20) is made of a non-magnetic material and is arranged parallel to the upper developing sleeve (14) behind the upper developing sleeve (14), with its lower end (24) facing the lower developing sleeve (14).
15) with a gear knob (Dbt), and a curved portion (21
) and an inclined portion (22) behind it. Also,
A magnetic plate (25) is attached to the curved surface (21) of the holder (20), and this magnetic plate (25) is attached to the developing sleeve (
A plurality of magnetic poles arranged in the axial direction of the developing sleeve (14) or obliquely thereto are provided in the rotating direction of the developing sleeve (14),
A dense magnetic field is formed between the magnet body (12) (
(See Figure 3). Further, the distance between the magnetic plate (25) and the developing sleeve (14) is constant, or the distance between the developing sleeve (14)
4) It becomes narrower toward the downstream side in the rotational direction.

A main developer stirring chamber (26) is formed behind the developing section (11).
), a packet roller (27) is arranged so as to be rotatable in the direction of arrow (d). This 71ke Nodorora (2
7) is a shaft (28) rotatably supported by the side plate (4).
A plurality of Noukets (29
) were constructed by erecting them at appropriate intervals. In addition, this bucket (29) has every other axial stirring blade (3
5) has multiple stages on the inner surface.

The packet (29) is a plate body with an I-shaped cross section, and includes a front plate (30) and a rear plate (32) located in front and behind with respect to the rotational direction of the packet roller (27), and a plate body (
31), and an opening (33) is formed in the front part of the plate body (31) in the rotational direction.

A bottom casing (5) is located at the rear of the developer stirring chamber (26).
An auxiliary developer stirring chamber (36) is formed by widening the auxiliary developer stirring chamber (36) to the rear.
) is rotatably supported by an auxiliary developer stirring blade (37) formed by attaching a blade (39) to a shaft (38) rotatably supported in the direction of arrow (e).

The opening (1) located above the auxiliary developer stirring chamber (36)
A magnet body (40) is fixed to the magnet body (40), and a magnetic roller (40) is attached to the outside of the magnet body (40), which can be rotated in the direction of the arrow (f).
1) is loosely fitted. In addition, a magnetic brush roller (41
) A regulating plate (42) is attached to the bottom casing (5) so as to face the rear outer peripheral surface of the bottom casing (5) at a predetermined distance.

Note that the magnet body (40) has a plurality of magnetic poles (S,...
~, S18, N, , N, , ) are arranged on the outer periphery, and the same S poles (S, , , S, , ) are arranged adjacent to each other in the part facing the packet roller (27). . Further, the magnetic brush roller (41) is connected to a ground terminal (43).

The housing (51) of the toner cartridge (50) is
Main body (52), roller cover (53), and lid 54)
and side plates (55), (55) (one not shown). Further, in the housing (51), there are formed a toner storage section (56), a toner supply section (57), a passageway (58) communicating these, and a roller storage chamber (59).

The toner storage section (56) has a side plate (55), and a stirring blade (60) formed by attaching a blade (62) to a shaft (61) that is rotatably supported by (55) is rotated in the direction of arrow (g). In addition, the tip (63) of this stirring blade (60) is formed in a shape protruding at an acute angle toward the rotation direction [direction of arrow (g)].
) is attached with a Mylar sheet (64) facing outward.

A toner empty detection plate (
65) is provided. This toner empty detection plate (6
5) is a support plate (671 ( 67
) and connect these tips with the tip connecting material (69).
It is formed by bonding via. Then, due to the rotation of the stirring blade (60), its tip (63) is pushed up by the push-up plate (
68) and is lifted to a predetermined position (the position shown by the solid line), and when the stirring blade tip (63) and the push-up plate 68) are disengaged, the toner is stored in the toner storage chamber (56). The toner is designed to fall onto the surface layer of the toner.

A gate plate (7) runs from the top of the passageway (58) to the bottom right side.
0) is suspended, and the lower end of the gate plate (70) is a free end and extends into the toner supply section (57). When no external force is applied, the passage (58) is closed as shown by the broken line in FIG.
58), and when a rightward external force is applied to the lower end, the passage (58) opens as shown by the solid line in the figure.

In the toner replenishing section (57), a replenishing blade (71) formed by attaching a blade (73) to a shaft (72) rotatably supported by the side plates (55) and (55) is attached in the direction of the arrow (+). It is arranged to be rotatable, and as the replenishment vane (71) rotates, the tip of the vane (73) periodically engages with the tip of the gate plate (70) to open the passage (58).

In the roller storage chamber (59), a toner supply roller (75) rotatably supported by the side plates (55), (55) via a support shaft (not shown) is rotatably driven in the direction of arrow (j).
And it is arranged so that the rotation speed can be controlled.

That is, in this embodiment, means is provided to predict the amount of toner used prior to development, and the rotation speed of the toner supply roller (75) is controlled based on this predicted value.

A plurality of flange-like protrusions are formed at appropriate intervals in the axial direction on the outer circumference of the toner supply roller (75), and the height thereof is 10 to 100 μm. may be hard plated or coated with Teflon to improve wear resistance.

In addition, the toner supply roller (75) is connected to an AC power source (80).
and a DC power supply (81) are connected in series, and the bias (VS)
is applied. The output waveform of the AC power supply (80) is not limited to a sine wave, but may be a pulse wave, a triangular wave, a sawtooth wave, etc. as long as the current and voltage change periodically.
It may be a complex distorted wave.

Further, on the outer periphery of the toner supply roller (75), there is a spill prevention plate (76) attached to the end of the main body (52) constituting the toner supply section (57), and a roller cover (53).
The tips of the regulating plates (77) supported by the toner supply roller (75) are in contact with the outer peripheral surface of the toner supply roller (75).

The regulation plate (77) consists of a magnet plate (78) attached to the roller cover (53) and a magnet plate (78) attached to the regulation plate (77).
The magnetic plates (78) and (79) each have a plurality of magnetic poles lined up in the axial direction of the toner supply roller (75). The pressure contact force against the toner supply roller (75) can be appropriately adjusted by the repulsive force and attraction force formed between the magnetic poles of the magnetic plates (78) and (79). ing.

The toner cartridge (50) having the above configuration is removably formed at the rear of the developing device (2).
), the toner supply roller (75) is opposed to the magnetic brush roller (41) with a small gap therebetween.

Next, the operation of the developing device (1) will be explained.

A developer consisting of toner and carrier in a predetermined ratio is stored in the developing device (2), and this developer is mixed and stirred by a rotating packet roller (27) to bring the toner and carrier into frictional contact. They are charged to opposite polarities. In addition, the axial stirring blade (
35), the developer is also stirred in the axial direction.

As the packet roller (27) rotates, the developer is scooped up by the four parts (34) formed by the plate main body (31) and the rear plate (32) of the packet (29), and is transferred to the supply area (R).
) is supplied to the outer periphery of the lower developing sleeve (15). The developer scooped into the packets (29) reaches the recess (34) through the opening (33) of the plate body (31) from the area surrounded by each packet (29), and reaches the recess (34) in the bottom casing ( The developer located near the inner surface of the recess (3)
4) Don't get swept away.

The developer supplied to the supply area (R) is transferred to the magnet body (13).
It is held on the outer circumference of the developing sleeve (15) by the magnetic force of the developing sleeve (15), and is transported in the direction of arrow (C) as the developing sleeve (15) rotates, and the amount of transport is regulated by the lower end (24) of the holder (2o).

The developer that has passed through the lower end of the holder (20) is conveyed to the upper portion (Q) facing the developing sleeve (14). Here, in the facing part (Q), in the vertical direction, N4 pole and 86 pole, S4 pole
The N5 pole and the N5 pole face each other, and the 84 pole and S pole of the same pole are diagonally opposite.

The N4 pole and the N4 pole face each other, and a repulsive magnetic field is formed there.

Therefore, as shown in FIG.
) The developer conveyed in the direction of the arrow (C) is prevented from entering the opposing part (Q), and the developer is prevented from entering the magnetic pole (S, ).
At the opposing portion between and (N4), the developer held by the magnetic pole (S6) is smoothly transferred to the magnetic pole (N,). Note that the magnetic force of the magnetic pole (N4) in the receiving area is the same as the magnetic force of the magnetic pole (N4) in the receiving area.
By making the pressure stronger than S8) (approximately 200 Gauss or more), it is possible to receive and transfer the developer more smoothly.

The developer supplied to the developing sleeve (14) is transferred to the magnetic body (1
2), and is conveyed in the direction of arrow (b) as the developing sleeve (14) rotates, passing through the portion facing the magnet plate (25).

Here, as shown in FIG. 3, a dense magnetic field is formed between the magnetic poles of the magnet body (12) and the magnetic plate (25), so the developer in the magnetic brush state is transferred to the developing sleeve ( 14)
and the magnet plate (25) while being transported while undergoing shear failure. Therefore, the frictional contact between the toner and the carrier increases, and sufficient charging power is applied to both.

The developer that has passed through the area facing the magnet plate (25) is regulated by the spike height regulation plate (18), and the developer that has passed through the spike height regulation gap (Dbz) between the spike height regulation plate (18) and the developing sleeve (14). Only the agent is conveyed to the downstream side of the spike height regulating plate (18).

The developer regulated by the height regulating plate (18) falls into the main developer stirring chamber (26) along the inclined surface (22) on the back surface of the holder. Here, the lines of magnetic force formed by the magnet body (12) are focused on the magnet plate (25), there is no magnetic field on the back side of the magnet plate (25), and the holder (20) is made of a non-magnetic material. Due to this, the magnetic force of the magnet body (12) does not reach the back of this holder (20), and the height regulating plate (18)
The regulated developer quickly falls into the main developer stirring chamber (26) without staying in front of it, and the stress applied to the developer is alleviated.

The developer that has passed through the portion facing the height regulating plate (18) continues to be conveyed in the direction of arrow (b) as the developing sleeve (14) rotates, and is transported between the developing sleeve (14) and the photoreceptor drum (
100) (hereinafter referred to as the "development area") (P
,) comes into contact with the electrostatic latent image formed on the surface of the photoreceptor drum (100), and the above-mentioned Toner is applied electrostatically to the electrostatic latent image.

The developer that has passed through the development area (P,) is transferred to the development block 17-(
15), and there, the receiver is transferred to the developing sleeve (15). The developer receptacle here is formed in the opposing portion (Q) in the same way as the developer receptacle from the lower developing sleeve (15) to the upper developing sleeve (14) described above. Due to the repulsive magnetic field, the opposing part (
Q) is prevented from entering the magnetic pole (S4) to the magnetic pole (N,
) is carried out smoothly.

The developer supplied to the developing sleeve (15) is conveyed in the direction of arrow (C) as the developing sleeve (15) rotates, and in the developing area (P,), the electrostatic charge developed in the developing area (Pl) is transferred. Further toner is applied on top of the latent image. Also,
An electrostatic latent image for which toner was insufficiently supplied in the development area (PI) is also visualized with sufficient density.

The developer whose toner concentration has decreased after passing through the development areas (Pl) and (P,) is continuously conveyed in the direction of the arrow (C) as the development sleeve (15) rotates, and is transported between the magnetic poles (S8) and S7). area, the developing sleeve (15
) detaches from the surface.

The developer that has fallen from the surface of the developing sleeve (15) is taken into the rotation locus of the outermost periphery of the packet (29) by the developer conveying action caused by the rotation of the packet roller (27), and is transferred to the main developer stirring chamber ( 26).

Here, the front plate (30) of the packet (29) is arranged in an inclined state slightly rotated counterclockwise with respect to a line passing through the center of the shaft (28) of the packet roller (27). Since the side closest to (28) is located at a position slightly advanced in the rotational direction, the developer taken into the trajectory of the outermost circumference of the packet (29) does not enter the inside of the packet (29).
Conveyed along the bottom casing (5).

Therefore, the developer with a reduced toner concentration does not mix with the developer that is mixed at an appropriate toner concentration inside the packet (29). In addition, the board body (31)
The developer that has fallen from the developing sleeve (15) is also captured in the recess (34) formed by the rear plate (32), but the developer captured in the fourth part (34) is trapped in the bucket) (
Pass the packet (29) through the opening (33) from inside the packet (29).
9) The developer that is pushed out by the developer flowing out to the outside and whose toner concentration has decreased is not directly used for development.

The developer conveyed along the bottom casing (5) by the front plate (30) of the packet (29) is conveyed to the auxiliary developer stirring chamber (36), where it is transported by the auxiliary developer stirring blade (37).
) is mixed by rotation.

The developer mixed in the auxiliary developer stirring chamber (36) is held on the outer periphery of the magnetic brush roller (41) by the magnetic attraction force of the magnet body 40) located above it, and the developer is The regulation plate (
42), the toner is conveyed in the direction of arrow (f), and the insufficient amount of toner is replenished at a portion (hereinafter referred to as "replenishment area") (T) facing the toner supply roller (75). Note that the toner replenishment operation in the replenishment area (T) will be described in detail later.

The developer that has been newly replenished with toner in the replenishment area (T) is transported in the direction of arrow Cf>, and is moved to the magnetic pole (S12).
) is released from the magnetic force of the magnet body (40), and is replenished by falling into the main developer stirring chamber (26) while being dispersed in a spray form. At this time, some of the newly replenished developer containing uncharged toner will fall on the developer of the appropriate density held in the recess (34) of the packet (29), but these uncharged toner The developer containing charged toner is scraped off by the holder (20) when the packet (29) passes through a portion facing the holder (20), and is rarely supplied as is to the developing sleeve (15).

Replenishment of toner from the toner cartridge (50) is performed as follows.

The toner in the toner supply unit (57) is conveyed toward the toner supply roller (75) as the supply blade (71) rotates, and the toner supply roller (75) has a concave portion located near the outer peripheral concave portion between the convex portions of the toner supply roller (75). The toner is retained and the arrow (D
The toner is conveyed in the same direction, and excess material is scraped off from the surface of the toner supply roller (75) at the tip of the regulating plate (77).

The regulation plate (held on the surface of the toner supply roller (75)
The toner that has passed through the opposing portion 77) is conveyed to the replenishment area (T) along the direction of arrow D.

In the replenishment area (T), the developer in the auxiliary developer stirring chamber (36) is conveyed in the form of a magnetic brush over the magnetic brush roller (41), and the scraping action of this magnetic brush-like developer and the toner supply roller (75) and magnetic brush roller (4)
1) due to the potential difference [=bias (V S )],
From the toner supply roller (75) to the magnetic brush roller (41)
) is supplied with toner.

However, toner is supplied from the toner supply roller (75) to the magnetic brush roller (41) only when the toner concentration in the auxiliary developer stirring chamber (36) is below a predetermined reference toner concentration. Conversely, when the toner concentration of the developer conveyed from the agent stirring chamber (36) is equal to or higher than the reference toner concentration, excess toner is collected by the toner supply roller (75). That is, in the replenishment area (T), toner density control is performed to maintain the toner density within the developing device (2) appropriately.

Note that the rotation speed of the toner supply roller (75) is controlled based on the toner consumption amount predicted by an appropriate means as described above.

Further, in the toner replenishing section (57), the rotation of the replenishing blade (71) causes the blade (73) to periodically engage with the tip of the gate plate (70), changing the gate plate (70) from the dotted line state to the solid line state. A curved passage (70) partitioned by a gate plate (70)
58) from the wedge-shaped space portion (58a) of the toner supply portion (57).
) is refilled with toner. However, the toner supply section (57
) is filled with toner, the gate plate (70) hardly vibrates and toner supply stops.

On the other hand, the toner in the toner storage section (56) is absorbed by the stirring blade (6).
0), the toner is agitated and crosslinking phenomenon and blocking of the toner is prevented. In addition, the toner is removed from the blade (62).
And as the Mylar sheet (64) at the tip rotates, the arrow (
g) direction and fed into the passageway (58). Here, since the tip (63) of the blade (62) has a shape that projects at an acute angle toward the rotation direction, even if the blade (62)
62) is buried in the toner, or the blade (62) is buried in the toner.
) is started from the surface of the toner, it operates while easily crushing the toner with the tip (63).

Further, even if the toner is left unstirred for a long period of time and becomes compacted, it is easily crushed.

In addition, the empty detection plate (65) is configured such that the push-up plate (68) periodically engages with its tip (63) by the rotation of the stirring blade (60), and rotates in the direction of the arrow (h) to the solid line position. The toner is lifted up, and when the push-up plate (68) and the stirring blade tip (63) are disengaged, it rotates in the direction of arrow (h') and falls onto the surface layer of the accumulated toner.

At this time, the amount of rotation of the empty detection plate (65), that is, the amount of falling, varies depending on the amount of toner stored in the toner storage section (56). The amount of toner remaining is low (
As a result, the falling amount increases, and when the remaining amount of toner in the toner storage section (56) decreases, the tip of the empty detection plate (65) comes to descend into the wedge-shaped space (58a) of the passageway (58).

Here, the toner in the toner storage section (56) is moved by the stirring blade (
The mylar sheet (64) provided at the tip of the spacer (60) extends to the bottom of the wedge-shaped space (58a).
Therefore, toner is stably stored in the wedge-shaped space (58a), and the toner level there decreases when most of the toner in the toner storage part (56) is consumed. It is.

Therefore, when the level of the tip of the toner empty detection plate (65) descending into the wedge-shaped space (58a) falls below a certain level, this state is detected by a detection means (not shown), and the toner cartridge (50) is Toner is replenished.

Next, in the second invention, a B/W ratio (black and white ratio) measuring means (91) of the original is provided in the lens system (90) in the image exposure section (102).
), a document size detection means (93) is provided at an appropriate position near the document table glass (92), and a copy magnification detection means (94) is provided in the operation section, and measurements and detections from these means are provided. A signal from the means is input to the control means (95), and the control means (95) controls the toner supply roller (7).
5) is formed to perform rotation speed control.

Further, in this embodiment, the B/W ratio of the original.

Although the toner consumption amount is predicted based on the measurement and detection value of the original size and copying magnification, for example, any one of the original size detecting means (93) and the copying magnification detecting means (94) may be used. Alternatively, a copying density detecting means and a copying paper size detecting means are provided in place of both of them, and the toner consumption amount is predicted based on the signals from each of these means and the rotation speed of the toner supply roller (75) is controlled. This also includes those that are intended to be carried out.

Furthermore, in a third aspect of the invention, the rotation speed of the toner supply roller (75) is controlled by on-off control, and specifically,
The larger the amount of toner consumption predicted from the signals from each of the measuring and detecting means, the larger the on-time ratio becomes. Figure 5 illustrates four types of time charts with different time ratios.The time ratio increases from I to is selected.

(Effects of the Invention) As is clear from the above description, according to the first invention, the toner on the toner supply roller is scraped off with a magnetic brush, and a voltage is applied to each of the toner supply roller and the magnetic brush roller, In a developing device equipped with a toner supply means configured to maintain a constant toner concentration on a magnetic brush roller, a means for predicting the amount of toner used prior to development is provided, and the toner supply roller is adjusted based on this predicted value. The number of revolutions of the rotor can be controlled.

According to the second invention, the means for predicting the amount of toner used in the first invention is configured to predict the amount of toner used from the B/W ratio of the original, the original size, and the copying magnification.

Furthermore, according to the third aspect of the invention, the rotation speed of the toner supply roller is controlled on and off.

Therefore, the scraping effect of the magnetic brush prevents toner from fusing to the toner supply roller, making it possible to control toner density with high precision over a long period of time.

Further, the lifespan of the developing device and the developer can be extended.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a copying machine to which a developing device according to the first to third inventions is applied, FIG. 2 is a detailed cross-sectional view of the photoreceptor portion of the device shown in FIG. 1, and FIG. 3 is a section around the developing sleeve. FIG. 4 is a sectional view of the main part in FIG. 2, and FIG. 5 is a time chart showing the state of rotational speed control of the toner supply roller. l...Developing device, 41...Magnetic brush roller, 75
... Toner supply roller, 91 ... B/W ratio detection means,
93... Original size detection means, 94... Copy magnification detection means, 95... Control means. Patent applicant Minolta Camera Co., Ltd. Agent
1 patent attorney, 1 person, 1 figure, 3 figures

Claims (3)

[Claims] (1) A toner supply means configured to scrape off the toner on the toner supply roller with a magnetic brush, apply voltage to each of the toner supply roller and the magnetic brush roller, and maintain a constant toner concentration on the magnetic brush roller. 1. A developing device comprising: a means for predicting the amount of toner used prior to development, and the number of rotations of the toner supply roller can be controlled based on the predicted value. (2) The means for predicting the amount of toner used is
The developing device according to claim 1, wherein the developing device is predicted from the W ratio, the original size, and the copying magnification. (3) The developing device according to claim 1, wherein the rotation speed control is on-off control.