JPH01108569A - Developing device - Google Patents

Abstract

PURPOSE:To entirely remove and collect an old toner stuck to a frame for covering a developing roll at the time of changing a color by forming a magnetic brush of a developer on the developing roll so as to be always contactable and applying a voltage of the same polarity as that of a toner to the opposed surface to the developing roll of the frame. CONSTITUTION:At the time of collecting a toner before changing a color by selecting toner supplying means 63, 73, a developer consisting of a toner and a carrier on a developing roll 73 always is brought into contact with the inside surface of a frame for covering a developing roller 32, in a magnetic brush state. Accordingly, it does not occur that an unstable toner caused by an electrification failure in the developer is separated from the magnetic brush and scattered and dropped down due to centrifugal force, vibration, etc. Also, when the voltage of the same polarity as that of the toner is applied to a frame 31, the toner stuck to the inside surface of the frame 31 is subjected to an electrostatic repulsion together with a scraping action of the magnetic brush and separated from the inside surface of the frame 31 and returned to the developer on the developing roll 73. In such a way, said toner is collected entirely to an electrostatic latent image carrier side or to a toner supplying means 63, 73 side by a usual toner collecting operation.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an image forming apparatus using an electrophotographic copying process;
The present invention relates to a powder development type developing device capable of changing colors, which is used, for example, in copying machines, printers, and the like.

(Prior Art) Conventionally, this type of developing device includes a developing roller in which a plurality of magnetic poles are arranged along the inner circumferential surface, and a toner supply means for supplying toner onto the outer circumferential surface of the developing roller. An electrostatic latent image is developed by rubbing a magnetic brush of a developer made of toner and carrier formed on a developing roller against an electrostatic latent image carrier. It is possible to change the color of an image by providing a plurality of toners, each containing toner of a different color, and selecting an appropriate toner supply means.

When changing the color by selecting the toner supply means, if the previous toner remains in the developer on the developing roller, new toner of a different color will be supplied and color mixing will occur.
Prior to color change, the toner in the developer on the developing roller is removed and collected. This one-time rough toner removal operation involves either supplying the toner on the developing roller to the electrostatic latent image carrier, that is, developing and removing the electrostatic latent image, or collecting the toner on the developing roller to the toner supply means side. It is done by doing.

(Problem to be Solved by the Invention) However, poorly charged toner in the developer on the developing roller is scattered and falls due to centrifugal force, and adheres to the inner surface of the frame covering the developing roller. Even if the upper toner is removed and collected, the toner adhering to the inner surface of the frame remains unremoved and may mix with toner of a different color after the color change, resulting in a muddy image, or may be damaged due to vibrations, etc. There have been problems such as falling onto the developer on the developing roller, resulting in a splatter-like image, or falling outside the developing device, causing adverse effects.

The present invention has been made in view of such problems, and an object of the present invention is to provide a developing device that can remove and completely collect the previous toner adhering to the frame that covers the developing roller when changing colors. purpose.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a single developing roller having a plurality of magnetic poles arranged along its inner peripheral surface, and a single developing roller having a plurality of magnetic poles arranged along its inner peripheral surface, and a single developing roller having a plurality of magnetic poles arranged along its inner peripheral surface. a plurality of toner supply means for supplying toners of different colors, the color can be changed by appropriately selecting the toner supply means, and the developer magnetic brush made of toner and carrier is formed on the development roller. In a developing device that develops an electrostatic latent image by rubbing it on an electrostatic latent image carrier, the surface facing the developing roller of the frame that covers the outer peripheral surface of the developing roller is formed of a non-magnetic conductive material, and color change is possible. When collecting the toner in the developer on the previous developing roller, the magnetic brush of the developer on the developing roller is formed so that it can always be contacted, and a magnetic brush of the same polarity as the toner is placed on the surface of the frame facing the developing roller. It applies voltage.

(Function) Therefore, according to the above configuration, when collecting toner before selecting the toner supply means and changing the color, the developer consisting of toner and carrier on the developing roller is applied to the inner surface of the frame covering the developing roller in a magnetic brush state. Because they are in constant contact, unstable toner due to poor charging in the developer will not separate from the magnetic brush due to centrifugal force, vibration, etc., and will not scatter or fall. Furthermore, when a voltage of the same polarity as the toner is applied to the frame, the toner adhering to the inner surface of the frame is removed from the inner surface of the frame due to the scraping action of the magnetic brush and the electrostatic repulsive force, and onto the developing roller. The toner is returned to the developer and completely collected on the electrostatic latent image carrier side or toner supply means side by a normal toner collection operation.

(Example) Hereinafter, the present invention will be described with reference to the accompanying drawings showing one example thereof.

A. General Structure and Operation of Copying Machine FIG. 1 is a sectional view of a small-sized copying machine equipped with a developing device according to the present invention, and its structure will be explained together with its operation.

Approximately the central shaft of the copying machine body (1) is coated with selenium, for example, on the surface of a cylindrical body made of aluminum (for example, U30m+n).
A photoreceptor drum (3), which is an electrostatic latent image carrier on which zinc oxide, cadmium sulfide, or other organic photoconductor is deposited or coated, is disposed.

This photosensitive drum (3) is rotated in the direction of arrow (a) by the main motor (2) driven by the ON operation of a print switch (not shown), and the surface is heated to a predetermined level by the discharge of the electrostatic charger (4). charged to a potential.

In the optical system (8), an exposure lamp (9) is turned on, and the light is irradiated onto a document (not shown) placed on a document table (14) that scans in the direction of arrow (b), and the reflected light is The photoreceptor drum (3), which is charged to a predetermined potential as described above, is exposed to light from the exposure point (Xl) through the Selfox lens array (12), and the original image is formed on the surface of the photoreceptor drum (3). An electrostatic latent image corresponding to the image is formed. This electrostatic latent image is supplied with toner at a portion (X2) facing the developing device (5) and is visualized as a toner image. Note that this developing operation will be explained in detail later.

The copy paper (S) is transferred from the paper feed section (20) to the paper feed roller (21).
is fed one by one based on the rotation of the guide plate (22X
23), waits in front of the timing roller pair (24), and moves the transfer area (
X3), and the toner image is electrostatically transferred based on the discharge of the transfer charger (6).

The copy paper (S) onto which the toner image has been transferred is placed on the photosensitive drum (
After being separated from the surface of the copy paper (S), the toner image is transported by a transport belt (25) via a guide plate (26) to a fixing device (27), where the toner image is fused and fixed onto the copy paper (S). The paper is discharged onto the paper discharge tray (28).

The cleaning device (7) removes residual toner from the surface of the photosensitive drum (3) that has passed through the transfer area (X3), and then the light from the exposure lamp (9) passes through the opening (10) of the reflective shade (10). 11) and a mirror (13) to irradiate the region (X4) to remove residual charges.

B. Structure, etc. of the developing device (5) Next, the structure, etc. of the developing device (5) according to the present invention will be explained in the following order with reference to FIGS. 2 to 15.

i, Schematic configuration of the developing device (5) ■, Developing section (30) stone, Switching mechanism (41) iv, Vibration mechanism (47) v, Toner hopper (60X70) vi, Opening/closing mechanism (80) vi, Gap adjustment mechanism ( 90) Hitting, locking mechanism (100) ix, drive mechanism (120) As shown in FIG. 1.2, roughly speaking, a first toner hopper (60) that accommodates black toner, a second toner hopper (70) that accommodates color toner (for example, red toner) other than the toner, and a photosensitive The photoreceptor drum (3) moves in the directions of arrows (c) and (c'') along the outer peripheral surface of the photoreceptor drum (3), selectively receives toner from the toner hopper (60) or (70), and transfers the toner to the photoreceptor drum (3). ), and a developing section (30) that supplies the electrostatic latent image formed on the surface of the image forming apparatus.

■, Developing section (30X, see Figure 3.4) In the developing section (30), the developing frame (31), (3
1) (one not shown) is the photosensitive drum support shaft (16)
It is rotatably attached to the back and front sides of the

The developing frames (31), (31) are equipped with a developing roller (32).
) is supported by a method described later, and a predetermined gap is formed between the developing roller (32) and the photosensitive drum (3).

Note that the developing roller (32) has an outer diameter of 116 mm, for example.
conductive, non-magnetic aluminum cylindrical body with micro-recesses (depth 10 to 2002 m) formed on the outer peripheral surface by blasting, etc., or a resin or oxide film formed on the surface of the aluminum cylindrical body. An insulating or semi-insulating material, or one in which an organic polymer film is plasma-polymerized on the surface of an aluminum cylinder by glow discharge in a vacuum is used.

A magnetic roller (33) in which a plurality of magnets with magnetic poles extending in the axial direction are arranged in the circumferential direction is housed inside the developing roller (32), and one end of the spindle is attached to the developing roller (32).
The other end (34) of the spindle protrudes from the developing roller (32) and is fixed to the developing frame (31).
(see figure), and is fixed in a non-rotatable state relative to the developing frame (31). On the other hand, the developing roller (3
2) has one end rotatably supported by the developing frame (31) and the other end rotatably supported by the spindle of the magnetic roller (33).

Therefore, even if the developing section (30) moves along the outer peripheral surface of the photoreceptor drum (3), the magnetic pole of the magnetic roller (40) maintains a constant positional relationship relative to the photoreceptor drum (3). be. That is, the magnetic pole facing the photosensitive drum (3) always faces the photosensitive drum (3).

Further, between the developing frames (31), an upper frame (35) and a lower frame (36) made of a non-magnetic conductive material cover the upper and lower parts of the developing roller (32), respectively.
) is bridged, and the developing roller (32) is connected to the photoreceptor drum (
3) and only the opposite side thereof is open.

Then, this upper frame (35) and lower frame (
The surface facing the developing roller (32) of 36) is formed so that the developer conveyed on the developing roller (32) in a magnetic brush state is always in contact with the surface, and the surface of the magnetic brush facing the magnetic pole is particularly high. A recess (35a) is formed to prevent developer from clogging.

Further, as shown in FIG. 17, the lower frame (36) includes a fixed member (36a), an end member (36b), and a movable member (
36c). The end member (36b) is
It is attached to the tip of the fixing member (36a) on the side facing the photoreceptor drum (3) via an insulating agent. As shown in FIG. 18, the movable member (36c) has support arms (36cl) and (36d) attached to both ends thereof, and the developing roller (
32) is rotatably supported on a support shaft.

A stirring chamber (38) is formed along the axial direction from the fixed member (36a) to the movable member (36c) on the surface of the lower frame (36) facing the developing roller (32). The inner surface of the stirring chamber (38) is a curved surface that allows the developer to flow smoothly without stagnation, and the side wall of the stirring chamber (38) on the side of the movable member (36c) has a height regulating section that faces the developing roller (32) with a predetermined gap. (39) This is Toshishita.

As shown in FIG. 19, the movable member (36c) is movable by a height regulating member moving means (37). That is, the movable member (36C) is driven by a solenoid (SL) via a lever (37a) and a link member (37b), and is returned by a spring (37c). First, when the solenoid (SL) is off, the movable member (36c)
When the height regulating part (39) of the magnetic roller (33) is located at the center point A between the magnetic poles of the magnetic roller (33) and the solenoid (SL) is turned on, the movable member (31l-6c) moves clockwise in Fig. 17. The height regulating portion (39) moves toward the magnetic pole located on the upstream side of the developing roller (32) in the developer conveyance direction while maintaining a constant gap with the developing roller (32). , and stop at position B. At this time, the movable member (36c) goes around below the fixed member (36a), and the stirring chamber (38)
is becoming narrower.

By the way, the end member (36b) of the lower frame (36)
) is connected to the positive pole of the DC power supply, and a positive toner adhesion prevention bias voltage (Vt) is applied thereto. Also, a developing roller (32).

The fixed member (38a) and movable member (36c) of the upper frame (35) and lower frame (36) are connected to a DC power source via a bias changeover switch (SW).

At position l of this bias changeover switch (SW), a negative developing bias voltage (vb) is applied to the developing roller (32), and the upper frame (35)
A voltage having the same potential as that of the developing roller (32) is applied to the lower seven frames (36) excluding the end members (36b). Also, at position 2, the developing roller (32
) is applied with a negative developing bias voltage (vb), and a positive voltage, that is, with the same polarity as the toner, is applied to the lower frame (36) excluding the upper frame (35) and the end member (36b). There is. Furthermore, at position 3, a positive developing bias voltage (vb) is applied to the developing roller (32), and the lower seven frames (3
6) is also applied with a positive voltage, that is, with the same polarity as the toner.

Table 1 is a list of the polarities of the voltages applied to each of the above members.

(Hereinafter, blank space) Furthermore, there are development sections (30) above and below the development section (30), respectively.
The switches (Sl) and (S2) that detect this are installed.

As shown in Fig. 3, the developing section (30) having the above configuration is provided with the photosensitive drum (3), the charger (4), and the cleaning device (7) at the rear and front sides of these. The entire imaging unit (
The imaging unit (IU) is configured to be detachable from the copying machine main body (1).

The developing section (30) having the above configuration has a switching mechanism (41
), a vibration mechanism (47), etc. are attached, and these will be explained below.

■, Switching mechanism (41X, see Figure 4.5) Switching mechanism (41
) moves the developing section (30) along the outer peripheral surface of the photoreceptor drum (3), and changes the thermal development state (Pl) and the color development state (
P2).

In this switching mechanism (41), a switching lever (42) is fixed to the developing frame (31) of the developing section (30),
A toner hopper (60) is attached to the switching lever (42).

A plate (43) located on the top surface of (70) is a lock. Further, a window (44) is formed in the plate (43), and the lever (42) is rotated in the direction of arrow (c).
When the developing roller (32) is switched to the heat developing state (Pl) where it faces the supply roller (63) of the first toner hopper (60), the black mark provided on the upper surface of the toner hopper (60) is displayed in the window (44). (45) appears.

Conversely, by rotating the lever (42) in the direction of the arrow (C''), the developing roller (32) moves along an arc (Ll) with its center centered on the photoreceptor drum (3),
When switching to the color development state (P2) in which the developing roller (32) faces the supply roller (73) of the second toner hopper (70), the toner hopper (70) is placed in the window (44).
) so that the color mark (46) provided on the top surface appears.

A black mark (45) or a color mark (46) appears through the window (44) on a display section (not shown) provided on the copying machine main body (1), and whether the copy is a concrete development or a color development copy is displayed. Displays whether it is possible.

iv. Vibration mechanism (see 47X Figure 6) The vibration mechanism (47) uses the switching mechanism (41) to switch the developing section (30) between the thermal development state (pi) and the color development state (pi).
P2) and the upper and lower frames (3).
5) and (36), thereby peeling off toner mechanically or electrically adhered to the inner surface of the frame.

This vibration mechanism (47) includes a spring vibrator (48),
(52) are each provided with a striking portion (50) on the photoreceptor drum (3) side.
), (54), is swingably supported by the upper frame (35) and lower frame (36) via fulcrums (49) and (53), and is supported in one direction by springs (51) and (55). is energized by Further, the support shaft (1) of the photoreceptor drum (3) is attached to the frame (57) provided on the copying machine body (1).
An uneven portion (56) is continuously formed on an arc centered at 6), and a vibrator (48) is located there.

The outer end of (52) is engaged.

Therefore, when the lever (42) of the switching mechanism (41) is held to switch the developing section (30) from the thermal development state (PI) to the color development state (P2) or vice versa, the vibrator (48) ), (52) are repeatedly engaged with and released from the concavo-convex portion (56), causing the vibrators (48), (52) to vibrate, thereby causing the upper portions of the striking portions (50), (54) to The outer parts of the frame (35) and lower frame (36) are struck to give them vibration.

v, Toner hopper (60), (70X, see Figure 7)
The toner hoppers (60) and (70) supply black toner and color toner to the developing section (30), respectively.

These toner hoppers (60) and (70) are connected to the developing section (3O
) is removably located at the rear of the toner hopper (
At the front of the main bodies (61) and (71) of 60) and (70), there are supply rollers (63) in the openings (62) and (72).

(73) are arranged, and the respective supporting shafts (68), (78) are provided in the main bodies (61), (71) with bearings (94), (95).
(see Figure 10). Also,
The centers of the supply rollers (63) and (73) are located on an arc (L2) centered on the photoreceptor drum (3),
At a position where the outer peripheral surfaces of the supply rollers (63), (73) and the photosensitive drum (3) are closest to each other, the distance therebetween is slightly larger than the outer diameter of the developing roller (32).

The supply rollers (63) and (73) have an outer diameter of d16 mm, for example, and have a depth of 10 to 200 mm by blasting, etching, or knurling on the outer peripheral surface.
A cylindrical body made of conductive, non-magnetic aluminum or the like is used, which has microscopic recesses of μm in size formed therein.

Also, the openings (62) of the toner hoppers (61), (71)
), (72) are provided with regulating blades (64), (74) and toner outflow prevention films (65), (75), the tips of which are attached to the rear outer peripheral surfaces of supply rollers (63), (73). are pressed into contact with each other.

The rear portions of the toner hoppers (60) and (70) are provided with the supply rollers (63) and (73), and the regulation blades (64) and (7).
4) and toner outflow prevention films (65) and (75) to form toner storage tanks (66) and (76), respectively, and toner storage tanks (6) of the first toner hopper (60).
6) rotatably accommodates a stirring blade (67).

Note that the switches (S3) and (S4) are switches that detect whether or not the toner hoppers (60) and (70) are installed at predetermined positions, respectively, and their signals are output to a control device (not shown). It looks like this.

vi, opening/closing mechanism (see 80X Figure 7.8) opening/closing mechanism (80X)
0) is the opening (6) of the toner hopper (60), (70).
2) and (72) are opened and closed to cut off the supply of toner from unused toner hoppers and prevent toner from falling.

This opening/closing mechanism (80) includes a supply roller support shaft (68),
Frame (81x81) on both ends of (78), (85)
(85) is rotatably supported, and the frame (85) is rotatably supported.
81X81) and (85X85) have opening/closing covers (8
2) and (86) are bridged.

The frames (81) and (85) are each integrally provided with segment gears (83) and (87), and are moved in the closing direction [arrow (d)] by springs (84) and (88).

(e) direction)]. The springs (84), (88) are wound around the support shafts (68), (78), one end is locked to the main body (61), (71), and the other end is connected to the frame (81), ( 85) respectively.

On the other hand, a segment gear (89) is integrally provided in the developing frame (31) of the developing section (30), and this segment gear (89) is connected to the segment gear (83) of the toner hopper (60), (70), (87) meshes with the developing section (
30) in the black development state (Pl) or color development state (P2).
), either one of the openings (62) or (72) is opened.

More specifically, hold the lever (42) of the switching mechanism (41) and rotate the developing section (30) and segment gear (82O-9) in the direction of arrow (c) to set the black developing state (Pl). Then (solid line state in FIG. 8), as the segment gear (89) moves, the segment gear (83).

(87) rotate in the directions of arrows (d') and (e), respectively, and as shown in FIG.
The opening/closing cover (82) of the second toner hopper (70) is retracted to open the opening (62) of the second toner hopper (70).
) is closed with an opening/closing cover (86).

When holding the lever (42) and rotating the developing section (30) and the segment gear (89) in the direction of the arrow (C'') to set the color developing state (P2) (the state shown by the two-dot chain line in Fig. 8),
Segment gears (83) and (87) are respectively indicated by arrows (d)
, (e') direction, and the first toner hopper (6
The opening (62) of the second toner hopper (70) is closed by the opening/closing cover (82), and the opening/closing cover (86) of the second toner hopper (70) is retracted to open the opening (72).

vii, gap adjustment mechanism (see 90X figures 9 and 10)
The gap adjustment mechanism (90) adjusts the distance (
gap) is set to a predetermined value.

In this gap adjustment mechanism (90), the developing roller (32
) has gap adjustment rollers (91) on both ends of the support shaft (33).
is rotatably provided. In addition, the supply roller support shaft (68
), (78) have gap adjustment rollers (92) at both ends, respectively.
, (93) are rotatably provided.

On the other hand, the supply roller bearings (94) and (95) formed on the side walls of the toner hopper bodies (61) and (71) have a slightly larger diameter than the supply roller support shafts (68) and (78). A gap is formed between (68), (78) and the bearing (94), (95).

Further, stoppers (96) and (97) are formed on the side walls of the toner hopper bodies (61) and (71), and the stoppers (
Springs (98), (99) are interposed between the support shafts (68), (78) and the support shafts (68), (78).
8) and (78) are biased toward the developing section (30) in the direction of the arrow.

According to the gap adjustment mechanism (90) having the above configuration, as shown in FIG. 9, when the development roller (32) is in the black development state (Pi), the gap adjustment roller (91) is Gap adjustment roller (92) of toner hopper (60)
) are pressed into contact with each other, and the developing roller (32) and the supply roller (63
) A predetermined gap is set between the two.

When the developing roller (32) is switched to the color developing state (P2), the gap adjustment roller (91) of the developing roller (32)
) is the second toner hopper (70) gap adjustment roller (
93), and the developing roller (32) and supply roller (
73), a predetermined gap is set between the two.

Information, lock mechanism (100
In the state i), the first toner hopper (60) is locked, and in the color development state (P2), the second toner hopper (70) is locked.

In this locking mechanism (100), the developing frame (31)
Lock release parts (101) and (102) are provided on the outer surface of the release part (101).
The surface facing the stopper (104)] slopes upward in the direction of the arrow (C''), and the surface -23= of the release part (102) [the surface facing the stopper (104)] slopes upward in the direction of the arrow (C''). It is an upward slope.

On the other hand, the copying machine main body (1) is provided with stoppers (103) and (104) located on the sides of the toner hoppers (60) and (70), as shown in Fig. 12.13. The rear part is fixed to the copying machine main body (1) via fixing members (Io5) and (106), and stoppers (Io3) and (
The free end of 104) has retaining holes (107) and (108).
are formed respectively. Also, a toner hopper (60), (
The main bodies (61) and (71) of the supply roller (63)
), (73), the retaining holes (107), (1
Engagement protrusions (109) and (110) having approximately the same diameter as 08) are formed.

In the locking mechanism (100) having the above configuration, the 11th
As shown in the figure, the developing frame (31
) is set to the black development state (Pl), the release section (
102) slips into the tip of the stopper (104), the retaining hole (108) of the stopper (104) is released from the engaging protrusion (110) of the second toner hopper (70),
The toner hopper (70) is removable (see FIG. 13). On the other hand, the stopper (
As shown in FIG. 12, the tip of the toner hopper (103) comes into pressure contact with the side surface of the developing frame (31), the retaining hole (107) engages with the engagement protrusion (109), and the first toner hopper ( 60
) is locked in a non-removable state.

Hold the lever (42) of the switching mechanism (41) and turn on the developing section (3).
0) to the color development state (P2), the release part (101) sinks into the surface facing the stopper (103) and the first toner hopper (60) is set in a removable state, contrary to the above. and the release part (102) is pressed against the stopper (
The second toner hopper (7) is evacuated from the opposite part of the
0) is locked.

That is, when the developing section (30) is in the black developing state (Pl), the first
The second toner hopper (60) is locked and cannot be taken out, and only the second toner hopper (70) is set to be removable. Conversely, the developing section (30) is in a color developing state (
At the time of P2), the second toner hopper (70) cannot be taken out, and only the first toner hopper (60) is set to be removable.

ix, drive mechanism 020X (see Figure 14.15) In the drive mechanism (120), the support shaft (16
) is connected to the main motor (2) (see Figure 1), and the developing roller driving gear (122) attached to the spindle of the developing roller (32) is It is designed to rotate around the photosensitive drum drive gear (121) while meshing with it via the developing frame (31), and these gears (121) and (122)
) constitutes a differential gear device. Note that the gear ratio between the developing roller drive gear (122) and the photosensitive drum drive gear (121) is 1:2.

Note that the developing roller drive gear (122) is a one-way clutch (
131) to the supporting shaft. This one-way clutch (131) is configured so that when the developing roller drive gear (122) rotates clockwise when viewed from the left side in FIG. 20, the rotational torque is transmitted to the spindle of the developing roller (32). It has become.

Also, the support shaft (68) of the supply rollers (63) and (73).

The supply roller drive gears (124) and (126) are attached to (78) via a supply roller drive clutch (the clutch corresponding to the 127X supply roller (73) is not shown), and these supply roller drive gears (124), (1
26) mesh with idler gears (123) and (125), respectively.

Furthermore, although not shown, the stirring blade (67) provided on the first toner-popper (60) is connected to the supply roller drive l'ya (
124) so as to rotate together with the supply roller (63). In addition, the stirring blade (67)
may be connected to the drive system of the document table (14) so that it rotates as the document table moves.

In the drive mechanism (120) having the above configuration, the developing section (
30) is set to the thermal development state (Pl), as shown in FIG. It meshes with the gear (123).

Therefore, in this state, the main motor (2) is driven -27
= When the photosensitive drum drive gear (121) rotates in the direction of the arrow, the developing roller drive gear (122),
Idler gear (123) and supply roller drive gear (1
24) rotate in the direction of the arrow, respectively, and the photosensitive drums (3),
The developing rollers (32) rotate in the directions of the arrows. Also,
When the supply roller drive clutch (127) is turned on by a signal from a control device (not shown), the rotation of the supply roller drive gear (124) is transmitted to the supply roller (73).

When the developing section (30) is switched from the heat developing state (PI) to the color developing state (P2), the developing roller drive gear (12
2) moves along the circumference of the photosensitive drum drive gear (121) while meshing with it, and meshes with the idler gear (125) of the second toner hopper (70).

Therefore, when the main motor (2) is driven in this state and the photosensitive drum drive gear (121) rotates in the direction of the arrow, the developing roller drive gear (122), idler gear (125), and supply roller drive gear are rotated accordingly. (126
) rotate in the directions of the arrows, and the photosensitive drum (3) and the developing roller (32) rotate in the directions of the arrows, respectively. Further, when the supply roller drive clutch (not shown) is turned on, the rotation of the supply roller drive gear (126) is controlled to the supply roller (73).
transmitted to.

X, Speed change mechanism (130X Fig. 20) The developing roller (32) can change its rotational speed by a speed change mechanism (130) using an electromagnetic clutch.

That is, a first speed change gear (133) having a friction plate (132) is loosely fitted onto the support shaft (16) of the photoreceptor drum (3) while being supported by a plate spring (not shown). A clutch (135) including a clutch plate (134) facing a friction plate (132) of a transmission gear (133) is loosely fitted to a support shaft (16) with the support of a stopper portion (not shown). In addition, the clutch plate (134) is attached to the support shaft (16) in the circumferential direction.
) is fitted to be able to rotate integrally with the developing roller (32).
A second speed change gear (136) that meshes with the first speed change gear (133) is fixed to the support shaft, and the gear ratio of the second speed change gear (136) and the first speed change gear (133) is l:2.3. It becomes.

The clutch (135) moves the friction plate (132) shown in FIG. 20 by a signal from a control system (not shown).
34) direction, and as a result, the first transmission gear (133)
) is in pressure contact with the clutch plate (134), and the rotational torque of the support shaft (16) is transferred to the first transmission gear (133).
).

In the transmission mechanism (130) having the above configuration, the clutch (135) is in the OFF state during development, and when the photoreceptor drum drive gear (12]) rotates due to the drive of the main motor (2), the clutch (135) is in the OFF state. The photosensitive drum (3) and the clutch plate (134) rotate in the direction of the arrow in the figure via the shaft (16), and the developing roller drive gear (12
2) and the one-way clutch (131), the developing roller (32) rotates in the direction of the arrow in the figure. This developing roller (
32), the second transmission gear (136) also rotates in the same direction, but the friction plate (132) is not connected to the clutch plate (134).
Since the first speed change gear (133) meshing with the second speed change gear (136) rotates idly with respect to the support shaft (16).

Next, when the clutch (135) is activated during toner collection, the photosensitive drum drive gear (12) is transferred from the main motor (2).
1) is directly transmitted from the photoreceptor drum drive gear (121) to the development roller (32) via the development roller drive gear (122) and one-way clutch (131).
), and a route from the clutch (135) to the developing roller (32) via the first gear (133) and second gear (136). Since the gear ratio of is higher, the developing roller (32) receives rotational torque through the latter route and rotates at a higher speed than during development, and as a result, the one-way clutch ( )
31), the developing roller drive gear (122) idles.

xi,) Toner density control means (see FIG. 2) Next, the toner density adjustment means supplied to the developing section (30) will be explained.

The developing bias voltage (vb) is applied to the developing roller (32) of the developing section (30) via the bias changeover switch (SW) as described above, and the supply roller (63) -31=, (73) is applied with the developing bias voltage (vb). Recovery bias voltage (Vs) with AC bias (Vrms) connected in series to DC bias (Vss)
is applied, and the bias voltages (Vb) and (Vss) are variable, and by adjusting the voltage value, the toner density on the developing roller (32) can be adjusted.

xii. Developer A two-component developer consisting of a toner and a carrier is used in the developing device (5), which is composed of more than one component.

As the carrier, a binder type carrier having a particle size of 20 to 100 μm, a ferrite carrier, an iron powder carrier, or a carrier whose surface is overcoated with an appropriate resin is used, and the carrier is a developing roller (32).
The magnetic roller (40) is magnetically held on the outer peripheral portion of the magnetic roller (40).

The toner used has a particle size of 5 to 30 μm and is manufactured by a pulverization method or suspension polymerization method, or a capsule toner. As mentioned above, the first toner hopper (60) contains black toner. The second toner hopper (70) contains color toner (for example, red toner).
is accommodated.

C1 Black Developing Operation The silent image operation using black toner in the first toner hopper (60) will be described below.

Note that the developing section (30) is set to the silent image state (Pi) by the switching mechanism (41), and a black mark (see 45X Fig. 4) is displayed on the display section (not shown) of the copying machine main body (1). is displayed, and the developing roller (32) is opposed to the supply roller (63) of the first toner hopper (60).

Also, Table 1. As shown in FIG. 2, the position of the bias changeover switch (SW) is set to 1, and the lower frame (3) excluding the upper frame (35) and end member (36b)
A negative bias voltage having the same potential as the developing roller (32) is applied to the end member (6) of the lower frame (36).
A positive bias voltage is applied to 36b).

The movable member (36c) of the lower frame (36) is a solenoid (S), as shown in FIGS. 17 and 19.
L) is in the OFF state and its brush height regulating portion (39) is located at position A, that is, at the center between the magnetic poles of the magnetic roller (33).

On the other hand, it is assumed that the gap adjustment mechanism (100) and the like are set as described below.

That is, in the gap adjustment mechanism (90), as shown in FIG. 9, a predetermined gap is established between the developing roller (32) and the supply roller (63) by pressure contact between the gap adjustment rollers (91) and (92). is retained.

In the opening/closing mechanism (80), as shown in FIG. 7, the opening/closing cover (82) of the first toner hopper (60)
2), and in the second toner hopper (70), the opening (72) is closed by the opening/closing cover (86). Therefore, color toner does not fall from the second toner hopper (70) in such a state.

In the locking mechanism (100), as shown in FIG. 11, the first toner hopper (60) is locked in a non-removable state, and the second toner hopper (70) is set in a removable state.

In the drive mechanism (120), as shown in FIG. 15, the developing roller drive gear (122) is connected to the first toner hopper (60
), and the rotational force of the photoreceptor drum drive gear (121) is applied to the developing roller drive gear (
122), an idler gear (123), and a supply roller drive gear (124).

In the transmission mechanism (130), as shown in FIG. 20, the clutch (135) is in a disengaged state.

In the toner density adjustment means, the developing bias voltage (Vb),
A recovery bias voltage (Vss) is set in each developing state.

When the print switch is turned on with each part of the developing device (5) set as described above, as shown in FIG. ), the developing roller (32), and the stirring blade (67) rotate, and the supply roller drive clutch (1
27), the supply roller (63) rotates.

As a result, in the toner storage tank (66), the stirring blade (6
Based on the rotation of step 7), the black toner is conveyed forward while being mixed and stirred, and at this time, toner blocking and crosslinking phenomena are prevented.

At the outer periphery of the supply roller (63) facing the toner storage tank (66), as shown in FIG. and the excess material is scraped off at the tip contact portion of the regulating blade (64).

The toner taken into the minute recesses is removed by the regulation blade (64
), the toner is frictionally charged to a positive polarity by contact with the regulating blade (64), and a thin layer of charged toner is formed on the surface of the supply roller.

On the surface of the developing roller (32), as shown in FIG.
When the carrier is conveyed in a magnetic brush state along the lines of magnetic force generated by the magnet of the magnetic roller (33), and the toner thin layer is conveyed to the opposing portion between the supply roller (63) and the developing roller (32). , on the surface of the developing roller (32) based on the scraping action of the brush-like carrier and the difference between the bias voltages (Vb) and (Vs) applied to the developing roller (32) and the supply roller (63). Black toner is supplied.

Here, in the area where the developing roller (32) and the supply roller (63) face each other, not only the above-mentioned toner supply operation but also
In parallel, a collection operation is also performed to collect excess toner from the carrier on the developing roller (32) to the supply roller (63).

The toner supplied to the surface of the developing roller (32) is
As shown in FIG. 2a, the developing roller (32) rotates and is conveyed in the direction of the arrow, and first, the two are mixed on the peripheral surface of the developing roller. Next, the developer is conveyed to the stirring chamber (38), where it is further mixed well with the developer described later while forming a vortex in the direction of the arrow, and is charged to a predetermined value. The surface of the developing roller (32) that has passed through the part facing the developing roller (39) is coated with toner and carrier at a predetermined ratio (
The two-component developer mixed to a toner concentration of 20 to 1Qwt% is adjusted and set to a state ready for development.

If the upper frame (35) and lower frame (36) are in an electrically floating state while the two-component developer consisting of toner and carrier is adjusted and conveyed on the developing roller (32), A phenomenon in which the upper frame (35) and the lower frame (36) are charged due to frictional contact with the carrier in the developer and a positive charge is accumulated, resulting in the outer surface of the developing roller (32) being developed with toner. occurs, the developing bias becomes ineffective, and the image becomes foggy. This phenomenon is caused by the upper frame (3
5) and also occurs when a positive voltage is applied to the lower frame (36).

However, in this embodiment, a negative voltage having the same potential as the developing bias of the developing roller (32) is applied to the lower frame (36) excluding the upper frame (35) and the end member (36b), so the toner is The developing roller (32) is maintained in a stable charged state with the carrier, and the outer surface of the developing roller (32) is not developed with toner.

In this state, when the electrostatic latent image formed on the surface of the photoreceptor drum (3) is conveyed to the part facing the developing roller (32), the two-component developer is applied to this electrostatic latent image. It is rubbed and visualized as a black toner image.

The toner that scatters and falls from the developer trying to leave the photoreceptor drum (3) is removed from the lower frame (36).
The tip of the photoreceptor drum (3) side, that is, the end member (36
b), but this end member (36b
) is applied with a positive bias voltage (Vt) having the same polarity as the toner, so the toner does not adhere due to electrostatic repulsion.

The developer that has passed through the part facing the photoreceptor drum (3) is 1
As shown in Fig. 22a, most of the spikes are cut at the part facing the regulating member (39) and fall into the stirring chamber (38), and this fallen developer flows in the direction of the arrow along with the developer mixed here. The developer is mixed while forming a vortex, erasing the toner consumption pattern during development, and some of the developer is again held on the surface of the developing roller (32) and transferred to the supply roller (63).
), where the toner is supplied again.

The inner surface of the stirring chamber (38) is a smooth curved surface and is formed within the range of the magnetic binding force of the magnetic opening (33), so the developer does not stay in one place. ,
They are constantly mixed and agitated as the developing roller (32) rotates.

The toner collected by the supply roller (63) is conveyed in the direction of the arrow based on its rotation, passes through the contact portion of the toner outflow prevention film (65), and is collected into the toner supply tank (66).

When the development operation of the electrostatic latent image on the original image is completed in this way, the developing bias voltage (Vb) and/or recovery bias ( Vs) is switched from the developing state to the standby state, some toner is collected from the surface of the developing roller (32) into the toner storage tank (66), and the toner concentration on the developing roller (32) is 0.1~ 2. Q
wt%.

D. Development section switching operation Next, from the black development state (Pl) to the color development state (P2
), as shown in FIG. 4, hold the switching lever (42) and rotate the developing section (30) in the direction of arrow (C'). As a result, a color mark (46) is displayed on the display section (not shown) of the copying machine main body (1). Further, the vibration mechanism (47) etc. described below are operated as follows.

In the vibration mechanism (47) shown in FIG. 6, a vibrator (48),
The tips of (52) sequentially engage with the uneven portions (56) of the frame (57), and the striking portions (5) of each vibrator (48), (52)
0) and (54) are electrically and mechanically attached to the surfaces of the upper frame (35) and lower frame (36) by continuously hitting the upper frame (35) and lower frame (36), respectively. The black toner that is attached will be peeled off.

In the gap adjustment mechanism (90) shown in Figure 9.10, the gap adjustment roller (91) of the developing roller (32)
The supply roller (63) is separated from the gap adjustment roller (92) of the toner hopper (60), and is biased by a spring (98) to move slightly in the biasing direction.

Further, when the developing section (30) is switched to the color developing state (P2), the gap adjustment roller (9) of the developing section (30)
1) is pressed against the gear adjustment roller (93) of the second toner hopper (70), and the gap adjustment roller (93) is slightly moved in the direction opposite to the arrow direction against the biasing force of the spring (99). , move the developing roller (32) and the supply roller (
73), a predetermined gap is uniformly formed along the axial direction.

In the opening/closing mechanism (80) shown in Figure 7.8, the developing section (30
), the segment gear (89) moves in the direction of the arrow (C''
) direction, the toner hopper (6
The segment gears (83) and (87) of the first toner hopper (60) rotate in the directions of arrows (d) and (e''), respectively, and the opening (62) of the first toner hopper (60) is connected to the opening/closing cover (82). )
The opening (72) of the second toner hopper (70) is opened by retracting the opening/closing cover (86) therefrom. Therefore, in this state, the first toner hopper (60
) Black toner will not fall from the printer.

In the locking mechanism (100) shown in FIG. 11.12, as the developing frame (31) moves, the release part (101) slips into the opposite surface of the stopper (103), and the other release part (102) (104), the first toner hopper (60) is set in a removable state, and the second toner hopper (70) is locked in a non-removable state.

In the drive mechanism (120) shown in FIG. 14.15, the developing roller drive gear (122) moves as the developing section (30) moves.
The second toner hopper (70
), and the rotational force of the photoreceptor drum drive gear (121) is transmitted to the developing roller drive gear (125).
122) to the idler gear (125) of the second toner hopper (70) and the supply roller drive gear (126).
is set in a state where it can be transmitted.

E. Black toner removal operation As described above, the developing section (30) is in the silent image state (Pl)
When the color development state (P2) is detected by the switch (S2), the position of the bias changeover switch (SW) shown in FIG. 2 is set to 3, and the development roller (32) is switched to the color development state (P2).

A positive bias voltage having the same polarity as the toner is applied to the upper frame (35) and the lower frame (36). Further, as shown in FIGS. 17 and 19, the solenoid (SL) is turned on and the height regulating portion (39) is at the B position.
That is, it moves toward the upstream magnetic pole in the developer transport direction. Furthermore, the clutch (135) of the transmission mechanism (130) shown in FIG. 20 is engaged.

Then, after a predetermined period of time has elapsed, the main motor (2) is activated, and the photosensitive drum drive gear (121) and the developing roller drive gear (122) of the drive mechanism (120) shown in FIG.
, and the supply roller drive gear (124) start rotating, and the surface of the photoreceptor drum (3) is uniformly charged based on the discharge of the charger (4).

Here, the rotational speed of the developing roller (32) is increased by the speed change mechanism (130) compared to during development, and the circumferential speed ratio of the photosensitive drum (3) and the developing roller (32) is 1: during development.
2, whereas l:2.3. Further, the supply roller drive clutch (not shown) attached to the support shaft (78) of the supply roller (73) of the second toner hopper (70) is turned off, and the supply roller drive gear (126) is turned off. No rotation is transmitted to the supply roller (73).

Then, when switching the black toner remaining in the carrier held on the surface of the developing roller (32) and the developing section (30) from the silent image state (Pl) to the color developing state (P2), the vibration mechanism The black toner peeled off from the upper frame (35) and lower frame (36) based on the impact action of (50) is conveyed along the outer periphery of the developing roller (32) based on the rotation of the developing roller (32), and is transferred to the photosensitive drum (3). The developing roller (32) is electrostatically supplied to the surface of the developing roller (32).
Black toner is removed from the outer periphery.

During this black toner removal operation, the upper frame (35
) and the lower frame (36) are formed so that the magnetic brush of the developer on the developing roller (32) is always in contact with these frames (35). ).

It is prevented from scattering and falling towards (36).

In addition, the upper frame (35) and the lower frame (36)
Since a positive bias voltage, that is, the same polarity as the toner is applied, an electrostatic repulsive force acts and the toner adheres to the upper frame (35), lower frame (36), and developing roller (32). There isn't. Even if toner adheres to the upper frame (35) or the lower frame (36), the toner is scraped off by the magnetic brush and returned to the developer by the repulsive force. In this way, the black toner adhering to the upper frame (35) or lower frame (36) is supplied to the photosensitive drum (3) together with the toner on the developing roller (32) and is completely removed.

On the other hand, the height regulating portion (39) of the movable member (36c) of the lower frame (36) moves to the B position and approaches the magnetic pole of the magnetic roller (33), as shown in FIG. (38) is narrowed.

Therefore, as shown in FIG. 22c, as the black toner removal operation progresses, the toner concentration decreases, and the developer on which the magnetic binding force between the carriers is strongly acting is removed by the brush height regulating member (39
) when flowing in a spiral in the stirring chamber (38), the fluid is strongly influenced by the magnetic force of the magnetic roller (33), ensuring agitation performance and improving toner removal performance. Toner removal operation time is shortened. In addition, although the toner concentration of the developer has decreased and the bulk density has become smaller, the 22nd
As shown in Figure c, the stirring chamber (38) itself is also smaller in proportion to this, and there is no gap between the developer and the bottom of the stirring chamber (38), so there is no residual toner. , toner removal performance is improved.

The black toner thus supplied to the surface of the photoreceptor drum (3) is conveyed in the direction of arrow (a) based on the rotation of the photoreceptor drum (3) and collected by the cleaning device (7).

When the black toner removing operation described above is carried out for a predetermined period of time and most of the black toner is removed from the circumferential surface of the developing roller (32), color development becomes possible.

As a result, black toner is not supplied to the electrostatic latent image during color development, and image quality does not deteriorate due to color mixing or the like.

FIG. 21 shows the influence of the speed of the developing roller (32) on the toner removal performance during the above-described toner removal operation. 32), and the amount of developed toner (mg/cm) is plotted on the vertical axis, and the change in the amount of developed toner with respect to the change in toner supply capacity is shown for four cases with different system speeds. According to
It can be seen that this increases in proportion to the circumferential speed ratio of the developing roller (32). Therefore, during toner removal operation, the photoreceptor drum (
3) and the developing roller (32) higher than during development (increased from 2 to 2.3 in this example), the toner removal ability increases and the toner removal operation time is shortened. .

The toner removal operation is performed when the copying machine is powered on, after a power outage or jam removal, and even after the toner hopper is replaced, and toner is removed from the developing section (30). The toner removal operation after the copying machine is powered on is executed during the warming-up time of the fixing device (27), the temperature control time, and the leveling time of the applied oil.

Furthermore, in this embodiment, the removal of the toner on the developing roller (32) was achieved by developing it on the photosensitive drum (3), but the toner was collected via the supply roller (63) to the toner hopper (60) side. It is also possible to do so. That is, in this case, the bias changeover switch (
Set the position of the developing roller (SW) to 2, and
) is applied with a negative developing bias voltage (vb),
While applying a positive bias voltage to the upper frame (35) and lower frame (36), the supply roller (63)
) is applied to the recovery bias voltage (Vs). As a result, the toner in the developer on the developing roller (32) is
The toner is collected by the supply roller (63) based on the potential difference between the developing bias voltage (Vb) and the collecting bias voltage (Vs) without adhering to the upper frame (35) and lower frame (36).

F. Color development operation With the development device (5) set as described above,
When the print switch (not shown) is turned on, the bias changeover switch (SW) is switched to position 1 based on a signal from a control device (not shown), and the developing bias (Vb) and collection bias voltage (Vs) are set again. At the same time as the developing state is set, the brush height regulating portion (39) returns to position A, and the clutch (135) of the transmission mechanism (130) is disengaged.

Next, the photosensitive drum (3) rotates in the direction of the arrow (a) based on the drive of the main motor (2), and the developing roller (32) in the developing device (5) rotates in the direction of the arrow, and the supply roller is driven. A clutch (not shown) is turned on. As a result, in the second toner hopper (70), a thin layer of color toner is formed on the outer peripheral surface of the supply roller (73), and the color toner is supplied to the surface of the developing roller (32).
At the outer periphery of the developing roller (32), a predetermined concentration (toner concentration 26 to 1Qwt%) consisting of carrier and color toner is applied.
A two-component developer is prepared.

The surface of the photoreceptor drum (3) is equipped with a charger (
After being charged by the discharge in step 4), an electrostatic latent image is formed based on the image exposure from the optical system (8), and this electrostatic latent image is supplied with color toner at a portion opposite the developing roller (32). The image is visualized as a color toner image.

When the above development operation is completed, in the development device (5), the development bias voltage (vb) and recovery bias voltage (Vs)
is switched to the standby state, and the toner density on the surface of the developing roller (32) is in the standby state (toner density +0.1 to 2.
Set to [Owt%].

Further, when the developing section (30) is switched from the color development state (P2) to the heat development state (PI), the heat development state (P
In the same manner as the switching operation from I) to the color development state (P2), the upper frame (35) and the lower frame (35)
The color toner adhering to 6) is peeled off and the developing section (
When the switch (Sl) detects that the developing roller (30) has been switched to the thermal development state (PL), the developing roller (32)
starts driving, and the color toner remaining there is supplied to the surface of the photoreceptor drum (3) and sent to the cleaning device (
7), and the state is set such that almost no color toner exists on the outer circumference of the developing roller (32).

Therefore, even if thermal development is performed next time, =51- Color toner never appears.

In addition, as shown in FIG. 16, the cleaning device (7)
The toner collection section (170) includes a toner collection pipe (17).
1) is connected, and its tip is connected to the supply roller (63) or (
The supply roller (63) or (73) is rotatably connected to the toner collection section (170) and the toner collection pipe (171) via a bearing structure (not shown).
) is provided with a conveyance coil (172) having one end fixed to a support shaft (175) of a cleaning device drive gear (174) that meshes with the photoreceptor drum drive gear (121). Further, another conveyance coil (173) is fixed inside the supply roller (63) or (73).

Therefore, the toner collected by the cleaning device (7) is transferred from the toner collecting section (170) to the supply roller (63) or (73) via the toner collecting pipe (171) based on the rotation of the conveying coil (172). transported inside. The toner conveyed to the supply roller (63) or (73) is
Fixed conveyor coil (173) and supply roller (63)
Or, based on the rotation of (73), the supply roller (63) or (73) is gradually stored from the back side.

In the above embodiment, the surfaces of the upper frame (35) and the lower frame (36) facing the developing roller (32) are
The magnetic brush of the developer on the developing roller (32) is always in contact with the developing roller (32) not only during development but also when collecting toner.However, during development, the brush is not in contact with the magnetic brush to prevent developer clogging and toner collection. It may also be in contact with the magnetic brush only occasionally.

Further, an alternating current may be superimposed on the direct current voltage applied to the upper frame (35) or the lower frame (36) during toner recovery, similar to the recovery bias voltage.

In the embodiment, the movable member (3) of the lower frame (36)
6c) is rotatably provided on the spindle opening of the developing roller (32) so that its height regulating portion (39) moves while keeping the gap with the developing roller (32) constant.
The developing roller (32) may be configured to move parallel to the tangential direction of the outer circumferential surface of the developing roller (32), or the tip of the brush height regulating portion (39) may be configured to swing.

In the embodiment described above, the height regulating portion (39) was moved to the B position during the toner removal operation before color change.
It may also be performed during toner density control before and after the developing operation. That is, before the developing operation, the developing roller (32
) from a state where there is almost no developer on the supply roller (63
), (73) until the developer is adjusted and ready for development, or after the development operation, the toner on the visual image roller (32) is supplied to the supply roller (63),
While the toner is collected via the toner hoppers (73) to the toner hoppers (60) and (70), the toner concentration of the developer on the developing roller (32) is low and the agitation performance is poor as described above. (39) to narrow the agitation chamber (38) ensures agitation of the developer, speeds up the rise time, and improves recovery efficiency.

In the embodiment described above, only the rotational speed of the developing roller is increased, but the rotational speed of the photoreceptor drum may also be increased accordingly.

Furthermore, in the above embodiment, the developing device is configured to switch to a toner hopper containing toner of a different color by rotating the single developing roller (32) around the photoreceptor drum (3) with a certain gap. Although the invention is applied, the invention is not limited to this type, and there is also a method in which a plurality of toner supply means containing toners of different colors are arranged around a single fixed developing roller, or As shown in Japanese Patent No. 61201271, a plurality of toner supply means are arranged around a rotating shaft, and by rotating the rotating shaft, one of the toner supply means is made to face a developing roller. can also be applied.

(Effects of the Invention) As is clear from the above description, according to the present invention, before selecting the toner supply means and changing the color, when collecting the toner in the developer on the developing roller, the developing Since the surface of the frame covering the roller that faces the developing roller is always in contact with the developer's magnetic brush, there is no scattering or falling of the toner, and the scraping effect due to the contact of the magnetic brush is
The toner adhering to the frame is removed by electrostatic repulsion between the toner and the frame to which a voltage of the same polarity is applied.

Therefore, even if the toner is completely removed and collected from the developing roller and the frame that covers it before this color change, and then a different color of toner is supplied and development is performed,
This has the effect of producing beautiful images without muddy colors or smeared patterns.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a schematic configuration of a copying machine equipped with a developing device according to the present invention, FIG. 2 is a cross-sectional view of the main part of FIG. 1, FIG. Figure 4 is a perspective view of the switching mechanism, Figure 5 is a sectional view showing the movement of the developing roller, and Figure 6 is a perspective view of the switching mechanism.
7 is a sectional view of the toner hopper, FIG. 8 is a side view of the opening/closing mechanism, FIGS. 9 and 10 are side views of the gap adjustment mechanism, and FIG. 11 is a side view of the locking mechanism. FIG. 12 is a sectional view showing the locked state of the locking mechanism, and FIG.
The figure is a sectional view showing the unlocked state of the locking mechanism.
15 is an exploded perspective view of the drive mechanism, FIG. 15 is a side view showing the switching state of the drive mechanism, FIG. 16 is a sectional view of the toner collection mechanism, and FIG. 17 is a sectional view showing the structure of the lower frame of the developing roller. Fig. 18 is a sectional view showing the movable member of the lower frame, Fig. 19 is a side view showing the drive device for the movable member of the lower frame, Fig. 20 is a sectional view of the transmission mechanism, and Fig. 21 is a change in toner supply capacity. A diagram showing changes in the amount of developed toner for
22a to 22c are cross-sectional views showing the state of the developer on the developing roller during development, at low toner concentration (before the height regulating section moves), and at low toner concentration (after moving the height regulating section), respectively. . 3... Photosensitive drum (electrostatic latent image carrier), 5... Developing device, 31... Developing frame, 32... Developing roller, 33... Magnetic roller, 35... Upper frame, 3
6... Lower frame, 41... Switching mechanism, 60.70... Toner hopper (toner supply means), 6
3.73... Supply roller (toner supply means), SW・
...Bias selection switch. Patent Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Aohaku Ao and 2 others rilJ (2wp/'w)
'f-fist-111'%E&

Claims (1)

[Claims] (1) A single developing roller having a plurality of magnetic poles arranged along the inner circumferential surface, and a plurality of toner supply means for supplying toner of different colors onto the outer circumferential surface of the developing roller; A developing method that enables color change by appropriately selecting a supply means, and develops an electrostatic latent image by rubbing a magnetic brush of a developer made of toner and carrier formed on a developing roller against an electrostatic latent image carrier. In the apparatus, the surface of the frame that covers the outer peripheral surface of the developing roller, which faces the developing roller, is formed of a non-magnetic conductive material, and when collecting toner in the developer on the developing roller before color change, the developing roller A developing device characterized in that a magnetic brush of the upper developer is always in contact with the magnetic brush, and a voltage of the same polarity as that of the toner is applied to a surface of the frame facing the developing roller.