JPS62211675A - Electrostatic latent image developing device - Google Patents

Abstract

PURPOSE:To prevent a toner from being scattered to the upstream side by a seal member of the downstream side, by switching the seal member of a developing device of the downstream side from a selected developing device, to a non-contact position against the surface of an electrostatic latent image carrying body, when the selected developing device is operating. CONSTITUTION:When the first developing device 4 of the upstream side is executing a developing operation, a seal member 58 which has been supported so as to be rotatable is in a non-contact position against the surface of a photo sensitive drum 1, and in this case, a developer does not exist on the outside peripheral surface of a developing sleeve 51 of the second developing device 5 of the downstream side, therefore, it does not occur that a toner is mixed into the first developing device 4 from a developing area B of the second devel oping device 5. On the other hand, when the second developing device 5 of the downstream side is executing the developing operation, the seal member 58 is in a contact position against the surface of the photosensitive drum 1, and it is prevented that a toner powder smoke is scattered upward from the developing area B of the second developing device 5 and mixed into the first developing device 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrostatic latent image developing device using a magnetic brush method used in electrophotographic copying processes and the like.

Prior art and its problems In recent years, image forming devices such as electrophotographic copying machines and reader printers have been equipped with multiple developing devices around an electrostatic latent image carrier, and one developing device is used for regular development (positive development). The other developing device is used for reversal development (developing a negative original into a positive image, hereinafter referred to as N-P development). Alternatively, one developing device can be filled with a developer containing black toner, the other developing device can be filled with a developer containing monochrome toner such as red, yellow, blue, etc., and each developing device can be selectively switched. There are products that are designed to be developed.

However, in the developing device, there is a problem in that toner released from the developer in the development area where the developing sleeve faces the surface of the electrostatic latent image carrier is scattered from the gap between the surface of the electrostatic latent image carrier and the developer casing. It has points. Such toner scattering rises as powder smoke above the developing area and appears as spillage below. In particular, as mentioned above, in an image forming apparatus in which a plurality of developing devices are arranged around an electrostatic latent image carrier, scattered toner may not only get mixed into other developing devices, but also cause damage to non-image areas. This causes toner fog.

Therefore, it has been proposed to provide a suction duct at the toner scattering location, as described in, for example, Japanese Patent Application Laid-Open No. 120372/1982, but this would require a large-scale device and increase costs. There are problems.

In order to solve the above problems, the electrostatic latent image developing device according to the present invention has the following features: (a) A plurality of developing devices are installed around the electrostatic latent image carrier to In an electrostatic latent image developing device that is arranged in the direction of movement of the surface of the carrier and develops by selectively operating each developing device, (b) the most upstream side in the direction of movement of the surface of the electrostatic latent image carrier; An insulating sealing member whose tip can be switched between a contact position and a non-contact position with respect to the electrostatic latent image carrier surface is provided on the upstream side in the moving direction of the electrostatic latent image carrier surface in each developing area of the subsequent developing device. (C) A control means for switching a sealing member of a developing device downstream of the selected developing device to the non-contact position when the selected developing device is operating.

In other words, the simplest and most effective method for preventing toner scattering is to close the gap between the surface of the electrostatic latent image carrier and the developer casing with a sealing member, but this method does not cover the gap between the surface of the electrostatic latent image carrier and the developer casing. This causes an inconvenience in that the toner image developed by the upstream developing device at the tip of the member is disturbed. Therefore, in the present invention, when the selected developing device is in operation, the sealing member of the developing device downstream of the selected developing device is switched to a non-contact position with respect to the surface of the electrostatic latent image carrier. .

Embodiment [First embodiment, see FIGS. 1 to 8] (Schematic configuration of copying machine) First, with reference to FIG. The general configuration of the copying machine will be explained below.

The photosensitive drum (1) can be driven to rotate in the direction of arrow (a), and around it are a charger (2), an exposure device (3) using a slit exposure method, and a first A developing device (4), a second developing device (5), a transfer charger (7), a copy paper separation charger (8), a blade-type residual toner cleaning device (9), and a residual charge eraser lamp (10) are arranged. It is set up.

(Internal structure of the developing device) The first developing device (4) and the second developing device (5) both have the same magnetic brush type configuration. For example, the first developing device (4)
The second developing device (5) is for performing NP development, and the second developing device (5) is for performing PP development. First, the internal structure thereof will be explained.

Each developing device (4), (5) has a photosensitive drum (
The developing sleeves (41) and (51) are opposite to each other.
A magnetic roller (42) with magnetized poles and S poles.

(52) is built-in, and a developing sleeve (41).

Developer transport guide members (43) and (53) are installed close to the upper half of the outer peripheral surface of (51).

The developer transport guide members (43), (53) have an arc shape concentric with the developing sleeves (41), (51),
Stirring blades (44) rotated in the direction of arrow (d), (
54) from the developer supply section (A) to the development area (B), the development sleeves (41) and (51) are installed at a substantially constant interval. In addition, this member (43)
, (53) are made of an insulating material in this embodiment, but may be made of a conductive material.

The height regulating plates (40a), (50a) protrude so as to maintain the inner surfaces of the developer casings (40), (50) at a constant distance from the developer transport guide members (43), (53). It was forced upon me. Scraper (45), (55
) is made of an elastic thin plate, and its tips are lightly pressed against the developing sleeves (41) and (51).

Further, toner casings (100) and (110) are installed on the backs of the developer casings (40) and (50), and when the supply rollers (101) and (111) rotate, the rollers (
101).

The toner filled in the notches (101a) and (lla) of (111) is transferred to the developer casings (40) and (50).
The stirring blades (44) and (54) are replenished.

(Operation of developer when selecting development) By the way, the developing devices (4) and (5) of this embodiment rotate the magnetic roller from the developing area toward the developer supply section, and also rotate the developing sleeve with the magnetic roller. A method of rotating in the same direction is adopted. Therefore, the developing sleeve (41) during the developing operation.

(51), magnetic rollers (42), (52) are both indicated by the arrow (
b) Rotationally driven in the direction.

Here, the movement of the developer during the developing operation of the developing devices (4) and (5) will be explained with reference to FIGS. 2 and 5. The description will be made regarding the first developing device (4) on the upstream side in the rotational direction of the photosensitive drum (+), but the same applies to the second developing device (5) on the downstream side in the same rotational direction.

The developer is supplied to the supply section (A) by rotation of the stirring blade (44) in the direction of the arrow (d), and the developer is supplied to the supply section (A) by rotation of the stirring blade (44) in the direction of the arrow (d).
b) The developer transport guide member (43) based on the rotation in the direction.
It is conveyed upward in the direction of arrow (C) with the height of the ears being regulated by the head height regulating plate (40a). The developer transported in the direction of arrow (C) on the developer transport guide member (43)
The tip contacts the surface of the photoreceptor drum (1) and develops an electrostatic latent image previously formed on the surface of the photoreceptor drum (1). At the same time, the developer comes into contact with the outer peripheral surface of the developing sleeve (41), and as the developing sleeve (41) rotates in the direction of arrow (b), the developing sleeve (41) and the developer transport guide member (
43) in the direction of arrow (b), is scraped off by a scraper (45), and is removed from the developer casing (40).
returned inside.

In this case, the position (X,) where the developer ends contact with the surface of the photoreceptor drum (1) is the position where the developing sleeve (4I) is approaching the surface of the photoreceptor drum (1), It is slightly upstream of the closest position (xl) between the two. As a result, the developer does not exist on the outer circumferential surface of the developing sleeve (41) downstream of the closest position (xl) with respect to the moving direction (arrow a) of the photosensitive drum (1).

Here, the principle of the above-described movement of the developer in the above system will be explained.

In the above system, the developer is conveyed on the outer circumferential surface of the developing sleeve in a direction generally opposite to the rotational direction of the magnetic roller. Examining this in detail, we can see that the upper layer of the magnetic brush is conveyed while rotating in the opposite direction to the rotation direction due to the movement of the magnetic field based on the rotation of the magnetic roller, and the lower layer near the outer peripheral surface of the developing sleeve is transported. Based on the rotation of the sleeve, the developer is transported in the rotation direction thereof, that is, in the opposite direction to the overall developer transport direction. However, the conveyance speed is lower than the conveyance speed in the upper layer portion of the magnetic brush.

In the electrostatic latent image developing device of this embodiment, a developing electrode (e.g., a developing sleeve that also functions as a developing electrode) is brought close to an electrostatic latent image carrier (e.g., a drum having a photoreceptor layer on its surface). At a certain position or the closest position, the developer ends contact with the photoreceptor drum (the contact area is referred to as a development area). Therefore, in this method, the developer conveyance speed (Vs
+2) should be made larger than the developer conveyance speed (Vmg) by the magnetic roller so that the developer does not exist on the outer circumferential surface of the developing sleeve on the downstream side of the developing area.

Specifically, the conveyance speed [V
Ilg (II1m/5ec)] is VB=hp・
(WIl1g/60) ...■ However, h: Hotaka (IllIB) p: Number of magnetic poles Wmg: Magnetic roller rotation speed (rpm) It is expressed by the following formula.

The conveyance speed based on the rotation of the developing sleeve [VsQ(iI!
l/5ec)] is Vs(1=D・rr・cWsQ/60) −・−
(2) However, it is expressed by the following formula: D: developing sleeve diameter (mm) WsQ: developing sleeve rotation speed (rpm).

Therefore, the overall developer transport speed [V dev(m
m/5ee) is Vdev=Vmg-Vs12=(h-p-Wmg-D ・rr ・ws&)/ao
It is expressed by the formula −...■.

By the way, at the closest position between the developing sleeve and the photoreceptor drum, the hot height (h) is necessarily the closest position interval (
It becomes dυ. Therefore, in order to prevent the developer from existing on the outer circumferential surface of the developing sleeve downstream of the developing area, D・rr・WSQ > d+ ” p−Wmg
It is sufficient to satisfy the formula ``''■.In other words, the diameter of the developing sleeve, the number of magnetic poles of the magnetic roller, their rotational speed, the distance between the developing sleeve and the photosensitive drum, etc. must be set to satisfy the formula 0. Good.

(Specific Example of Development Conditions) Next, the present developing device and specific numerical values of the development conditions will be explained based on experiments conducted by the inventors.

Developing sleeves (41), (51): Material: stainless steel Diameter: 31 mm Number of rotations: 60 rpm Magnetic rollers (42), (52): Number of poles = 8 Magnetic force: 100OG (on the surface of the developing sleeve) Number of revolutions: l 200'rpm Closest position interval: 0.4mm Brush height regulation interval: 1.5mm Distance between developer transport guide member and developing sleeve: 1.2m
1Il In addition, under the above conditions, the developer should be moved to the nearest position (X
A developing sleeve (41) on the downstream side of l).

It goes without saying that the above-mentioned formula 0 must be satisfied so as not to exist on the outer circumferential surface of (51).

(Function of developer transport guide member) In addition, in this embodiment, the developer transport guide member (43)
, (53) is provided to eliminate a decrease in toner concentration in the developer in the development area (B) regarding the developer using a carrier. That is, the magnetic roller (42)
, (52), the developer before development is conveyed in the direction of arrow (c), and the developing sleeves (41), (51).
The developer with a reduced toner concentration after development, which is conveyed in the direction of arrow (b) based on the rotation, is transferred to the developer conveyance guide member (4).
3) and (53), and there is no exchange of developer in both transport paths.

By the way, the distance between the developer conveyance guide members (43), (53) and the developing sleeves (41), (51) is considerably wider than the distance between the closest positions, and according to this method, the distance between the developing sleeves (41), (51)
Strictly speaking, the developer conveyed in the direction of arrow (b) on the outer circumferential surface of 41) and (51) is member (43).

Since the upper layer has a height of up to (53), the upper layer receives a conveying force in the direction of arrow (c) expressed by the above equation 0 based on the rotation of the magnetic rollers (42) and (52). However, according to the experimental results, the developing sleeves (41), (51)
The developer between the members (43) and (53) was being conveyed in the direction of arrow (b) by the rotation of the developing sleeves (41) and (51). This is considered to be due to the following reasons. The conveying force associated with the rotation of the developer due to the rotation of the magnetic rollers (42) and (52) changes depending on the density of the developer. As the developer becomes more dense, it becomes difficult to move, so the conveying force associated with the rotation becomes weaker. . Developing sleeves (41), (51) and member (43).

(53), the density of the developer is relatively high, and therefore it is considered that the developer as a whole moves in the direction of arrow (b).

(Operation of developer when development is not selected) On the other hand, when developing, for example, if the first developing device (4) is selected, the second developing device (5) is simply connected to the developing sleeve (51), the magnetic roller ( 52), the developer present on the outer peripheral surface of the developing sleeve (51) will come into contact with the toner image developed by the first developing device (4) in the developing area (B). Unnecessary adhesion of toner and disturbance of toner images occur.

Further, when the second developing device (5) is selected, unnecessary adhesion of toner occurs in the first developing device (4) as well.

Therefore, if the magnetic roller (42) or (52) of the unselected developing device (4) or (5) is rotated in the direction of the arrow (C) in the opposite direction to that during development, the developing sleeve (4I) or ( 51) and the developer on member (43) or (53) is transported in the direction of arrow (b) and is eventually removed from the development area (B).

Such movement of the developer will be explained with reference to FIGS. 3 and 6.

As the magnetic rollers (42) and (52) are driven to rotate in the direction of arrow (c), the developer transport guide member (43).

The developer on (53) is conveyed in the direction of arrow (b) and passes through the height regulating plates (40a) and (50a) to the casing (4).
0), (50). At the same time, the developing sleeve (
The developer on the outer peripheral surfaces of 41) and (51) is also conveyed in the direction of arrow (b), scraped off by scrapers (45) and (55), and returned into the casings (40) and (50).

That is, the developing device (4
) or (5), the developer is supplied to the developing sleeve (41
) or (51) does not exist on the outer peripheral surface.

In addition, in this embodiment, the developing sleeve (41) or (5
I) is rotated in the direction of arrow (b) even when not selected, and this rotation causes the developing sleeve (41) or (5) to rotate.
The developer on the outer peripheral surface of the casing (40) or (5)
0) receives the conveying force that is returned to the inside.

However, the developer is attached to the magnetic roller (42) or (52).
The developing sleeve (41) or (51) may be controlled to stop its rotation when it is not selected, in order to receive sufficient conveying force in the return direction by rotating in the direction of arrow (c).

That is, in this embodiment, each of the magnetic rollers (42) and (52) can be driven to rotate in opposite directions by one drive source, and by switching the drive direction by the drive source,
The developing sleeve (41) of the non-selected developing device (4) or (5)
) or (51) is removed from the development area (B).

(Drive Mechanism for Magnetic Rollers) The drive mechanism for the magnetic rollers (42) and (52) will now be described with reference to FIG. 7.

The drive motor (130), which is a drive source and can rotate forward and backward, is installed on the main body of the copying machine, and is connected to a pulley (130) fixed to its output shaft.
A belt (133) is stretched between the pulley (132) fixed to the spindle end of the magnetic roller (42) of the first developing device (4). In addition, the second developing device (
The magnetic roller (52) of 5) is installed at a distance from the magnetic roller (42) so that their magnetic force can reach each other.

Therefore, when the drive motor (i:to) is driven in the direction of arrow (b), the magnetic roller (42) is also rotationally driven in the direction of arrow (b). However, the magnetic roller (52) is rotationally driven in the direction of arrow (C) by magnetic induction based on the rotation of the magnetic roller (42). With this, the first developing device (4) performs development, and the second developing device (5) develops the developing sleeve (51).
) The developer is removed from the outer circumferential surface. On the other hand, when the drive motor (130) is switched and driven in the direction of arrow (C), the magnetic roller (42) is rotationally driven in the direction of arrow (c), and the magnetic roller (52) is rotated by magnetic induction in the direction of arrow (b).
) direction. With this, the second developing device (5
), and the developer is removed from the outer peripheral surface of the developing sleeve (41) of the first developing device (4).

The means for selecting a developing device for performing development is to turn on a selection key provided on the operation panel of the main body of the copying machine.

It is done off-line. This signal is transmitted to the drive motor (130
), and the driving direction is switched.

By using such a drive system, the magnetic roller (42
) and (52) can be switched.

In addition to this magnetic induction method, the magnetic roller (52) of the second developing device (5) may be driven by, for example, a belt method in the opposite direction to the magnetic roller (42) of the first developing device (4). It may also be rotated.

(Drive mechanism for developing sleeves, etc.) On the other hand, the drive mechanisms for the developing sleeves (41), '(51), etc. provided at the back of each developing device (4), (5'') will be explained with reference to FIG. do.

The drive gear (140) is connected to the main motor of the copying machine body via a gear (not shown), and is connected to the developing sleeve (41),
A gear (142) fixed to the end of the spindle of (51).

(144) is connected to the lever drive gear (140) via gears (141) and (143) fixed to the ends of the spindles of the stirring blades (44) and (54). Therefore, when the main motor rotates the drive gear (140) in the direction of arrow (b) at the same time as the copying operation starts, the gears (141), (1
43) rotates in the direction of arrow (c), stirring blade (44),
(54) rotate in the same direction, and the gear (142),
(144) rotates in the direction of arrow (b), and the developing sleeve (
4,1) and (51) rotate in the same direction.

That is, in this embodiment, the developing sleeve (41) or (
5I) and the stirring blade (44) or (54) are rotationally driven even if they are not selected. Developing sleeve (4
1) or (51) is conveniently driven to rotate even when not selected, to remove the developer from the development area (B).
Similarly, the reason why the stirring blade (44) or (54) is rotationally driven is to ensure sufficient stirring and mixing of the developer.

In addition, by adopting such a drive system, the rotation direction of the magnetic rollers (42) and (52) can be switched by a single drive system without intervening a clutch or the like as described above. It becomes possible to simplify the drive mechanism of the developing devices (4) and (5).

(Means for preventing toner scattering) On the other hand, in this type of magnetic brush type developing device, toner scattering outside the developing device, that is, toner powder smoke rising above the developing area (B) and spilling downward. It is important to prevent this.

Therefore, in this embodiment, in order to prevent the toner powder smoke from scattering upward, in the first developing device (4) on the upstream side,
A seal member (48) made of a flexible insulating material is adhered to the upper end surface of the developer casing (40), and its tip is in contact with the surface of the photoreceptor drum (1).

In the second developing device (5) on the downstream side, a sealing member (58) made of a flexible insulating material is attached to a rotatable support shaft (59).
Fixed. The support shaft (59) is connected to a solenoid (116) provided with a return spring (117) via a lever (115), as shown in FIG.

When the solenoid (116) is off, the sealing member (58) is biased by the return spring (117) in the direction opposite to the arrow (e), and its tip is pressed against the surface of the photoreceptor drum (1).
and maintain contact-free status. And solenoid (11
6) is turned on, it swings in the direction of arrow (e), and the tip maintains contact with the surface of the photoreceptor drum (1). The solenoid (116) is linked to the on/off of the selection keys of the developing devices (4) and (5), and is turned off when the first developing device (4) is selected, and the sealing member (58)
maintains a non-contact position, and when the second developing device (5) is selected, it is switched to the on state, and its tip comes into contact with the surface of the photoreceptor drum (1).

That is, when the first developing device (4) on the upstream side is performing a developing operation, the sealing member (58) is not in contact with the surface of the photoreceptor drum (1). 4
), and since there is no developer on the outer circumferential surface of the developing sleeve (51) of the downstream second developing device (5) as described above,
Toner does not enter the first developing device (4) from the developing area (B) of the developing device (5).

On the other hand, when the second developing device (5) on the downstream side is performing a developing operation, the sealing member (58) comes into contact with the surface of the photoreceptor drum (1). Toner powder smoke is prevented from scattering upward from the developing area (B) and entering the first developing device (4). Furthermore, at this time, since no development is performed in the first developing device (4), there is no risk of disturbing the toner image with the sealing member (58).

Furthermore, in this embodiment, in order to prevent toner from spilling downward, the developing area (B) of each developing device (4), (5) is
Seal members (46) and (56) made of elastic material below the
The lower part is the developer casing (40).

(50) is installed by fixing it to the lower end surface of the photoreceptor drum (1), and the distance between the tip and the surface of the photoreceptor drum (1) (see Fig. 4) is determined by the spacer ( 47) and (57) are sealing members (46).

It is regulated by the elasticity of (56) coming into contact with the outer peripheral surfaces of the developing sleeves (41) and (51). for example,
The seal members (46) and (56) are made of phosphor bronze plates with a thickness of O and I mm, and the spacers (47) and (57) are made of acrylic resin.

Although the tips of the sealing members (46) and (56) cannot be brought into contact with the surface of the photoreceptor drum (1) in order not to disturb the toner image, in order to effectively prevent toner from spilling, the distance (D2) ) should be as narrow as possible. Therefore, the developing sleeve <41) is used as a positioning reference member to install the tips at the narrowest possible interval (D).
, (51) was used. Developing sleeve (41
) and (51) are accurately positioned at intervals (D, ) from the surface of the photoreceptor drum (1) in the axial direction. This allows other positioning means to be installed to position the tips of the sealing members (46) and (56), or to maintain the straightness of the tips of the sealing members (46).

There is no need to form (56) itself with a thick member, and the interval (D,) can be set sufficiently narrowly and accurately using a thin member.

In addition, as in this embodiment, the developing sleeve (41).

The reason why it is possible to adopt a configuration in which the spacers (47) and (57) are in contact with the lower side of (5[) is that under the above-mentioned development conditions, the developer does not exist downstream of the development area (B). It is. Also, a spacer (47).

(57) is not necessarily necessary, and the sealing members (46) and (56) are directly attached to the developing sleeve (41).
, (51).

Alternatively, the spacers (47) and (57) are made insulative, the seal members (4G) and (s e) are made conductive, and the seal members (46) and (56) are made with a polarity opposite to that of the toner. By applying a polar bias, toner collection efficiency is further improved.

[Second Embodiment, see FIG. 9] In this second embodiment, another developing device (6) is provided to form a three-stage configuration, and each developing device (4), (5), and (6) is connected to the third stage. A developer transport guide member (43) in one embodiment.

(53) is omitted, and a magnetic roller (42).

(52) and (62) are fixed to form a developing sleeve (41).

This system adopts a system in which only (51) and (61) are rotated in the direction of arrow (C) to transport the developer in the same direction, and in addition, instead of stirring blades (+4) and (54), they are Packet rollers (113) and (123) are installed with Yu-shaped packets (113a) and (123a) attached thereto.

In addition, the height regulation plates (114), (124), (134)
are attached to the support shafts (115), (125), (H5), and the short pieces (114a), (124a), (L34a)
and long pieces (114b) and (124b).

(134b), which turns on a solenoid (not shown).3. By turning it off, the short piece or the long piece comes to face the developing sleeves (41), (51), and (61). Short pieces (114a), (124a), (
134a) regulates the height of the developer conveyed to the development area (B) in the same way as during normal development. Long piece part (114b)
, (124b).

(134b) regulates the height of the developer to be short so that the developer does not come into contact with the surface of the photoreceptor drum (1) in each development area (B). The solenoid is connected to the developing device (4).
'), (5), and (6), and if the selected developing device, for example, the middle developing device (5), is selected, only the short piece of the height regulating plate (124) of that developing device is selected. The portion (124a) faces the developing sleeve (51) and enables development. The developing device (4) that was not selected (
The height regulating plates (114) and (134) of 6) are the long pieces (1
14b) and (134b) are the developing sleeves (41) and (6
1), the height of the developer conveyed to the development area (B) is low, and the developer does not come into contact with the surface of the photoreceptor drum (1).

On the other hand, the developing device (6) also has a sealing member (68) fixed to a support shaft (69) to prevent toner powder smoke from scattering, and is oscillated by a solenoid (not shown). There is. The two seal members (58) and (68) are a seal member (58) of a developing device located downstream in the rotational direction of the photoreceptor drum (1) from the selected developing device when the selected developing device is in operation; (68) is switched to a non-contact position with respect to the surface of the photoreceptor drum (1).

That is, when the developing device (4) is selected, the seal member (
58) and (68) both remain switched to the non-contact position. As shown in Figure 9, the developing device (5)
is selected, the sealing member (5) of the developing device (5) is selected.
8) is switched to the contact position, and the seal member (68) of the developing device (6) downstream thereof maintains the non-contact position. Furthermore, when the developing device (6) is selected, the sealing member (68) of the developing device (6) is switched to the contact position, and the sealing member (58) of the developing device (5) is switched to the non-contact position. . However, in the latter case, the seal member (5
8) may hold the contact position.

With this switching operation, the development area (B
) to prevent toner powder smoke from scattering upward.
Disturbance of the developed toner image is prevented.

[Other Examples] Note that the electrostatic latent image developer device according to the present invention is not limited to the above-mentioned embodiments, and can be extensively modified within the scope of the gist. For example, a copying machine in which the photoreceptor drum (1) is driven to rotate in the direction opposite to the arrow (a), and the electrostatic latent image moves from below to above with respect to the developing devices (4) and (5). In this case, the seal members (48) and (58) are installed on the upstream side in the rotational direction of the photoreceptor drum (1), that is, at the positions of the seal members (46) and (56) in the first embodiment.

In this case, the seal members (48) and (58) function to prevent toner from scattering downward in each developing area (B).

Further, it goes without saying that the developing device may use an l-component developer instead of a two-component developer.

Effects of the Invention As is clear from the above explanation, according to the present invention, the electrostatic latent image carrier surface of each development region of the developing device after the most upstream side in the direction of movement of the electrostatic latent image carrier surface is The disposed insulating seal member can be switched between a contact position and a non-contact position with its tip against the surface of the electrostatic latent image carrier. Since the sealing member of the side developing device is switched to the non-contact position, it is possible to prevent the toner from scattering upstream in the direction of movement of the surface of the electrostatic latent image carrier with a simple member called the sealing member. It is possible to eliminate the possibility that the toner image developed on the upstream side will be disturbed by the seal member on the downstream side.

[Brief explanation of drawings]

1 to 8 show a first embodiment of an electrostatic latent image developing device according to the present invention, FIG. 1 is a schematic configuration diagram of a copying machine, and FIG.
The figure is a cross-sectional view when the magnetic roller of the first developing device is rotated in the normal direction, Figure 3 is a cross-sectional view when the magnetic roller is rotated in the reverse direction, Figure 4 is a cross-sectional view around the spill prevention member, and Figure 5 is the second
Cross-sectional view when the magnetic roller of the developing device is rotated in the normal direction, No. 6
The figure is a sectional view when the magnetic roller is reversed, FIG. 7 is a front view showing the drive mechanism for the magnetic roller, and FIG. 8 is a rear view showing the drive mechanism for the developing sleeve and the like. FIG. 9 is a sectional view showing the second embodiment. (A)...Developer supply section, (B)...Development area, (
1)...Photosensitive drum, (4), (5), (6)...
- Developing device, (41), (51), (61)...Developing sleeve, (42). (52), (62)...magnetic roller, (58), (6
8)... Seal member, (59), (69)... Support shaft, (116)... Solenoid. Patent applicant Minolta Camera Co., Ltd. Representative Patent attorney Aoyama Aoyama and 2 others Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. A plurality of developing devices are provided around the electrostatic latent image carrier for conveying developer along the outer peripheral surface of the developing sleeve toward a developing area facing the surface of the electrostatic latent image carrier. The electrostatic latent image developing device is arranged in the moving direction of the surface of the electrostatic latent image carrier, and each developing device is selectively operated to perform development. On the upstream side in the moving direction of the electrostatic latent image carrier surface of each developing area of the developing device after the upstream side,
An insulating seal member whose tip can be switched between a contact position and a non-contact position with respect to the surface of the electrostatic latent image carrier, and a seal member located downstream of the selected developing device when the developing device is operating. An electrostatic latent image developing device comprising: a control means for switching a sealing member of the developing device to the non-contact position.