JPS63169677A - Magnetic brush developing device - Google Patents

Abstract

PURPOSE:To exactly prevent the color mixture of a different color toner by providing a toner eliminating part for eliminating a toner existing in a magnetic brush of at least a developing area at the time of nondevelopment, on a developing roller. CONSTITUTION:In a development supply part 6 of a selected magnetic brush developing device 10, a black developer 3 is supplied to a developing roller 12 and a magnetic brush 16 is formed. On the other hand, this magnetic brush 16 is carried to a developing area 4 by an action of carrying poles N1-N3 and S4, slide-rubs against the surface of a photosensitive drum 2 and an electrostatic latent image is converted to a developed image. Subsequently, a rotation of a sleeve 18 is stopped through a control part. Immediately before the rotation of the sleeve 18 stops, a bias roller 13 starts to turn, and also, from a power source V1, a DC bias is applied, and a toner in the magnetic brush 16, remaining on the developing roller 12 is absorbed electrostatically by the roller 13 and eliminated. The toner which has been eliminated by the roller 13 is peeled off by a blade 17 for abutting on the roller 13 and collected into a housing 11.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention forms a magnetic brush composed of toner and magnetic carrier on a developing roller, and uses this magnetic brush to reduce the electrostatic potential of a latent image carrier. It relates to magnetic brush developing devices that develop images by rubbing, and in particular, a plurality of magnetic brush developing devices are arranged along the moving path of a latent image carrier, and each magnetic brush developing device is operated independently to form a multicolor image. This invention relates to an improvement of a magnetic brush developing device for multicolors.

[Prior Art] Conventionally, as a developing device suitable for forming a multicolor image, there has been a jumping method in which a developing roller and a latent image carrier are placed apart and the toner on the developing roller is flown toward the latent image carrier to perform development. A one-component developing device of this type is known. In this device, the latent image carrier and the toner on the developing roller are in a non-contact state, and the toner image formed on the latent image carrier does not come into contact with different color toner in other developing devices. It has the advantage that toner color mixing does not occur between devices, but on the other hand, the developer used in this type of device is mainly magnetic toner containing magnetic material, so
The presence of this magnetic material has the disadvantage that the color tone of the developed image deteriorates.

Therefore, conventionally, a magnetic brush developing device has been mainly used as a developing device for forming multicolor images.
Devices disclosed in Japanese Patent Application Laid-Open No. 60-254065 and the like are known.

Zunawara's scale device is, for example, a device incorporated in a two-color copying machine. As shown in FIG. The main part consists of two magnetic brush developing devices (b) and (b2) that are arranged along the outer peripheral surface of the photosensitive drum (a), operate independently of each other, and house different colored toners. and this magnetic brush developing device (bl
) (b2) is a cylindrical sleeve (C) disposed facing the photosensitive drum (a) and a magnet (d) provided inside the cylindrical sleeve (C).
A developing roller ('e) consisting of this developing roller ('e),
) is provided on the back side of the paddle (
Q) and a mixer (h) which is provided on the back side of the paddle (g) and mixes the developer (f).

In this magnetic brush developing device (bl) (b2'), in order to prevent color mixing of toner between the devices (b > (b2)), the device housing (j) is installed as shown in FIG.
This device housing (j >
(j2) in the direction of separating it from the photosensitive drum (a), and a spring (k) that urges the device housing (j) (j2) toward the photosensitive drum (a> side) against the urging force of this spring (k). The main part consists of an eccentric cam (m) that moves the two magnetic brush developing devices (b) (b2) closer to each other from a developing position to a non-developing position. The magnetic brush developing device (bl
The above-mentioned photosensitive drum ( The electrostatic latent image (a) is rubbed and the toner in the magnetic brush (p) is transferred to the latent image forming surface of the photosensitive drum (a), thereby making this latent image visible.

For this reason, the conventional magnetic brush developing device (BL) (B2)
In this case, a retracting means (n>(n2) consisting of the above-mentioned spring (k), eccentric cam (m), etc. is required, which makes the device large and expensive. Moreover, the device housing (b) The moving position of (b2) may change over time, and the moving position of photosensitive drum (a) and developing roller (
e) There was a drawback that the distance between the two layers changed and the developing conditions became unstable.

Therefore, we changed to the above configuration in which the developer@Vti is retracted from the photosensitive drum, and applied a DC bias to the developing roller in a direction that cancels out the electrostatic charge on the photosensitive drum, so that the toner on the developing roller is moved toward the photosensitive drum during non-development. The main pole of the magnet constituting the developing roller is formed to be movable, and the developing roller is provided with a developer separating device that separates the developer formed on the outer circumferential surface of the developing device. A developing device M (see Japanese Unexamined Patent Application Publication No. 58-34469) which is provided so as to prevent a magnetic brush from being formed on the developing roller during non-development, and a plurality of magnets, the magnetic poles of which are displaceable; A developing device (see Japanese Unexamined Patent Publication No. 59-2057) has been developed in which color mixing of toners is prevented by increasing or decreasing the contact depth between a photosensitive drum and a magnetic brush formed on a developing roller.

Note that (q) in Fig. Wi5 shows a trimmer bar for regulating the height of the ears of the magnetic brush (p) formed on the developing roller (e).

[Problems to be Solved by the Invention] However, a developing device that applies a DC bias to the developing roller has the advantage that the gap between the developing roller and the photosensitive drum does not change over time; If polar toner exists, this toner may be transferred to the photosensitive drum side, and there is a problem that toner-color mixing cannot be reliably prevented. Although it has the same advantages as the above-mentioned device, it has the problem that it requires a developer separation device to separate the developer on the sleeve, making the mechanism complicated.
In addition, when the diameter of the developing roller is made smaller due to the demand for smaller devices, the distance between the main pole of the magnet and the transport pole becomes narrower, so even if the main pole of the magnet is displaced, a magnetic brush is not formed on the developing roller. There was a problem that color mixing of the toners occurred as a result.

On the other hand, the developing device described in Japanese Patent Application Laid-Open No. 59-2057 has the advantage that the gap between the developing roller and the photosensitive drum does not change because it does not employ retracting means. That is, even if measures are taken to reduce the contact depth between the photosensitive drum and the magnetic brush by arranging the magnetic poles of the magnet so as to face the photosensitive drum,
There is a problem in that a developer is present on the developing roller and this developer comes into contact with the different color toner transferred onto the photosensitive drum, causing color mixing of the toners.

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems, and its object is to provide a magnetic brush that can reliably prevent color mixing of different color toners without using retracting means. The purpose is to provide a developing device.

That is, in the present invention, a magnetic brush made of toner and magnetic carrier is formed on a developing roller made up of a cylindrical sleeve and a magnet disposed inside the sleeve, and a latent image carrier is placed opposite to the developing roller. A magnetic brush developing device is used, which develops an electrostatic latent image by rubbing it with the magnetic brush in the development area, and the development roller is loaded with toner present in the magnetic brush in the development area at least when not being developed. The invention is characterized in that it is provided with a toner removing section for removing toner from a developing roller.

In such technical means, for the toner removing section, for example, a bias roller is provided near the developing roller,
During non-development, a bias is applied to the bias roller to electrostatically attract and remove the toner present in the magnetic brush.

Regarding the method of controlling the toner removing section, for example, a recording device such as a copying machine in which this developing device is incorporated has a detecting means for detecting the end of development, and a signal from the detecting means is used to control the toner removing section. It is possible to appropriately control the operation timing of the toner removing section by means of the detection means and the control means.

Specific examples of the detection means include a detection member that acts on the latent image carrier to directly detect the end of development of the electrostatic latent image, or a detection member that acts on the latent image carrier to directly detect the end of development of the electrostatic latent image, or This is formed by a detection member that detects the end of formation of the electrostatic latent image, for example, a member that detects the end of movement of the original table of a copying machine or the end of movement of the optical system, and at this detection time, the above-mentioned It may be configured to indirectly detect the end point of development by adding the required set time until the electrostatic latent image on the latent image carrier passes through the development area of the development device.

On the other hand, specific examples of the control means include a switching circuit, a microcomputer, etc., which control the operation of the toner removing section based on a detection signal from the detection means.

Further, the specific content of the above control will be explained using an example in which the toner removing section is configured with a bias roller.
Just before the rotation of the developing roller stops, the bias circuit of the bias roller is turned on to apply a bias, and the toner existing in the magnetic brush is removed at the same time as development is completed, or the toner is removed based on the detection signal. The driving of the developing roller is stopped, and the developing roller is rotated for a short time before the driving of other developing devices installed in parallel with this developing device is started, and the bias circuit also transfers the toner present in the ONL magnetic brush to the other developing devices. It may be removed just before the start of driving, and the timing is arbitrary. still,
The toner removed from the magnetic brush can be collected in the device housing and reused.

Further, the scope of application of the magnetic brush developing device according to the present invention is a flat color copying machine in which a plurality of developing devices are arranged along the moving path of the latent image carrier and each developing device is operated independently to obtain multicolor copies. This applies to full-color copying machines that make color copies from color originals.

[Function] According to the above-mentioned technical means, the developing roller is provided with a toner removing section, and the toner present in at least the magnetic brush in the developing area is removed during non-development, so that the latent image bearing is removed from the developing roller. Transfer of toner to the body is eliminated, making it possible to reliably prevent color mixing of different color toners.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the magnetic brush developing device of the present invention applied to a two-color copying machine, similar to the conventional device, and this copying machine has a document mounting table (
1) and a photosensitive drum (2) installed inside the copying machine main body.
Two magnetic brush developing devices (10) (2) for black and red are arranged around the photosensitive drum (2).
The main part is composed of 0).

As shown in FIGS. 2 and 3, the magnetic brush developing device <10) <20) includes a device housing (1) that is disposed facing the photosensitive drum (2) that rotates in the direction of the arrow.
1) (21) and this device housing (11) (2
1) A developing roller (12) rotatably provided inside
(22) and this developing roller (12) (22)
A bias roller (13) (23) is rotatably provided above and to which a DC bias is applied during non-development, and a bias roller (13) (23) is rotatably provided on the back side of the developing roller (12) (22). Paddle (14) (24) for supplying developer (3) to developing roller (12) (22)
), a mixer (1s><25) which is rotatably provided on the back side of the paddle (14) (24) and stirs and mixes the developer (3), and a developing roller (12) (
The developing roller (12) (
Trimmer bar (17) (27) that regulates the height of the magnetic brush (16) (26) formed on the magnetic brush (22)
The main part is composed of.

Further, the developing roller (12) (22> includes a rotatably provided cylindrical sleeve <18) (28),
It consists of magnets (19) (29) fixedly arranged inside this, and these magnets (19) (29) are arranged in the developing area (4) of the photosensitive drum (2) and the developing roller ( 12) (22) magnetic brush (16
) (26) onto the surface of the photosensitive drum (2), and a pair of main poles (Sl) that are arranged in the developer peeling section (5) and peel off the developer on the developing roller (12) (22). repulsion wA (S2) (S3), the developer supply section (6
) to transport the magnetic brushes (16) (26) formed in ) to the development area (4) and the developer stripping section (5) (N2) (N3) (S4). .

On the other hand, as shown in FIG. 1, an optical sensor (7) is arranged on the lower side of the original platen (1), and a reflective part (8) provided on the base end side of the original platen (1) is arranged. Detects and places the document on the document mounting table (
1), and this signal is configured by a switching circuit as shown in Fig. 4, and is connected to the sleeve (18) (2g) and the bias roller (13) (23). The signal is configured to be input to a control unit (9) that controls the drive source of the device.

That is, when the signal from the optical sensor (7) is input to this control WJ section (9), the switching circuit is activated and after a predetermined time, the developing device <10) (
20) Sleeve (18) Motor (M) for (28)
(M3) stops driving and bracket sleeve (18)
The motors (M2) (M4) for the bias roller (13) (23) start driving the bias roller (13) (23) when the rotation of the bias roller (28) stops.
) is configured so that a DC bias is applied from the DC power supply (■) (■2) to the motors (M2) (M4) and the DC power supply (Vl) (v2) after a predetermined time.
Ffftl is a sea urchin.

Magnetic brush developing device (10) (2) configured in this way
0), when the operating section (not shown) located on the top side of the copying machine body is operated to select a developing color of black, a selection signal from this operating section (30) is sent to the control section as shown in FIG. (9), and based on this signal, the motor (Ml) for the sleeve (18) of the magnetic brush developing device (10) on the selected side starts driving. In addition, this Togi paddle (14
) and mixer (15) also start driving.

Next, when a start button (not shown) is operated, the document placement table (1) moves in the direction of the arrow, and the document placed on the top surface is exposed to slit light by the illumination lamp (40), and the slit image is projected onto the photosensitive drum (2). ) surface, and an electrostatic latent image of the document is formed on the surface of the photosensitive drum (2). This latent image is conveyed to the development region (4) of the selected development device (1G) as the photosensitive drum (2) rotates, and is developed and visualized in this region.

That is, in the selected magnetic brush developing device (10), the black shell image agent (3) is supplied to the developing roller (12) in the developer supply section (6) as shown in FIG. ) is formed while this magnetic brush (
16> is transported to the development area (4) by the action of transport poles (N) (N2) (N) (S4), and rubs against the surface of the photosensitive drum (2) to visualize the electrostatic latent image. It is something. In addition, regarding the rubbed magnetic brush (16), the repulsion pole (S2
) (S3), the developer is peeled off at the developer peeling section (5) and collected into the device housing (11).

On the other hand, when the movement of the document platform (1) is completed, the optical sensor (7) detects the reflective part (8) of the document platform (1), and this signal is input to the control section (9). Based on this signal, the sleeve (18), paddle (14), and mixer (15) of the selected magnetic brush developing device (1G) are stopped.

Since the bias roller (13) starts rotating immediately before the sleeve (18) stops rotating, and a DC bias is applied to the bias roller (13), the developing roller (12) The toner in the magnetic brush (16) remaining on the magnetic brush (16) is electrostatically attracted to the bias roller (13) and removed.

Therefore, after copying is completed, the other magnetic brush developing device Q (2
0) is selected, as there is no toner on the magnetic brush (16) on the developing roller (12) of one magnetic brush developing device (10) as shown in FIG. Attire! ! (2G) onto the photosensitive drum (2) on which the red toner image was formed, the magnetic brush developing device that was not selected! Since black toner is no longer transferred from (1G), it has the advantage of reliably preventing color mixing of different color toners.

The toner removed by the bias roller (13) is peeled off by a blade (51) placed in contact with the bias roller (13) and transferred to the flow plate (61).
is collected into the device housing (11) via the mixer (15) and stirred by the mixer (15). They are then combined and made available for reuse.

[Effect of R Light] As described above, in the present invention, since toner is not present in the magnetic brush at least in the development area during non-development, no toner is present on the latent image carrier on which a toner image has been formed by another magnetic brush development device. This has the effect of reliably preventing color mixing of toners since different color toners are no longer transferred.

[Brief explanation of the drawing]

1 to 4 show embodiments of the present invention, in which FIG. 1 is an explanatory diagram of the configuration of a two-color copying machine to which the magnetic brush developing device of the present invention is applied, and FIGS. 2 to 3 are FIG. 4 is a sectional view of this magnetic brush developing device, and FIG. 4 is an explanatory diagram of its control system, and FIG. 5 is an explanatory diagram of the configuration of a two-color copying machine to which the conventional magnetic brush developing device is applied. [Description of symbols] (2)...Photosensitive drum (10) (2G)...Magnetic brush developing device (11
) (21)...Device housing (12) (22)
...Developing roller (13) (23)...Bias roller (14)
(24)...Paddle (15) (25)...Mixer (16) (26)...Magnetic brush (18) (
28)...Sleeve (19) (29)...Magnet (3)...Developer (4)...Development area (5)...Developer peeling section (6)...Developer Supply section (A)... Optical sensor (8)... Reflection section (9)... Control section Patent Applicant: Fuji Xerox Co., Ltd. Agent Patent attorney: Tomohiro Nakamura (2 others) 8 13.23 Bias roller 14.24 /Vo dollar + 8.28° sleeve 19.29: , Magnet Figure 3

Claims (2)

[Claims] (1) A magnetic brush made of toner and magnetic carrier is formed on a developing roller composed of a cylindrical sleeve and a magnet disposed inside the sleeve, and a magnetic brush made of toner and a magnetic carrier is formed on the developing roller, and the latent image carrier is statically disposed opposite to this developing roller. In a magnetic brush developing device that develops an electrolytic latent image by rubbing it with the magnetic brush in its development area, the developing roller is provided with a toner removal section, and when non-development, toner exists at least in the magnetic brush in the development area. 1. A magnetic brush developing device, characterized in that toner is removed from a developing roller. (2) Claim 1, characterized in that the toner removing section is constituted by a bias roller that is disposed near the developing roller and electrostatically attracts the toner present in the magnetic brush. The magnetic brush development device described.