JP2521938B2 - Magnetic brush developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention forms a magnetic brush composed of toner and a magnetic carrier on a developing roller, and the magnetic brush is used to form an electrostatic latent image carrier. Involved in a magnetic brush developing device for rubbing an image to develop it, in particular, a plurality of magnetic brush developing devices are arranged along a moving path of a latent image carrier, and each magnetic brush developing device is independently operated to form a multicolor image. The present invention relates to an improvement of a multicolor magnetic brush developing device.

[Prior Art] Conventionally, as a developing device suitable for forming a multicolor image, a developing roller and a latent image carrier are spaced apart from each other, and toner on the developing roller is caused to fly to the latent image carrier side to perform development by jumping. One-component developing devices of the type are known. In this apparatus, the latent image carrier and the toner on the developing roller are not in contact with each other, and the toner image formed on the latent image carrier does not come into contact with the different color toner in other developing devices. Although there is an advantage that toner color mixing does not occur between devices, on the other hand, the developer used in this type of device is mainly a magnetic toner containing a magnetic substance, and therefore the presence of this magnetic substance results in a developed image. There was a drawback that the color tone of the became worse.

Therefore, conventionally, a magnetic brush developing device has been mainly used as a developing device for forming a multicolor image.
There are known devices disclosed in Japanese Patent Laid-Open No. 178379, Japanese Patent Laid-Open No. 60-254065 and the like.

That is, this type of apparatus will be described, for example, as an apparatus incorporated in a copying machine for two colors. This copying machine has a photosensitive drum (a) provided inside the copying machine body as shown in FIG.
And is arranged along the outer peripheral surface of the photosensitive drum (a),
Two magnetic brush developing devices (b ₁ ) and (b ₂ ) that operate independently of each other and that store different-color toners form the main part, and the magnetic brush developing device (b ₁ )
(B ₂ ) is a developing roller (e) including a cylindrical sleeve (c) disposed facing the photosensitive drum (a) and a magnetic roller (d) provided therein, and the developing roller (e). The main part is composed of a paddle (g) which is provided on the back side of e) and supplies the developer (f) composed of toner and magnetic carrier to the developing roller (e).

In this magnetic brush developing device (b ₁ ) (b ₂ ), in order to prevent toner color mixing between the devices (b ₁ ) and (b ₂ ), as shown in FIG. 5, the device housings (h ₁ ) (h ₁ ) _On the rear side of ₂ ), a spring (i) for urging the device housing (h ₁ ) (h ₂ ) in a direction of separating from the photosensitive drum (a).
And the eccentric cam (j) that brings the device housings (h ₁ ) (h ₂ ) closer to the photosensitive drum (a) side against the biasing force of the spring (i), the retracting means (k) that constitutes a main part. ₁ ) (k ₂ ) is provided so that the two magnetic brush developing devices (b ₁ ) and (b ₂ ) are alternately moved from the developable position to the non-developable position, and the magnetic brush developing devices are arranged at the developable position. A magnetic brush (p) composed of toner and a magnetic carrier formed on the developing roller (e) by rotating the cylindrical sleeve (c) or the magnetic roller (d) of the magnetic brush developing device (b ₁ ). Accordingly, the electrostatic latent image on the photosensitive drum (a) is rubbed to remove the toner in the magnetic brush (m) from the photosensitive drum (a).
Is transferred to the latent image forming surface to visualize this latent image.

Therefore, the conventional magnetic brush developing devices (b ₁ ) and (b ₂ ) require retract means (k ₁ ) (k ₂ ) including the spring (i) and the eccentric cam (j). The device is large and expensive, and the moving position of the device housing (b ₁ ) (b ₂ ) may fluctuate over time, causing a gap between the photosensitive drum (a) and the developing roller (e). There is a drawback that the distance changes and the developing conditions become unstable.

Therefore, instead of retracting the developing device from the photosensitive drum, a DC bias is applied to the developing roller in the direction to cancel the electrostatic charge on the photosensitive drum, and the toner on the developing roller is transferred to the photosensitive drum side during non-developing. The developing device and the developing roller that are prevented from rotating are rotationally driven during development and non-development, and the supply roller that supplies the developer is stopped during non-development and the magnetic brush remains on the development roller. Developing device in which a magnetic brush is not formed on the developing roller by dropping the toner (Japanese Patent Laid-Open No. 58-1958).
No. 60), the main pole of the magnetic roller constituting the developing roller is formed displaceably, and the developing roller is provided with a developer separating device for separating the developer formed on the outer peripheral surface thereof so as to be separable. A developing device (see Japanese Patent Laid-Open No. 58-34469) in which a magnetic brush is not formed on the developing roller during non-developing, or a magnetic roller having a plurality of magnets is formed to be displaceable to form a photosensitive drum. There has been developed a developing device (see Japanese Patent Laid-Open No. 59-2057) in which color mixture of toner is prevented by increasing or decreasing the contact depth with a magnetic brush formed on the developing roller.

Incidentally, (n) in FIG. 5 shows a trimmer bar for regulating the height of the spikes of the magnetic brush (m) 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, but on the other hand If polar toner is present, this toner may be transferred to the photosensitive drum side, and there is a problem in that toner color mixture cannot be reliably prevented. Further, the developing device described in Japanese Patent Laid-Open No. 195860/1983 also has a developing roller. This is effective when the device is installed at a position where the magnetic brush easily drops from the device. However, when the device is installed at a position where the magnetic brush does not easily drop, the magnetic brush remains on the developing roller. There was a problem that color mixing could not be prevented.

On the other hand, the developing device described in JP-A-58-34469 has the advantage that the gap between the developing roller and the photosensitive drum does not change because no retract means is used as in the above device. There is a problem that a developer separating device for peeling off the developer on the sleeve is required, and its mechanism is complicated, and when the diameter of the developing roller is reduced due to the demand for downsizing of the device, the magnetic roller Since the gap between the main pole and the transport pole is narrowed, there is a problem that even if the main pole of the magnetic roller is displaced, a magnetic brush is formed on the developing roller and toner color mixture occurs.

The developing device disclosed in Japanese Patent Laid-Open No. 59-2057 has the same advantages as those of the above devices because it does not employ the retract means, but it displaces the magnetic poles of the magnetic roller during non-developing, that is, the magnetic roller Even if the magnetic poles are arranged so as to face the photosensitive drum and a means for reducing the contact depth between the photosensitive drum and the magnetic brush is taken, the developer is still present on the developing roller, and this developer is transferred onto the photosensitive drum. In addition, there is a problem in that toner is mixed because it comes into contact with different color toners.

[Means for Solving Problems] The present invention has been made in view of the above problems, and a problem thereof is that a magnetic brush capable of reliably preventing color mixture of different color toners without employing a retracting means. To provide a developing device.

That is, according to the present invention, a magnetic brush made of toner and a magnetic carrier is formed on a developing roller composed of a cylindrical sleeve and a magnetic roller disposed inside the sleeve, and the sleeve or the magnetic roller is rotationally driven to develop the magnetic brush. Based on the premise of a magnetic brush developing device that develops an electrostatic latent image of a latent image carrier rotatably arranged on the opposite side of a roller by rubbing the electrostatic latent image with the magnetic brush in the developing area, the development by the magnetic brush is performed. The detection means for detecting the end time and the drive of the sleeve or the magnetic roller are stopped based on the signal from the detection means, and when the drive is stopped, the latent image carrier is rotated and the charger is operated to operate the latent image. It is characterized in that a control means for forming a high-potential portion is provided on a part of the image carrier.

In such a technical means, the detecting means may be constituted by a detecting member that acts on the latent image carrier to directly detect the development end time of the electrostatic latent image, or the detecting means may be connected to the latent image carrier. A detection member for detecting the end time of the formation of the electrostatic latent image, for example, a member for detecting the end time of the movement of the document table of the copying machine or the like incorporating this developing device or the end of the movement of the optical system. It is configured to indirectly detect the development end point by adding the required set time until the electrostatic latent image of the latent image carrier passes through the developing area of the developing device to this detection time. You can

As the control means, the drive of the sleeve or the magnetic roller is stopped based on a signal from the detection means,
When the driving is stopped, the latent image carrier is rotated to operate the charging device to form the high-potential portion in a part of the latent image carrier. Examples include circuits and microcomputers.

Regarding the timing of forming the high-potential portion on the latent image carrier when the drive of the sleeve or the magnetic roller is stopped, the drive source of the sleeve or the magnetic roller is stopped based on the signal of the detection means, and in this state While rotating the latent image carrier, the charging device is operated to form the high potential portion, and the high potential portion is brought into contact with the magnetic brush in the developing area to remove the toner existing in the magnetic brush at the same time as the development is completed. Even if it is a method of removing by electrostatic attraction,
Alternatively, based on the detection signal, the drive of the sleeve or the magnetic roller and the drive of the latent image carrier are sequentially stopped, and the latent image carrier is rotated before the start of the driving of another developing device provided with this developing device. However, the charging device may be operated to form the high-potential portion, and thus the toner existing in the magnetic brush may be removed immediately before the start of driving of another developing device, and the timing may be set arbitrarily.

When the high potential portion of the latent image carrier is brought into contact with a magnetic brush to electrostatically remove the toner in the magnetic brush, a developing bias applied to a developing roller having the magnetic brush during normal development is applied. It is desirable to apply a low bias or drop the developing roller to ground potential. By thus setting a large potential difference between the high potential portion of the latent image carrier and the developing roller, electrostatic attraction of the toner from the developing roller to the latent image carrier can be promoted. . The toner removed from the magnetic brush and adsorbed to the latent image carrier is separated and collected by the cleaning means provided on the latent image carrier.

On the other hand, a bias equal to or higher than a normal developing bias is applied to the developing roller while the other developing device is operating during non-developing to set a small potential difference between the developing roller and the high potential portion. Is desirable.
This is because such a setting makes it possible to more reliably prevent transfer of the toner remaining in the magnetic brush to the latent image carrier.

Further, regarding the applicable range of the magnetic brush developing device according to the present invention, a flat color copying machine for obtaining a multicolor copy by arranging a plurality of developing devices along the moving path of the latent image carrier and independently operating each developing device. The target is a full-color copying machine that makes color copies from color originals.

[Operation] According to the technical means as described above, the detection means for detecting the development end time point and the drive of the sleeve or the magnetic roller are stopped based on the signal from this detection means, and the latent image is carried at this stop time. A control means for operating the charging device while rotating the body to form a high-potential portion on a part of the latent image carrier is provided. Since the toner is electrostatically sucked and removed by the portion, the toner transfer from the developing roller to the latent image carrier is eliminated, and it is possible to reliably prevent the color mixture of different color toners.

EXAMPLES Examples of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a two-color copying machine to which the magnetic brush developing device of the present invention is applied, as in the conventional apparatus. This copying machine is a document mounting table (reciprocally movable) provided on the upper surface of the copying machine main body. 1), a photosensitive drum (2) provided inside the copying machine main body, an optical system (4) including a charger (3) and an illumination lamp (4) sequentially arranged around the photosensitive drum (2).
0), the inter-image lamp (5), the two magnetic brush developing devices (60) (70) for black and red, and the cleaning device (8) constitute the main part.

The magnetic brush developing device (60) (70) has a second
As shown in FIGS. 3 to 3, a device housing (61) disposed opposite to the photosensitive drum (2) which rotates in the arrow direction.
(71), developing rollers (62) and (72) rotatably provided inside the device housings (61) and (71), and rotatable to the back side of the developing rollers (62) and (72) Paddles (64) (74) provided on the developing rollers (62) (72) for supplying the developer (9) to the developing rollers (62) (72), and the developing rollers (64) (74) provided on the upper side of the developing rollers (62) (72). The main parts are constituted by the trimmer bars (66) (76) that regulate the height of the ears of the magnetic brushes (65) (75) formed on the 62 (72).

The developing rollers (62) (72) are composed of rotatably provided cylindrical sleeves (67) (77) and magnetic rollers (68) (78) fixedly arranged therein. The magnetic rollers (68) (78) are arranged in the developing area (10) of the photosensitive drum (2) and the developing rollers (6
2) The main pole (S ₁ ) for rubbing the magnetic brushes (65) (75) of (72) against the surface of the photosensitive drum (2) and the developer peeling portion (2
0) and a pair of repulsive poles (S ₂ ) (S ₃ ) for peeling off the developer on the developing rollers (62) (72), and the main pole (S ₁ ) and repulsive pole (S ₂ ) ( The magnetic brushes (65) (75) formed in the developer supply section (30) disposed between the S ₃ ).
And a carrier electrode (N ₁ ) (N ₂ ) (N ₃ ) (S ₄ ) for carrying the toner to the developing area (10) and the developer peeling section (20).

On the other hand, as shown in FIG. 1, an optical sensor (50) is arranged below the document placing table (1), and a reflection section (51) is provided on the base end side of the document placing table (1). The detection is made to detect the end time of movement of the document placing table (1), and this signal is constituted by a switching circuit as shown in FIG. 4, and the sleeves (67) (77) are charged. It is configured to be input to the control unit (52) that controls the drive system of the device (3), the inter image lamp (5), and the photosensitive drum (2).

That is, when a signal from the optical sensor (50) is input to the control unit (52), the sleeve (of the developing device (60) (70) (developing device (60) (70)) which is in the developing operation for a predetermined time after the switching circuit operates. 67) (77) motor (M ₆₀ ) (M ₇₀ ) stops driving. Meanwhile photosensitive drum (2) motor (M ₂₎ is continuously driven, the charging device (3) as well as inter-image lamp (5) for supply (V ₃₎ (V ₅₎ is also adapted to be turned ON, and after a predetermined time, the photosensitive drum (2) motor (M ₂₎ and a power supply (V ₃₎ (V ₅₎ is adapted to be OFF. Incidentally, while the sleeves (67) (77) are stopped by this switching circuit and the photosensitive drum (2) on which the high potential portion is formed is being rotated, the developing rollers (62) (72) are supplied with a power source (V ₆₂ ) (V ₇₂ ) is controlled so that a bias lower than the developing bias at the time of development is applied, while the sleeves (67) (77) are stopped and other developing devices are operating, The developing rollers (62) and (72) are controlled so that a bias slightly higher than the developing bias at the time of development is applied from a power source (V ₆₂ ) (V ₇₂ ).

The magnetic brush developing device (60) (7
In (0), when a black developing color is selected by operating an operation section (not shown) arranged on the upper surface side of the copying machine main body, a selection signal from this operation section (53) is sent to the control section as shown in FIG. The motor (M ₆₇ ) for the sleeve (67) of the magnetic brush developing device (60), which is input to (52) and is selected based on this signal, starts driving. At this time, the paddle (64)
Is also starting to drive.

Next, when a start button (not shown) is operated, the original placing table (1) moves in the direction of the arrow, the original placed on the upper surface is slit-exposed to the illumination lamp (4), and the slit image is formed on the photosensitive drum (2). ) Surface, the electrostatic latent image of the document is formed on the photosensitive drum (2) surface. Then, this latent image is conveyed to the developing area (10) of the selected developing device (60) as the photosensitive drum (2) rotates,
It is developed and visualized in this area.

That is, in the selected magnetic brush developing device (60), the black developer (9) is supplied to the developing roller (62) in the developer supplying section (30) as shown in FIG. This magnetic brush while formed (65)
Is transported to the developing area (10) by the action of the transport poles (N ₁ ) (N ₂ ) (N ₃ ) (S ₄ ), and the electrostatic latent image is visualized by rubbing the surface of the photosensitive drum (2). It will be transformed. The magnetic brush (65) that has already been rubbed should be peeled off in the developer peeling section (20) by the action of the repelling poles (S ₂ ) (S ₃ ) and collected in the device housing (61). Has become.

On the other hand, when the movement of the document placing table (1) is completed, the optical sensor (50) detects the reflecting section (51) of the document placing table (1), and this signal is input to the control section (52). The drive of the sleeve (67) and the paddle (64) of the magnetic brush developing device (60) selected based on this signal is stopped.

At this time, the photosensitive drum (2), the charger (3) and the inter-image lamp (5) are controlled to be continuously driven, and the charger (3) and the inter-image lamp (5) are controlled.
As a result, a high potential portion is formed on the surface of the photosensitive drum (2), so that the toner in the magnetic brush (65) remaining on the developing roller (62) is electrostatically attracted to the high potential portion and removed.
The toner adsorbed on the photosensitive drum (2) is peeled off by the cleaning device (8) provided on the photosensitive drum (2) and collected in the container.

Therefore, after copying, the other magnetic brush developing device (7
When (0) is selected, toner is not present in the magnetic brush (65) on the developing roller (62) of the one magnetic brush developing device (60) as shown in FIG. The black toner is not transferred from the unselected magnetic brush developing device (60) onto the photosensitive drum (2) on which the red toner image is formed by the device (70), and it is possible to reliably prevent the color mixture of different color toners. have.

When performing continuous copying of the same color with this copying machine, operating the continuous copy button (not shown) of the operation section to input the signal to the control section (52) causes the optical sensor (50 ) And the reflection unit (51) are stopped so that the developing roller (62) sleeve (67) continuously rotates to make continuous copies of the same color. It has become.

EFFECTS OF THE INVENTION As described above, according to the present invention, since toner does not exist in the magnetic brush at least in the developing area at the time of non-development, the latent image carrier on which a toner image is formed by another magnetic brush developing device, The different color toner is not transferred, and the color mixing of the toner can be surely prevented.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is an explanatory view of the structure of a two-color copying machine to which the magnetic brush developing device of the present invention is applied, and FIGS. FIG. 4 is a sectional view of this magnetic brush developing device, FIG. 4 is an explanatory diagram of its control system, and FIG. 5 is a structural explanatory diagram of a two-color copying machine to which a conventional magnetic brush developing device is applied. [Explanation of symbols] (2) Photosensitive drum (3) Charger (5) Inter image lamp (60) (70) Magnetic brush developing device (61) (71) Device housing (62) ) (72) …… Developing roller (64) (74) …… Paddle (65) (75) …… Magnetic brush (67) (77) …… Sleeve (68) (78) …… Magnetic roller (9)… … Developer (10) …… Development area (20) …… Developer peeling section (30) …… Developer supply section (50) …… Optical sensor (51) …… Reflecting section (52) …… Control section

Claims (1)

(57) [Claims] 1. A magnetic brush made of toner and a magnetic carrier is formed on a developing roller composed of a cylindrical sleeve and a magnetic roller disposed inside the sleeve, and the sleeve or the magnetic roller is rotatably driven to develop. In a magnetic brush developing device for performing development by rubbing an electrostatic latent image of a latent image carrier rotatably arranged on the opposite side of a roller with the magnetic brush in the developing area, at the time of completion of development by the magnetic brush. And a driving means for stopping the drive of the sleeve or the magnetic roller based on a signal from the detecting means, and when the driving is stopped, the latent image carrier is operated while rotating the latent image carrier to carry the latent image. A control means for forming a high-potential portion is provided on a part of the body so that the toner existing in the magnetic brush in the developing area is electrostatically charged by the high-potential portion of the latent image carrier when not developing. The magnetic brush development apparatus being characterized in that as remove and pull.