JPS63198086A - Developing device - Google Patents

Abstract

PURPOSE:To decrease the number of parts of a device, and to make a developing device compact and inexpensive by constituting it so that two developer tanks are placed to one developing electrode, and developers in both the developer tanks are supplied selectively to an electrostatic latent image carrying body. CONSTITUTION:The titled device is provided with two developer tanks 4, 5 storing a developer, a developing sleeve 11, developer carrying and guiding means 7, 7' for carrying the developer, and thereafter, returning it to each developer tank 4, 5, and switching means 8, 8' for switching alternately carriage of the developer extending from the developer tanks 4, 5 to an electrostatic latent image carrying body 2 between two developers. In such a way, the carrying of the developer to the electrostatic latent image carrying body 2 is switched alternately as a time between two developers by the switching means 8, 8', therefore, it does not occur that the developers of two developer tanks 4, 5 are mixed, and a development is executed in a state that a contact of the developer to the electrostatic latent image carrying body 2 is secured by the carrying and guiding means 7, 7'. Accordingly, by using a mixture of a toner and a carrier electrified to the opposite polarity of positive and negative as two developers, bipolar copying of N-P and P-P can be executed, and by using developers of different colors, dichromatic copying can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device used in an electrophotographic process, and particularly to a developing device used in an electrophotographic process. The present invention relates to a developing device capable of performing PP copying to obtain an image, or performing two-color copying to selectively obtain an image of a desired color using two types of developers of different colors.

(2) As a technique for achieving so-called bipolar copying, in which both N-P copying and P-P copying are performed with one copying machine, conventionally there are two methods: 1. Using a bipolar photoreceptor. 2. Using a developing device. A method of arranging two units on the surface of a photoreceptor drum is known.

However, in the conventional method (2), the types of photosensitive materials are limited, so there are many restrictions in terms of photoreceptor sensitivity and cost.

On the other hand, although the conventional method (2) does not have the above-mentioned problems, it is expensive because it requires two developing devices, and it also occupies a large space, making it difficult to miniaturize. .

Especially in the current situation where photoreceptor drums are becoming smaller,
There is a problem in that it becomes substantially difficult to provide two developing devices. This problem is N-P.

The same problem occurs not only in the case of P-P bipolar copying but also in the case of two-color copying.

The present invention was made in view of the above-mentioned problems, and it is possible to perform bipolar copying or two-color copying of N-P and P-P without using a bipolar photoreceptor or two developing devices. The object of the present invention is to provide an extremely useful developing device.

Means for Solving the Problems In order to solve the above object, the present invention provides two developer tanks for storing developer, and a structure provided between both developer tanks and an electrostatic latent image carrier. one developing sleeve that conveys developer;
The developer is transported from each developer tank to the position where the developing sleeve approaches the surface of the electrostatic latent image carrier or the closest position, and then the developer is returned to each developer tank. It is characterized by comprising a guide means and a switching means for alternately switching the conveyance of the developer from the developer tank to the electrostatic latent image carrier between two kinds of developer.

According to the above configuration, the switching means temporally alternates the conveyance of the developer to the electrostatic latent image carrier between the two developers, so that the development in the two developer tanks is Development is carried out in a state where the developer is not mixed with the developer and the developer is in contact with the electrostatic latent image carrier by the conveyance guide means. Therefore, the toner and the carrier are charged as two developers with opposite polarities. By using a mixture, N-P and P-P bipolar copying can be performed, and by using developers of different colors, two-color copying can be performed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sectional view of an embodiment of a developing device according to the present invention. In the figure, reference numeral 1 denotes a developing device that performs magnetic brush type development, and the developing device 1 is provided at a position slightly separated from a photosensitive drum 2 that functions as an electrostatic latent image carrier. This developing device 1 includes two developer tanks 4 and 5 for storing developer in one housing 3, one developing electrode 6, a developer conveying guide means 7, and a switching means 8.

The developer tanks 4 and 5 are partitioned by a partition plate 3a, and each developer tank 4 and 5 is provided with packet rollers 9 and 9° that are rotationally driven by a motor (not shown) or the like. The developer is agitated by the rotation of the packet rollers 9, 9' and is conveyed in the direction of the developer conveyance guide means 7, 7'. The developer used in this embodiment is a mixture of toner and carrier.

In this embodiment, the developing electrode 6 is constituted by a developing sleeve 11 containing a magnetic roll 10, and is disposed between the two developer tanks 4 and 5 and the photosensitive drum 2 as shown.

The magnetic roll 10 and the developing sleeve 11 are driven to rotate with a relative speed difference by a motor or the like (not shown), and the direction of rotation can be freely switched between forward and reverse directions. The normal rotation direction is the direction of arrows S and C shown in FIG.

In this embodiment, the developer conveyance guide means 7 moves two arc-shaped plate members made of non-magnetic material at an angle of 7.7 degrees onto each semicircumference of the developing sleeve 11 as shown in the figure.
The configuration is such that it is placed at a distance from the By arranging the developer in this manner, the developer transport path from each developer tank 4.5 to the photoreceptor drum 2 is separated from the side 13a, 14a far from the developing sleeve 11 and the side 13b, 14b near the developing sleeve 11.
It is divided into As will be described later, the conveyance paths 13a and 14a on the side far from the developing sleeve 11 serve as outward paths for conveying the developer from the developer tank 4.5 to the surface of the photoreceptor drum 2.
Conveyance paths 13b and 14b on the side closer to the developing sleeve 11
is a return path for returning the developer that has been subjected to development on the surface of the photoreceptor drum 2 to the developer tanks 4 and 5. The end portion 7a17a' of the arcuate plate-like bodies 7, 7' on the side closer to the photoreceptor drum is the turning point of the developer conveyed from the outward path to the return path, and the developer is brought into contact with the surface of the photoreceptor drum. Since it is an element that defines the limit point at which contact ends, its ends 7a+7a'
is located at the closest position between the developing sleeve 11 and the photosensitive drum 2, or at a position in front of the developing sleeve 11 in the developer conveying direction.

In this embodiment, the switching means also serves as a pair of spike height regulating blades 8, 8'' for regulating the spike height of the developer. Each spike height regulating blade 8.8'' passes through the housing 3 and connects two developer outgoing paths 13a. , 14a, and are alternately driven by a driving means (not shown) to the outgoing path 13a,
14a' and close the outgoing routes 13a and 14a. Reference numerals 12 and 12'' designate a scraper, one end of which is lightly pressed against the outer peripheral surface of the developing sleeve 11, and the other end connected to the end of the extension plate piece 3a.

FIG. 2 is a diagram illustrating how the developer is transported by the developing electrode 6 of the developing device 1, and in the figure, G indicates the developer.

The photosensitive drum 2 is rotated in the direction of the arrow a by a driving means (not shown), and the developing sleeve 11 and the magnetic roll 10 are rotated by a motor (not shown) in the direction opposite to that of the photosensitive drum 2, that is, in the direction of the arrows (a) and (c) shown in the figure. The developing sleeve 11 rotates faster than the magnetic roll 10 by a difference. The developer G discharged from the developer tank 4 onto the developer transport guide means 7 is caused to move in the opposite direction to the rotation direction of the magnetic roll 10, that is, in the direction of arrow e, due to the movement of the magnetic field based on the rotation of the magnetic roll IO. and comes into contact with the surface of the photoreceptor drum 2.

This contact ends at a position where the developing sleeve 11 is approaching the surface of the photoreceptor drum 2, or at a position where it is closest to the surface of the photosensitive drum 2. The movement of the developer G due to rotation is also related to the density of the developer G, and the higher the density, the slower the movement speed.

Therefore, in order to terminate the contact between the developer G and the photosensitive drum 2 at the above-mentioned position, it is necessary to regulate the height of the developer G using the height regulating blades 8, 8'. Furthermore,
At the closest position between the developing sleeve 11 and the photosensitive drum 2, D ・π・Wsl/60>dt ・P-Wag/60 where D: developing sleeve diameter (mm) Wsl: developing sleeve rotation speed (rpm) dI : Nearest position (m+w) Wtsg: Magnetic roll rotation speed (rpm) P: Magnetic roll number of poles It is necessary to hold the following relationship (D・π・W s l
/60 is the conveyance speed due to the rotation of the developing sleeve, d, -P
・Wag/60 is the conveyance speed due to the rotation of the magnetic roll).

The excess developer that has finished contacting the surface of the photosensitive drum 2 moves on the developing sleeve 11 in the direction indicated by the arrow as the developing sleeve 11 rotates. Calculatedly, the flow of the developer G in the interval (d3) between the developer transport guide means 7 and the developer sleeve 11 and the return path of the developer G is opposite to the direction indicated by the arrow shown in the figure. However, since the density of the developer G is high at this position, the movement of the developer G due to its rotation is small, and the movement due to the rotation of the developing sleeve 11 is larger, and as a result, the flow of the developer G is As shown in the figure.

The developer G that has moved on the developing sleeve 11 is scraped off from the developing sleeve 11 by the scraper 12 and returned to the developer tank 4 again.

As is clear from the above explanation, the developer G passes through the outward path 13a.
From there, the developer is turned back at the tip of the developer transport guide means 7, and the return path 13 is completed.
The movement of the developer through b and back to the developer tank 4 is caused by the magnetic roll 10.
This is due to the fact that the rotation direction of the developing sleeve 11 is in the directions S and C, so when the magnetic roll 10 and the developing sleeve 11 are rotated in the direction opposite to the directions S and C, the development in the other developer tank 5 is Agents can be transported in the same way.

3 and 4 show two developer tanks 4 by changing the rotational directions of the magnetic roll 10 and the developing sleeve 11.
, 5 is shown in the drawing. The specific development conditions are: D=31mm Wsl=7Orpm dt-0.5mm dx=1.5+s dl-IJmw+ Wag-130Orpm P=8 (various 1000 Gauss) @ d++ d2. dl is the dimension of the location shown in FIG.

In order to avoid mixing of the other developer when developing with one developer, in FIGS. 3 and 4, the height regulating blade 8' (8) is used to convey the other developer. The road is closed. Also, at this time, the developer remaining in the return path 13b (14b) when the other developer is being developed has a low density, so the flow due to the rotation of the magnetic roll 8 is faster (the magnetic roll 80 The moving speed of developer G due to rotation is 1.2 x 8 x 1300/6
060-2O7/sec, the moving speed of the developer G due to the rotation of the developing sleeve 11 is 31×πX”70/60-1
13.6wn/sec), there is no fear that the developer G' returned to the developer tank 5 will mix with the developer G on the photoreceptor drum 2.

Incidentally, the transition from the state shown in FIG. 3 to the state shown in FIG. 4 and the transition in the opposite direction are not performed immediately, but after the two outgoing paths 13a and 14a are rotated once in a closed state. Since the state shifts to the next state, there is no possibility that the two developers G and G' will be mixed even at the instant of developer switching.

In the developing device configured as described above, the conveyance of the two developers from the two developer tanks to the photoreceptor drum is alternated over time, and two developers are used for one developing sleeve. For example, if two developer tanks are filled with developers with different polarities and development is performed, N-
P and P-P development can be performed easily and at low cost.

Further, if developers of different colors are used, two-color development can be similarly performed easily and inexpensively.

In the above embodiment, the developer is stirred by a packet roller, but as shown in FIG. 5, a stirring rod 13.degree. 13.degree. may be used instead of the bucket roller. In that case, the developing device becomes more compact. Furthermore, although an application example has been shown in which the developer is composed of two components, namely toner and carrier, the present invention is also applicable to the case where a -component magnetic toner is used.

As described above, according to the developing device of the present invention, two developer tanks are arranged for one development electrode, and the developer in both developer tanks is selectively used to form an electrostatic latent image. Since the structure is such that the developing device has a small number of parts, it is compact and inexpensive. Furthermore, N-P, P-P development and two-color development are easy and inexpensive. It also has the effect of being able to do this.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the developing device of the present invention, FIG. 2 is a sectional view showing a part of the embodiment of FIG. 1, and FIG. FIG. 4 is a diagram illustrating the state when developing is performed using the other developer tank. FIG. 5 is a diagram showing another embodiment of the developing device of the present invention. be. 1... Developer tank, 2... Photosensitive drum, 4, 5...
・Developing device, 7.7°...developer transport guide means, 10
...Magnetic roll, 11...Developing sleeve, 8,8゛...Hot height regulation board. Patent applicant: Minolta Camera Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) Two developer tanks that store developer, one developing sleeve that is provided between both developer tanks and the electrostatic latent image carrier and that transports the developer, and the development from each developer tank. a developer conveying guide means for conveying the developer to a position where the sleeve is approaching or closest to the surface of the electrostatic latent image carrier, and then returning the developer to each developer tank; A developing device comprising: switching means for alternately switching the conveyance of developer from a tank to an electrostatic latent image carrier between two types of developer. (2) The developer conveyance guide means is a plate-shaped guide member that extends from the vicinity of the developer tank to the vicinity of the electrostatic latent image carrier and is arranged in a state separated from the development electrode. The transport path for the agent is divided into two transport paths, one near the developing electrode and one far away.The far transport path transports the developer to the electrostatic latent image carrier, and the near transport path transports the developer used for development. The developing device according to claim 1, further comprising a return path for returning the developer to the original developer tank. (3) The developing sleeve has a built-in porcelain roll therein, and the means for switching the conveyance of the developer includes a means for switching the rotation direction of the magnetic roll and the developing sleeve, and an electrostatic charge from the two developer tanks. The developing device according to claim 1, further comprising a shutter that alternately opens and closes a developer conveyance path to the latent image carrier.