JPH0277076A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of leak and to reduce the cost of the title device by providing a magnetic flux generator which outputs magnetic flux to a developer carrier which carries magnetic developer inside a photosensitive drum. CONSTITUTION:An electromagnet 15 is provided by being opposed to a sleeve 2 inside the photosensitive drum 1. When the electromagnet 15 is excited, toner 5 carried in the sleeve 2 is attracted and made to soar to the electromagnet 15 to adhere to the photosensitive drum 1. At such a time, since the end part 15a of the electromagnet 15 opposed to the sleeve 2 is tapered, the magnetic flux is focused and intensive local magnetic field is generated in the direction of the sleeve 2. Therefore, the toner 5 is allowed to surely adhere only to the fine range of the photosensitive drum 1. Thus, the toner 5 is attracted toward the photosensitive drum 1 by the electromagnet 15 to adhere to the photosensitive drum 1 and high voltage is not impressed between the photosensitive drum 1 and the sleeve 2, so that the occurrence of the leak can be prevented and the reduction of the cost of the device can be accomplished.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention is used in an electrophotographic recording device such as an electronic copying machine, and is used to record an electrostatic latent image formed on the photosensitive surface of a photoreceptor. The present invention relates to a developing device for developing.

(Prior Art) Currently, as one of the developing methods used in electrophotographic recording apparatuses, there is a developing device in which a photoreceptor drum and a developer carrier are made non-contact, and toner is caused to fly.

FIG. 3 is a diagram showing an example of the configuration of the above-mentioned developing device. In the figure, 1 is a photosensitive drum, and a sleeve 2 is provided in parallel to this. A magnet 3 is provided inside the sleeve 2, and the sleeve 2 and the magnet 3 form a toner carrier drum. A hopper 4 stores toner 5 as a magnetic developer. The sleeve 2 is located at the opening of the hopper 4 with a portion of the sleeve 2 in contact with the toner 5 in the hopper 4. Reference numeral 6 denotes a blade which, when the sleeve 2 is rotated, is attached to the sleeve 2 by the magnetic force of the magnet 3, moves with the rotation of the sleeve 2, and is guided to the outside of the hopper 4 (toner layer). thickness) is kept constant. Reference numeral 7 denotes a power supply device, which applies a voltage of several kilovolts between the photosensitive drum 1 and the sleeve 2 at a pp value with a DC bias superimposed thereon.

Note that 8 to 14 constitute an electrostatic recording device together with this developing device, 8 is a charging unit that charges the photoreceptor drum 1, and 9 is an exposure unit that exposes the photoreceptor drum 1 to form an electrostatic latent image. 10 is a transfer unit that transfers the image developed on the photoreceptor drum 1 by the developing device onto the recording paper 11; 12 is a peeling unit that peels off the recording paper 11 from the photoreceptor drum 1; A fixing section 14 is a cleaning section that cleans the photosensitive drum 1 by fusing and fixing the image.

The developing device having such a structure applies a high voltage of several kilovolts in pp value between the photoreceptor drum 1 and the sleeve 2 by the power supply device 7, and Generates an electric field. When the sleeve 2 is rotated to transport the toner 6 toward the photoreceptor drum 1, the toner 6 is drawn toward the photoreceptor drum 1 by the action of the electric field.

However, with the above configuration, the photosensitive drum 1
Since a high voltage is applied between the sleeve 2 and the sleeve 2, a leak occurs, which disturbs the electrostatic latent image formed on the photosensitive surface of the photosensitive drum 1, making it impossible to obtain an accurate image.
If the leakage is large, there is a risk that the photosensitive drum 1 itself may be damaged. Further, the power supply device that generates high voltage is expensive, and there is a problem that the price of the device increases.

(Problem to be Solved by the Invention) As described above, in the conventional developing device, an electric field is generated by applying a high voltage between the photoreceptor drum and the sleeve, and the toner is attracted to the photoreceptor drum. Therefore, there is a risk that leakage may occur from the sleeve to the photoreceptor drum. In addition, since the power supply device that generates high voltage is expensive, there is a problem in that the price of the device increases.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a developing device that does not cause leakage and is inexpensive.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a developing device that develops an electrostatic latent image formed on the photosensitive surface of a photosensitive drum. A developer carrier is provided in parallel and supports a magnetic developer by magnetic force, and a magnetic field line generator such as an electromagnet is provided inside the photosensitive drum and emits magnetic lines of force toward the developer carrier. I decided to do so.

(Function) By taking such measures, the magnetic developer supported on the developer carrier is blown away by the action of the magnetic field generated by a magnetic field generator such as an electromagnet, and the photosensitive surface of the photosensitive drum is Attach to.

Since electromagnets can be driven at low voltages, an inexpensive power supply that generates low voltages is sufficient. In addition, since the voltage handled is low and is not applied directly to the photoreceptor drum, there is no risk of leakage and adverse effects on the electrostatic latent image formed on the photoreceptor drum or its photosensitive surface. There is no.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the configuration of a developing device according to this embodiment. Note that the same parts as in FIG. 3 are given the same reference numerals, and detailed explanation thereof will be omitted.

Here, the developing device according to this embodiment is characterized in that an electromagnet 15 is provided inside the photosensitive drum 1 and facing the sleeve 2. The electromagnet 15 has a pointed end 15a facing the sleeve 2. Also, 16
is a power supply device, and the magnetic force generated by the electromagnet 15 is shown in Fig. 2 (
The electromagnet 15 is driven as shown in a). Here, the magnetic force change as shown in Fig. 2(a) is caused by the second
This can be obtained by supplying a varying current from the power source 16 to the electromagnet 15 as shown in FIG. 1(b).

Thus, in the developing device configured as described above, when the electromagnet 15 is excited, the toner 5 carried on the sleeve 2 is attracted by the electromagnet 15, flies, and adheres to the photoreceptor drum 1. At this time, since the end 15a of the electromagnet 15 facing the sleeve 2 has a pointed shape, lines of magnetic force are focused, and a strong local magnetic field is generated in the direction of the sleeve 2. Therefore, the toner 5 is reliably attached only to a very small area of the photoreceptor drum 1.

Then, when the excitation of the electromagnet 15 is stopped, the toner 5 adhering to the part of the photoreceptor drum 1 where the electrostatic latent image is not formed loses its holding force on the photoreceptor drum 1, and the magnetic force of the magnet 3 causes the toner 5 to stick to the sleeve 2 due to the magnetic force of the magnet 3. Return to. Therefore, the toner 5 adheres only to the portion of the photoreceptor drum where the electrostatic latent image is formed.

As described above, according to this embodiment, the electromagnet 15 attracts the toner 5 toward the photoreceptor drum 1 so that it adheres to the photoreceptor drum 1, and the toner 5 is attached to the photoreceptor drum 1 and the sleeve 2.
Since no high voltage is applied between the photoreceptor and the photoreceptor, leakage can be prevented, and the electrostatic latent image formed on the photoreceptor drum will not be disturbed or the photoreceptor drum will be damaged. In addition, the electromagnet 15 can be driven at a low voltage, and by making the end of the electromagnet 15 pointy, it is possible to obtain the necessary magnetic force at an even lower voltage, so the power supply 16 generates a low voltage. can be made cheaply,
Equipment costs can be reduced.

Note that the present invention is not limited to the above embodiments.

For example, in the above embodiment, an electromagnet is used as the magnetic field line generator, but any other device may be used as long as it intermittently generates a magnetic force that attracts toner toward the photoreceptor drum, such as by rotating a permanent magnet.

In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, in a developing device that develops an electrostatic latent image formed on the photosensitive surface of a photosensitive drum, the developing device is provided in parallel at a predetermined distance from the photosensitive drum, and is provided in parallel with the photosensitive drum at a predetermined distance from the photosensitive drum. Since the structure includes a developer carrier that carries magnetic developer and a magnetic force line generator such as an electromagnet that is provided inside the photosensitive drum and emits magnetic lines of force toward the developer carrier, leakage can be prevented. A developing device that does not occur and is inexpensive.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining one embodiment of the present invention. FIG. 1 is a sectional view showing the configuration of a developing device according to the embodiment, and FIG. Figure 2 (b) is a diagram showing changes in the current applied to the electromagnet;
FIG. 3 is a sectional view showing an example of the configuration of a conventional developing device. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Sleeve, 3... Magnet, 4... Hopper, 5... Toner, 6... Blade, 15... Electromagnet, 16... Power supply device . Applicant's agent Patent attorney Takehiko Suzue Figure 2 (a) Figure 2 (b) Figure 3

Claims (1)

[Claims] In a developing device that develops an electrostatic latent image formed on a photosensitive surface of a photosensitive drum, a developer carrier is provided parallel to the photosensitive drum at a predetermined distance and supports a magnetic developer using magnetic force. . A developing device comprising: a magnetic line of force generator that is provided inside the photosensitive drum and emits lines of magnetic force toward the developer carrier.