JPH0153464B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner developing device used in copying machines, printers, etc. that utilize an electrophotographic process.

FIG. 1 is a side sectional view showing a conventional magnetic toner developing device of this type. In the figure, 1 indicates magnetic toner, 2
1 is a toner hopper containing this magnetic toner 1, and as shown, this toner hopper 2 has an opening on the side of the object to be developed, which will be described later.

3 is a non-magnetic metal cylinder made of non-magnetic metal such as aluminum, 4 is a cylindrical permanent magnet arranged concentrically within this non-magnetic metal cylinder 3, and this permanent magnet 4 has N in the circumferential direction. It has a structure in which poles and south poles are arranged alternately, and is usually called a magnet roll. The non-magnetic metal cylinder 3 and the permanent magnet 4 are each rotatable, and the two are usually referred to as a developing roll as an integrated structure.

In this developing roll, the permanent magnet 4 uses its magnetic attraction force to attract the magnetic toner in the toner hopper 2.
is adsorbed onto the non-magnetic metal cylinder 3. The magnetic toner 1 usually has a particle size of 5 to 20 μm, and a plurality of magnetic toner particles are arranged in a row along the lines of magnetic force to form a toner brush on the non-magnetic metal cylinder 3.

5 is a doctor blade that regulates the height of the toner brush.

Reference numeral 6 denotes a rotatable developing object such as an electrostatic drum or a photosensitive drum, the surface of which is coated with a dielectric material, and an electrostatic latent image is formed by an optical system (not shown) at a position before the developing area. It will be sent to. The conductive base material of the object to be developed 6 and the non-magnetic metal cylinder 3 of the developing roll are electrically connected, or
Alternatively, in the case of reversal development, a development bias voltage is applied.

The positional relationship of each of these members is as follows.

First, the toner hopper 2 containing the magnetic toner 1
is arranged near the object to be developed 6 with its opening facing toward the object to be developed 6. Then, the non-magnetic metal cylinder 3 is placed inside the opening of the toner hopper 2.
A developing roll consisting of a permanent magnet 4 and a doctor blade 4 is fixed to the toner hopper 2 so that its tip faces the metal cylinder 3 at a constant distance.

In the magnetic toner developing device having such a configuration, by rotating the non-magnetic metal cylinder 3 and the permanent magnet 4, the non-magnetic metal cylinder 3 and the object to be developed 6 are separated.
Development is carried out by conveying the magnetic toner 1 to a development area between the two, and the development will be described in detail below.

In the development area, there is a potential difference between the non-magnetic metal cylinder 3 and the object to be developed 6, and when the toner brush is moved from the state where the magnetic toner 1 is sandwiched between the surfaces of the two, the non-magnetic metal cylinder 3
The magnetic toner 1 that was in contact with the non-magnetic metal cylinder 3 receives an electric charge from the non-magnetic metal cylinder 3 and becomes charged. This phenomenon is called contact charging, and the magnetic toner 1 is attracted to and adheres to the electrostatic latent image formed on the object to be developed 6 due to the electrical charge, thereby performing development.

Here, when the magnetic toner 1 has a high resistance, the above-mentioned charging is a factor that determines the image quality of development, and this will be explained.

FIG. 2 is a diagram showing the magnetic flux density in the vertical direction (solid line) and the circumferential direction (broken line) due to the permanent magnet 4 at a certain position X along the circumferential direction of the non-magnetic metal cylinder 3 of the developing roll. FIG. 3 is an explanatory diagram showing how the toner brush rotates.

As seen in this figure, the position a is above the north pole, and the toner brush made of a plurality of connected magnetic toners 1 stands up. Next, at position b, which is between the north and south poles, the horizontal component becomes stronger, and the toner brush takes on a tilted shape. And S best c
At the position, the toner brush assumes an upright shape again.

Therefore, if the non-magnetic metal cylinder 3 and the permanent magnet 4 are rotated to rotate the toner brush, the toner brush will fall from the position a to the position b, and then fall to the position c. Now, the rearranged toner brush stands up. Therefore, when the toner brush is in the development area, the charged toner that comes into contact with the non-magnetic metal cylinder 3 cannot reach the tip of the toner brush because the toner brush does not rotate sufficiently and is rearranged midway through. As a result, the charged toner cannot efficiently adhere to the electrostatic latent image because other toners get in the way, making it impossible to perform efficient development.

Therefore, when a high-resistance magnetic toner is used in a conventional developing device, efficient development cannot be carried out as described above, resulting in a disadvantage that the image quality of the developed image is poor.

The present invention aims to solve these drawbacks.

Therefore, the present invention includes a toner hopper containing magnetic toner with an opening on the side of the object to be developed where an electrostatic latent image is formed, a rotatable metal cylinder, and an N-pole and a S-pole arranged rotatably within the metal cylinder. and a cylindrical permanent magnet arranged in the circumferential direction.
A developing roll disposed inside the opening of the toner hopper so as to face the object to be developed, and a toner brush made of magnetic toner attracted onto a metal cylinder by a permanent magnet of the developing roll, the height of which is regulated. A doctor blade is provided on the toner hopper with its tip facing the metal cylinder, and the toner brush is rotated by the mutual rotation of the metal cylinder and the permanent magnet, and the toner brush is supplied to the object to be developed to develop the electrostatic latent image. In the magnetic toner developing device, the metal cylinder of the developing roll is formed by alternately arranging magnetic materials and non-magnetic materials at substantially equal intervals in the circumferential direction, and both the magnetic materials and the non-magnetic materials By making the height of the toner brush equal to or slightly larger than the height of the toner brush regulated by the doctor blade, the area where the toner brush exists is reduced and the toner brushes are prevented from overlapping each other during rotation, and the height of the toner brush is The electrostatic latent image is sufficiently rotated so that the charged toner can be efficiently attached to the electrostatic latent image.

Embodiments of the present invention will be described below with reference to FIGS. 4 and 5.

FIG. 4 is a partially enlarged sectional view showing the first embodiment of the present invention.

In the figure, reference numeral 9 denotes a metal cylinder formed by integrating magnetic materials 7 and non-magnetic materials 8 which are arranged alternately at approximately equal intervals in the circumferential direction. A developing roll is constructed by arranging cylindrical permanent magnets 4 with north and south poles arranged alternately in the direction, and this developing roll is assembled with the toner hopper 2, doctor blade 5, etc. shown in FIG. Together, they constitute a magnetic toner developing device.

That is, a developing roll consisting of a rotatable permanent magnet 4 arranged inside a rotatable metal cylinder 9 is placed inside the opening of the toner hopper 2 containing the magnetic toner 1, and its tip is opposed to the metal cylinder 9. By fixing the doctor blade 5 to the toner hopper 2, a magnetic toner developing device is constructed.

Here, as the magnetic material 7, metals and alloys such as iron, cobalt, and nickel, or various ferrites can be used, and as the non-magnetic material 8, metals such as aluminum and stainless steel can be used.

Further, the pitch of both the magnetic material 7 and the non-magnetic material 8, that is, the combined length of one magnetic material 7 and one non-magnetic material 8, is the same as or less than the height of the toner brush regulated by the doctor blade 5. It is assumed to be slightly larger.

In this configuration, as in the conventional case, the permanent magnet 4 and the metal cylinder 9 are rotated, thereby conveying the magnetic toner 1 to the developing area and attracting it to the electrostatic latent image on the developing object 6. However, since this embodiment uses a metal cylinder 9 made of alternating magnetic materials 7 and non-magnetic materials 8, the state of development by the toner brush made of magnetic toner 1 is It differs from the conventional method as follows.

In other words, in general, in a magnetic circuit, magnetic flux flows to a place with low magnetic resistance (a place with high magnetic permeability), so most of the magnetic flux passes through the inside of the place with low magnetic resistance, and almost all of it flows from its outer surface into the air. Although it rarely comes out, on the other hand, in areas with high magnetic resistance, there is little magnetic flux passing through the interior, and most of the magnetic flux goes out into the air.

Therefore, in the case of the developing roll of this embodiment in which the permanent magnet 4 is arranged in the metal cylinder 9 which is made up of the magnetic material 7 and the non-magnetic material 8 arranged alternately, the magnetic material 7 with low magnetic resistance in the metal cylinder 9 is Since the magnetic flux of the permanent magnet 4 hardly comes out into the air from the outer surface of the magnetic material 7, a toner brush is not formed on this magnetic material 7, and as shown in FIG. A toner brush is formed standing up on the magnetic material 8.

This toner brush has a metal cylinder 9 and a permanent magnet 4.
The metal cylinder 9 of this embodiment rotates due to the mutual rotation of the magnetic material 7 and the non-magnetic material 8.
The height of the toner brush is the same as or slightly larger than the height of the toner brush regulated by the doctor blade 5, and is alternately arranged in the circumferential direction.
From the state of standing up on the non-magnetic material 8, it falls onto the adjacent magnetic material 7, and then stands up again on the non-magnetic material 8 adjacent to this magnetic material 7, and as the toner brush rotates, the toner brush When the brush falls on the magnetic material 7, there are almost no other toner brushes on the magnetic material 7, so it is possible to prevent the toner brushes from overlapping each other, and
The toner brush can also rotate sufficiently.

In this way, the toner brush sufficiently rotates on its own axis without almost overlapping with other toner brushes, contacts the metal cylinder 9, and is uniformly charged, and then in the development area between the metal cylinder 9 and the object to be developed 6. , is attracted to and adheres to the electrostatic latent image on the object to be developed 6, and development is performed.

Next, FIG. 5 is a partially enlarged sectional view showing a second embodiment of the present invention, in which a cylindrical non-magnetic material 10 is regulated at regular intervals along its circumferential surface, that is, by a doctor blade 5. Magnetic material 11 with a pitch that is the same as or slightly larger than the height of the toner brush.
is arranged to form a metal cylinder 12, and a permanent magnet 4 is arranged inside this metal cylinder 12 to constitute a developing roll.
Then, move this developing roll to the toner hopper 2 in Figure 1.
This is combined with a doctor blade 5 and the like to form a magnetic toner developing device.

Note that the non-magnetic material 10 and the magnetic material 11 are made of the same metal as in the first embodiment. Also, the metal cylinder 12
can be easily formed by etching technology.

Even in the second embodiment with the above configuration, the metal cylinder 12 has a structure in which the non-magnetic material 10 and the magnetic material 11 are arranged alternately in the circumferential direction, so that the effect on the toner brush made of the magnetic toner 1 is This is similar to Example 1, and development can be performed in the same manner.

As explained above, in the present invention, the magnetic material and the non-magnetic material are arranged alternately at equal intervals in the circumferential direction, and the pitch between the two is the same as or slightly larger than the height of the toner brush regulated by the doctor blade. Inside the metal cylinder formed by arranging the
Since the developing roll is constructed by arranging cylindrical permanent magnets in which N poles and S poles are arranged alternately in the circumferential direction, the toner brush is formed upright on the non-magnetic material of the metal cylinder. become. Therefore, the area where the toner brush exists is reduced compared to the conventional one, and it is possible to prevent the toner brushes from overlapping each other when they rotate on their own axis, and it is possible to perform sufficient rotation on their axis.
High-resistance magnetic toner contact-charged with a metal cylinder can be efficiently attracted and adhered to the electrostatic latent image on the object to be developed, resulting in the effect that high-quality image development can be performed.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing a conventional magnetic toner developing device, Fig. 2 is a drawing showing its magnetic flux density, Fig. 3 is an explanatory diagram showing how the toner brush rotates on its axis in the conventional device, and Fig. 4 is a bookmarking diagram. FIG. 5 is a partially enlarged sectional view showing the first embodiment of the invention, and FIG. 5 is a partially enlarged sectional view showing the second embodiment of the invention. 1: Magnetic toner, 2: Toner hopper, 4: Permanent magnet, 5: Doctor blade, 6: Developing object,
7: Magnetic material, 8: Non-magnetic material, 9: Metal cylinder, 1
0: non-magnetic material, 11: magnetic material, 12: metal cylinder.

Claims (1)

[Scope of Claims] 1. A toner hopper containing magnetic toner with an opening facing the side to be developed where an electrostatic latent image is formed, a rotatable metal cylinder, and a N-pole rotatably disposed within the metal cylinder. a developing roll, which is arranged in the opening of the toner hopper so as to face the object to be developed; and the permanent magnet of the developing roll forms a metal cylinder. a doctor blade fixed to the toner hopper with its tip facing the metal cylinder so as to regulate the height of a toner brush made of magnetic toner that is attracted to the toner brush; In a magnetic toner developing device that develops an electrostatic latent image by rotating a toner brush and supplying it to an object to be developed, the metal cylinder of the developing roll has a magnetic material and a non-magnetic material arranged at approximately equal intervals in the circumferential direction. A magnetic toner developer formed by alternately arranging magnetic materials and non-magnetic materials, and characterized in that the pitch of both magnetic materials and non-magnetic materials is equal to or slightly larger than the height of a magnetic brush regulated by a doctor blade. Device.