JP3252604B2 - Magnetic particle ejection type image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image by ejecting magnetic particles. More specifically, the present invention relates to an apparatus that creates an image by ejecting magnetic particles in a specific direction based on a change in a magnetic field.

[0002]

2. Description of the Related Art Image forming apparatuses such as electrophotographic copying machines and printers generally employ a developing method in which a charged toner is attached to an electrostatic latent image formed on a photoreceptor to form a visible image. Has adopted. This developing method can be divided into a two-component developing method using a two-component developer composed of a toner and a carrier, and a one-component developing method using only a toner.

[0003]

However, in the two-component developing system, the mixing means for mixing the toner and the carrier uniformly and for uniformly charging the toner by contact with the carrier, and for keeping the mixing ratio of the toner and the carrier constant. It is necessary to provide a mixing ratio control unit for maintaining the toner and a replenishing unit for replenishing an amount of toner corresponding to the consumed toner amount. In addition, the toner components adhere to and accumulate on the carrier together with the printing endurance, and the charging ability and developing ability of the toner are reduced, causing toner scattering and background fog.

On the other hand, in the one-component developing system, the toner is charged by disturbance by a toner conveying member, or a blade is pressed against a rotating sleeve that conveys the toner, and the toner is charged by stress generated when the blade is rubbed through the pressing portion. But
Since charging time is limited, poor charging may occur. Further, in the case of using a blade, the charging ability decreases with time due to wear of the blade. Further, in order to compensate for the charging failure, the toner needs to be devised, so that the toner becomes expensive.

[0005] As described above, all of the above-mentioned development methods require charging of the toner, and in order to stably charge the toner, extremely advanced techniques are required in the material design and manufacturing method of the toner and the carrier. I do. Further, since charging is greatly affected by environmental conditions, the storage environment and the use environment are also significantly restricted.

In recent years, an ink jet system and a thermal system have been proposed as alternatives to the electrophotographic system. However, the ink jet method is inferior in high-speed response and has an environmental problem of discharging a solvent. In addition, the thermal method cannot print on normal paper without a special ink ribbon, and has a problem in high-speed compatibility.

As described above, each of the methods proposed to date has a problem, and therefore, it is necessary to develop an image forming method that can respond at high speed, is resistant to disturbances such as the environment, and has a simple configuration. Was desired.

[0008]

SUMMARY OF THE INVENTION The present invention has been made based on such a demand. The magnetic particle jetting type image forming apparatus comprises: a magnetic particle carrier for holding magnetic particles on a surface; Forming a moving magnetic field on the surface of the carrier,
The first magnetic field generating means for moving the magnetic particles based on the movement of the magnetic field is opposed to the surface of the magnetic particle carrier in a non-contact manner, and generates a magnetic field having a polarity opposite to that of the moving magnetic field at the facing portion. And a second magnetic field generating means for causing the magnetic particles to fly, and an image carrier made of a magnetic material and holding and transporting the flying magnetic particles.

Another magnetic particle ejection type image forming apparatus includes:
A magnetic particle carrier for holding magnetic particles on the surface, a first magnetic field generating means for forming a moving magnetic field on the surface of the magnetic particle carrier, and moving the magnetic particles based on the movement of the magnetic field; A second magnetic field generating means for causing the magnetic particles to fly by generating a magnetic field having a polarity opposite to that of the moving magnetic field at the opposed portion in a non-contact manner with the surface of the magnetic particle carrier, and a magnetic material; And an image holding member carrier for conveying the image holding member and holding the flying magnetic particles on the image holding member. The image forming apparatus may include a heating unit that heats and fixes the magnetic particles held on the image holding member.

Further, in the magnetic particle jetting type image forming apparatus, it is desirable to use magnetic particles having a coercive force of 100 [Oe] or more.

[0011]

According to the image forming apparatus, a moving magnetic field is formed on the surface of the magnetic particle carrier by the first magnetic field generating means, and the moving magnetic field conveys the magnetic particles on the surface of the magnetic particle carrier. On the other hand, the second magnetic field generating means is opposed to the magnetic particle carrier in a non-contact manner, and a magnetic field having a polarity opposite to that of the moving magnetic field is formed in the facing portion, and is conveyed between these two magnetic fields. Magnetic particles fly. Then, the flying magnetic particles are held by an image carrier made of a magnetic material and transported to the next step.

In another image forming apparatus, the flying magnetic particles are held by an image holding member carried by an image holding member carrier made of a magnetic material and carried to the next step. In the case of the apparatus having the heating means, the magnetic particles held by the image holding member are heated and fixed.

Further, the coercive force of the magnetic particles is 100 [O
e) In the case described above, a sufficient flying force of the magnetic particles can be obtained with a small content of the magnetic powder.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of a magnetic particle jetting type image forming apparatus 1. The magnetic particle jetting apparatus generally designated by reference numeral 2 has a housing 3 made of a non-magnetic material. , A toner container 5 located above the sleeve container 4, and a nozzle 6 extending laterally from the bottom of the sleeve container 4 and having an opening at the end.

The sleeve accommodating portion 4 accommodates a cylindrical aluminum sleeve 7 which is a magnetic particle carrier, and a regulating portion 8 projecting from a wall constituting the toner accommodating portion 4 is provided on the sleeve 7. It is opposed to the upper outer peripheral surface at a predetermined interval. The toner container 4 contains magnetic particles 9 made of synthetic resin containing magnetic powder or the like, that is, magnetic toner.

Inside the sleeve 7, a magnet roller 10 as first magnetic field generating means is accommodated.
The magnet roller 10 includes a plurality of magnetic poles (eight magnetic poles: N1,
S1, N2, S2, N3, S3, N4, and S4) are formed at equal intervals in the circumferential direction and alternately arranged with N poles and S poles. Hereinafter, the magnetic poles provided on the magnet roller 10 are referred to as “moving magnetic poles”. The magnet roller 10 is rotatably disposed inside the sleeve 7 and is drivingly connected to a motor 11. When the magnet roller 10 rotates in the direction of arrow a based on the driving of the motor 11, a moving magnetic field is generated around the sleeve 7. Form.

Below the housing 3, there is provided a magnetic particle ejection control unit 12, which is a second magnetic field generator. As shown in FIG. 2, the injection control unit 12 includes a number of magnetic needles 13. These magnetic needles 13 are arranged at predetermined intervals in the axial direction of the sleeve 7, and their tips are opposed to the bottom of the sleeve 7. A coil 14 is wound around each of the magnetic needles 13 and connected to an AC power supply 16 via a switch 15.
Each switch 15 is opened and closed based on a signal output from. The frequency of the AC power supply 16 is
The magnetic needle 13 and the sleeve 7 are adjusted so that the opposite part of the housing of the magnetic needle 13 is excited to have a polarity opposite to that of the moving magnetic pole passing through the flying area 18 facing the sleeve 7. Hereinafter, the magnetic pole generated in the magnetic needle 13 is referred to as “excitation pole”.

Subsequently, the image bearing device generally designated by reference numeral 19 has a cylindrical image bearing drum 20. As shown in FIG. 3, the image bearing drum 20 is formed of a cylindrical body 21 made of a non-magnetic material such as aluminum, the outer peripheral portion of which is coated with a magnetic material 22, or a cylindrical body made of a magnetic material. The motor 2 is disposed at a predetermined distance from the opening of the motor 2.
The driving is performed in the direction of arrow b based on the driving of No. 3. As the magnetic material, MO.Fe ₂ O ₃ , MO
・ FeO.Fe ₂ O ₃ (MO: divalent metal ion, M
n, Ni, Cu, Zn, ferrite or represented by Mg, etc.), magnetite represented by _{FeO · Fe 2 O 3, Fe} 2 O 3, or iron is preferably used.

In the image forming apparatus 1 having the above configuration, the magnet roller 10 rotates in the direction of the arrow a based on the driving of the motor 11. As a result, a moving magnetic field is formed on the outer peripheral portion of the sleeve 7 based on the movement of the magnetic poles N1 to S4, and the movement of the magnetic field causes the magnetic particles 9 located near the sleeve 7 in the toner container 5 to move in the direction of arrow a '. Transported to After the magnetic particles 9 are regulated to a certain amount by the regulating section 8, the area 18 where the sleeve 7 and the magnetic needle 13 face each other is controlled.
Transported to

The injection control unit 12 includes an image information output device 17
Switches 15 are respectively opened and closed based on signals from
An exciting pole having a polarity opposite to that of the moving magnetic pole of the magnet roller 10 passing through the region 18 is formed at the tip of the magnetic needle 13. As a result, the magnetic particles 9 passing through the region 18 between the moving magnetic pole and the magnetic needle 13 magnetized to a polarity different from the moving magnetic pole are given a flying force toward the opening of the nozzle 6, and the flying force is applied by the flying force. The magnetic particles 9 ejected from the nozzle 6 are held on the image bearing drum 20 by the residual magnetic force of the magnetic particles 9. The ejection phenomenon of the magnetic particles 9 will be described later in detail. Then, the magnetic particles held on the image bearing drum 20 are conveyed in the direction of arrow b with the rotation of the image bearing drum 20, and are transferred to an image bearing member such as a sheet or a film sheet by a transfer unit (not shown). The transferred magnetic particles are heated and fixed to the image bearing member.

In the above embodiment, the image bearing drum 20
The magnetic particles are directly held at the outer peripheral portion of FIG.
As shown in FIG. 2, a transport drum 24 made of the same material as that of the image bearing drum is provided in place of the image bearing drum.
4, the magnetic particles 9 are held on the image holding member 25 supported on the outer periphery of the sheet 4, that is, paper, based on the residual magnetic force.
Heat fixing means having a heater 26 (for example, heat roller 2
7), the magnetic particles 9 may be fixed to the image holding member 25.

Further, as shown in FIG.
The heater 28 is provided in the inside of the
May be heated immediately to fix the toner. Further, as shown in FIG. 6, a heating resistor layer 29 may be provided on the inner peripheral portion of the transport drum 24, and electricity may be applied to the heating resistor layer 29 to heat and fix the held toner. By doing so, it is not necessary to provide a separate fixing device, and the size of the image forming apparatus can be reduced.

The injection phenomenon of the magnetic particles 9 will be described in detail.
As shown in FIGS. 7 to 10, the magnetic particles 9 conveyed on the sleeve 7 are connected to form a chain, that is, a magnetic brush 30, and a magnetic pole of the opposite polarity is provided on the moving magnetic pole side of each magnetic particle 9. The magnetic pole having the same polarity as the moving magnetic pole is excited on the opposite side, so that the root portion of the magnetic brush is magnetized in the opposite polarity to the moving magnetic pole as a whole, and the tip portion is magnetized in the same polarity as the moving magnetic pole. Therefore, the magnet roll 1
When the moving magnetic pole moves in the direction of arrow a based on the rotation of 0, a rotating force acts on each magnetic particle, and the magnetic particles at the root of the magnetic brush are pulled in the direction of arrow a with the movement of the moving magnetic pole. Since the magnetic particles at the tip of the brush are attracted to the moving magnetic pole on the upstream side with respect to the rotation direction, the magnetic brush 30 falls down toward the moving magnetic pole on the upstream side. It moves in the direction opposite to the direction of rotation.

When the magnetic pole faces the magnetic needle 13 and the tip of the magnetic needle 13 is magnetized in the opposite polarity to the moving magnetic pole, the magnetic particles at the tip of the magnetic brush are attracted to the excitation pole (S). The magnetic particles at the root of the magnetic brush are attracted to the moving magnetic pole N2. as a result,
The magnetic brush 30 receives a force in the moving direction of the moving magnetic pole N2 as a whole. The magnetic particles 9 at the root of the magnetic brush are restricted by the moving magnetic pole N2, and the magnetic particles at the distal end are restricted by the excitation pole (S) at the distal end of the magnetic needle. However, the magnetic particles 9 'in the middle part of the magnetic brush 30 have small magnetic restraining forces received from the moving magnetic pole N2 and the exciting pole (S).
On the contrary, since the repulsive force received from these magnetic poles is large, the tangential direction (arrow c)
In the direction).

The magnetic particles used in the magnetic particle jetting type image forming apparatus will be described. In this image forming apparatus, the flying force of the magnetic particles is affected by the repulsive force received from the moving magnetic pole and the induction magnetic pole. When the repulsive force is increased, the flying speed of the magnetic particles, that is, the image forming speed is improved. In order to increase the repulsive force, the coercive force of the magnetic powder contained in the magnetic particles (that is, the strength of the magnetic field at which the magnetization becomes zero in the hysteresis curve of the magnetic substance) may be increased.

In the following, an experiment was conducted to determine an appropriate coercive force of the magnetic powder. In Experiment 1, in a magnetic field of 1,000 [Oe], coercive force Hc: 150 [Oe], saturation magnetization σ
A cubic magnetite having m: 60 [emu / g] and a particle diameter of 60 µm was added to 30 parts by weight based on 100 parts by weight of a styrene-acrylic resin having a number average molecular weight Mn of 8,000 and a weight average molecular weight Mw of 100,000. Parts and then melt-kneaded with an extruder. Further, the kneaded material was cooled, finely pulverized by a jet mill, and then classified by an airflow classifier to prepare a magnetic toner having an average particle diameter of 12 μm. When the toner was accommodated in the housing of the image forming apparatus to form an image, the toner quickly and linearly flowed in the nozzle, and a good image was obtained. Further, the fixing property of the toner to paper was also good.

As a comparative example, coercive force Hc: 30 [Oe]
Identical images were made using the magnetite. Other conditions were the same as in Experiment 1. As a result, the number of flying toners was smaller than in Experiment 1, and the flying power was weaker.
The density is lower than the image created in Experiment 1, the image is disturbed,
Dirt due to toner drop was conspicuous.

As another comparative example, the coercive force Hc: 3
A toner was prepared using 0 [Oe] magnetite with a magnetic powder amount of 200 parts by weight, and a toner image formed using the toner was fixed on paper at 160 ° C. and a pressure of 40 Kg. I dropped out.

In Experiment 2, the coercive force Hc: 100 [O
e) An identical image was made using the magnetite. Other conditions were the same as in Experiment 1. As a result, good results were obtained as in Experiment 1.

In Experiment 3, a coercive force Hc: 250 [O
e) An identical image was made using the magnetite. The mixing ratio of magnetite to resin was 20 parts by weight, and other conditions were the same as in Experiment 1. As a result, good results were obtained as in Experiment 1.

In Experiment 4, the coercive force Hc: 400 [O
e], saturation magnetization σm: 55 [emu / g], major axis diameter of 0.
A 6 μm acicular magnetite was mixed at a ratio of 15 parts by weight with respect to 100 parts by weight of the resin to form a magnetic toner, and the same image was formed using this magnetic toner. Was done.

From the above, the magnetic powder contained in the magnetic particles has a coercive force Hc of 100 [Oe] or more, preferably 2 [Oe].
If it is not less than 00 [Oe], the composition ratio of the magnetic powder is 20% by weight.
Even below, sufficient flying power of the toner can be obtained, and an image having good fixability can be obtained. The composition ratio of the magnetic powder is 20% by weight.
As described above, the flying power can be improved without increasing the melt viscosity of the toner.

[0033]

As is apparent from the above description, the magnetic particle ejection type image forming apparatus according to the present invention has the following advantages. (A) Since the magnetic particles are ejected by the action of the magnetic field, the post-treatment agent adhered to the particle surface by electric force does not separate from the particles, and the chargeability and fluidity of the particles are properly adjusted. Can be maintained. (B) Since the strength of the magnetic field is not affected by environmental conditions such as humidity and temperature, the particles can be stably ejected even if the environment changes. (C) There is no need to use a high voltage because no electric field needs to be formed to eject the particles. (D) Since the particles are disturbed between the magnetic member and the moving magnetic field during the flight of the particles, when charged particles are used as the particles, the particles can be uniformly charged. In addition, the charge further promotes the dispersion of the particles. (E) The flying magnetic particles are reliably magnetically held on the surface of the image bearing pair made of a magnetic material by the coercive force of the magnetic particles, and an image is formed. (F) In the case where the image holding member is transported by the image holding member carrier made of a magnetic material, the magnetic particles are surely deposited on the surface of the image holding member by the coercive force of the flying magnetic particles and the magnetic force of the image holding member carrier. Will be retained. (H) When the image holding member carrier has heating means,
Since the magnetic particles held by the image holding member can be immediately heated and fixed, a separate fixing device is not required, and the size of the device can be reduced. (I) By setting the coercive force of the magnetic particles to 100 [Oe] or more, a sufficient flying force of the magnetic particles can be obtained with a small content of the magnetic powder. Further, since the melt viscosity of the magnetic particles is not greatly increased, the fixing strength is high.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a magnetic particle ejection type image forming apparatus.

FIG. 2 is a perspective view of a magnetic particle ejecting apparatus.

FIG. 3 is a sectional view of an image bearing drum.

FIG. 4 is a diagram illustrating the principle of ejecting magnetic particles.

FIG. 5 is a diagram illustrating the principle of ejecting magnetic particles following FIG. 4;

FIG. 6 is a view for explaining the principle of ejecting magnetic particles following FIG. 5;

FIG. 7 is a diagram illustrating the principle of ejecting magnetic particles together with FIGS.

FIG. 8 is a sectional view showing a second embodiment of the magnetic particle ejection type image forming apparatus.

FIG. 9 is a sectional view showing a third embodiment of the magnetic particle ejection type image forming apparatus.

FIG. 10 is a cross-sectional view of a transport drum provided with a heater.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic particle ejection type image forming apparatus, 2 ... Magnetic particle ejection apparatus, 6 ... Nozzle, 7 ... Sleeve, 8 ... Regulator, 9 ... Magnetic particles, 10 ... Magnet roller, 12 ... Ejection controller, 1
9: image carrying device, 20: image carrying drum, 24: transport drum, 25: image holding belt, 26: heater.

────────────────────────────────────────────────── (5) References JP-A-53-45922 (JP, A) JP-A-59-93478 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/385

Claims (4)

(57) [Claims] 1. A magnetic particle carrier for holding magnetic particles on a surface, and a first magnetic field that forms a moving magnetic field on the surface of the magnetic particle carrier and moves the magnetic particles based on the movement of the magnetic field. And a second magnetic field generating means for generating a magnetic field having a polarity opposite to that of the moving magnetic field at the facing portion so as to fly the magnetic particles.
A magnetic particle ejection type image forming apparatus comprising: a magnetic field generating means; and an image carrier made of a magnetic material and holding and transporting the flying magnetic particles. 2. A magnetic particle carrier for holding magnetic particles on a surface thereof, and a first magnetic field that forms a moving magnetic field on the surface of the magnetic particle carrier and moves the magnetic particles based on the movement of the magnetic field. And a second magnetic field generating means for generating a magnetic field having a polarity opposite to that of the moving magnetic field at the facing portion so as to fly the magnetic particles.
A magnetic field generating means, and an image holding member carrier made of a magnetic material, which carries the image holding member and holds the flying magnetic particles on the image holding member. Image forming apparatus. 3. The image forming apparatus according to claim 2, further comprising heating means for heating and fixing the magnetic particles held by the image holding member. 4. The coercive force of the magnetic particles is 100 [Oe].
4. A magnetic particle ejection type image forming apparatus according to claim 1, wherein: