JPS62153882A - Developing device - Google Patents

Abstract

PURPOSE:To reduce a load applied to a developer and to prevent the deterioration of a magnetic grain by specifying the size of a flux formed between a plural magnetic field generation means. CONSTITUTION:The titled device is composed of a developer container 21, a developing sleeve 22 being a developer holding member, a magnet 23 being a magnetic field generation means, a regulating blade 24 controlling the amount of a developer conveyed to a developing part, etc. The magnet 23 has a magnetic pole S1 controlling the applying amount of a developer to the sleeve 22 in cooperation with a developing magnetic pole N1 and the blade 24, a magnetic pole S3 lifting and conveying a developer in cooperation with magnetic poles N1 and N2 and a magnetic pole S2 dropping the developer on a screw 44 in cooperation with the magnetic pole S2. It is assumed that a flux formed between the magnetic poles S1 and N2 is less than half a flux formed between the magnetic poles N2 and S3. Thus the load applied to the developer can be remarkably reduced due to the regulating action of the blade 24, thereby prolonging the life of the developer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device for developing a latent image formed by electrophotography, electrostatic recording, or the like.

At present, the mainstream developing methods are the l-component developing method using an l-component magnetic toner, and the two-component magnetic brush developer method using a two-component developer made by combining magnetic particles and toner. ing.

While the one-component development method is simple and does not require a means to maintain a constant developer concentration like the two-component development method, it does have problems such as transferability, halftone reproducibility, and stability of development characteristics against temperature and humidity. Moreover, since the toner generally contains a brown or black magnetic material, it is unsuitable for developing non-black colors.

On the other hand, the two-component magnetic brush development method allows for a stable developer and is a simple development method suitable for non-black or full-color development. There is a problem of agent deterioration.

L Mini Top 1 An object of the present invention is to provide a developing device with less deterioration of magnetic particles.

Another object of the present invention is to provide a developing device that reliably removes developer from the surface of a developer carrier.

Another aspect of the present invention is to provide a development device that ensures mixing of the removed developer with developer in a developer container.

According to the present invention, the static latent image on the JFI carrier is I! A developing device that develops a latent image, which uses toner particles, magnetic particles,
a developer container containing a developer having the above-mentioned static-1;
1i fi R, a developer carrying member that forms a developing section that supplies toner particles to the electrostatic Hq image carrying member, and carries and conveys developer from the container to the developing section; A developer regulating member is positioned upstream of the developing section in the direction of the rotational force of the developer carrying member and has a regulating section tip that is spaced apart from the surface of the developer carrying member; The developer that has passed through the developing section and is conveyed to the developer carrying member is received downstream of the developing section, and is conveyed into the developer container.

A developing section is provided, characterized in that it has a transport stirring member that mixes the developer reversed into the developer container by the developer regulating member, so that the load on the developer is small and the magnetic particles are Deterioration can be prevented.

Figure 1 is a cross-sectional view of each developing section according to an embodiment of the present invention.

In this figure, l is an electrostatic latent image carrier that carries an electrostatic layer image to be imaged, and specifically, it is an endlessly movable photosensitive drum, a belt, a dielectric drum, a belt, or the like. The method of forming an electrostatic latent image on this "-" is not the gist of the present invention, and any known method may be used.In this embodiment, an electrostatic latent image 1! The photosensitive drum is rotatable in the direction of arrow a.

The apparatus of this embodiment has a developer container 21. A developing sleeve 22 (hereinafter simply referred to as a sleeve) that is a developer holding member, a magnet 23 that is a magnetic field generating means, and a regulating blade 24 (hereinafter simply referred to as a blade) that controls the amount of developer conveyed to the developing section on the sleeve 22. ), a power source 3 which is an alternating electric field forming means
4 etc. Each configuration will be explained below.

Container 21 contains a developer having a mixture of magnetic particles 27 and toner particles 28 . In this embodiment, the toner particles are non-magnetic toner particles having a particle size of 7 to 20 gm and are formed mainly of, for example, 10 parts of carboxylic acid and 90 parts of polystyrene. Regarding toner particles and magnetic particles, in this embodiment, the concentration of magnetic particles is high near the sleeve 22;
Container 2 , which may be contained in a homogeneous mixture within container 21 , although it is contained low at a distance from
1 has an opening at the lower left in FIG.

The sleeve 22 is made of a non-magnetic material 4 such as aluminum, and is provided at the opening of the container 21, with a part of its surface exposed and the other surface protruding into the container 21. The sleeve 22 is rotatably supported about an axis perpendicular to the drawing and is rotationally driven in the direction indicated by the arrow. Although the sleeve 22 is a cylindrical sleeve in this embodiment, it may be an endless belt.

The sleeve 22 opposes the photosensitive drum 1 with a small gap therebetween and constitutes a developing section. Toner and magnetic particles are conveyed to this developing section by a sleeve 22.

The magnet 23 is statically fixed inside the sleeve 22 and remains stationary even when the sleeve 22 rotates. The magnet 23 cooperates with a first magnetic pole Nl, which is a developing magnetic pole, a second magnetic pole si, which controls the amount of developer applied onto the sleeve 22 in cooperation with a blade 24, which will be described later, and a third magnetic pole N2) and a 31a pole N2. The sleeve 22 also has a fifth magnetic pole S2 that cooperates with the fourth magnetic pole S3 to lift and convey the developer and drop the developer onto the screw 44. Although this magnet is a permanent magnet in this embodiment, an electromagnet may be used instead.

In this embodiment, the blade 24 has at least its tip made of a non-magnetic material such as aluminum, and the blade 24 is made of a non-magnetic material such as aluminum.
extending in the longitudinal direction of the sleeve 22 near the top of the opening;
Its base is fixed to a container 21, and its distal end is fixed to a sleeve 22.
The two magnetic poles are opposed to each other at a position between the second magnetic pole S1 and the third magnetic pole N2 with a gap between the surfaces thereof. The gap between the tip of the blade 24 and the surface of the sleeve 22 is 50 pm to 2 mm, preferably 10,100 gmN1, and in this example, 5008 Lm.
It is. If this gap is smaller than 50pm.

Magnetic particles tend to get clogged in this gap, and if a resin-coated carrier with a diameter of 2 mm or more is used, the quenching effect becomes very large, which is undesirable. Photosensitive drum l and sleeve 2
2. In order to create a developer layer with such a thickness, which is smaller than any gap (however, the thickness of the developer at this time is the thickness at the sleeve 22-H when no magnetic force is applied), The gap between the blade tip and the sleeve surface is preferably equal to or smaller than the gap between the sleeve surface and the photosensitive drum surface, but it is also possible to make it larger.

The power source 34 applies an alternating electric field between the photosensitive drum 1 and the sleeve 22, thereby improving developing performance. The voltage from the m source 34 may be a symmetrical alternating voltage in which the peak voltage on the positive side and the negative side are the same, or an asymmetrical alternating voltage in which a DC voltage is superimposed on such an alternating voltage. For example, dark area potential -600V, light area potential -2
For an electrostatic latent image of 00■, for example, direct current Ichikawa
Superimpose 300■ to increase the peak-to-peak voltage from 300 to 20
00 V P P , I,', 1 wave number 200-300
A 0 Hz alternating voltage is applied to the sleeve 22 side to maintain the photosensitive drum l at ground potential. In addition, when performing reversal development, the toner should be of the same polarity as the static latent image, and a DC voltage of -50
It is sufficient to superimpose 0■ and apply the lij interpolation I'L voltage.

At the bottom of the developer device there is provided a bottom housing 36 having a central partition 38 and thereby forming a feed screw chamber 40 and a return screw chamber 42 extending perpendicularly to the drawing. The central partition wall 38 is connected to the bottom device of the container 21 or is formed integrally with the central partition wall 3
8 has an opening 38a on the lower back side and an opening 38b on the front side to open the feed screw chamber 4, as shown in FIG.
The opening 38b on the front side also serves to cause the developer from above to fall into the return screw 42. A feed screw 44 that rotates in the direction of the arrow is provided in the feed screw chamber 40, and a return screenie 46 that rotates in the direction of the arrow is rotatably supported in the return screw chamber 42 so as to extend in the longitudinal direction. A hopper 50a for storing toner for replenishing toner is provided in the upper part of the developing device, and a toner replenishing port 50b is provided near the end of the return screw chamber 42 on the near side in the drawing, and toner is supplied to the return screw chamber 42. . The feed screw 44 receives the developer that has not been consumed during development and also serves to send the developer from the back side of the drawing to the front side of the drawing.The return screw 46 receives the developer that has fallen through the opening 1 m 38 b. It has the function of mixing and agitating the toner with the toner supplied from the toner supply port, sending it from the front side of the drawing to the back side, and passing it to the feed screw 44 near the end on the back side of the drawing.

FIG. 3 shows the strength of the superimposed magnetic flux density on the surface of the sleeve 22 due to each magnetic pole.

The magnetic flux of the 4th & i pole S3 is the integral value of the magnetic flux density, which is the surface JX
It is represented by IA, and the &i end of the third magnetic pole N2 is represented by a plane JAB which is an integral value of the magnetic flux. 4th magnetic pole S3 to 5th magnetic pole
Because the magnetic flux toward raJ43z is 0.

The rii east of the 41a pole S3 all goes toward the third magnetic pole N2. Therefore, the magnetic flux from the third magnetic pole N2 toward the second magnetic pole S1 becomes AB. In the present invention, this magnetic flux AB is made small. Specifically, A-B≦(B/2), that is, the magnetic flux formed between the second magnetic pole Sl and the third magnetic pole N2 is formed between the third magnetic pole N2 and the feed screw 44. less than 1/2 of the magnetic flux. As a result, the load on the developer at the blade portion is significantly reduced, and the life of the developer is extended.

Next, the operation of the developing device of this embodiment will be explained. A mixture of magnetic particles and toner is introduced into the container 21 and the sleeve 22 is rotated in the direction of the arrow.

The magnetic particles rise from the bottom of the container 21 in a direction along the surface of the sleeve 22 and reach the vicinity of the blade 24 . Therefore, some of the magnetic particles pass through the gap between the tip of the blade 24 and the surface of the sleeve 22 together with the toner, and the other part passes through the gap between the tip of the blade 24 and the surface of the sleeve 22.
After colliding with the magnetic particles 6, the magnetic particles reverse and descend by gravity on the outside of the ascending path of the magnetic particles, reach the lower part of the container 21, rise again near the sleeve 22, and repeat the above operation.

In this way, the magnetic particles that turn around and fall near or in front of the blade 24 take in toner particles from the outer toner layer.

By circulating in this way as the sleeve 22 rotates, the toner 28 is mixed with the magnetic particles 27 and the sleeve 22.
2 Due to friction with the surface (1 ton).

Near the front of the plate 24, the magnetic particles 27 near the surface of the sleeve 22 are attracted to the surface of the sleeve 22 by the magnetic flux between the second magnetic pole S1 and the third magnetic pole N2, and as the sleeve 22 rotates, the magnetic particles 27 move below the blade 24. Come out and container 2
1. Go outside. At this time, the magnetic particles 27 carry out the toner attached to the surface thereof, and the blade 24
The amount of developer coated 711 on 2 is regulated. Here, as mentioned above, the magnetic flux formed between the second fii pole S1 and the third magnetic pole N2 is less than 1/2 of the magnetic flux formed between the third magnetic pole N2 and the fourth magnetic pole S3. The load on the developer is significantly reduced by the regulating action of the blade, and the life of the developer is extended.

The developer layer (82 combinations of magnetic particles 27 and toner 28) thus formed on the surface of the sleeve 22 reaches a developing section facing the photosensitive drum 1 as the sleeve 22 rotates.

The photosensitive drum 1 has 111 charges constituting a latent image, and in this embodiment, the charges constituting the electrostatic latent image are of negative polarity, and the toner is positively charged (in the case of reversal development, the toner In this embodiment, the photosensitive drum 1 and the sleeve 22 rotate as shown by the arrows so as to move in the same circumferential direction. The above-mentioned alternating voltage is applied to the space between these by the power supply 34, and an alternating electric field is formed.

- The magnetic pole N1 of the magnet 23 is located inside the sleeve 22 corresponding to the closest portion between the photosensitive drum l and the sleeve 22.

In this space, there is a sleeve 22 like +iii 'yL.
The magnetic particles 27 and toner 2 transported by the rotation of
There is a developer which is a mixture with 8.

In the developing section, spikes of developer are formed and rub against the photosensitive drum, and at the same time, the developer is activated by an alternating electric field to improve developing performance.

As the sleeve 22 rotates, the toner particles and magnetic particles that have not been consumed for development reach the vicinity of the fifth magnetic pole S2. Since a repulsive magnetic field is formed between the fifth magnetic pole S2 and the fourth magnetic pole S3, the attraction force to the sleeve 22 disappears, and the feed screw chamber 401 falls due to gravity, is stirred by the feed screw 44, and the feed As the screw 44 rotates as shown in 14, the agitated developer is
It is picked up by the magnetic pole S3, transported by the third magnetic pole N2, and moved into the container 21. The angle between the fourth magnetic pole S3 and the fifth magnetic pole S2 as viewed from the rotation center of the sleeve 21 is preferably within 120 degrees, so that the developer is sufficiently attracted into the container. Is the developer collected in the container 21 a container? 1
During the circulation, a portion of the developer is repeatedly coated on the sleeve 221 by the above-mentioned circulation action, and a portion of the developer has a center width of IV38.

1i? It passes through the first side opening 38b and falls, and enters the Noise screw chamber 42. Inside the return screw chamber 42,
The developer that has not been subjected to the above-mentioned development is mixed and stirred by the A screw 46 and sent from the front side of the figure to the back side of the drawing, and is passed into the feed screw chamber 40 at the opening 38a. In the feed screw chamber 44, the developer is mixed and stirred with the developer described above by the feed screw 44, and is sent from the back side of the figure to the front side of the figure f. A portion of the agitated developer that has come to the central partition wall side by the feed screw 44 while being fed is lifted by the fourth magnetic pole S3 and returned to the container 21.

The toner consumed by the development is supplied from the toner replenishing port 50b, stirred and mixed with the developer that has fallen through the opening 38b, and is sent to the rear side of the drawing by the return screw 46 and into the feed screw chamber 42.

In this embodiment, since the developer and toner circulation paths are formed as described above, (1) the developer is stirred by a portion of the screw and further m tt in the container 21; It will be a minute. (2) Since the developer rotates within the container 21, the developer is not compressed by the regulation blade, so developer deterioration does not occur. (3)
When the developing device is made more compact, the developer container il+L is particularly affected by the container 2 due to the wood circulation route which has a large effect on developer deterioration.
Since a sufficient amount of developer can be stored in the container 1, the developer capacity is large.

Furthermore, since the developer on the sleeve surface is removed by one of the magnetic poles that forms a repulsive magnetic field, removal is ensured, and the removed developer is reversed by the screw at the developer regulating member and directed inside the container. Since the developer is sent to the mixing section to be mixed with the developer returned to the mixing section, mixing is ensured. Also, since the mixing section has the other magnetic pole that forms a repulsive magnetic field, the removed developer is not transferred to the mixing section. Intake is ensured.

Even if each magnetic particle consists only of magnetic material.

It may be a combination of a magnetic material 1 and a non-magnetic material, or the magnetic particles as a whole may be a mixture of two similar types of magnetic particles.

Next, an example of a case using the developing device shown in FIG. 1 will be described. In FIG. 1, the sleeve 22 has a diameter of 20 mm.
The surface of the aluminum sleeve was subjected to amorphous sandblasting using 7 random abrasive grains, and the magnet 23 was magnetized with five poles as shown in FIG. 2.

As the blade 24, non-magnetic stainless steel with a thickness of 1.2 mm was used.

As the magnetic particles, ferrite (large magnetization resistance 60 emu/g) with a particle size of 70 to 50 μm (250/300 mesh) coated with silicone resin on one surface was used.

JI/a? l) As a toner, 0.6% of colloidal silicate was externally added to a toner powder with an average particle size of 10 mm consisting of 100 parts of a styrene/butadiene co-π composite resin and 15 parts of a copper phthalocyanine type polymer. The distance between the sleeve 22 surface coated with blue toner and the blade 24 is 500 mm.
I got involved.

When the electric current jI4 was measured by the blow-off method, the toner charge value of magnetic particles 1- was +10 C/g.

In this developing device, the distance between the photosensitive drum 3 (made of an organic photosensitive material) and the surface of the sleeve 22 was 700 gm. T/C
= 10%, frequency 1000Hz as bias power supply 34
, -300V to AC voltage with a peak-to-peak value of 1300V
When development was carried out using a DC voltage of Higashi 11, a good blue image was obtained.

l! 1! During continuous operation, image fogging, density reduction, etc. can generally occur as a result of deterioration of magnetic particles, but in the developing device of the present invention, such phenomena are not observed even after continuous operation, and toner lipo II8゜4+1:
(F was also stable, confirming the effectiveness of the present invention.

As the material 1 of the 22, in addition to aluminum, conductive materials such as brass and stainless steel, paper t,), and synthetic resin circles f and 2 can be used. Furthermore, if the surface of these cylinders is subjected to a quaternary treatment or made of a conductor, they can function as developing electrodes. Furthermore, a core roll may be used and a conductive adhesive material, such as a conductive sponge, may be wrapped around the circumferential surface of the core roll.

Regarding the magnetic pole N of the developing section, although the magnetic pole is arranged at the center of the developing section in the embodiment, it may be placed at a position shifted from the center, or the developing section may be arranged between the magnetic poles.

The toner may be externally added with silica particles to improve fluidity, or abrasive particles to polish the surface of the photosensitive drum 3, which is a latent image holding member in a transfer image forming method, for example. A toner containing a small amount of magnetic particles may be used. In other words, a magnetic toner can also be used as long as it has significantly weaker magnetism than magnetic particles and has zero tripo-charging ability.

A mechanism may be provided that detects the concentration of magnetic particles and toner and automatically replenishes toner according to this output.

As explained above, deterioration of the magnetic particles (carrier) can be prevented and the life of the developer can be extended.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention. 2 is a perspective view of the central partition wall of FIG. 1; FIG. FIG. 3 is a graph showing how the magnetic flux density of the magnet of the developing device shown in FIG. 1 is reduced. Explanation of No. 21 1...Latent image carrier (photosensitive drum) 21...Developer container (container) 22...Developer holding member (sleeve) 23...Magnetic field generating means (magnet) 27...Magnetic particles 28 ...Toner particles (toner) Representative drawing Figure 1 Applicant's agent Il+ 11.1 Length - Missing 1 Figure Il

Claims (3)

[Claims] (1) A developing device for developing an electrostatic latent image on an electrostatic latent image carrier, comprising: a developer container containing a developer having toner particles and magnetic particles; and the electrostatic latent image carrier. a developer carrying member that faces and forms a developing section that supplies toner particles to the electrostatic latent image carrier, and carries and conveys developer from the container to the developing section; and rotation of the developer carrying member. a developer regulating member having a regulating portion distal end located upstream of the developing section in the direction and spaced apart from the surface of the developer carrying member; The developer conveyed on the developer carrying member is received at the downstream side of the developing section, the developer is conveyed into the developer container, and the developer is reversed into the developer container by the developer regulating member. A developing device comprising: a transport stirring member that mixes the developer. (2) In the developing device according to claim 1, the magnetic particles are further provided on a side of the developer carrying member opposite to the latent image carrier, and the magnetic particles are brought into contact with the developer carrying member in the developing section. a first magnetic field generating means provided on a side of the developer carrying member opposite to the regulating member, downstream of the developer regulating member with respect to the rotational direction of the developer carrying body and further from the first magnetic field generating means; A second magnetic field generating means is also provided upstream. A third magnetic field generator provided on a side of the developer carrying member opposite to the regulating member, upstream of the developer regulating member with respect to the rotational direction of the developer carrying member, and at a position facing inside the container. means, provided on a side of the developer carrying member opposite to the regulating member, upstream of the third magnetic field generating means with respect to the rotational direction of the developer carrying member, and provided at a position facing inside the container; a fourth magnetic field generating means; and an alternating electric field forming means for forming an alternating electric field in the developing section to transfer the toner particles conveyed to the developing section and carried on the surface of the developer carrying member to the electrostatic latent image carrying member. and the magnetic flux formed between the second magnetic field generating means and the third magnetic field generating means is 1/2 or less of the magnetic flux formed between the third magnetic field generating means and the fourth magnetic field generating means. A developing device characterized by: (3) In the developing device according to claim 1, the conveyance stirring member has a conveyance screw that conveys the developer in the longitudinal direction of the developer carrier, and is arranged in parallel with the conveyance screw and opposite to the conveyance screw. A developing device comprising: a second conveyance screw that conveys developer in the direction; and a partition plate that is installed between both conveyance screws and is open at both ends in the longitudinal direction.