JPH0229675A - Developing device - Google Patents

Abstract

PURPOSE:To prevent image fault due to the leakage of magnetic grains by specifying an angle made by a vertical straight line passing the rotating center of a developer carrier and a straight line passing both an abutting position and the rotating center, and an angle made by straight lines which lies upstream of the abutting position and connect the position of a magnetic pole closest to the abutting position and the center of rotation. CONSTITUTION:The vertical line (l) passes the rotating center 0 of a developing sleeve 2, the straight line (m) passes the abutting position on the developing sleeve 2 of a blade 4 and the rotating center 0, and the straight line (n) passes the position of a magnetic pole N and the rotating center 0. When the angle made by the straight lines (l) and (m) is denotes by (x) and the angle made by the straight lines (m) and (n) by (y), then, it is defined that 0 deg.<x, 20 deg.<=y and x+y<140 deg.. Thus, a toner 7 alone is uniformly applied to the developing sleeve 2 to form a thin layer while a carrier 6 is regulated with the blade 4. Then, an image free of a ghost phenomenon can be obtained without being affected by a previous original pattern.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is utilized in the field of development technology that uses a two-component developer containing toner and magnetic particles, and in particular, transports only the toner of the developer to the development area. The present invention relates to a developing device that performs development.

[Prior Art and Problems to be Solved by the Invention] As a developing device using a conventionally known two-component developer of toner and magnetic particles (hereinafter referred to as carrier), a magnetic field generating means or an internally installed developer carrier is used. It is known that a developing sleeve is provided with a so-called blade that comes into contact with the circumferential surface of the developing sleeve and regulates the carrier so that only toner of a predetermined thickness is conveyed to the developing area. In such an apparatus, the magnetic binding force from the magnetic field generating means is applied to the carrier even near the blade, and it is difficult to reliably separate the carrier from the circumferential surface of the developing sleeve using only the blade. A problem arises in that some parts of the image leak out, causing image disturbances.

Also, regarding a similar device, JP-A No. 62-969
There is one shown in Publication No. 56. In this device, a blade is brought into elastic contact with a developing sleeve, and the toner is agitated by circulating carrier in the vicinity of the blade, ensuring a sufficient so-called tribo to apply the toner.

However, in order to circulate the carrier sufficiently, sufficient space is required, and the amount of carrier must be kept to a small amount in order to obtain tribo. The presence rate of carriers on the surface must be 10% or less. As a result, with such a small amount of carrier, the amount of toner conveyed is insufficient,
This method has a problem in that the toner cannot be sufficiently transported to the developing area, resulting in a so-called ghost phenomenon.

Furthermore, in devices where the plate itself is a magnetic member and magnetic force is used to regulate the carrier, an immobile layer of the carrier is created near the blade, which hinders the circulation of the carrier and the supply of toner to the developing sleeve. There was also the problem that this was insufficient and a ghost phenomenon occurred.

[Means for Solving the Problems] The present invention solves the problems of the above-mentioned conventional device, and it is possible to prevent the leakage of magnetic particles while ensuring a sufficient tribo on the developer carrier. It is an object of the present invention to provide a developing device that can uniformly and sufficiently apply toner and that does not cause image defects.

In order to achieve the above object, the present invention utilizes a cylindrical developer carrier, which includes a toner, a two-component developing agent having magnetic particles having a diameter larger than the toner diameter, and a cylindrical developer carrying member having a cylindrical shape and a two-component developing agent having a diameter larger than that of the toner. A magnetic field generating means is disposed at a fixed position, and serves as a developer carrier that rotates and conveys the two-component developer to a development area facing the latent image carrier, and a development area on the peripheral surface of the developer carrier. In a developing device including a regulating member that abuts at a position upstream in the developer conveyance direction from the above-mentioned developer transport direction and regulates the passage of magnetic particles, a vertical line l passing through the rotation center of the developer carrier and the above-mentioned abutting member are provided. The angle formed by the contact position and a straight line m passing through the center of rotation is X, and the position of the straight line m and the magnetic pole of the magnetic field generating means that is upstream from the contact position and closest to the contact position; When the angle formed by the straight line n connecting the above rotation centers is y, X is greater than 0 degrees, y is greater than 20 degrees, and the sum of X and y is less than 140 degrees. It is composed of C.

Further, in a case where an endless belt is used as a developer carrier, a two-component developer having toner and magnetic particles having a diameter larger than the toner diameter, and a magnetic field generating means disposed inside at a fixed position, are used. A developer carrier that rotates and conveys a two-component developer to a development area facing the latent image carrier, and a developer carrier that is upstream in the developer conveyance direction from a position on the circumferential surface of the developer carrier that becomes the development area. In the developing device, the developer carrier includes an endless belt that is stretched around at least two rollers, and a regulating member that is in contact with a position and regulates the passage of magnetic particles. A magnetic field generating means is provided near the inner side of the endless belt on the side that is conveyed to the contact position of the regulating member, and the magnetic pole of the magnetic field generating means closest to the regulating member side is the regulating member. It is also provided that the contact point of the member is separated by a distance of at least 5 millimeters.

[Embodiment] Hereinafter, a device according to an embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, a developing sleeve 2 serving as a developer carrier rotatable in direction B is disposed with a portion protruding from the front opening of a hopper 5 for storing two-component developer. A fixed magnet 3 serving as a magnetic field generating means is disposed inside the developing sleeve 2, and the magnet 3 has two magnetic poles, an N pole and an S pole. As clearly shown in the figure, these two magnetic poles are arranged such that the S pole is arranged near the bottom of the developing sleeve 2, and the N pole is arranged near the inside of the hopper 5 at an intermediate position.

The two-component developer stored in the hopper 5 is a mixture of toner 7 and magnetic particles (hereinafter referred to as carrier 6) at a constant ratio, and the particle size of carrier 6 is larger than that of the toner. .

The developing sleeve 2 rotates in the direction B, and the carrier 6 of the two-component developer to be transported to the developing area 9 comes into contact with the circumferential surface of the developing sleeve 2 to be regulated at a position upstream of the developing area in the transport direction B. A non-magnetic elastic blade 4 is provided.

Further, a photosensitive drum 1 as a latent image carrier is arranged to face the circumferential surface of the developing sleeve 2. A bias power source 8 is connected to the developing sleeve 2 and the photosensitive drum l.

The apparatus of this embodiment, which has the above-mentioned basic configuration, has the following characteristic configuration in order to cause large circulation of carriers as indicated by arrow C in FIG. 1.

That is, the contact position of the non-magnetic and elastic blade 4 on the developing sleeve 2 and the blade 4 of the magnet 3
Since the relationship with the side magnetic pole N is characteristic, this will be explained in detail below.

The circulation C of the carrier 6 is formed by the magnetic force of the magnet 3 and the rotational force of the developing sleeve 2 in the first half, and by gravity by releasing the magnetic force near the plate 4 in the second half. This circulation is important for triboelectrically imparting the toner 7 and applying the toner 7 to the developing sleeve. Therefore, in order for the carrier 6 to be easily released from the circumferential surface of the developing sleeve 2 when the carrier 6 is regulated by the blade 4 at the contact position of the blade 4, it is preferable that the influence of the magnetic force by the magnet 3 be small.

Therefore, the relationship between the pole N of the magnet 3, which is located upstream of the blade 4 and closest to the blade 4 in the rotational direction B of the developing sleeve 2, and the blade contact position was experimentally confirmed.

While reliably regulating the carrier 6 with the blade 4, the toner 7
It has been found that the following conditions (■, ■, and ■) must be satisfied in order to apply a uniform thin layer of only on the developing sleeve 2 and to obtain an image that is not affected by the previous original pattern and does not cause a ghost phenomenon. did.

To explain based on FIG. 1, the linear or developing sleeve 2
is a vertical line passing through the rotation center O of the blade 4, and the straight line m is the vertical line passing through the rotation center O of the blade 4
The straight line n is a straight line passing through the position of contact on the developing sleeve 2 and the rotation center O, and the straight line n is a straight line passing through the position of the magnetic pole N and the rotation center O.

When the angle between the above straight line and the straight line m is X, and the angle between the straight line m and the straight line n is y, it is necessary that: ■ O'< x, ■ 20°≦y, and ■ X+3/<140°. It has been found.

Furthermore, regarding the angle It has been found that this causes a tendency to occur and prevents good circulation of the carrier 6. Considering this relationship of gravity, the more preferable range of angle X is 5@<x<60'
It is. The relationship between the angles X and y will now be explained based on FIG. 2. In the figure, the angle X is 10°, 30°,
60", 10° is indicated by O mark, 30" is indicated by 0 mark, and 60° is indicated by Mu mark. ), the degree of carrier leakage when the angle y is changed by lOo is plotted on the vertical axis, and is shown in three stages: no leakage, small leakage, and large leakage. Further, the angle x+y is plotted on the horizontal axis to show the relationship. As is clear from this, no carrier leakage is observed when y≧20°, regardless of the value of the angle X. This is because when y<20', the strong magnetic force of the magnet 3 causes carriers to stay near the tip of the blade 4 more than necessary. This is thought to be because it acts as a force to separate the tip from the circumferential surface of the developing sleeve 2.

In addition, as shown in FIG. 2, X + y > 140
”, a ghost phenomenon appeared in the image. The reason for this is that the carrier 6 was not conveyed properly over the developing sleeve 2 to the position of the blade 4, and the carrier 6 was separated by the force of gravity, and the plate 4 This is thought to be due to the fact that the toner 7 is not sufficiently applied because there is no carrier 6 to carry the toner while circulating it to a position near the .

Next, the setting method and material of the blade 4 will be explained. The blade 4 may be brought into pressure contact with the developing sleeve 2 at the edge corner of its tip, or brought into contact with the developing sleeve 2 at its ventral surface. However, in the case of pressure contact with the ventral surface, if the edge corner rises from the surface of the developing sleeve 2, the carrier 6 will pass through the contact position and leak, which will have a negative effect on image quality. It is preferable to set the

In addition, as shown in FIG. 1, the plate 4 is set in a reverse direction, which is inclined so that the gap between the blade 4 and the circumferential surface of the developing sleeve 2 gradually increases with respect to the rotating direction B of the developing sleeve 2. Opposite to pressure welding, there is forward pressure welding which is inclined so as to gradually decrease. Either is possible, but when forward pressure welding is used, the carrier 6 and toner 7 may stay in the gap between the blade 4 and the developing sleeve 2. It is preferable to use pressure welding in the opposite direction since this may cause the carrier 6 to leak easily.

Regarding the material of the blade 4, it is preferable to select and use a material that is used as a regulating member for the carrier 6 and also provides the expected charge polarity to the toner 7 through friction when it comes into contact with the toner 7. For example, to positively charge a toner whose main component is polystyrene, ethylene propylene, fluorine rubber, natural rubber, polychlorobutadiene, N, B, R, etc. are effective; to negatively charge a toner, silicone is effective. Rubber, polyurethane, styrene-butadiene rubber, etc. are effective.

The hardness of the rubber described above is preferably 50 to 70'' according to JIS.

If it is over 70 degrees, the elasticity of the rubber will be too strong and the pressure at the abutting area will be too high, making the toner layer too thin and insufficient image density.On the other hand, if it is less than 50 degrees, the elasticity of the rubber itself will become too high. is weak, making it difficult to obtain sufficient pressure at the contact portion.

The two-component developer used in the apparatus of this embodiment will be explained below.

In order to reliably control the carrier 6 by the blade 4 described above, the particle size of the toner 7 is 1 to 20 liters, and the carrier 6 is
The particle size ranges from 40 to 100 g m. 40m end
Below this, it becomes difficult for the plate 4 to regulate the carrier, and conversely, when it exceeds HIOP■, the toner 7 retention ability is significantly reduced.

Since the carrier 6 transports the toner 7 and applies tribo to the toner, its amount and the mixing ratio with the toner 7 greatly influence the amount of toner transported onto the developing sleeve 2 . Regarding this point, the inventor of the present application has measured that the amount sufficient to form the above-mentioned large circulation C by the carrier 6 is 1.0 to 5.0 g per unit length of the circumferential surface of the developing sleeve 2.
It was confirmed that it is sufficient to set the value within the range of /cm.

The gap between the photosensitive drum 1 and the developing sleeve 2 in the apparatus of this embodiment is 50 to 500 gm, preferably 200 to 400 gm. It was experimentally confirmed that a high-resolution toner image without fogging was formed within the above range.

Further, the above-mentioned bias voltage #i8 connected to the photosensitive tram 1 and the developing sleeve 2 during development is preferably a direct current or one in which an alternating current is superimposed on a direct current.

According to the apparatus of this embodiment having the configuration described in detail above, the toner 7 attached to the carrier 6 carried on the circumferential surface of the developing sleeve 2 as the developing sleeve 2 rotates.
is applied to the circumferential surface of the developing sleeve 2 and is simultaneously conveyed and reaches the blade 4. Thereafter, only the carrier 6 is regulated by the blade 4 and separated from the circumferential surface of the developing sleeve 2, and only the toner 7 is applied onto the circumferential surface of the developing sleeve 2.

Here, the separated carrier 6 falls to the bottom of the hopper 5 due to the action of gravity, forming a large circulation as indicated by arrow C in FIG. By circulating the carrier 6, the toner is constantly supplied and replaced, so that it is possible to apply the toner 7 onto the developing sleeve 2 while ensuring an appropriate amount and tribo.

Next, a case where the embodiment device shown in FIG. 1 described above is actually produced will be explained while showing specific numerical values.

The developing sleeve 2 shown in the figure has a diameter of 20! I
The circumferential surface of the aluminum sleeve of No. 11 was subjected to an amorphous sandblasting process using arantum abrasive grains with a #40 diameter. Magnet 3 has a magnetic flux density of 70
A two-pole magnet with a N pole of 0 G (Gauss) and an S pole of 6000 G is used, and its placement position meets the conditions described above.
Adapted to ■.

Further, as the non-magnetic elastic blade 4, urethane rubber (rubber hardness JIS A66°, thickness 1.2 mm) was used.

The carrier 6 has a particle size of 50 to 70uw+ (250
/:100 mesh) ferrite particles coated with acrylic and fluorine resin are used, and toner 7 is made of 100 parts of a copolymer of styrene/acrylic resin and styrene-butadiene resin and 5 parts of perylene red pigment. The average particle size becomes 1. JL■ toner powder containing 1.0% colloidal silica was used.

As a result of a test conducted using this apparatus, a uniform coating layer of about 0.5 g/cm<2> was obtained on the developing sleeve 2 by the coating action.

When the amount of charge (triboelectric charge) of this layer was measured by a blow-off method, a sufficient value of +12 pcoul/g was obtained.

In addition, as a bias power supply 8, an AC voltage of 1500 Hz and a peak-to-peak voltage of 1400 Vp-p is used.
The surface potential of the latent image on the photosensitive drum l was set to -540 V in the dark area and -220 V in the bright area using a DC current of
When actual development was carried out with the gap between the developing sleeve 2 and the photosensitive tram 1 set at 250 tons, a good image with a reflection density of 1.1 and no ghost phenomenon could be obtained. Note that similarly good images were obtained when the amount of carrier in the circumferential direction of the developing sleeve 2 was within a range of 1.0 to 5.0 g/am.

In addition, in the above example, a magnetic flux density of 700G was used for the developing sleeve with a diameter of 20mm, or 400-800G and a diameter of 30mm for a diameter of lO~20mm. For those with I11 or higher, similar effects were obtained by setting the force in the range of 600 to 1200G.

In this test example, so-called normal development in which a toner image is formed in an area where electric charges exist has been described.

It is similarly effective when performing reversal development in which a toner image is formed in an area where charges have been erased.

Next, another example device shown in FIG. 3 will be explained. In the apparatus of the above embodiment, a cylindrical developing sleeve was used as the developer carrier, but in the present embodiment, the developer carrier was hooked on two rollers that had a driving means and rotated in a predetermined direction. It uses an endless belt that is stretched across the belt.

Hereinafter, this embodiment will be explained based on FIG. The installed magnet 3o will be explained.

The developer carrier 20 includes a roller 21 which has a driving means (not shown) and rotates in direction B, a roller 2Z disposed at a predetermined distance from the roller 21, and these two rollers 21 and 22. It consists of an electrically conductive endless belt 23 that is stretched and stretched. This developer carrier 20 is disposed at the surface opening of the hopper 5 as in the above example, but in this device the roller 21 is disposed outside the hopper 5, and the roller 21 is disposed outside the hopper 5.
A straight line k passing through the center of rotation of 1 and roller 22 is a horizontal line H and 7
It forms the corner of 0@.

Further, a fixed rod-shaped magnet 30 consisting of two poles and serving as a magnetic field generating means disposed inside the developer carrier 20 is
Near the inner side of the endless belt 23 that transports the developer to the contact position of the blade 4, it is fixedly arranged with the north pole facing the blade 4 in a state substantially parallel to the transport direction. This N pole and the contact position where the plate 4 contacts the endless belt 23 have a distance of 5 m+s or more.

Note that as the two-component developer used in this device, carrier 6 and toner 7 similar to those described above can be used, and the particle size of the carrier is 40 to 100 gts, and the particle size of the toner is 1 to 20 gts. It is within the scope of the seal.

According to the apparatus of this embodiment having the above configuration, as the roller 21 rotates in the B direction, the endless belt 23 stretched between the roller 21 and the roller 22 also rotates, and the toner 7 is deposited on the surface. The carrier 6 on which the particles are attached is supported and conveyed to the vicinity of the blade 4.

As the carrier 6 is conveyed toward the blade 4 side, the magnetic restraining force from the F magnet 30 is weakened, the carrier 6 is reliably regulated by the blade 4 at the contact position, and is separated from the surface of the endless belt 23. Ru. This carrier 6 falls to the bottom of the hopper 5 under the action of gravity. Then, the endless belt 23 receives the magnetic force of the magnet 30 again.
It is carried on top and transported upwards. In this way, in the device of this embodiment, the carrier 6 shown by the arrow C is similar to that of the above-mentioned embodiment.
A cycle is formed.

When an image was formed using the apparatus of this example, an image with good reflection density and no ghost image was obtained without carrier leakage. Further, similarly good images were obtained when the amount of carrier present in the circumferential direction of the developer carrier was in the range of 1.0 to 5.0 g/cm.

[Effects of the Invention] According to the developing device of the present invention having the above-described special configuration, the passage of magnetic particles is reliably regulated by the regulating member, so that the problem of image disturbance due to leakage of magnetic particles does not occur.

Furthermore, since the magnetic particles form a large circulation path within the hopper to constantly replace toner and apply triboelectricity, only toner with sufficient triboelectricity is applied to the developer carrier even near the regulating member. A uniform thin layer of toner is formed with sufficient triboelectric force by the member, making it possible to provide a clear image with good gradation and no ghost phenomenon.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a device according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the magnetic pole position of the device shown in FIG. 1 and the degree of carrier leakage, and FIG. 3 is a diagram showing another embodiment It is a figure showing an apparatus. 7...--Toner 6...Magnetic particles (carrier) 2
20 (21, 22, 23)--Developer carrier (2...Developing sleeve, 21.22...Roller 2
3...Endless belt)

Claims (2)

[Claims] (1) A two-component developer having a toner and magnetic particles having a diameter larger than the toner diameter, and a cylindrical shape with a magnetic field generating means disposed at a fixed position, and the two-component developer is transferred to a latent image carrier. A developer carrier is rotated and conveyed to a development area facing the developer, and the developer carrier is brought into contact with a position upstream in the developer conveyance direction from a position on the circumferential surface of the developer carrier that becomes the development area, and the magnetic particles are passed through. In the developing device, x is an angle formed by a vertical line l passing through the center of rotation of the developer carrier and a straight line m passing through the contact position and the center of rotation;
When the angle formed by the straight line m and the straight line n connecting the position of the magnetic pole of the magnetic field generating means that is upstream from the contact position and closest to the contact position and the rotation center is y. , x is greater than 0 degrees, y is greater than 20 degrees, and the sum of x and y is less than 140 degrees. (2) A two-component developer having a toner and magnetic particles having a diameter larger than the toner diameter, and a magnetic field generating means disposed inside at a fixed position, and a development in which the two-component developer is opposed to a latent image carrier. A developer carrier that rotates and conveys to a region, and a regulation that is brought into contact with a position on the circumferential surface of the developer carrier at a position upstream in the developer transport direction from a position that becomes a development region to restrict the passage of magnetic particles. In the developing device, the developer carrier includes an endless belt stretched around at least two rollers, and a member on the side that conveys the two-component developer to a contact position of the regulation member. The endless belt has a magnetic field generating means disposed near the inner side, and the magnetic pole of the magnetic field generating means closest to the regulating member is spaced from the contact position of the regulating member by at least 5 mm. A developing device characterized by: