JPH10339994A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of reducing driving torque and maintaining high image quality for a long period by setting the magnetic developer of a quantity for obtaining a desired service life. SOLUTION: The device is constituted to provide a sleeveless developing roller 4 consisting of a magnet member whose surface is moved in a state where the developer 3 including toner and magnetic carriers is carried on this surface where plural magnetic poles are arranged, so as to carry the developer 3 to a developing region A facing a photoreceptor drum 1 and a doctor 5 for removing a part of the magnetic developer on the developing roller 4 and regulating the thickness of a layer of the developer on the developing roller 4 for attaining carrying to the developing region A. In such a case, a part of the developer 3 removed from the developing roller 4 is guided to a region where magnetic constraining force exerted on the developer 3 is smaller than gravity, by the doctor 5 and a part of the developer guided by the doctor 5 is supplied to a supplying position in which the magnetic constraining force is greater than the gravity and which is adjacent to the doctor 5 from the upstream side in the rotational direction of the developing roller, by an agitator 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for an image forming apparatus such as a copying machine, a facsimile, a printer, and the like. More specifically, the present invention relates to a developing device in which a magnetic developer is carried on an outer peripheral surface on which a plurality of magnetic poles are arranged. The present invention relates to a developing device provided with a developer carrier including a roller-shaped magnet member that conveys the developer to a development area facing an image carrier by rotating.

[0002]

2. Description of the Related Art Conventionally, as a developing device of this type, for example, JP-A-8-22177 discloses a developer supply chamber for containing a magnetic developer comprising at least a toner and a magnetic carrier; A developer carrier (magnet roll) disposed inside the chamber; and a developer replenishment chamber containing toner. The developer supply chamber and the developer replenishment chamber are connected through a through-hole through which toner can be supplied. And a developing device in communication with the developing device. In this developing device, a predetermined amount of developer is stored in advance in a developer supply chamber in which a developer carrier is arranged.

[0003]

In the above-mentioned conventional developing device, the magnetic developer accommodated in the developer supply chamber covers the magnetic field of the developer carrier over a relatively large area on the surface of the developer carrier. Since the structure is such that it is attracted to the surface by the binding force, there is a problem that the driving torque required to drive the developer carrier increases.

It is conceivable to reduce the amount of the magnetic developer set in the developing device in order to reduce the driving torque. However, if the amount of the magnetic developer is reduced, the deterioration of the developer is accelerated and the image quality is reduced. There was a problem that it was difficult to maintain for a long time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the driving torque and set an amount of magnetic developer capable of obtaining a desired life in an apparatus so as to obtain good image quality. The purpose of the present invention is to provide a developing device capable of maintaining the image quality for a long time.

[0006]

According to a first aspect of the present invention, there is provided an image carrier having a plurality of magnetic poles, the image bearing member being rotated while a magnetic developer is carried on an outer peripheral surface thereof. A developer carrying member formed of a roller-shaped magnet member for transporting the developer to a developing region facing the developing device; and a magnetic developer transported to the developing region by removing a part of the magnetic developer on the developer carrying member. A developer regulating member for regulating the layer thickness of the developer, wherein a part of the magnetic developer removed from the developer carrier by the developer regulating member is applied to the magnetic developer. A developer guide member that guides the developer carrying member to a region where the magnetic binding force is smaller than gravity, and a part of the magnetic developer guided by the developer guide member, wherein the magnetic binding force is larger than gravity and From the upstream side in the developer carrier rotation direction Serial is characterized in that provided a developer supply member for supplying the supply position adjacent to the developer regulating member.

According to the first aspect of the present invention, when the developer carrying member composed of a roller-shaped magnet member carrying a magnetic developer on the outer peripheral surface on which the plurality of magnetic poles are arranged is rotated by the developer regulating member, A part of the magnetic developer carried on the developer carrier is removed. Then, the magnetic developer removed from the developer carrier is guided by the developer guide member to a region where the magnetic binding force of the developer carrier acting on the magnetic developer is smaller than gravity. A part of the magnetic developer guided by the developer guide member is adjacent to the developer regulating member from the upstream side in the direction of rotation of the developer carrier in which the magnetic binding force is larger than the gravity and the developer supply member. Supply position. The magnetic developer supplied to the supply position is carried on a developer carrier, and after the layer thickness is regulated by a developer regulating member, the magnetic developer is conveyed to a development area and used for developing a latent image on the image carrier. .

As described above, by exchanging between the magnetic developer on the developer carrier and the developer in the region where the magnetic binding force is smaller than the gravity, almost all of the developer set in the developing device is set. The amount of the magnetic developer attracted to the developer carrier by the magnetic binding force is smaller than that in the configuration in which the magnetic binding force exists in a region where the magnetic binding force is larger than gravity. Further, the magnetic developer on the developer carrier and the magnetic developer in the developer accommodating portion are exchanged so that the same magnetic developer in the developing device is not continuously used for development.

According to a second aspect of the present invention, in the developing device according to the first aspect, as the developer supply member, the developer is supplied to the supply position while stirring the developer in a region where the magnetic binding force is smaller than gravity. It is characterized in that an agent stirring member is provided.

In the developing device according to the present invention, a part of the magnetic developer agitated by the developer agitating member provided in a region where the magnetic binding force is smaller than gravity is moved to a supply position to the developer carrier. Supply.

According to a third aspect of the present invention, in the developing device of the second aspect, the rotation trajectory of the developer stirring member is set within an area where the magnetic binding force is smaller than gravity. is there.

According to the third aspect of the present invention, since the developer stirring member rotates in a region where the magnetic binding force is smaller than the gravity, the developer by the magnetic developer on which the magnetic binding force acts is used. An increase in the driving torque of the stirring member can be suppressed.

According to a fourth aspect of the present invention, in the developing device of the first aspect, the magnetic developer is a developer containing a toner and a magnetic carrier, and the magnetic binding force is vertically above a region where the magnetic binding force is smaller than gravity. And a toner container communicating with the area.

According to a fourth aspect of the present invention, a part of the toner supplied from the toner container provided vertically above the region where the magnetic binding force is smaller than the gravity is a part of the magnetic carrier in the region. The magnetic carrier reaches a position where the magnetic binding force is larger than gravity and the magnetic carrier is moving relatively intensely (spin motion or the like), and is strongly friction-mixed.

According to a fifth aspect of the present invention, in the developing device according to the first aspect, the magnetic developer is a developer containing a toner and a magnetic carrier, and the region in which the magnetic binding force is smaller than the gravitational force is applied to the developer carrier. A toner accommodating portion provided in a horizontal direction of the body, and a toner accommodating portion communicating with the region is provided on a lateral side of the region opposite to the developer carrier with the region interposed therebetween; A toner conveying and stirring member for conveying the toner to the area while stirring the toner.

According to a fifth aspect of the present invention, the toner in the toner storage portion provided on the side in the horizontal direction of the area opposite to the developer carrier with the area where the magnetic binding force is smaller than gravity interposed therebetween. Is stirred by the toner conveying and stirring member and is conveyed to the area. Then, the magnetic developer in the area to which the toner has been supplied is supplied to the supply position located on the side in the horizontal direction.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device used in an electrophotographic copying machine (hereinafter, referred to as a copying machine) as an image forming apparatus will be described. [Embodiment 1] FIG. 1 is a schematic configuration diagram of a developing device according to the present embodiment. The developing device is disposed on a side of a cylindrical photosensitive drum 1 used as an image carrier of a copying machine.
A case member 2, a developing roller 4 as a developer carrying member for carrying a magnetic developer 3 (hereinafter, simply referred to as a "developer");
A doctor 5 also serves as a developer guide member and a developer regulating member, an agitator 6 also serves as a developer supply member and a developer stirring member, a developing bias power source 7, a seal member 9, and the like.

The case member 2 has an opening in a developing area A opposed to the photosensitive drum 1, and has a magnetic holding force of the developing roller 4 on the opposite side to the developing area A with the developing roller 4 interposed therebetween. Form a developer accommodating portion B, which is an area smaller than gravity, and a toner accommodating portion C vertically above the developer accommodating portion B.

The developing roller 4 is partially exposed from the opening of the case member 2 and has a toner and a magnetic carrier (hereinafter simply referred to as “carrier”) on an outer peripheral surface on which a plurality of magnetic poles are arranged.
That. ) Is carried and transported to the development area A.

The doctor 5 regulates the layer thickness of the developer on the developing roller 4 conveyed to the developing area A.
This doctor 5 is also used as a developer guide member,
A part of the developer 3 carried on the developing roller 4 is removed,
It is arranged so that the magnetic binding force Fm of the developing roller 4 acting on the developer 3 is guided and collected in the developer accommodating portion B whose gravity is smaller than the gravity Fg. Further, the doctor 5 is fixed to be inclined toward the developer accommodating portion B so that the developer 3 removed from the developing roller 4 can easily move toward the developer accommodating portion B by gravity. Note that a two-dot chain line D in the drawing indicates a surface on which the magnetic binding force Fm of the developing roller 4 acting on the developer 3 is substantially equal to the gravity Fg. In the area inside the two-dot chain line, the magnetic binding force Fm of the developing roller 4 acting on the developer 3 is larger than the gravity Fg.

The agitator 6 includes a developer container B together with toner supplied from an upper toner container C.
The developer 3 is stirred. Further, the agitator 6 removes a part of the developer 3 of the developer accommodating portion B from the developing roller 4 when the magnetic binding force Fm is larger than the gravitational force Fg.
The developer is supplied from the upstream side (upper side in FIG. 1) to a supply position adjacent to the developer removal position.

The seal member 9 provided above the developing roller 4 is a member that prevents toner leakage and toner scattering and does not prevent the transport of the developer. As the seal member 9, a polyurethane rubber sheet of 0.3 mm or less, a PET film of 0.15 mm or less, or the like is suitable.

The photosensitive drum 1 and the developing roller 4 are
In the developing area A, the surfaces are rotationally driven by driving means (not shown) so as to move in opposite directions. It is preferable that the ratio (Vd / Vp) of the linear velocity Vd of the developing roller 4 to the linear velocity Vp of the photosensitive drum 1 be set within a range of 1 <(Vd / Vp) ≦ 5. This linear velocity ratio (Vd / Vp) is set to 1
When the size is larger than the above range, background stain and insufficient image density hardly occur, and when the size is 5 or less, toner scattering and developer deterioration hardly occur.

The developing gap Gp, which is the gap between the photosensitive drum 1 and the developing roller 4 in the developing area A,
Is slightly larger than a doctor gap Gd, which is a gap between the surface of the developing roller 4 and the tip of the doctor 5. The developing gap Gp and the doctor gap Gd
Is (Gd + 0.05) ≦ Gp ≦ (Gd + 0.15)
[Mm] is preferably set. (G
By setting (d + 0.05) ≦ Gp [mm], it is possible to prevent the developer from remaining in the developing area A or dropping out. Further, by setting Gp ≦ (Gd + 0.15) [mm], it is possible to prevent image density shortage and the like.

The developer 3 has, for example, a particle size of 7.5.
A developer containing a non-magnetic toner of μm and a carrier made of spherical ferrite having a particle size of 50 μm can be used.
The charge polarity of the toner of the developer 3 is set to a polarity opposite to the polarity of the developing electric field which is the polarity of the potential VL of the photosensitive drum 1 with respect to the surface potential VB of the developing roller 4. For example,
When the surface potential VB of the developing roller 4 is -600 V and the potential VL of the photosensitive drum 1 is -50 V and the polarity of the developing electric field is positive, the charging polarity of the toner of the developer 3 is set to a negative polarity.

As shown in FIG. 1, a large number of magnetic poles having different polarities (N pole, S pole) are provided on the outer peripheral portion of the developing roller 4 in the circumferential direction.
Are formed alternately. The magnetic field generated by these magnetic poles generates a magnetic binding force on the carrier of the developer 3, and the developer 3 containing the carrier and the toner is carried on the surface of the developing roller 4. The developing roller 4 can be manufactured by a conventionally known method in which, for example, ferrite, which is a magnet member, is sintered on the outside of a shaft and then magnetized by a magnetizing device. This developing roller 4
The preferred range of the magnetic pole pitch is 1.5 to 3.0 mm,
The preferred range of the magnetic flux density (peak) on the magnet surface is 40
６０60 mT. For example, a developing roller 4 having a diameter of 20 mm, a number of magnetic poles of 32, a magnetic pole pitch of about 2 mm, and a magnetic flux density on the magnet surface of 55 mT can be used.

A developing bias voltage having a DC component and an AC component (rectangular wave, sine wave, etc.) is applied to the developing roller 4 by a developing bias power supply 7. The preferred range of the absolute value (| VDC |) of the DC component of the developing bias voltage is 300 V to 600 V. The preferred range of the AC component peak-to-peak voltage Vp-p is 0.5 kV to 2.0 kV, and the preferred range of the frequency F is 500 Hz to 6 kHz.

In the developing device having the above structure, when the developing roller 4 rotates, the layer thickness of the developer 3 carried and conveyed by the developing roller 4 by the doctor 5 is regulated. Then, a part of the developer 3 on the developing roller 4 is removed by the doctor 5 and is guided and collected by the developer accommodating portion B. In the developer accommodating section B, the agitator 6 stirs the developer 3 together with the toner supplied from the upper toner accommodating section C. Then, a part of the developer 3 in the developer accommodating portion B is changed by the agitator 6 to the magnetic binding force Fm.
Is supplied to a supply position which is larger than the gravity Fg and located above the developer 3 removal position. After a part of the developer 3 supplied to the supply position is regulated in thickness by the doctor 5, the developer 3 is carried on the developing roller 4 and transported to the development area A, where it is formed on the photosensitive drum 1. Used for developing electrostatic latent images.

As described above, according to the present embodiment, the developing roller 4
By removing and supplying the developer 3 in the areas adjacent to each other on the upper side, the magnetic binding force Fm of the developing roller 4 is reduced by the gravitational force Fm.
The driving torque of the developer carrying member is reduced by reducing the amount of the developer 3 existing in the region larger than g, that is, the amount of the developer 3 bound by the magnetic force so as to be attracted to the surface of the developing roller 4. be able to. Further, the developing roller 4
Since the upper developer 3 is exchanged with the developer in the developer accommodating section B to prevent the same developer 3 in the developing device from being used continuously for development, good image quality can be maintained. Can be maintained for a period.

According to the present embodiment, the developing roller 4
In the above-mentioned region where the magnetic binding force is larger than the gravity, a portion where a part of the developer 3 stays is one place. Thus, the driving torque of the developing roller 4 can be reduced as compared with the case where the developer 3 stays.

Further, according to the present embodiment, the agitator 6 in the developer accommodating portion B is also used as a developer supply member for supplying a part of the developer 3 in the developer accommodating portion B to the supply position. Therefore, the cost of the apparatus can be reduced. In addition, the agitator 6 serving also as the developer supply member is moved to the developer storage portion B where the magnetic binding force Fm is smaller than the gravitational force Fg.
, The drive torque of the agitator 6 can be reduced.

Further, according to the present embodiment, while a part of the toner supplied from the toner container C is mixed with a part of the carrier in the developer container B, the magnetic binding force Fm
Reaches a position where the carrier is larger than the gravity Fg and the carrier is relatively intensely moving (spin motion or the like), and is strongly friction-mixed. Due to the strong frictional mixing, the amount of toner in the developer 3 carried on the developing roller 4 can be sufficiently increased without causing an insufficient amount of toner.

[Embodiment 2] Next, another embodiment of the present invention will be described. FIG. 2 is a schematic configuration diagram of the developing device according to the present embodiment. The same parts as those of the developing device of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The developing device of the present embodiment is different from the developing device of the first embodiment in that a toner storage section C is provided on the side of the developer storage section B in the horizontal direction opposite to the developing roller 4 with the developer storage section B interposed therebetween. This is different from the developing device of the first embodiment. The toner accommodating section C communicates with the developer accommodating section B. Inside the toner accommodating section C, there is provided a toner agitator 10 as a toner conveying and stirring member for conveying the toner to the developer accommodating section B while stirring. Have been.

According to this embodiment, the same effects as those of the first embodiment can be obtained, and the toner accommodating section C, the developer accommodating section B, and the developing roller 4 are arranged side by side in the horizontal direction. The vertical dimension of the device can be reduced.

[Embodiment 3] Next, still another embodiment of the present invention will be described. FIG. 3 is a schematic configuration diagram of the developing device according to the present embodiment. The same parts as those of the developing device of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The developing device according to the present embodiment is configured such that the position of the doctor 5 and the case
Is different from the developing device of the first embodiment in that the shape is set.

According to this embodiment, the same effect as that of the first embodiment can be obtained, and the developer carried and conveyed by the developing roller 3 is restricted by the doctor 5 and exists in the stagnation area E. Since the distance of frictional contact with the developing agent becomes longer, the developer on the developing roller 4 can be frictionally charged well.

In the above embodiment, a developing device using a two-component magnetic developer containing a non-magnetic toner and a magnetic carrier has been described. However, the present invention relates to a one-component magnetic developer containing a magnetic toner. This can be applied to the case where a developer is used.

[0038]

According to the first, second, third and fourth aspects of the present invention, most of the developer to be set in the developing device is in comparison with the configuration in which the magnetic binding force exists in a region where the magnetic binding force is larger than gravity. As a result, the amount of the magnetic developer attracted to the developer carrier by the magnetic binding force is reduced, so that the driving torque of the developer carrier can be reduced. In addition, since the same magnetic developer in the developing device is not continuously used for development, it is possible to set an amount of magnetic developer that can obtain a desired life in the device and maintain good image quality for a long time. There is an effect that can be.

In particular, according to the invention of claim 2, the developer stirring member in the region where the magnetic binding force is smaller than the gravity is
Since a part of the magnetic developer in the area is also used as a developer supply member for supplying the developer to the developer supply member, the cost of the apparatus can be reduced.

In particular, according to the third aspect of the present invention, since the developer stirring member is rotated in a region where the magnetic binding force is smaller than gravity, the magnetic developer on which the magnetic binding force acts. Thus, there is an effect that the increase in the driving torque of the developer stirring member due to the above can be suppressed.

According to the fourth aspect of the present invention, a part of the toner supplied from the toner storage portion provided vertically above the region where the magnetic binding force is smaller than the gravity is reduced by the magnetic force in the region. While being mixed with a part of the carrier, the magnetic binding force is larger than the gravity and reaches a position where the magnetic carrier is relatively intensely moving (spin motion or the like), and is strongly friction-mixed. There is an effect that the triboelectric charge amount of the toner can be sufficiently raised without running out of the toner amount in the magnetic developer carried.

According to the fifth aspect of the present invention, the toner storage portion, the region where the magnetic binding force is smaller than gravity, and the developer carrier can be provided in a horizontal direction. There is an effect that the dimension in the vertical direction can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a developing device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a developing device according to another embodiment.

FIG. 3 is a schematic configuration diagram of a developing device according to still another embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 case member 3 developer 4 developing roller 5 doctor 6 agitator 7 developing bias power supply 9 seal member 10 toner agitator A developing area B developer accommodating section C toner accommodating section

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Nobuhiko Umezawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (5)

[Claims] 1. A roller-shaped magnet member which conveys a developer to a development area opposed to an image carrier by rotating while a magnetic developer is carried on an outer peripheral surface on which a plurality of magnetic poles are arranged. A developer carrying member, and a developing device including a developer regulating member that removes a part of the magnetic developer on the developer carrying member and regulates a layer thickness of the magnetic developer conveyed to the developing region. A developer that guides a part of the magnetic developer removed from the developer carrier by the developer regulating member to a region where the magnetic binding force of the developer carrier acting on the magnetic developer is smaller than gravity. A guide member, and a part of the magnetic developer guided by the developer guide member, the magnetic binding force being greater than the gravity, and supplying the developer adjacent to the developer regulating member from the upstream side in the rotation direction of the developer carrier. Developer supply to supply position Developing apparatus is characterized in that a and. 2. The developing device according to claim 1, wherein the developer supply member includes a developer stirring member that supplies the developer to the supply position while stirring the developer in a region where the magnetic binding force is smaller than gravity. A developing device. 3. The developing device according to claim 2, wherein the rotation locus of said developer stirring member is set within a region where said magnetic binding force is smaller than gravity. 4. The developing device according to claim 1, wherein the magnetic developer is a developer containing a toner and a magnetic carrier, and the magnetic developer communicates with the region vertically above a region where the magnetic binding force is smaller than gravity. A developing device provided with a toner storage section. 5. The developing device according to claim 1, wherein the magnetic developer is a developer containing a toner and a magnetic carrier, and a region where the magnetic binding force is smaller than gravity is a horizontal side of the developer carrier. A toner storage section communicating with the area is provided on the side in the horizontal direction of the area opposite to the developer carrying member with the area interposed therebetween, and the toner in the toner storage section is agitated. A developing device provided with a toner conveying and stirring member for conveying the toner to the area.