JPH11161001A - Electrostatic latent image developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely transfer a developer being carried in the state where it is magnetically attracted to a periphery, to the sleeve member of a magnetic carrying means by magnetizing a magnetic pole and the magnetic pole of a reverse polarity forming a developer peeling area in a position facing it. SOLUTION: A developer peeing area 263 provided in a second magnet means 262 constituting a second developer applying means 26 is formed on the upstream side in the rotational direction of a second sleeve member 261. Then, in a magnet means 322 constituting a magnetic transfer means 32, an S pole of N pole-N pole and a reverse polarity forming the developer peeling area 263 at a position facing to the developer peeling area 263, of the magnet means 262 is magnetized. Therefore, the developer being carried in the state that it is magnetically attracted to the periphery of the second sleeve member 261 constituting the second developer applying means 26 can be surely transferred to the sleeve member 321 of the magnetic carrying means 32 without increasing the driving torque of the both sleeve members 261 and 321.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image developing apparatus for developing an electrostatic latent image into a toner image in an image forming machine such as an electrostatic copying machine or a laser printer, and more particularly, to an image forming apparatus. The present invention relates to an electrostatic latent image developing apparatus including a plurality of developer applying means for applying a developer including carrier particles and toner to an electrostatic latent image formed on a carrier.

[0002]

2. Description of the Related Art In an image forming machine such as an electrostatic copying machine or a laser printer, as is well known, an electrostatic latent image is formed on a peripheral surface of a photosensitive drum, and this electrostatic latent image is formed into a toner image. Developing. Such development is performed by applying a developer to the peripheral surface of the photosensitive drum by a developer applying unit when the peripheral surface of the photosensitive drum is moved through the developing area. An electrostatic latent image developing apparatus having a plurality of developer applying means for reliably applying the developer to the peripheral surface of the photosensitive drum has been proposed in response to the improvement of the image forming speed. JP-A-60-68364 and JP-A-3-31876 disclose an electrostatic latent image developing apparatus having two developer applying means. The electrostatic latent image developing devices disclosed in these publications include a first developer application unit disposed in a development area so as to face a peripheral surface of a photosensitive drum, and a first developer application unit. And a second developer applying means disposed upstream of the peripheral surface of the photosensitive drum in the moving direction, that is, above the first developer applying means, facing the peripheral surface of the photosensitive drum. A developer composed of carrier particles and toner is applied to the peripheral surface of the photosensitive drum by two developer applying means, and the electrostatic latent image is developed into a toner image.

More specifically, the first developer applying means in the electrostatic latent image developing device includes a first sleeve member driven to rotate and a first sleeve member provided in the first sleeve member. It is composed of magnet means. Also,
Similarly to the first developer applying means, the second developer applying means is constituted by a second sleeve member which is driven to rotate, and a second magnet means provided in the second sleeve member. I have. The peripheral surface of the first sleeve member is moved in the developing region in the forward direction with respect to the movement of the peripheral surface of the photosensitive drum, and the peripheral surface of the second sleeve member is formed on the peripheral surface of the photosensitive drum in the developing region. It is moved in the opposite direction to the movement. Such an electrostatic latent image developing device is also provided with a developer stirring / conveying mechanism, and the developer stirred and conveyed by the developer stirring / conveying mechanism constitutes the first developer applying unit. A part of the developer magnetically attracted and held on the peripheral surface of the first sleeve member, and then a part of the developer attracted and held on the peripheral surface of the first sleeve member is transferred to the second sleeve member.
Is transferred to the peripheral surface of the second sleeve member constituting the developer applying means, and is magnetically attracted and held there, and is applied to the peripheral surface of the photosensitive drum in the developing area. Also,
The developer that is not transferred to the peripheral surface of the second sleeve member and is continuously suction-held on the peripheral surface of the first sleeve member is also applied to the peripheral surface of the photosensitive drum in the development area.

[0004] The first developer constituting the first developer application means.
Even after being applied to the peripheral surface of the photosensitive drum in the developing area by being attracted and held by the peripheral surface of the sleeve member and the peripheral surface of the second sleeve member forming the second developer applying means, the first The developer sucked and held on the peripheral surfaces of the sleeve member and the second sleeve member temporarily
It is important that the developer is separated from the peripheral surface of the sleeve member and the peripheral surface of the second sleeve member and is again stirred and conveyed by the action of the developer stirring and conveying mechanism. That is, the developer detached from the peripheral surfaces of the two sleeve members is
The toner concentration is reduced due to the consumption of the toner by the developing action, and therefore, if the toner is repeatedly conveyed to the developing area and applied repeatedly to the peripheral surface of the photosensitive drum,
It will not be possible to achieve good development as required. Thus, the first developer constituting the first developer applying means is provided.
The developer agitated and transported by the developer agitating and transporting mechanism acts on the peripheral surface of the first sleeve member on the downstream side of the developing area as viewed in the rotational direction of the first sleeve member. As a result, the developer that has been suction-held on the peripheral surface of the first sleeve member is peeled off, and is mixed with the developer being stirred and conveyed. However, with respect to the second sleeve member that constitutes the second developer applying unit disposed above the first developer applying unit, the developer stirred and conveyed by the developer stirring and conveying mechanism is not used. It does not act on the peripheral surface of the second sleeve member. Therefore, in the conventional electrostatic latent image developing device, the second developer applying unit applies the developer to the peripheral portion of the second sleeve member on the downstream side of the developing area when viewed in the rotation direction of the second sleeve member. A developer peeling area is formed to reduce or significantly reduce the magnetic attraction force attracted to the surface, and a developer return guide plate is provided facing the peripheral surface of the second sleeve member. The developer on the peripheral surface of the second sleeve member is peeled off by the developer return guide plate, and the peeled developer is transported into the developer stirring transport mechanism. In order to smoothly guide the developer conveyance by the developer return guide plate, it is necessary to increase the inclination angle of the developer return guide plate. Therefore, a sleeve member that is driven to rotate in the same direction as the second sleeve member between the second developer application unit and the developer return guide plate, and a magnet unit that is disposed in the sleeve member. A magnetic transport unit is provided, and the developer transported by the second sleeve member is magnetically attracted and held on the peripheral surface of the sleeve member of the magnetic transport unit, and transported to the developer return guide plate. What has been proposed.

[0005]

The developer magnetically attracted and conveyed to the peripheral surface of the second sleeve member constituting the second developer applying means is transferred to the magnetic conveying means. It is desirable that all be transferred to the sleeve member. If the developer which has not been transferred to the sleeve member of the magnetic transport means and is magnetically attracted to the peripheral surface of the second sleeve member and has passed between the two members, it can be used for development again as it is or by gravity. Fall. When the developer is again subjected to development in a state where it is magnetically attracted to the peripheral surface of the second sleeve member, the amount of developer used for development increases, and image density unevenness occurs. Since the amount of the developer passing between the first sleeve member forming the first developer applying unit and the second sleeve member forming the second developer applying unit increases, the driving of both sleeves is performed. As the torque increases, there is a problem that the friction between the developers becomes strong and the developer is easily deteriorated.

The present invention has been made in view of the above-mentioned facts, and its main technical problem is that the second magnet means constituting the second developer applying means and the magnet means constituting the magnetic conveying means are provided. By setting the magnetic poles to be formed in a predetermined relationship, the developer magnetically attracted and conveyed to the peripheral surface of the second sleeve member constituting the second developer applying means can be surely transferred to the magnetic transporter. It is an object of the present invention to provide an electrostatic latent image developing device which can be transferred to a sleeve member of the means.

[0007]

According to the present invention, an electrostatic latent image formed on a peripheral surface of a photosensitive drum which is moved through a developing area is solved by the present invention. An electrostatic latent image developing apparatus for developing a toner image by applying a developer including carrier particles and toner to a peripheral surface of the photosensitive drum in a developing area, a developing housing, and a front end in the developing housing; A first sleeve member disposed in parallel with the photosensitive drum and rotatably driven to move in a forward direction with respect to a movement direction of a peripheral surface of the photosensitive drum in the developing area; A first developer application unit including a first magnet unit disposed in the sleeve member, and a first developer application unit upstream of a peripheral surface of the photosensitive drum in a movement direction with respect to the first developer application unit. With the photosensitive drum A second sleeve member disposed in a row and rotatably driven to move in a direction opposite to a moving direction of the peripheral surface of the photosensitive drum in the developing area; and a second sleeve member disposed in the second sleeve member. A second developer applying means comprising a second magnet means, and a developer disposed behind the first developer applying means and transporting the developer to the first developer applying means while stirring the developer. A developer stirring / conveying mechanism;
A magnetic conveying means comprising a sleeve member disposed behind the developer applying means and being driven to rotate in the same direction as the second sleeve member, and a magnet means disposed in the sleeve member; A developer return guide plate disposed behind the transporting means and feeding the developer transported by the magnetic transporting means to the developer stirring and transporting mechanism side, the electrostatic latent image developing device comprising: The second magnet means constituting the developer applying means has the same polarity at a position upstream of the closest position between the second sleeve member and the sleeve member of the magnetic transport means in the rotation direction of the second sleeve member. The magnetic poles of the first and second magnetic poles are provided adjacent to each other, and the magnet unit constituting the magnetic transport unit is located at a position opposed to the developer stripped region formed on the second magnet unit. A magnetic pole forming the developer peeling area Pole polarity are magnetized, the electrostatic latent image developing device is provided, characterized in that.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an electrostatic latent image developing device constructed in accordance with the present invention will be described below in further detail with reference to the accompanying drawings.

FIG. 1 shows a preferred embodiment of an electrostatic latent image developing apparatus constructed according to the present invention, together with a part of a photosensitive drum 2 constituting an image carrier. The photosensitive drum 2 has an appropriate electrostatic photosensitive member disposed on a peripheral surface thereof.
It is configured to rotate in a direction indicated by an arrow 4 in the figure by an appropriate driving means (not shown) and pass through the developing area 6. The developing area 6 extends in the vertical direction in the moving direction of the peripheral surface of the photosensitive drum 2, and therefore, the peripheral surface of the photosensitive drum 2 that is rotated in the direction indicated by the arrow 4 in FIG. The developing zone 6 can be moved downward. On the upstream side of the developing area 6, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 2 by a proper electrostatic latent image forming means known per se. In the developing zone 6, the electrostatic latent image formed on the peripheral surface of the photosensitive drum 2 is developed into a toner image by an electrostatic latent image developing device generally designated by the numeral 10 according to the present invention. The toner image thus developed is transferred to a transfer member such as plain paper by a transfer unit (not shown) on the downstream side of the development area 6. Then, the toner image transferred to the transfer member is heat-fixed by a fixing unit (not shown) to obtain a copy or printed matter.

Next, the electrostatic latent image developing device 10 will be described with reference to FIGS. Electrostatic latent image developing device 1
Reference numeral 0 denotes a developing housing 12. The developing housing 12, which can be formed from a suitable synthetic resin, includes a front end wall 18 and a rear end wall 2 together with a bottom wall 14 and a rear wall 16 extending substantially vertically upward from the rear edge of the bottom wall 14.
Contains 0. A cover member 22 made of a suitable synthetic resin and covering the upper surface is provided on the developing housing 12 configured as described above.

At the forefront of the developing housing 12 (the leftmost part in FIG. 1 and the uppermost part in FIG. 2), a first developer applying means 24 disposed in the developing area 6 and the first developing means 24 are provided. A second developer applying unit 26 disposed above the developer applying unit 24, that is, an upstream side in the moving direction of the photosensitive drum 2 in the developing region 6, and a second developer applying unit 26 below the first developer applying unit 24, that is, in the developing region 6. The third developer application unit 28 is disposed downstream of the photosensitive drum 2 in the moving direction.

The first developer application means 24 extends substantially horizontally in the developing area 6 in the width direction (the direction perpendicular to the paper surface in FIG. 1 and the left-right direction in FIG. 2). First sleeve member 241 arranged in parallel
And the first sleeve member 241
And the magnet means 242. The first sleeve member 241 is formed of a non-magnetic material such as aluminum, and is rotatably mounted on the developing housing 12. The first magnet means 242 is constituted by a stationary permanent magnet, and is fixed at a predetermined position in the first sleeve member 241. On the outer peripheral surface of the stationary permanent magnet as the first magnet means 242, an N pole and an S pole are formed as shown in FIG. That is, on the outer peripheral surface of the stationary permanent magnet,
The N pole and the N pole are magnetized adjacent to each other at a position opposed to the third developer applying unit 28, and the developer is applied to the surface of the first sleeve member 241 between the adjacent N poles. A developer peeling area 243 where a magnetic attraction force for suction does not substantially exist or is slight is defined. An N pole is magnetized on the outer peripheral surface of the stationary permanent magnet at a position facing the second developer applying unit 26, and an S pole is provided between the N pole and the developer peeling region 243. Each is magnetized. FIG.
As shown in FIG. 5, the rotation shaft 245 to which the first sleeve member 241 is fixed is projected rearward through the rear end wall 20 of the developing housing 12. This rotating shaft 24
An input gear (not shown) is fixed to the protruding end of 5, and the input gear can be an electric motor via a suitable transmission gear (not shown).
Drive-coupled. The first sleeve member 241 of the first developer applying unit 24 having the above-described structure is configured as shown in FIG.
Is rotated in the direction indicated by arrow 240, that is, in the developing area 6 so as to move in the forward direction with respect to the movement of the photosensitive drum 2.

The second developer applying unit 26 is located upstream of the photosensitive drum 2 in the moving direction of the photosensitive drum 2 with respect to the first developer applying unit 24 in the developing zone 6 (the first developer applying unit in FIG. 1). (Above the means 24). The second developer applying unit 26 is also the first developer applying unit 2.
Similarly to 4, the second sleeve member 261 extends substantially horizontally in the width direction (the direction perpendicular to the plane of FIG. 1 and the horizontal direction in FIG. 2) and is disposed in parallel with the photosensitive drum 2.
And second magnet means 262 provided in the second sleeve member 261. The second sleeve member 261 is formed of a non-magnetic material such as aluminum, and is rotatably mounted on the developing housing 12.
The second magnet means 262 is formed of a stationary permanent magnet having a circular cross-sectional shape, and is fixed at a predetermined position in the second sleeve member 261. An N-pole and an S-pole are formed on the outer peripheral surface of the stationary permanent magnet as the second magnet means 262 as shown in FIG. That is, on the outer peripheral surface of the stationary permanent magnet, an S pole having a polarity opposite to the N pole magnetized by the first magnet means 242 is magnetized at a position facing the first developer applying means 24, In FIG. 1, an N pole and an N pole are adjacently magnetized at the upper right portion, and a magnetic attraction force for attracting the developer to the peripheral surface of the second sleeve member 261 is provided between the adjacent N poles. Is substantially absent or slightly defined. As shown in FIG. 3, the developer peeling area 263 is located closer to the closest position P between the second sleeve member 261 of the second developer application unit 26 and the sleeve member 321 of the magnetic transport unit 32 described later. It is important that the second sleeve member 261 is formed on the upstream side in the rotation direction. In addition, on the outer peripheral surface of the stationary permanent magnet, between the S pole provided at a position facing the first developer applying unit 24 and the N pole on the side of the developing area 6 forming the developer peeling area 263. Has an N pole and an S pole magnetized. As shown in FIG. 2, the second sleeve member 2
The rotating shaft 265 to which the fixing member 61 is fixed is
2 and is projected rearward through the rear end wall 20. An input gear (not shown) is fixed to the protruding end of the rotating shaft 265, and the input gear (not shown) is fixed to the rotating shaft 245 of the first developer applying unit 24. ). The second sleeve member 261 of the second developer applying unit 26 having the above-described configuration is arranged in a direction indicated by an arrow 260 in FIG. 1, that is, in a direction opposite to the movement of the photosensitive drum 2 in the developing area 6. Is driven to rotate.

The third developer applying means 28 is located downstream of the photosensitive drum 2 in the moving direction of the photosensitive drum 2 in the developing zone 6 with respect to the first developer applying means 24 (in FIG. 1, the first developer applying means 28). (Under the means 24). The third developer applying means 28 is also the first developer applying means 2
Like the fourth and second developer application means 26, they extend substantially horizontally in the width direction (the direction perpendicular to the paper surface in FIG. 1, the left-right direction in FIG. 2) and are disposed in parallel with the photosensitive drum 2. The third sleeve member 281 and the third magnet means 282 provided in the third sleeve member 281 are provided. The third sleeve member 281 is formed of a non-magnetic material such as aluminum and the like.
2 is rotatably mounted. The third magnet means 2
Reference numeral 82 denotes a stationary permanent magnet having a circular cross-sectional shape, and is fixed at a predetermined position in the third sleeve member 281. An N-pole and an S-pole are formed on the outer peripheral surface of the stationary permanent magnet as the third magnet means 282 as shown in FIG. In the illustrated embodiment, the left half of the stationary permanent magnet is magnetized, and the right half in the figure is not magnetized. The left half of the stationary permanent magnet, ie, the center of the third magnet means 282 and the first developer applying means 24
On the side of the developing region 6 from the line connecting the center of the first magnet means 242 constituting the first magnet means 242, the N magnetized by the first magnet means 242 is positioned at a position facing the first developer applying means 24. An S pole having a polarity opposite to that of the pole is magnetized, and an N pole is magnetized adjacent to the S pole, and an S pole is magnetized adjacent to the N pole. On the other hand, the right half of the stationary permanent magnet, that is, the third magnet means 2
A non-magnetized developer is separated from the line connecting the center of the first magnet applying means 24 to the center of the first magnet applying means 24 on the side of the developer stirring and conveying mechanism 40 described later. An area 283 is defined. As shown in FIG. 2, the rotation shaft 285 to which the third sleeve member 281 is fixed is protruded rearward through the rear end wall 20 of the developing housing 12. An input gear (not shown) is fixed to the protruding end of the rotating shaft 285, and the input gear is connected to the rotating shaft 245 of the first developer applying unit 24.
And an input gear (not shown) fixed to the transmission gear. The third sleeve member 281 of the third developer applying unit 28 thus configured is directed in the direction indicated by an arrow 280 in FIG. 1, that is, in the forward direction with respect to the movement of the photosensitive drum 2 in the developing area 6. Is driven to rotate.

The first developer applying unit 24, the second developer applying unit 26, and the third developer applying unit 28 configured as described above are arranged with predetermined gaps at positions facing each other. Has been established. First developer applying means 24
The gap (G1) at the closest position between the first sleeve member 241 constituting the second developer application means 26 and the second sleeve member 261 constituting the second developer applying means 26 is magnetically formed on the peripheral surface of the first sleeve member 241. It is desirable to set a value at which substantially half of the developer sucked and held is transferred to the peripheral surface of the second sleeve member 261. In the illustrated embodiment, the value is set to 2.0 to 4.0 mm. ing. If the gap (G1) is larger than 4.0 mm, the amount of the developer transferred from the first sleeve member 241 to the second sleeve member 261 decreases, and if the gap (G1) is smaller than 2.0 mm, the amount of the developer becomes smaller. The amount of the developer transferred from the first sleeve member 241 to the second sleeve member 261 increases, and both the first sleeve member 241 and the second sleeve member 261 are increased.
The transport balance of the developer amount is destroyed due to the above. Also,
A gap (G) at the closest position between the first sleeve member 241 constituting the first developer applying unit 24 and the third sleeve member 281 constituting the third developer applying unit 28
2) is that all of the developer magnetically attracted and held on the peripheral surface of the first sleeve member 241 is
It is desirable to set the value to be transferred to the peripheral surface of 1.
It is desirable to set the gap (G1) to 1/3 to 1/2, and in the illustrated embodiment, it is set to 0.67 to 2.0.
It is set to 0 mm. If this gap (G2) is larger than の of the gap (G1), the first sleeve member 2
All of the developer magnetically attracted and held on the peripheral surface of 41 cannot be transferred to the third sleeve member 281, and image density unevenness occurs due to insufficient developer. On the other hand, when the gap (G2) is smaller than 1/3 of the gap (G1),
First sleeve member 241 and third sleeve member 2
As the drive torque of 81 increases, the stress of the developer increases and causes early deterioration.

Continuing the description with reference to FIG. 1, the electrostatic latent image developing device 10 further includes a head cutting means 30. In the embodiment shown in the drawings, the cutting device 30 extends along the first developer applying device 24 in a width direction (a direction perpendicular to the paper surface in FIG. 1 and a horizontal direction in FIG. 2). 300. This cutting board 300
Is formed of an aluminum alloy in the illustrated embodiment, and includes a horizontal portion 301 and a first portion of the horizontal portion 301.
An end portion 302 of the developer application means 24 side (left side in FIG. 1) is bent downward at a substantially right angle, and a horizontal portion 3
In FIG. 1, the right end portion includes a weir portion 303 which is bent upward at a substantially right angle. The leading edge of the cutting part 302 constituting the cutting board 300 is located in the developing area 6 when viewed in the rotation direction (the direction indicated by the arrow 240) of the first sleeve member 241 constituting the first developer applying means 24. On the upstream side,
In addition, on the upstream side of the opposing position of the first sleeve member 241 and the second sleeve member 261, it is disposed close to the peripheral surface of the first sleeve member 241.
The gap (G3) between the leading edge of the cutting edge 302 constituting the cutting board 300 and the peripheral surface of the first sleeve member 241 is
In the illustrated embodiment, it is set to about 0.5 to 1.0 mm.

A magnetic transfer means 32 is disposed behind the second developer applying means 26 (right side in FIG. 1). The magnetic transfer means 32 extends substantially horizontally in the width direction (the direction perpendicular to the plane of FIG. 1 and the horizontal direction in FIG. 2) and is arranged in parallel with the second developer applying means 26. The member 321 and the sleeve member 321
And magnet means 322 disposed therein.
The sleeve member 321 is formed of a non-magnetic material such as aluminum and is rotatably mounted on the developing housing 12. The magnet means 322 is constituted by a stationary permanent magnet, and is fixed at a predetermined position in the sleeve member 321. An N pole and an S pole are formed on the outer peripheral surface of the stationary permanent magnet as the magnet means 322 as shown in FIG. That is, the outer peripheral surface of the stationary permanent magnet is magnetized in a substantially upper half area, and the developer of the second magnet unit 262 constituting the second developer applying unit 26 as shown in FIG. The developer peeling area 263 is located at a position facing the peeling area 263.
, And the S pole having the opposite polarity to the N pole is magnetized. An N pole and an N pole are adjacently magnetized on the outer peripheral surface of the stationary permanent magnet on the upper side and the right side in FIG. 1, and a portion between the adjacent N poles is provided on the surface of the sleeve member 321 with the developer. A developer peeling area 323 is defined in which there is substantially no or little magnetic attraction force for attracting the developer. The gap (G4) at the closest position between the sleeve member 321 constituting the magnetic transfer means 32 and the third sleeve member 281 constituting the third developer applying means 28 is:
In the illustrated embodiment, it is set to 0.67 to 2.00 mm. As shown in FIG.
The rotating shaft 325 to which is fixed penetrates the rear end wall 20 of the developing housing 12 and protrudes rearward. An input gear (not shown) is fixed to the protruding end of the rotating shaft 325, and the input gear is fixed to the rotating shaft 265 of the second developer applying means 26 (not shown). ). The sleeve member 321 of the magnetic transport means 32 thus configured is driven to rotate in a direction indicated by an arrow 320 in FIG.

Behind the magnetic transfer means 32 (on the right side in FIG. 1), a developer return guide plate 34 extends along the magnetic transfer means 32 in the width direction (the direction perpendicular to the plane of FIG. 1; Direction). The developer return guide plate 34 is formed of non-magnetic stainless steel, and has a horizontal portion 341 having a leading edge disposed opposite to a lower portion of the developer peeling area 323 of the magnetic transfer means 30; The inclined portion 342 is inclined downward from the rear end (the right end in FIG. 1) of the horizontal portion 341. Horizontal portion 34 constituting developer return guide plate 34
A gap (G5) between the leading edge of the sleeve 1 and the peripheral surface of the sleeve member 321 constituting the magnetic transfer means 32 is set to 0.5 to 3.0 mm in the illustrated embodiment. Also,
The lower end of the inclined portion 342 constituting the developer return guide plate 340 is located above the upstream side of the developer stirring and conveying mechanism 40 described later.

Next, the developer stirring and transporting mechanism 40 will be described with reference to FIGS. A developer stirring / conveying mechanism 40 is disposed behind the first developer applying unit 24 and the third developer applying unit 28. The developer stirring / conveying mechanism 40 in the illustrated embodiment is in the width direction (the direction perpendicular to the paper surface in FIG. 1 and the left-right direction in FIG. 2).
Stirring and conveying means 4 extending in parallel to each other
2 and a second stirring and conveying means 44 and a third stirring and conveying means 46 are provided.

The first stirring and conveying means 42 includes the first stirring and conveying means 42.
Developer applying means 24 and third developer applying means 28
, That is, at the most upstream position. As shown in FIG. 2, the first stirring and conveying means 42 includes a rotating shaft 421 rotatably mounted between both end walls 18 and 20 of the developing housing 12 and an axial direction of the rotating shaft 421, that is, a width direction. The spiral blades 422 are formed, and are integrally formed of a suitable synthetic resin. The rotating shaft 421 constituting the first stirring and conveying means 42 penetrates the rear end wall 20 of the developing housing 12 and is projected rearward. An input gear (not shown) is fixed to the protruding end of the rotating shaft 421, and the input gear is operatively connected to a drive mechanism (not shown) for driving each of the developer applying means. The first stirring and conveying means 42 thus configured is indicated by an arrow 42 in FIG.
The developer is rotated in the direction indicated by 0 and transports the developer on the rear wall 16 of the developing housing 12 from the near side to the far side as indicated by an arrow in FIG. 2 while stirring.

The second stirring and conveying means 44 includes the first stirring and conveying means 44.
Of the first stirring and conveying means 4, that is, the first stirring and conveying means 4
It is arranged between the second and third stirring and conveying means 46.
Similarly to the first stirring and conveying means 42, the second stirring and conveying means 44 includes a rotating shaft 441 rotatably mounted between both end walls 18 and 20 of the developing housing 12, and an axis of the rotating shaft 441. The spiral blades 442 are formed in the direction, that is, in the width direction, and are integrally formed of an appropriate synthetic resin. The rotating shaft 441 constituting the first stirring and conveying means 44 is connected to the rear end wall 2 of the developing housing 12.
0 and project rearward. An input gear (not shown) is fixed to the protruding end of the rotating shaft 441, and the input gear is operatively connected to a drive mechanism (not shown) for driving each of the developer applying means. The second stirring / transporting means 44 thus configured is driven to rotate in a direction indicated by an arrow 440 in FIG. 1, and the developer transported from the near side to the back side by the first stirring / transporting means 42 is removed. While stirring, the sheet is conveyed from the back side to the front side as indicated by the arrow in FIG.

The third stirring and conveying means 46 is provided with the first stirring and conveying means 46.
Developer applying means 24 and third developer applying means 28
Are arranged in parallel adjacent to each other. The third stirring and conveying means 46 includes a rotating shaft 461 rotatably mounted between both end walls 18 and 20 of the developing housing 12, a cylindrical member 462 mounted on the rotating shaft 461, and a cylindrical member 462. And a plurality of paddles 463 provided so as to protrude therefrom, and these are integrally formed of an appropriate synthetic resin. The rotating shaft 461 constituting the third stirring and conveying means 46 penetrates the rear end wall 20 of the developing housing 12 and projects rearward. This rotation shaft 461
An input gear (not shown) is fixed to the protruding end of this, and this input gear is operatively connected to a drive mechanism (not shown) for driving each of the developer applying means. The third stirring / conveying means 46 thus configured is driven to rotate in the direction indicated by an arrow 460 in FIG. 1, and is moved from the back side to the near side by the second stirring / conveying means 44 as indicated by the arrow in FIG. The developer conveyed and the developer conveyed by the third developer applying unit 28 are agitated, and the stirred developer is supplied to the first developer applying unit 24.

Continuing the description with reference to FIG. 1, a circular opening 141 is formed at a predetermined portion of the bottom wall 14 of the developing housing 12 below the second stirring and conveying means 44. The opening 141 is provided with a detector 52 for detecting the toner concentration in the developer 50 including the carrier particles and the toner contained in the developing housing 12. This detector 52 has an aperture 141
Detecting the toner concentration in the developer 50 by detecting the magnetic permeability of the developer 50 present on the upper surface exposed in the development housing 12 through the through hole may be of a known form. The electrostatic latent image developing device 10 includes:
New toner is supplied by toner supply means (not shown) according to the toner concentration in the developer 50 detected by the detector 52. When the toner concentration of the developer detected by the detector 52 falls below a predetermined value, a toner supply unit (not shown) is operated, and
2, a new toner is dropped on the front end of the first stirring and conveying means 42 (the left end in FIG. 2). When the toner density detected by the detector 52 exceeds a predetermined value, a toner not shown The operation of the conveying means is stopped, and the supply of the toner into the developing housing 12 is stopped.

Next, the operation and effect of the electrostatic latent image developing device 10 as described above will be summarized and described as follows. The toner dropped by the toner supply means (not shown) onto the front end of the first stirring and conveying means 42 is mixed with the developer 50 in the developing housing 12 to constitute the first stirring and conveying means 42. Spiral blade 422
While being stirred by the action of (1), the sheet is conveyed from the near side to the far side (from the left end to the right end in FIG. 2). The developer conveyed from the near side to the back side by the first stirring / conveying means 42 is transferred to the back side end of the second stirring / conveying means 44 at the back side end, and the second stirring / conveying is performed. While being stirred by the action of the spiral blade 442 constituting the means 44, it is conveyed from the back side to the front side (from the right end to the left end in FIG. 2). In this way, the developer conveyed from the back side to the front side by the second stirring and conveying unit 44 is transferred to the front side end of the first stirring and conveying unit 42 at the front side end. It is circulated. As described above, the developer transported from the back side to the front side by the second stirring and transporting unit 44 is the third developer.
Is stirred up by the paddle 463 of the stirring and conveying means 46 and sent to the first developer applying means 24.

Continuing the description with reference to FIG. 1, the first sleeve member 241 of the first developer applying means 24
It is rotated in the direction indicated by 40. Figure 2 shows number 2
In the developer pumping area indicated by reference numeral 44, the developer agitated by the paddle 463 of the third stirring / transporting means 46 while being scraped up and sent toward the first developer application means 24 as described above. A part is pumped to the peripheral surface of the first sleeve member 241 due to the magnetic field formed by the first magnet means 242. The developer pumped to the peripheral surface of the first sleeve member 241 is moved in the direction indicated by the arrow 240 accompanying the rotation of the first sleeve member 241. The ear-cutting plate 300 constituting the ear-cutting means 30 acts on the developer which is magnetically held and moved on the peripheral surface of the first sleeve member 241, and removes excess developer from the first sleeve member 241. From the first sleeve member 24
1. The thickness of the developer held on the peripheral surface of the first member is appropriately regulated. The first sleeve member 241 constituting the first developer applying unit 24 and the second sleeve member 261 constituting the second developer applying unit 26 pass through the gap (G1) at the closest position to the first sleeve member 241. When the sleeve member 241 is moved, part of the developer held on the peripheral surface of the first sleeve member 241 is formed by the second magnet unit 262 of the second developer application unit 26. Is transferred to the peripheral surface of the second sleeve member 261 due to the generated magnetic field. At this time, a gap (G1) at the closest position between the first sleeve member 241 and the second sleeve member 261 is substantially equal to the developer magnetically attracted and held on the peripheral surface of the first sleeve member 241. Since the half is set to 2.0 to 4.0 mm, which is a value transferred to the peripheral surface of the second sleeve member 261, the peripheral portion of the first sleeve member 241 after passing through the gap (G 1). About half of the developer magnetically attracted and held on the surface is transferred to the peripheral surface of the second sleeve member 261.

The second developer constituting the second developer applying means 26
The developer transferred to the peripheral surface of the sleeve member 261 and magnetically held therein is moved accompanying rotation of the second sleeve member 261 in the direction indicated by the arrow 260,
Therefore, it is moved through the upstream part (upper part in FIG. 1) of the developing zone 6. For this reason, in the upstream part of the developing zone 6, the developer held on the surface of the second sleeve member 261 rubs the peripheral surface of the photosensitive drum 2, and
Is developed on the electrostatic latent image formed on the peripheral surface of.

On the other hand, the developer magnetically held on the peripheral surface of the first sleeve member 241 without being transferred to the peripheral surface of the second sleeve member 261 is the arrow 240 of the first sleeve member 241. Are moved in association with the rotation in the direction indicated by the arrow, and are thus moved through the central part of the developing zone 6. The developer held on the peripheral surface of the first sleeve member 241 rubs the peripheral surface of the photosensitive drum 2 to apply a developing action to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 2. You.

The first developer constituting the first developer applying means 24
The developer held on the peripheral surface of the first sleeve member 241 and passing through the developing area 6 is used as the first sleeve member 241 and the third sleeve member 281 constituting the third developer application unit 28.
When the first sleeve member 241 is moved through the gap (G2) at the closest position to the third sleeve member 281, the first sleeve member 241 is transferred to the peripheral surface of the third sleeve member 281. That is, at the position where the first sleeve member 241 and the third sleeve member 281 face each other, the first magnet unit 242 constituting the first developer applying unit 24 is provided with the developer peeling area 243. Therefore, when the developer magnetically held on the peripheral surface of the first sleeve member 241 attempts to pass through the developer peeling area 243, the developer is separated from the peripheral surface of the first sleeve member 241 and the Third developer application means 28
Due to the magnetic field formed by the third magnet means 282 of FIG.
Is transferred to the peripheral surface of the sleeve member 281. The layer thickness of the developer magnetically held on the peripheral surface of the first sleeve member 241 is increased by the action of centrifugal force and gravity caused by the rotation of the first sleeve member 241.
Since it is larger than 1/2 of 1), it is transferred to the peripheral surface of the third sleeve member 281 on the photosensitive drum 2 side from the closest position between the first sleeve member 241 and the third sleeve member 281. At this time, the first sleeve member 24
The gap (G2) at the closest position between the first sleeve member 281 and the third sleeve member 281 is such that all of the developer magnetically attracted and held on the peripheral surface of the first sleeve member 241 is around the third sleeve member 281. The gap (G), which is the value transferred to the surface,
Since the ratio is set to 1/3 to 1/2 of 1), all the developer magnetically attracted and held on the peripheral surface of the first sleeve member 241 is transferred to the peripheral surface of the third sleeve member 281. Is done.

The third developer constituting the third developer applying means 28
The developer transferred to the peripheral surface of the sleeve member 281 and magnetically held therein is moved accompanying rotation of the third sleeve member 281 in the direction indicated by the arrow 280,
Therefore, it is moved through the downstream part (the lower part in FIG. 1) of the developing area 6. For this reason, in the downstream part of the developing area 6, the developer held on the surface of the third sleeve member 281 rubs the peripheral surface of the photosensitive drum 2,
Is developed on the electrostatic latent image formed on the peripheral surface of.

As described above, the electrostatic latent image formed on the peripheral surface of the photosensitive drum 2 is subjected to the developing action of the second developer applying means 26 in the upstream part of the developing area 6, and then the developing area The central part of the developing unit 6 receives the developing action of the first developer applying unit 24, and the downstream part of the developing area 6 receives the developing action of the third developer applying unit 28, thereby forming an image on the toner image. In the illustrated embodiment, the developing zone 6
About half of the developer that has been pumped up by the first developer applying means 24 disposed in the center of the developer and regulated to have an appropriate layer thickness by the ear cutting means 30, approximately half of the developer is applied to the second developer applying means 2.
The developer transferred to the developing unit 6 and performs a developing action in an upstream portion of the developing area 6, and is kept in the first developer applying unit 24 without being transferred to the second developer applying unit 26. After the developing action is performed at the central portion of the developing zone 6, the developer is transferred to the third developer applying means 28 and transported so as to perform the developing action at the downstream portion of the developing zone 6, so that the developer transportability is good. Become.

The developer retained on the peripheral surface of the third sleeve member 281 constituting the third developer applying means 28 and passed through the developing area 6 has a magnetic attraction force in the developer peeling area 283. The developer agitated and conveyed by the paddle 463 of the third agitating / conveying means 46 in the developer peeling area 283 due to the fact that the developer is substantially absent or small is present on the peripheral surface of the third sleeve member 281. , The third sleeve member 2
The developer 81 is separated from the peripheral surface of the developer 81 and mixed with the developer being stirred and conveyed by the paddle 463 of the third stirring and conveying means 46. In the illustrated embodiment, the third magnet means 28 constituting the third developer applying means 28
No. 2 has no magnetic pole behind the line connecting the center thereof and the center of the first magnet means 242 constituting the first developer applying means 24, that is, on the side of the developer stirring and conveying function 40. The third sleeve member 281 does not pump up the developer. Therefore, the third stirring and conveying means 46
The developer sent by the paddle 463 is pumped up only by the first sleeve member 241 constituting the first developer applying means 24, so that the early deterioration of the developer can be prevented, and the first sleeve member 241 and The driving torque of the third sleeve member 281 can be reduced.

The developing agent 6 is held on the peripheral surface of the second sleeve member 261 of the second developer applying means 26 and
When the developer is passed through the developer removing area 263 located downstream of the developing area 6 when viewed in the rotation direction of the second rotating sleeve member 261, the magnetic attraction force substantially disappears or becomes small. Is detached from the surface of the second sleeve member 261. Then, the developer separated from the surface of the second sleeve member 261 is transferred to the peripheral surface of the sleeve member 321 due to the magnetic field formed by the magnet unit 322 constituting the magnetic transfer unit 32.
As described above, in order to reliably transfer the developer held on the surface of the second sleeve member 261 to the peripheral surface of the sleeve member 321, as described above, the second developer application unit 2 is used.
As shown in FIG. 3, the developer peeling area 263 provided in the second magnet unit 262 constituting the second magnet unit 6 has the second sleeve member 261 and the sleeve of the magnetic transport unit 32 constituting the second developer applying unit 26. The magnet means 3 which is formed on the upstream side in the rotation direction of the second sleeve member 261 from the closest position P to the member 321 and constitutes the magnetic transfer means 32
Reference numeral 22 denotes a developer peeling area 2 of the second magnet unit 262.
It is important that an N-pole and an S-pole having a polarity opposite to that of the N-pole forming the developer peeling region 263 are magnetized at a position opposed to 63. According to experiments by the inventors, the developer peeling area 263
Is provided across the closest position P between the second sleeve member 261 and the sleeve member 321.
It has been found that a part of the developer held on the peripheral surface of the sleeve member 261 passes between the second sleeve member 261 and the sleeve member 321 by the action of gravity. Further, the developer peeling area 263 is moved from the closest position P between the second sleeve member 261 and the sleeve member 321 to the second sleeve member 2.
The magnet means 322 which is formed on the upstream side in the rotation direction of the magnet 61 and constitutes the magnetic transfer means 32 has a developer peeling area 263 at an opposite position between the developer peeling area 263 and the closest position P.
Is formed, the transfer position of the developer held on the peripheral surface of the second sleeve member 261 to the sleeve member 321 is set to the second position. The second sleeve member 261 is closer to the closest position P between the sleeve member 261 and the sleeve member 321.
Further, it was found that the drive torque of the sleeve member 321 increased and the developer was easily deteriorated. However, in the illustrated embodiment, the developer separating area 263 provided in the second magnet means 262 constituting the second developer applying means 26 has the second developer applying means 26 as shown in FIG.
Sleeve member 261 and magnetic transport means 3
The magnet means 322 which is formed on the upstream side in the rotation direction of the second sleeve member 261 from the closest position P to the second sleeve member 321 and which constitutes the magnetic transfer means 32.
The developer peeling area 263 of the second magnet means 262
Since the N-pole and the S-pole having the opposite polarity to the N-pole forming the developer peeling region 263 are magnetized at a position opposed to the second portion, the drive torque of the two sleeve members does not increase and the second
Second sleeve member 2 constituting the developer applying means 26
The developer magnetically attracted and conveyed to the peripheral surface of 61 can be reliably transferred to the sleeve member 321 of the magnetic conveying means 32.

The developer transferred to the peripheral surface of the sleeve member 321 constituting the magnetic transfer means 32 is magnetically attracted to the peripheral surface of the sleeve member 321 rotating in the direction indicated by the arrow 320 and is conveyed. The developer is peeled off from the peripheral surface of the sleeve member 321 in a developer peeling area 323 provided on the upstream side of the position facing the return guide plate 34. The developer peeled from the peripheral surface of the sleeve member 321 is sent onto the developer return guide plate 34 by the action of centrifugal force and gravity caused by the rotation of the sleeve member 321. Developer return guide plate 3
The developer sent to the upper side 4 is guided by the inclined portion 342 and is guided above the first stirring and conveying means 42 on the upstream side of the developer stirring and conveying mechanism 40 to drop. As described above, the developer held on the peripheral surface of the second sleeve member 261 of the second developer application unit 26 and passed through the development area 6 is moved to the magnetic transfer unit 32 and the developer return guide plate 34. The developer is returned to the upstream side of the developer agitating and conveying mechanism 40 via the developer agitating and transporting mechanism 40, so that it is reliably agitated and mixed with the developer in the developing housing 12 and the new toner supplied on the first agitating and transporting means 42, and is again subjected to development. Is done. In the illustrated embodiment, the second developer application means 26 and the developer return guide plate 34
And the magnetic transfer means 32 is disposed between the developer return guide plate 34 and the inclination angle of the inclined portion 342 constituting the developer return guide plate 34 can be increased, so that the developer can be moved upstream of the developer stirring and conveying mechanism 40. Can be reliably returned to the side.

Although the present invention has been described based on the embodiment in which the present invention is applied to an electrostatic latent image developing apparatus having three developer applying means, the present invention is not limited to only the illustrated embodiment. Instead, the present invention can be applied to an electrostatic latent image developing device having two developer applying units.

[0035]

The electrostatic latent image developing device according to the present invention is constructed as described above, and has the following effects.

That is, the second magnet means which constitutes the second developer applying means is arranged so that the second sleeve member is rotated in the rotational direction of the second sleeve member from the closest position between the second sleeve member and the sleeve member of the magnetic transport means. An upstream side is provided with a developer stripping area in which magnetic poles of the same polarity are adjacent to each other and magnetized, and the magnet unit constituting the magnetic transport unit includes the developer stripping unit formed on the second magnet unit. Since the magnetic pole of the opposite polarity to the magnetic pole forming the developer peeling area is magnetized at the position facing the area,
Without increasing the driving torque of the two sleeve members,
The developer magnetically attracted and conveyed to the peripheral surface of the second sleeve member can be reliably transferred to the sleeve member of the magnetic conveying means.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a preferred embodiment of an electrostatic latent image developing device configured according to the present invention.

FIG. 2 is a plan view of the electrostatic latent image developing device shown in FIG. 1 with a cover member covering an upper surface of a developing housing omitted and a part thereof cut away.

FIG. 3 is an explanatory diagram showing a relationship between magnetized positions of a second magnet unit forming a second developer applying unit and a magnet unit forming a magnetic conveying unit in the electrostatic latent image developing device shown in FIG. 1; .

[Explanation of symbols]

 2: photosensitive drum 6: developing area 10: electrostatic latent image developing device 12: developing housing 24: first developer applying means 241: first sleeve member 242: first magnet means 26: second developing Agent applying means 261: Second sleeve member 262: Second magnet means 28: Third developer applying means 281: Third sleeve member 282: Third magnet means 30: Hot cutting means 300: Hot cutting plate 32: Magnetic transfer means 321: Sleeve member 322: Magnet means 34: Developer return guide plate 40: Developer stirring and conveying mechanism 42: First stirring and conveying means 421: Spindle 422: Spiral blade 44: Second stirring and conveying Means 441: Spindle 442: Spiral blade 46: Third stirring and conveying means 461: Spindle 462: Cylindrical member 463: Paddle 50: Developer 52: Toner density detector

Claims (1)

[Claims] 1. An electrostatic latent image formed on a peripheral surface of a photosensitive drum moved through a developing area, and a developer comprising carrier particles and toner is coated on the peripheral surface of the photosensitive drum in the developing area. An electrostatic latent image developing device for developing the toner image by applying the developing device; a developing housing; and a front end portion inside the developing housing, which is disposed in parallel with the photoconductive drum, and is provided in the developing area. A first sleeve member rotatably driven to move in a forward direction with respect to a moving direction of the peripheral surface;
A first developer applying means comprising a first magnet means disposed in the sleeve member, and an upstream side in a moving direction of a peripheral surface of the photosensitive drum with respect to the first developer applying means. And a second sleeve member disposed in parallel with the photosensitive drum and rotationally driven to move in a direction opposite to a moving direction of a peripheral surface of the photosensitive drum in the developing area. A second developer application unit including a second magnet unit disposed in the member, and a developer disposed behind the first developer application unit and having the first developer application unit. A developer stirring and conveying mechanism for conveying while stirring the
A sleeve member disposed behind the second developer application unit and driven to rotate in the same direction as the second sleeve member; and a magnetic transport unit including magnet means disposed in the sleeve member. An electrostatic latent image developing device, comprising: a developer return guide plate disposed behind the magnetic transport unit and configured to send the developer transported by the magnetic transport unit to the developer stirring and transporting mechanism side. The second magnet means constituting the second developer applying means is located upstream of the closest position between the second sleeve member and the sleeve member of the magnetic transport means in the rotational direction of the second sleeve member. A magnetic field having the same polarity is adjacently provided with a developer peeling area which is magnetized. The magnet means constituting the magnetic conveying means is provided in the developer peeling area formed on the second magnet means. Forming the developer peeling area at the opposite position Pole opposite polarity magnetic pole of being magnetized, the electrostatic latent image developing device, characterized in that.