JPH09106187A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the developing device which minimizes an increase in cost and can obtain an image of high quality having no density unevenness by making the difference in the longitudinal direction of the stroke of a developer conveying member as small as possible. SOLUTION: Of the developing device constituted including at least a developer, a developer carrier which carries the developer, a toner conveyance member (developer conveyance member) 30 which move reciprocally at right angles to the axis of the developer carrier so as to convey the developer to the developer carrier, and a swing member 31 which rotates reciprocally so as to make the toner conveyance member 30 move reciprocally, the sectional area of the swing member 31 is made different along the length. Consequently, the strength against torsion nearby the fulcrum of the swing member 31 increases to make an angle of rotation nearby the fulcrum of the swing member 31 larger than before and also increases the stroke of the toner conveyance member 30 nearby the fulcrum of the swing member 31. Consequently, the amount of the developer supplied to the developer carrier can be increased and a deficiency of the supply of the developer is evaded to obtain an image of high quality having no irregularity in density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device provided in an electrophotographic image forming apparatus such as a laser beam printer or a copying machine.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus such as a laser beam printer or a copying machine, which uses an electrophotographic method, has been reduced in size and price. Along with this, the charging means, the photoconductor,
A process cartridge, which is the heart of an electrophotographic process in which a developing unit, a cleaning unit, and a developer are integrated, is rapidly miniaturized. Under such circumstances,
Various developments have been made for each component of the process cartridge to achieve miniaturization without degrading image quality.

Among them, the toner container equipped with a stirring / conveying mechanism is one of the factors that are difficult to miniaturize because the toner must be efficiently conveyed to the vicinity of the developing sleeve in a small space.

Conventionally, as a toner stirring / conveying mechanism,
The rotary stirring mechanism has been widely used because of its extremely simple structure. In this rotary stirring mechanism, a thin rod having a diameter of about 2 mm is arranged in parallel with the developing sleeve, and the rod is rotated in the toner container.

However, in the rotary stirring mechanism, the toner carrying force to the vicinity of the developing sleeve is weak and it is difficult to effectively use up the toner. In order to assist this, it has been necessary to make the angle of the bottom surface of the toner container steep and to provide another transport mechanism near the developing sleeve.

On the other hand, it is effective to increase the radius of rotation of the stirring member in order to increase the conveying force of the toner to the vicinity of the developing sleeve with the single stirring mechanism, but this increases the size of the toner container, There was a contradiction with the goal of miniaturization.

Therefore, in order to satisfy the demand for obtaining a sufficient toner transporting force to the vicinity of the developing sleeve while reducing the size of the toner container, a slide type stirring mechanism has been proposed and already put into practical use. This sliding type stirring mechanism is roughly divided into two elements, namely, a toner conveying member that reciprocates in the developing sleeve direction in order to convey the toner to the vicinity of the developing sleeve along the bottom surface of the toner container, and to operate the toner conveying member. And a swing member connected to the toner conveying member. One end of the swing member is fitted in a hole provided in the toner container, and the other end receives a drive from outside the process cartridge to perform a reciprocating rotary motion, and this motion is transmitted to the toner conveying member. The toner conveying member and the swinging member, which are these two components, are made of a resin such as polystyrene which is inexpensive and easy to mold.

[0008] Such a slide type agitating mechanism requires a smaller spatial ratio of operating members than the rotary agitating mechanism, and since the toner conveying member reaches the vicinity of the developing sleeve, the toner agitating force is rich, and the toner is a final member. It has the advantage that it can be used up easily.

As described above, the slide type stirring mechanism is an excellent stirring mechanism which is effective in reducing the size of the toner container and has a sufficient toner conveying force.

[0010]

However, the slide type stirring mechanism has the following problems.

That is, in order to extend the life of the process cartridge, that is, in order to increase the number of printable sheets, the toner container is filled with as much toner as possible, but the toner volume occupies the volume of the toner container. When the ratio becomes large, a large load is applied to the toner conveying member due to the weight of the toner. When a large load is applied to the toner conveying member, the rocking member that is driven is twisted, and the rotation angle of the rocking member varies in the longitudinal direction.

By the way, since the stroke of the reciprocating motion of the toner conveying member is proportional to the rotation angle of the swinging member, when the swinging member is twisted, the rotation angle near the fulcrum of the swinging member becomes the rotation angle near the driving. As a result, the stroke of the toner conveying member near the fulcrum becomes smaller than that near the driving point. When the stroke of the toner conveying member is small, the amount of toner supplied to the developing sleeve facing the toner conveying member decreases, and as a result, the density of the image portion corresponding to the portion of the developing sleeve where the toner supply amount decreases decreases to another value. It becomes thinner than the part. The phenomenon of this density unevenness is remarkable especially in the initial use of the process cartridge. When the amount of toner decreases due to repeated image formation, the load on the toner conveying member decreases, and the rotation angle near the fulcrum of the oscillating member increases, resulting in the vicinity of the fulcrum of the oscillating member. The amount of toner supplied to the developing sleeve is increased, and uneven density is improved.

In order to solve the density unevenness that occurs in the initial stage of use of the process cartridge, the rocking member may be made of a stronger material, for example, a metal such as aluminum, instead of a resin material such as polystyrene. Then
Although the stroke difference as described above is greatly improved, metal such as aluminum is more difficult to mold than resin,
In addition, the cost is inevitably increased.

Further, the same effect can be obtained by increasing the cross-sectional area of the oscillating member uniformly, that is, by thickening the oscillating member with the resin material as it is, but the raw material cost increases and the cost increases. Invite.

The present invention has been made in view of the above problems, and an object of the present invention is to minimize the cost increase, minimize the difference in the lengthwise direction of the strokes of the developer conveying member, and reduce the density unevenness. An object of the present invention is to provide a developing device capable of obtaining a high quality image.

[0016]

In order to achieve the above object, the invention according to claim 1 provides at least a developer, a developer carrier for carrying the developer, and development on the developer carrier. It includes a developer transport member that reciprocates in a direction perpendicular to the axial direction of the developer carrier for transporting the developer, and a swing member that performs reciprocal rotary motion to reciprocate the developer transport member. In the developing device configured, the swing member has a different cross-sectional area in the longitudinal direction.

Further, in the invention according to claim 2, at least a developer, a developer carrier for carrying the developer, and a developer carrier for carrying the developer to the developer carrier. A developing device including a developer transporting member that reciprocates in a direction perpendicular to an axial direction, and a swinging member that performs a reciprocating rotary motion to reciprocate the developer transporting member. The auxiliary member is provided so as to cover a part of the.

Therefore, according to the first or second aspect of the present invention, the strength of the rocking member near the fulcrum against twisting is increased, and the rotation angle of the rocking member near the fulcrum is made larger than in the conventional case. As a result, the stroke of the developer transport member near the fulcrum of the swing member can be increased as compared with the conventional case, and the amount of developer supplied to the developer carrier can be increased. As a result, it is possible to avoid the low density due to the insufficient supply of the developer, which has occurred in the past.
It is possible to obtain a high quality image without density unevenness. Further, since the strength of the swinging member can be increased by the inexpensive member, the cost increase can be suppressed to a low level.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a schematic configuration diagram of an image forming apparatus including a developing device according to a first embodiment of the present invention, FIG. 2 is a perspective view of a stirring means of the developing device, and FIG. 3 is the same. FIG. 4 is a diagram showing the relationship between the longitudinal position of the oscillating member of the developing device, the rotation angle of the oscillating member, and the stroke of the toner conveying member. FIG. 4 is a diagram showing changes in the longitudinal sectional area of the oscillating member of the developing device. Is.

First, a schematic structure of the image forming apparatus according to the present embodiment will be described with reference to FIG.

The image forming apparatus according to the present embodiment is roughly classified in terms of electrophotographic process, a charging device, a latent image carrier,
It is composed of an exposure unit, a developing device, a transfer device, a cleaning device, and a fixing device.

A process cartridge K is detachably mounted in the main body of the image forming apparatus. The process cartridge K includes a charging roller 1 which is a charging means, a photosensitive drum 2 which is a latent image carrier, a developing device 17 and a cleaning device. Device 1
9 is compactly integrated. Further, in the process cartridge K, an opening is provided between the charging roller 1 and the developing device 17 for exposing the photosensitive drum 2 with an image by the exposing means 20.

The exposing means 20 is a laser scanner using a semiconductor laser as a light source.
A video controller 21 for converting target image information into a time series electric digital image signal is connected.

The photosensitive drum 2 has an outer diameter of 24 mm obtained by applying a photosensitive layer on a hollow cylindrical aluminum substrate.
Is an induction photoconductor of the peripheral speed 36 in the direction of arrow a in the figure by a drive system (not shown) provided on the main body of the image forming apparatus.
It rotates at mm / sec and is grounded via a metal ground plate (not shown).

Further, the charging roller 1 is pressed against the photosensitive drum 2 from both ends and has a predetermined contact width with the photosensitive drum 2. Then, the charging roller 1 is rotated in the direction of the arrow c shown by the rotation of the photosensitive drum 2 in the direction of the arrow a shown in the figure, and a predetermined bias is applied by the charging bias power source 23.

Thus, the developing device 17 according to the present invention includes the developing sleeve 6 which is a hollow cylindrical developer carrier having an outer diameter of 16 mm and which rotates in the direction of the arrow b in the drawing with a constant distance from the photosensitive drum 2. A cylindrical magnet roller 4 having both ends fixed inside the developing sleeve 6 and having a plurality of magnetic poles inside, and a coating layer thickness of the developer 8 on the developing sleeve 6 that is in contact with the developing roller 6 is regulated. Elastic rubber blade 5 as a developer regulating member, a metal member 7 supporting the elastic rubber blade 5, and a one-component magnetic developer for visualizing an electrostatic latent image formed on the photosensitive drum 2. (Hereinafter, referred to as toner) 8 and a developer storage chamber 13 that stores the toner 8.
It is composed of The peripheral speed of the developing sleeve 6 is set to 36 mm / sec, which is the same as that of the photosensitive drum 2, and the developing bias power source 24 supplies a predetermined A to the developing sleeve 6.
C voltage and DC voltage are applied. In addition, the developer storage chamber 13
Inside, a stirring means 12 for stirring the toner 8 and transporting it to the developing sleeve 6 is provided.

The stirring means 12 is, as shown in FIG.
A toner conveying member 30 that reciprocates in the direction of the arrow X in the figure to convey the toner 8 to the vicinity of the developing sleeve 6, and a reciprocating rotational movement in the direction of the arrow Y in the figure within a predetermined angle to transmit drive to the toner conveying member 30. Swinging member 31 and a swinging member driving gear 32 that rotates in the direction of arrow Z in the drawing for transmitting drive from the driving means (not shown) of the image forming apparatus main body to the swinging member 31 via the developing sleeve driving gear 34. And a swing assist member 33 for converting the rotary motion of the swing member drive gear 32 into a reciprocating rotary motion within a predetermined angle.

The swing member 31 is made of polystyrene resin which is inexpensive and easy to mold. Further, the rocking member drive gear 32 is provided with a projection 32 a, and the projection 32 a is a long hole 33 formed in the rocking assisting member 33.
a.

The swinging member 31 is composed of a shaft portion 31a and a connecting portion 31b connected to the toner conveying member 30, and one end 31d of the shaft portion 31a is provided in the developer accommodating chamber 13. The rocking member 31 is fitted in a hole (not shown).
And the other end of the coaxial portion 31a is connected to the swing assist member 33, and the swing member drive gear 32
Acts as a force point that receives the swing of.

By the way, the length of the shaft portion 31a is 220 mm.
Has been set, the feature of this embodiment, as the closer to the fulcrum sectional area of the shaft portion 31a of the swinging member 31 as shown in FIG. 4 from the power point 70mm ² ~105mm ²
And the point is set to increase linearly.

On the other hand, below the developing sleeve 6, in order to prevent the toner 8 from leaking out of the process cartridge K, a thickness of 30 μm is provided at least over the entire longitudinal width of the developing sleeve 6 covered with the toner 8. PET sheet 4
0 is in contact with the developing sleeve 6 with an extremely light pressure.

Further, the cleaning device 19 has a cleaning blade 9 for scraping off the toner 8 remaining on the surface of the photosensitive drum 2 after the transfer process, and the scraped toner 8 (hereinafter referred to as waste toner). And a waste toner storage chamber 14 for storing the toner.

Next, an image forming method in this image forming apparatus will be described with reference to FIG.

A desired potential of -700 V is applied by the charging roller 1.
The surface of the photosensitive drum 2 that has been charged to 1 is exposed by the laser beam 10 corresponding to the time-series electric digital image signal of the target image information sent from the video controller 21.

The toner 8 is conveyed to the developing sleeve 6 by the stirring means 12, and is carried on the surface of the developing sleeve 6 by the magnetic force of the conveying pole of the magnet roller 4. And
The toner 8 is conveyed to the contact surface between the developing sleeve 6 and the elastic rubber blade 5 by the rotation of the developing sleeve 6, and is rubbed by the developing sleeve 6 and the elastic rubber blade 5 to be given a desired negative charge. A rectangular wave AC voltage having a frequency of 2000 Hz and an amplitude of 1800 V is superimposed on the DC voltage of −400 V and applied to the developing sleeve 6. As a result, an alternating electric field is formed between the developing sleeve 6 and the photosensitive drum 2.

Thus, the toner 8 to which a desired charge is applied
Reach a position facing the photosensitive drum 2 and fly to the image exposure portion (bright potential portion) on the photosensitive drum 2 by the alternating electric field formed between the developing sleeve 6 and the photosensitive drum 2 as described above. The latent image is visualized by reversal development to form a toner image on the photosensitive drum 2.

The portion of the photosensitive drum 2 carrying the visualized toner image contacts the transfer roller 16 via the transfer material P. Then, the toner image on the photosensitive drum 2 contacts the transfer roller 16 and is transferred onto the transfer material P by applying a positive DC voltage having a polarity opposite to that of the toner 8 to the transfer roller 16.

The toner image transferred onto the transfer material P is pressed and heated in the fixing device 25 to be fixed on the transfer material P, and the transfer material P on which the toner image has been fixed is output as an output image to the outside of the image forming apparatus. Is discharged. The toner 8 remaining on the surface of the photosensitive drum 2 after the transfer is removed by the cleaning device 19
It is scraped off by the cleaning blade 9 and stored in the waste toner storage chamber 14.

Next, the operation of the developing device 17 according to the present invention will be described with reference to FIGS. 2 to 4 and 7. FIG. 7 is a perspective view showing the structure of a conventional stirring means, and in this figure, the same elements as those shown in FIG. 2 are designated by the same reference numerals.

When the developing sleeve drive gear 34 is driven by the drive system of the image forming apparatus main body (not shown) and the developing sleeve drive gear 34 rotates in the direction of arrow W in FIG. 2, the developing sleeve drive gear 34 meshes with the developing sleeve drive gear 34. Swing member drive gear 3
2 rotates in the direction of arrow Z in the figure. At this time, the rocking member drive gear 3 is inserted into the long hole 33a formed in the rocking assisting member 33.
Since the protrusion 32a protruding from the second member is fitted, the swing assisting member 33 converts the rotational movement of the protrusion 32a into reciprocating rotational movement. This causes the swinging member 31 to move about 3 degrees around the rotation axis.
A reciprocating rotary motion is performed in the direction of the arrow Y in the drawing within an angle range of 0 °. The reciprocating rotational movement of the swinging member 31 is transmitted to the toner conveying member 30, and the toner conveying member 30 reciprocates in the arrow X direction in the figure. Here, the connecting portion 3 of the swinging member 31
Since the elongated hole 31c is formed in 1b and the toner conveying member 30 is fitted in the elongated hole 31c, the toner conveying member 30 can make a smooth reciprocating motion.

When the toner 8 is not contained in the developer accommodating chamber 13 of the developing device 17, that is, when the load of the toner 8 is not applied to the toner conveying member 30, the rotation angle of the swinging member 31 is as shown in FIG. As indicated by a broken line in FIG. 3 (A), it is uniform over the longitudinal direction of the toner conveying member 30. Therefore, the stroke of the reciprocating motion of the transport member 30 is also uniform in the longitudinal direction, as indicated by the broken line in FIG.

However, when the toner 8 is actually filled in the developer accommodating chamber 13 by a predetermined amount, a load due to the weight of the toner 8 is applied to the toner conveying member 30, so that the swinging member 31 is deformed and twisted. Therefore, the drive of the rocking member drive gear 32 does not reach the vicinity of the fulcrum. Therefore, in the conventional case, as shown by the solid line in FIG.
The rotation angle in the vicinity of the fulcrum of 1a is significantly smaller than that in the vicinity of the force point. As a result, as shown by the solid line in FIG. 3B, the stroke of the toner conveying member 30 varies greatly in the longitudinal direction, and the stroke near the fulcrum becomes significantly smaller than near the force point.

On the other hand, in the present embodiment,
As shown in FIG. 4, the cross-sectional area of the shaft portion 31a of the rocking member 31 is increased from the point of application toward the fulcrum, so that the rocking member 31 becomes stronger against twisting near the fulcrum, and the fulcrum of the rocking member 31 is reinforced. The rotation angle in the vicinity can be increased as compared with the conventional one, as shown by the thick line in FIG. As a result, the stroke of the toner conveying member 30 near the fulcrum of the swinging member 31 can be increased as compared with the conventional case as shown by the thick line in FIG.
The amount of supply of can be increased. As a result, it is possible to avoid the thin density due to the insufficient supply of toner, which has occurred in the past. Moreover, since the increase in volume can be suppressed to be small as compared with the case where the cross-sectional area of the rocking member 31 is uniformly increased, there is also an advantage that cost increase can be suppressed to a low level.

As described above, according to the present embodiment, the cost increase is minimized, and the difference in the lengthwise direction of the stroke of the toner conveying member 30, which is a slide type stirring member, is minimized to achieve high quality without density unevenness. It is possible to obtain a clear image.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. 5 is a perspective view of the stirring means of the developing device according to the present embodiment, and FIG. 6 is a relationship between the longitudinal position of the swinging member of the developing device, the rotation angle of the swinging member, and the stroke of the toner conveying member. FIG.

Since the developing device according to the present embodiment is different from the developing device according to the first embodiment only in the structure of the stirring means,
Only the stirring means will be described in detail.

Agitating means 1 of the developing device according to the present embodiment
The structure of 2 is the stirring means 1 according to the first embodiment shown in FIG.
2, but the shape of the rocking member 31 and the rocking member 3
The difference is that the auxiliary member 35 is provided on the surface near the fulcrum 1.

In the stirring means 12 shown in FIG. 5, the cross-sectional area of the shaft portion 31a of the rocking member 31 is set to a constant 70 mm ² in the longitudinal direction as in the conventional case. The auxiliary member 35 is made of polystyrene resin and has a thickness of 2 mm and a length of 10
The auxiliary member 35 has a L-shaped cross section of 0 mm.
Is attached near the fulcrum of the swinging member 31. still,
As a method of attaching the auxiliary member 35 to the swinging member 31, adhesion, screwing, or the like can be adopted.

Thus, the stirring means 12 according to the present embodiment.
In the above, by attaching the reinforcing member 35 to the swing member 31, the strength of the swing member 31 in the vicinity of the fulcrum against twisting becomes stronger than in the conventional case. Therefore, as shown in FIG. 6A, the rotation angle near the fulcrum of the swinging member 31 becomes larger than that of the conventional one, and as a result, as shown in FIG. 6B, near the fulcrum of the toner conveying member 30. The stroke can be increased, and the amount of toner supplied to the developing sleeve 6 can be increased. As a result, it is possible to avoid the local thinness of the toner due to the insufficient supply of toner that has occurred in the past. In addition, compared with making the cross-sectional area of the rocking member 31 uniformly large and changing the material of the rocking member 31, there is an advantage that the cost increase can be suppressed low.

As described above, according to the present embodiment, the cost increase is minimized, and the difference in the lengthwise direction of the stroke of the toner conveying member 30, which is a slide type stirring member, is minimized to prevent uneven density. A high quality image can be obtained.

[0052]

As is apparent from the above description, according to the present invention, at least a developer, a developer carrying member for carrying the developer, and a developer carrying the developer carrying member. For this purpose, a developing member including a developer conveying member that reciprocates in a direction perpendicular to the axial direction of the developer carrier and a swing member that reciprocally rotates to reciprocate the developer conveying member. In the apparatus, since the cross-sectional area of the rocking member is made different in the longitudinal direction or the auxiliary member is provided so as to cover a part of the rocking member, the cost increase is minimized and the stroke of the developer conveying member is minimized. It is possible to obtain a high-quality image having no density unevenness by minimizing the difference in the longitudinal direction of the image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus including a developing device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a stirring unit of the developing device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the longitudinal position of the swinging member, the rotation angle of the swinging member, and the stroke of the toner conveying member of the developing device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a change in cross-sectional area in the longitudinal direction of the swing member of the developing device according to the first embodiment of the present invention.

FIG. 5 is a perspective view of a stirring unit of the developing device according to the second embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the longitudinal position of the swinging member, the rotation angle of the swinging member, and the stroke of the toner conveying member of the developing device according to the second embodiment of the present invention.

FIG. 7 is a perspective view of a stirring unit of a conventional developing device.

[Explanation of symbols]

 6 Developing Sleeve (Developer Carrier) 8 Toner (Developer) 12 Stirring Means 17 Developing Device 30 Toner Conveying Member (Developer Conveying Member) 31 Swinging Member 35 Auxiliary Member

Claims (2)

[Claims] 1. A developer, a developer carrier for carrying the developer, and a direction perpendicular to the axial direction of the developer carrier for transporting the developer to the developer carrier. In a developing device including a reciprocating developer transport member and a swing member that performs reciprocating rotary motion for reciprocating the developer transport member, a cross-sectional area of the swing member is different in a longitudinal direction. A developing device characterized in that 2. A developer, a developer carrier for carrying the developer, and a direction perpendicular to the axial direction of the developer carrier for transporting the developer to the developer carrier. In a developing device including a reciprocating developer transport member and a swinging member that performs reciprocating rotary motion to reciprocate the developer transporting member, an auxiliary device is provided to cover a part of the swinging member. A developing device provided with a member.