JPH03146979A - Developing device - Google Patents

Abstract

PURPOSE:To remove residual developer on the surface of a developing roll without giving useless stress by rubbing the respective blades of a cleaning roll against the circumferential surface of the developing roll with a time lag. CONSTITUTION:The rectangular blades 6b are planted at equal intervals in a circumferential direction on the circumferential surface of the shaft 6a of a rotary impeller 6. The, the impeller 6 is arranged so that the leading edge of the blade 6b may contact with the circumferential surfaces of developing rolls 3 and 4 with respect to a photosensitive roll 1. With the rotation of the impeller 6, the leading edge of the blade 6b contacts with the circumferentail surfaces of the rolls 3 and 4. After the blade 6b rubs the circumferential surfaces of the rolls 3 and 4 in a bent state, an action that it separates from the circum ferential surface is repeated to remove the residual toner stuck to the circumfer ential surfaces of the roller 3 and 4. At such a timer, the interval between the blades 6b and the length thereof are appropriately set lest the blades 6b should be bent and loads applied to the rolls 3 and 4 simultaneously. Thus, the residual toner is removed without imparting useless stress and the life of the developer is prolonger.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a developing device used in a copying machine, etc., which develops an electrostatic latent image with a developing roll having a magnetic brush formed with a developer such as toner on its surface. Regarding equipment.

[Conventional technology]

This type of developing device has been proposed in the past with various structures, and an example is shown in Fig. 8 (1).
1. s, P, No. 4436055).

FIG. 8 is a sectional view showing a conventional developing device for a copying machine.
In the figure, 21 is a photosensitive drum, 22 is a supply roll, 23, 24
indicates the developing roll.

The replenishment roll 22 and the developing rolls 23 and 24 are located in a developing box 25 disposed below the photosensitive drum 21, and each of the developing rolls 23 and 24 is placed on the outer periphery of the photosensitive drum 21 at a position shifted in the circumferential direction. The replenishment roll 22 is arranged parallel to the parent image rolls 23 and 24 below and in parallel with them at a required distance.

A hopper 26 for toner, which is a developer, is arranged at the upper part of the developing box 26 on one side, and the toner is transferred to the developing box 25 through a cutting roll 26a installed below the hopper 26.
From there, it is conveyed below the replenishment roll 22.

The replenishment roll 22 and the development roll 23.24 both have fixed shafts 22a, 23a, 2 with magnetic poles arranged on their outer peripheral surfaces.
The sleeves 22b, 23b, 21b are rotatably fitted onto the sleeve 4a, and each sleeve 22b
, 23b, 24b are fixed shafts 22a by a drive source (not shown).
, 23a, and 24a, respectively, in the directions indicated by arrows. Fixed shaft 22a
, 23a, and 24a are formed by embedding a permanent magnet in the shaft surface or by embedding a permanent magnet in the shaft surface so that magnetic poles of the same magnetic pole or different magnetic poles are adjacent to each other at a predetermined corner in the circumferential direction on the outer circumferential surface, or by embedding a magnetic material. It is formed by magnetizing the shaft surface, and the magnetic flux density of each magnetic pole is set to be appropriately large within a predetermined range along the toner transport direction.

As a result, the toner magnetically attached to the surface of the sleeve 22b is sequentially transferred from the surface of the sleeve 22b to the surface of the sleeve 23b and then to the surface of the sleeve 24b as the sleeve 22b rotates, and is transferred to both sides at a position facing the surface of the photosensitive drum 1. The electrostatic latent image on the surface of the photosensitive drum 21 is developed by magnetic brushes of toner formed on the surfaces of the sleeves 23b and 24b.

On the peripheral surface of the photosensitive drum 21 on which an electrostatic latent image is formed, the potential of the image area is higher than the potential of the background area. A bias voltage at an intermediate level is applied to the developing roll 2 according to the set value of this bias voltage.
The toner on the surfaces of the sleeves 23b and 24b of 3.24 is adsorbed onto the surface of the photosensitive drum 21, and the electrostatic latent image is developed. However, if the bias voltage is high, the developing roll 2
3. The adhesion of the toner to the surfaces of the sleeves 23b and 24b of 24 is strong, and uneven background fog, which is image noise, is likely to occur during subsequent copying.

Also, part of the toner supplied from the supply roll 22 to the developing roll 23.24 is supplied to the surface of the photosensitive drum 21, and the rest remains on the developing roll 23.24. Looking at the thickness of the remaining toner, there is a difference in toner thickness between areas where a large amount of toner was consumed for development and areas where little toner was consumed.

Therefore, if the next development is carried out as is, the level difference will be slightly reduced due to toner replenishment from the replenishment roll 22, but the level difference itself will remain as it is, and a difference will occur in the bias voltage in this area, which will cause the next development. This sometimes appears as a difference in image density, resulting in variations in image clarity.

For this reason, normally, the magnetic poles in the circumferential direction of the circumferential region of the developing roll 23, 24 after facing the photosensitive drum 21 and the fixed shafts 22a, 23a, 24a of the supply roll 22 after facing the developing roll 23 are the same. In addition, in addition to setting the respective magnetic flux densities appropriately, a scraper 27 is provided in this revolving area to once remove residual l/ner on the surfaces of the sleeves 23b and 24b, and the lubricant is replenished from the replenishment roll 22 during the next development. Development is performed using only toner.

[Problem to be solved by the invention]

Incidentally, in such a conventional developing device, a scraper 27 is used as one of the means for removing residual toner on the circumferential surface of the developing roll 24, but the use of the scraper 27 may impart unnecessary stress to the developer. This causes problems such as coagulation of the toner, degrading the quality of the toner and shortening its lifespan.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a developing device that can remove residual developer on the surface of a developing roll without adding unnecessary stress to it. .

[Means to solve the problem]

The developing device according to the present invention is constructed by fitting a non-magnetic sleeve to the outer periphery of a shaft portion having a plurality of magnetic poles arranged in the circumferential direction so as to be relatively rotatable. A plurality of developing rolls for developing a latent image, and one or more elastic blades extending in the axial direction around the periphery, each blade sliding into contact with the circumferential surface of each of the developing rolls at staggered times. It is characterized by comprising a cleaning roll which is rotationally driven.

[Effect]

According to the present invention, the residual developer on the circumferential surface of the developing roll can be brushed off by the impeller that rolls into contact with the circumferential surface of the developing roll without applying excessive stress to the developer.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically explained below based on drawings showing a case where the present invention is applied to a copying machine.

FIG. 1 is a schematic vertical cross-sectional view of a developing device according to the present invention (hereinafter referred to as the device of the present invention), and FIG. 2 is a partially enlarged view showing the manner in which toner, which is a developer, is conveyed between a bucket roll, a replenishment roll, and a developing roll. In the figure, 1 is a photosensitive drum, 2 is a supply roll, 3.4 is a developing roll, and 5 is a bucket roll.

A developing box 10 is provided on the side facing the circumferential surface of the photosensitive drum 1.
The inside of the developing box 10 is divided into an area facing the photosensitive drum 1 and an area separated from the photosensitive drum 1 by a partition wall 10a provided in the middle. In the area of the developing box 10 facing the photosensitive drum 1, there is a bucket roll 5 located in the toner reservoir A at the bottom thereof, and a bucket roll 5 facing the circumferential surface of the photosensitive drum 1 at a required interval in the circumferential direction. Further, a supply roll 2 is located above the rear of the developing rolls 3, 4 relative to the photosensitive drum 1, and an impeller 6.4 which is a cleaning roll is located behind the developing roll 3.4. A blade 7, a screw conveyor 11 for toner circulation, and the like are provided.

On the other hand, in an area separated from the photosensitive drum 1 in the developing box 10, a hopper 12 for toner, which is a developer, is disposed above the hopper 12, and a screw conveyor 13 is disposed below the hopper 12. The hopper 12 has a cutting roll 12a at the bottom.
The toner is cut out into the developing box 1O by rotation of the cutting roll 12a, and is supplied onto the screw conveyor 13. The screw conveyor 13 is configured to feed the supplied toner to one end on the same side as the inclined lower end of the screw conveyor 11, and from there to the screw conveyor 11 through a hole bored in the partition wall 10a. The screw conveyor 11 is disposed on the side of the bucket roll 5 so as to be inclined upwardly and downwardly, and the inclined lower end side is connected to the lower part of one end of the toner pool A, and the inclined upper end side is connected to the other end of the toner pool A. The toner conveyed by the screw conveyor 13 is conveyed together with the toner in the toner reservoir A to the upper side of the other end of the toner reservoir A, and returned there for circulation. There is.

The bucket roll 5 includes a plurality of bucket portions 5a having a length substantially equal to the length of the photosensitive drum 1 at approximately equal intervals in the circumferential direction, and includes blades 5b formed by cutting and raising a part of the bucket portions 5a. The toner in the toner pool A is scooped up into the bucket part 5a, splashed onto the surface of the replenishment roll 2, and supplied thereto.
The toner is stirred and transferred toward one end on the same side as the lower end of the toner pool A, and the toner in the toner pool A is forcibly circulated to promote charging of the toner.

Supply roll 2. The developing rolls 3.4 are fixed shafts 2a, 3, respectively.
a.

The sleeves 2b, 3b, 4b made of non-magnetic material are rotatably fitted onto the sleeve 4a, and the sleeves 2b, 3b, 4b are rotatably driven by a drive source (not shown).

The fixed shafts 2a, 3a, 4a have a plurality of different magnetic poles or the same magnetic poles in the circumferential direction by embedding permanent magnets in their circumferential surfaces or by partially magnetizing the surfaces of the fixed shafts 2a, 3a, 4a made of magnetic material. They are arranged at required intervals.

Supply roll 2. The arrangement of the magnetic poles on the surface of the developing roll 3.4 is as shown in FIG. 1.2. That is, in the replenishment roll 2, the magnetic pole S2. However, there is also a magnetic pole N2c in the part facing the developing roll 3.
Further, magnetic poles SZa are respectively arranged at positions facing the rotating blades 6, and the magnetic poles S! Between the magnetic pole N2c and the magnetic pole Nza + in the direction of rotation of the sleeve 2b,
S tb + Nzb + S zc are arranged at equal intervals. The magnetic flux density of each of these magnetic poles is 400
-1000 Gauss is set to an appropriate value in the direction of rotation of the sleeve 2b so that the developer is smoothly conveyed.

A magnetic pole S is provided on the circumferential surface of the fixed shaft 3a of the developing roll 3 at a position facing the magnetic pole N2c on the fixed shaft 2a of the replenishment roll 2.
. However, there is also a magnetic pole NII at a position facing the photosensitive drum 1.
Furthermore, magnetic poles S3C are arranged at positions facing the developing roll 4, respectively, and the magnetic poles S3. From magnetic pole N7. , the magnetic pole N is in the direction of the arrow, which is the direction of rotation of the sleeve 3b. , S3
．． are arranged at predetermined intervals. The magnetic flux density of each of these magnetic poles is set to an appropriate value within the range of 400 to 1500 Gauss in the direction of rotation of the sleeve 3b so that the developer can be conveyed smoothly.

On the circumferential surface of the fixed shaft 4a of the developing roll 4, a magnetic pole N41 is disposed at a position facing the circumferential surface of the developing roll 3, and a magnetic pole S4° is disposed at a position facing the circumferential surface of the photosensitive drum 1. Between S4i and magnetic pole N41, there is a magnetic pole N in the direction of the arrow.
ab+Sab+Nac are arranged in this order at appropriate intervals. The magnetic flux density of each of these Ml poles is 400~
It is set to an appropriate value within the range of 1500 Gauss in the direction of rotation of the sleeve 4b.

FIG. 3 is an enlarged perspective view of the impeller 6, in which the rotary impeller 6 is made of a non-magnetic material and is arranged on the circumferential surface of the shaft 6a at eight equally spaced positions in the circumferential direction and is made of a non-magnetic material. A rectangular blade 6b having a length substantially equal to the axial dimension of the developing rolls 4 is installed substantially parallel to the axial center line of the shaft 6a, and the shaft 6a is connected to the developing rolls 3 and 4. The perpendicular bisector L of the straight line Q-Q' connecting the axial center line is the rear side of the developing roll 3.4 with respect to the photosensitive roll 1, and the tip of the wing 1'i6b is approximately 111 cm long. It is pivotally supported in such a manner that it overlaps the 40° circumferential surface. The blade 6b is made of a urethane sheet or the like with a thickness of about 0.1 mm to provide appropriate elasticity, and a gear 6C is provided at the end of the shaft 6a, and the gear 6c is provided on the output shaft of the motor M4. The developing roller 3.4 is meshed with a worm gear 6d and rotated by the motor M4, so that it rolls into contact with the circumferential surface of the developing roll 3.4 and brushes off residual toner.

The circumferential speed of the impeller 6 is 700 m when the developing roll 3.4 has a circumferential speed of 700 m.
In terms of m/sec, it is set to about 1150++ m/sec.

FIG. 4 is an explanatory diagram of the operation of the impeller 6, and FIG.
As shown in (b), as the impeller 6 rotates, the tips of the blades 6b contact the circumferential surfaces of the developing rolls 3 and 4, and the blades 6b are bent further into the developing rolls 3 and 4.
After slidingly contacting the circumferential surface of the developing rolls 3 and 4, the operation of separating from the circumferential surfaces of the developing rolls 3 and 4 is repeated to remove residual toner adhering to the circumferential surfaces of the developing rolls 3 and 4. As shown in Figure 4 (A) 1], when the - blade a is in sliding contact with the circumferential surface of the developing roll 4 in a bent state, other blades a, c, etc. The blades C may not be in sliding contact with each other, or may be in sliding contact without being bent even if they are in sliding contact, or the - blades C should be in a bent state with respect to the circumferential surface of the developing roll 3 as shown in FIG. 4 (b). When the blades a, b, and d are in contact with the peripheral surface of the developing roll 4, the other blades a, b, and d do not come into sliding contact with the peripheral surface of the developing roll 4, or even if they do come into sliding contact, they do not bend. In other words, the impeller The blades 6b of No. 6 are bent simultaneously with respect to the circumferential surfaces of the developing rolls 3 and 40,
That is, the distance between the blades and the length of each blade are set appropriately so that the maximum load is not applied simultaneously.

FIG. 5 shows the blades 6b of the impeller 6 relative to the developing roll 3.4.
The graph shows the change in load due to the change in load, with time plotted on the horizontal axis and load plotted on the vertical axis. Solid line A in the graph is blade a
The dotted line B is the load applied to the developing roll 4 by the blade C, the solid line C is the load applied by the blade C to the developing roll 3, and the dashed line B is the load applied by the blade d to the developing roll 4. are shown respectively. As is clear from this graph, the loads applied by the blades 6b of the impeller 6 to the developing rollers 3.4 are not maximized at the same time, in other words, the maximum loads are applied alternately to the developing rollers 3 and 4. Setting and developing roll 3
, 4 are simultaneously subjected to the maximum load, their circumferential speeds fluctuate, and image noise such as horizontal stripes or the like is generated in the halftone portion of the image is suppressed.

FIG. 6 is an explanatory diagram showing the drive system of the main members in the device of the present invention, Ml, M2. M3 indicates a motor. A gear provided on the output shaft of the motor M is meshed with a gear 5c provided on the shaft end of the bucket roll 5.
The packet roll 5 is rotated in the direction of the arrow by the drive of +.

A gear provided on the output shaft of the motor M2 is meshed with a gear 2c provided on the shaft end of the supply roll 2.
The rotational drive causes the sleeve 2b of the supply roll 2 to rotate in the direction of the arrow.

A gear provided on the output shaft of the motor M3 is meshed with gears 3c and 4c provided on each shaft end of the developing roll 3.4, and each sleeve 3b of both the developing rolls 3 and 4 is rotated by the rotational drive of the motor M. , 4b are rotated in the direction of the arrow.

The operation of the apparatus of the present invention will be explained with reference to the timing chart shown in FIG.

FIG. 7 shows a drive timing chart of the main components in the apparatus of the present invention. First, when the print switch is turned on as shown in FIG. An electrostatic latent image is formed and rotated to a position corresponding to the developing roller 3.4.

On the other hand, due to the rotation of the bucket troll 5, the charged toner is splashed onto the surface of the sleeve 2b of the supply roll 2,
After being magnetically attached to the surface of the sleeve 2b, as the sleeve 2b rotates, adjacent magnetic poles of opposite polarity take over, and after adjusting the thickness of the toner with the blade 7, the sleeve 2b
When the toner is moved to a position corresponding to the magnetic pole N2c of the fixed shaft 2a while being magnetically attached to the surface, the toner faces the magnetic pole S3° of the fixed shaft 3a of the developing roll 3, and the toner is transferred to the developing opening.
The receiver is passed over the surface of the sleeve 3b of the handle 3.

The toner supplied to the surface of the sleeve 3b of the developing roll 3 and magnetically attached thereto is sequentially taken over by magnetic poles of opposite polarity similarly formed on the surface of the fixed shaft 3a, and is transported while being attracted to the surface of the sleeve 3b. It reaches a position facing the photosensitive drum 1.

A magnetic brush made of toner is formed on the circumferential surface of the sleeve 3b of the developing roll 3, and a sleeve bias voltage appropriate for the potential of the image area and background area of the photosensitive drum 1 is applied to the developing roll 3. The toner on the surface of the sleeve 3b of the developing roll 3 is delivered to the image area of the photosensitive drum 1, where it is developed. When the residual toner is magnetically attached to the surface of the sleeve 3b and moved to a position corresponding to the magnetic poles S and c of the fixed shaft 3a, it faces the magnetic pole N4m of the fixed shaft 4a of the developing roll 4, and also moves to the position corresponding to the magnetic poles S and c of the fixed shaft 3a. The next magnetic pole 3 of magnetic pole S3c in the direction of rotation of
3m5 are of the same polarity, almost all of the toner is transferred to the sleeve 4b of the developing roll 4.

A magnetic brush for toner is also formed on the surface of the sleeve 4b of the developing roll 4, and the toner is delivered to the image area of the electrostatic latent image at a position facing the surface of the photosensitive drum 1, thereby performing development.

The residual toner remains magnetically attached to the surface of the sleeve 4b and moves to the magnetic pole N.
When it reaches the position opposite to magnetic pole 4c, there is a long distance between it and the next magnetic pole N4° (and since they are the same pole, the toner will move to magnetic pole N,
After passing the position corresponding to c, most of the sleeve 4b
The toner is separated from the surface and falls into the toner pool A.

On the other hand, the impeller 6 is connected to the circumferential surface of the sleeve 3b between the magnetic poles SXa and S3C of the fixed shaft 3a of the developing roll 3, and the magnetic pole N4 of the fixed shaft 4a of the developing roll 4. and N4C
The toner is in rolling contact with the circumferential surface of the sleeve 4b between the sleeves 3b and 4b, and the toner remaining on the circumferential surface of each of the sleeves 3b and 4b is knocked off and removed.

When the supply of toner to the developing roll 3.4 is completed, the replenishing roll 2 first stops as shown in FIGS. The supply of toner to the roll 3.4 is cut off, and after a time period of Δ, when all the toner on the circumferential surface of the developing roll 3.4 is removed, the developing rolls 3, 4 and the impeller 6 are turned off.
stops. As a result, after copying is completed, the developing roll 3.
The peripheral surface of No. 4 is maintained in a clean state free of residual toner.

〔effect〕

As described above, in the apparatus of the present invention, the residual developer on the peripheral surface of the developing roll is brushed off by the rotation of the impeller, so unnecessary stress is not applied to the toner to be removed. The present invention has excellent effects such as significantly extending the life of the developer without causing quality deterioration such as coagulation of the developer.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of the apparatus of the present invention, Fig. 2 is a partially enlarged view thereof, Fig. 3 is an enlarged perspective view of the impeller, Fig. 4 is an explanatory diagram of the operation of the impeller, and Fig. 5 is a developing roll. 6 is an explanatory diagram showing the drive transmission system of the main components, FIG. 7 is a timing chart of the main components of the device of the present invention, and FIG. 8 is a schematic cross-sectional view of the conventional device. be.

Claims (1)

[Claims] 1. A non-magnetic sleeve is fitted around the outer periphery of a shaft portion with a plurality of magnetic poles arranged in the circumferential direction so as to be relatively rotatable. A plurality of developing rolls for developing latent images, and one or more elastic blades extending in the axial direction around the periphery, each blade slidingly contacting the circumferential surface of each of the developing rolls at staggered times. 1. A developing device comprising: a cleaning roll that is rotationally driven.