JPH1069154A - Developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make density definite and to obtain a stable, harmonious and sharp color image by specifying the thickness of the root of the spiral blade part of a stirring screw and the pitch of the stirring screw. SOLUTION: The stirring screw 145 is constituted of the spiral blade part 145a formed in a spiral shape and a rotary shaft part 145b freely rotatably supported by bearing members provided on both sidewalls of a developing unit housing. Components of force in horizontal and vertical direction Fh and Fv are added to a developer by the slope 145 of the spiral blade part 145a, by the rotation of the stirring screw 145. The component of force in the horizontal direction Fh carries the developer in the axial direction of the stirring screw 145 and the component of force in the vertical direction Fv carries the developer in a direction perpendicular to an axis. At this time, an F-value with respect to the pitch (p) of the screw of the spiral blade part 145a of the stirring screw 145 is designed within the range of 0.6<=(F/p)<=1. Thus, the property of stirring supplied toner is improved.

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 image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, and more particularly, to a developing device in a color image forming apparatus having a plurality of developing devices. The present invention relates to improvement of developer stirring means.

[0002]

2. Description of the Related Art As a developing method of an electrophotographic apparatus, there are known a normal developing method used for a normal electrophotographic copying machine and the like, and a reversal developing method used for a digital printer and a digital electrophotographic copying machine. The reversal development method generally uses a laser, LED, or the like as a light source, develops a latent image formed on the photoconductor by charging and exposure with a toner charged to the same polarity as the charging polarity of the photoconductor, and forms a toner image. It is a method to be. For example, when the charge polarity of the photoconductor is negative, the polarity of the toner is also negative, and development is performed using a potential difference caused by exposure to form a toner image on the photoconductor. After the development process, the transfer material is charged to a polarity opposite to that of the toner by a transfer device using corona discharge or the like, and the toner image on the photoconductor is transferred by the transfer material. Thereafter, the potential of the transfer material is lowered by an AC corona discharge or a DC corona discharge to reduce the adhesive force between the transfer material and the photoreceptor. Then, the transfer material is peeled off from the photoreceptor surface, and the process proceeds to the next process.

In a conventional developing device, a developer carrier (developing sleeve) that rotates in close proximity to a rotating image forming body is used.
Is arranged. The developer carrier is formed in a hollow cylindrical shape, and is housed in a housing having an opening on a side facing the image forming body. The developer carrier is supplied with a DC voltage of, for example, 600 V, 1700 V, 8000 Hz.
The developing bias voltage on which the AC voltage is superimposed is applied. The developer carrier has a fixed magnet inside, and carries a two-component developer in which toner particles and magnetic particles (carrier) are mixed on the outer peripheral surface of the developer carrier.

The developing device is a developer housing which contains a two-component developer composed of the toner and the carrier, and a developer conveying means having a magnetic field generating means (magnet roll) having a fixed magnet inside. A carrier (developing sleeve), a developer supply roller (hereinafter, referred to as a supply roller), a developer layer thickness regulating member for regulating a developer layer thickness on the developer carrier to a predetermined amount, and a developer stirring screw (hereinafter, referred to as a developer stirring screw) , Referred to as a stirring screw). The toner replenished from the toner cartridge into the developing device housing at the toner replenishing port opened at the upper portion of the developing device housing is stirred and mixed with the developer contained in the developing device housing by the rotating stirring screw. Then, the toner concentration becomes uniform, and the toner is supplied onto the outer peripheral surface of the developer carrier by the rotating supply roller.
A layer thickness regulating member is provided to regulate the layer thickness of the two-component developer on the developer carrier.

[0005]

In order to reduce the size of an image forming apparatus such as an electrophotographic copying machine or a printer, it is necessary to reduce the size of a developing device. In particular, in a color image forming apparatus in which a plurality of developing devices are arranged, it is necessary to reduce the size of the developing devices in order to achieve a small-diameter image carrier. However, by reducing the size of the developing device, the storage space of the stirring means (stirring screw) for stirring the developer in the developing device and the stirable developer transport distance are reduced.
In the conventional agitating means, insufficient agitation is caused. Insufficient agitation and mixing of the developer does not result in a uniform toner concentration, resulting in insufficient developability during development processing and toner scattering.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the improvement of the stirring means (stirring screw) makes it possible to reduce the size of the developing device and to reduce the size of the developing device. A developing device that can improve the agitation of the replenished toner supplied to the toner, eliminate insufficient development and toner scattering due to running, stabilize the density, and obtain stable, harmonious and clear color images It is an object to provide an image forming apparatus.

According to a first aspect of the present invention, there is provided a developing device comprising: a developer carrying member for transporting the developer to a developing area of the image carrier; and a stirring screw for agitating and transporting the developer. Wherein the thickness (F) of the root of the spiral blade portion of the stirring screw and the pitch (p) of the stirring screw satisfy 0.6 ≦ (F / p) ≦ 1. It is characterized by the following.

According to a second aspect of the present invention, there is provided a developing device for transporting a developer to a developing area of an image carrier, and for agitating and transporting the developer. In the developing device provided with the stirring screw, the thickness (F) of the root of the spiral blade portion of the stirring screw and the pitch (p) of the stirring screw are set to 0.4 ≦ (F / p).
≦ 1, p ≧ 6 mm.

Further, in order to achieve the above object, a developing apparatus according to a third aspect of the present invention includes a developer carrier for transporting a developer to a developing area of an image carrier and an agitator for transporting the developer. A developing device having a stirring screw; a thickness (F) of a root of a spiral blade portion of the stirring screw;
The thickness (f) of the tip of the spiral blade of the stirring screw and the pitch (p) of the stirring screw are set to satisfy 5f ≦ F ≦ p.

According to a fourth aspect of the present invention, there is provided a developing device for transporting a developer to a development area of an image carrier, wherein the developer is stirred and transported. A stirring screw of the developing device,
Thickness (F) at the root of the spiral blade portion of the stirring screw
And the tip thickness (f) of the stirring screw spiral blade portion
And the pitch (p) of the stirring screw is 0.3 ≦ (F +
f) /2p≦0.7.

According to a fifth aspect of the present invention, there is provided a developing device for conveying a developer to a developing area of an image carrier, agitating the developer, and carrying the developer. In a developing device provided with a stirring screw for transporting to the body, the stirring screw includes a rotating shaft and a spiral blade provided on the rotating shaft, and the spiral angle (θ) of the blade in the axial direction is 30. ７５75 °.

According to a further aspect of the present invention, an image forming apparatus for carrying an electrostatic latent image and a developer for developing the electrostatic latent image are provided. In an image forming apparatus including a developing device that forms a developing region opposed to a developer carrier, the developing device includes a stirring screw that stirs the developer and conveys the developer to the developer carrier. Is any one of claims 1 to 6
It is a stirring screw described in item.

Furthermore, an image forming apparatus according to claim 11 of the present invention, which achieves the above object, is a developing apparatus according to any one of claims 1 to 6, wherein at least two of A developing device is provided around the image carrier.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of an embodiment of the present invention, the structure of a color printer as an example of an image forming apparatus equipped with a plurality of developing devices of the present invention and the operation thereof will be described with reference to the sectional structural view of FIG. It will be explained by.

In this color printer, after each color toner image sequentially formed on an image carrier is superimposed, the color image is formed on a recording paper by a transfer unit once, and then the image is formed by a separation unit. This is a color image forming apparatus of a method of peeling off from a surface of a carrier.

In FIG. 1, reference numeral 10 denotes a photosensitive drum serving as an image bearing member, which is formed by applying an OPC photosensitive member (organic photosensitive member) on a drum base, and is grounded and driven to rotate clockwise in the drawing. . 11 is a scorotron charger, provided by a corona discharge by a grid and the corona discharge wire which is the potential held at grid potential V _G uniform charging of the high voltage V _H to the photosensitive drum 10 peripheral surface. Prior to the charging by the scorotron charger 11, in order to eliminate the history of the photoreceptor up to the previous print, exposure is performed by a PCL (pre-charging static eliminator) 12 using a light emitting diode or the like, and the peripheral surface of the photoreceptor is discharged. deep.

After the photosensitive drum 10 is uniformly charged, the image exposure means 13 performs image exposure based on the image signal. The image exposing means 13 is a main scanning performed by bending a light path by a reflection mirror 134 through a polygon mirror 131, an fθ lens 132, and a cylindrical lens 133 which rotate by using a laser diode (not shown) as a light emitting light source. A latent image is formed by (sub-scan). In this embodiment, the character portion is exposed,
An inverted latent image is formed such that the character portion has a lower potential _VL .

Around the periphery of the photosensitive drum 10, a developing device 14Y containing a two-component developer including a toner such as yellow (Y), magenta (M), cyan (C), and black (K) and a carrier. , 14M, 14C, and 14K are provided.

First, the development of the first color yellow is performed by a developer carrier (hereinafter referred to as a developing sleeve) 141 which rotates with a built-in magnet and holding the developer. The developer consists of a carrier with ferrite as the core and an insulating resin coated around it, and a toner with polyester as the main material and a pigment according to the color, a charge control agent, silica, titanium oxide, etc. The developer is deposited on the developing sleeve 141 by the developer layer forming means in an amount of 100 to 6
The developer is conveyed to the developing area while being regulated to the thickness of the developer layer of 00 μm.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is larger than the developer layer thickness.
2 to 1.0 mm, during which the AC bias V _AC and D
C bias _VDC is applied in a superimposed manner. DC bias V
_{Since DC} , high potential V _H , and toner charge have the same polarity, A
Toner given the opportunity to leave the carrier by C bias V _AC will not adhere to the portion of the DC bias V _DC high potential than the high potential V _H, the low low potential V _L portion of potential than the DC bias V _DC Adhesion and visualization (reversal development)
Is performed.

After the visualization of the first color is completed, the magenta image forming process of the second color is started, and the scorotron charger 1 is again turned on.
1 is performed, and a latent image based on the image data of the second color is formed by the image exposure unit 13. At this time 1
The charge elimination by the PCL 12 performed in the color image forming process is not performed because the toner attached to the image portion of the first color scatters due to a sharp drop in the surrounding potential.

[0022] Similar latent image and the first color is made for the re-out of the photosensitive member became potential of the high potential V _H over the entire surface of the photosensitive drum 10 peripheral surface, without first color image portion Although development is performed, 1 is again part for developing image to the portion where there is the color, the latent image potential V _M by the charge possessed by the shading of the toner itself by the toner adhering the first color is formed, DC bias V developing in response to a potential difference between the _DC and the potential V _M is performed. In the overlapping portion of the images of the first color and the second color, if the development of the first color is performed by forming a latent image having a low potential _VL , the balance between the first color and the second color is lost. Therefore, the intermediate potential may be V _H > V _M > V _L.

The same image forming process as that for the second color magenta is performed for the third color cyan and the fourth color black, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10.

Each of the developing units 14Y, 14M, 14C, 1
A toner supply device for controlling and replenishing each new color toner in 4K includes a plurality of detachable toner cartridges 15.
(Y, M, C, K), toner storage means 16 (Y, M,
C, K) and the toner conveying means 17 (Y, M, C, K).

On the other hand, the half-roller 1
One transfer material (transfer paper or the like) P carried out via 81 temporarily stops, and is fed to the transfer area by the rotation of the pair of registration rollers 182 of the paper feed unit when the transfer timing is adjusted. You.

In the transfer area, the transfer means 19 is pressed against the peripheral surface of the photosensitive drum 10 in synchronization with the transfer timing, and the fed transfer material P is sandwiched to transfer the multicolor image at once. You.

Next, the transfer material P is neutralized by the separating means 20, separated from the peripheral surface of the photosensitive drum 10 and conveyed to the fixing device 22, where the heat roller (upper roller) 221 and the pressure roller (lower roller) 222 After the toner is welded by heating and pressing, the toner is discharged onto a discharge tray 24 outside the apparatus via a discharge roller 23. The transfer unit 19 is retracted from the peripheral surface of the photosensitive drum 10 after passing the transfer material P to prepare for the formation of the next toner image.

On the other hand, the photosensitive drum 1 from which the transfer material P has been separated
In the case of No. 0, the residual toner is removed and cleaned by the pressure contact of the blade 211 of the cleaning device 21, and the charge is again removed by the PCL 12 and charged by the scorotron charger 11, and the next image forming process is started. The blade 211
Moves immediately after the cleaning of the surface of the photoconductor and retreats from the peripheral surface of the photoconductor drum 10. The waste toner scraped into the cleaning device 21 by the blade 211 is
After being discharged by the screw 212, it is stored in a waste toner collecting container (not shown).

FIG. 2 shows a plurality of developing units 14Y, 14M, 14
FIG. 4 is a cross-sectional view illustrating a configuration of a developing device including C and 14K. Around the periphery of the photosensitive drum 10, a developing device 1 containing a developer including a toner such as yellow (Y), magenta (M), cyan (C), and black (K) and a carrier, respectively.
A developing device 14 including 4Y, 14M, 14C, and 14K is provided. The developing device housing 140 includes the developing device 1
A developing unit housing 140Y for the 4Y, a developing unit housing 140M for the developing unit 14M, and a developing unit housing 140C for the developing unit 14C are arranged in a three-tiered configuration, and a top plate 140A is mounted on the uppermost position. By stacking, positioning and integrating the above members, three developer chambers isolated from each other are formed. These developing units 14Y,
Since 14M, 14C, and 14K have almost the same configuration, these developing units will be described as a developing device 14 and a developing housing 140 as representatives.

FIG. 3 is a sectional view of the developing device 14. In the drawing, reference numeral 140 denotes a developing device housing for accommodating a two-component developer composed of a toner and a carrier, and 141 denotes a magnetic field generating means (magnet roll) 1 having a fixed magnet inside.
A developing sleeve which is a developer conveying means having 42;
3 is a developer supply roller (hereinafter, referred to as a supply roller), 1
Reference numeral 44 denotes a developer layer thickness regulating member that regulates the thickness of the developer layer on the developing sleeve 141 to a predetermined amount. Reference numerals 145 and 146 denote developer stirring screws (hereinafter, referred to as stirring screws).
The stirring screw 145 and the stirring screw 146 are connected to the partition wall 14 standing upright from the bottom of the developing device housing 140.
The first agitating chamber 140b and the second agitating chamber 140c formed on both sides of Oa are disposed in parallel with each other.

Reference numeral 140d denotes a toner supply port opening at the top of the developing device housing 140.
From the toner storage means 16 and the toner transport means 17, and is supplied to the first stirring chamber 140b.

FIG. 4 is a plan sectional view of the developing device 14.
The vicinity of both shaft ends of the developing sleeve 141 is a support member 147A.
Are supported rotatably by a ball bearing (ball bearing) 148A provided on the support member 148B and a ball bearing 148B provided on the support member 148B. In the vicinity of both shaft ends of the developing sleeve 141, butting rollers 149A and 149B are rotatably supported via ball bearings. Butt roller 149
A and 149B are in contact with both ends of the outer peripheral surface of the photosensitive drum 10 so that the photosensitive drum 10 and the developing sleeve 14 are in contact with each other.
The gap with 1 is kept constant. Both ends of the magnetic field generating means 142 having a plurality of magnetic poles are fixedly supported by support members 147A and 147B. The developing sleeve 141 is driven and rotated by a driving source (not shown) connected to a gear G1 fixed to one shaft end. G2 is a gear for transmitting drive to the rotation shaft of the stirring screw 146, and G3 is a stirring screw 145.
And a gear for transmitting the drive to the rotating shaft of the stirring screw 146.

From the toner cartridge 15 through the toner storage means 16 and the toner transport means 17, the first stirring chamber 140
The toner supplied to the toner supply port 140d above the upper portion b is conveyed in the direction indicated by the left arrow in FIG.
0e and is sent into the second stirring chamber 140c. The toner sent into the second stirring chamber 140c is
The toner is conveyed by the stirring screw 146 in the direction of the right arrow in the drawing, mixed with the developer contained in the second stirring chamber 140 c, mixed, and supplied to the supply roller 143.

Stirring screw 145 and stirring screw 1
Since 46 has almost the same shape, the stirring screw 1
45 will be described as a representative.

FIG. 5A shows the stirring screw 14 of the present invention.
5 (b) and FIG. 5 (c) are AA partial sectional views of the stirring screw 145. FIG. Stirring screw 1
45 is a spiral blade portion 145 formed in a spiral shape.
a and a rotating shaft 145b rotatably supported by bearing members provided on both side walls of the developing device housing 140. The spiral blade 145a and the rotating shaft 145b may be formed by integral molding.
Further, the spiral blade portion 145a may be formed by joining a plurality of portions divided in the longitudinal direction.

The spiral blade 14 of the stirring screw 145
As a material forming 5a, Eflite FL202
(Manufactured by Nippon FTB) was used. In addition, Eflight FL302, Eflight FL201, Eflight F
L362 (all manufactured by Japan FTB) may be used. Further, ABS, modified PPE, PC, PE, PETP, P
F, POM, PS, PBT, PP, PA, PMMA, P
AI, PPS, PPO, PAR, PSF, PES, PE
Resins such as I, POB, and PEEK may be used. Furthermore,
Metals such as iron alloys, copper alloys, stainless steels, aluminum alloys and nickel alloys may be used.

FIG. 5B is a partial sectional view of the spiral blade 145a of the stirring screw 145 taken along the line AA shown in FIG.
Is the thickness of the root of the spiral blade, f is the thickness of the tip of the spiral blade, p is the pitch of the screw, and θ is the angle of inclination of the inclined surface 145c of the blade with the axis. Also,
D shown in FIG. 5A is the outer diameter of the spiral blade 145a of the stirring screw 145, d is the outer diameter of the rotating shaft 145b, h
Is the height of the peak of the spiral blade, and h = (D−d) / 2.

In the stirring screw 145 shown in FIG. 5C, the rotation of the stirring screw 145 causes the developer to apply a horizontal component Fh and a vertical component Fv by the inclined surface 145c of the spiral blade portion 145a. Can be The horizontal component force Fh transports the developer in the axial direction of the stirring screw 145, and the vertical component force Fv agitates the developer in a direction perpendicular to the axis.

In this case, the F value with respect to the screw pitch p of the spiral blade part 145a of the stirring screw 145 is
By designing in the range of “0.6 ≦ (F / p) ≦ 1”, the stirring property of the replenished toner supplied to the developing device 14 is improved,
Insufficient development and toner scattering due to running could be eliminated, and a stable image could be output.

For the stirring screw 145 in which the screw pitch p of the spiral blade portion 145a is 6 mm or more, the F value with respect to the screw pitch p is defined as:
“0.4 ≦ (F / p) ≦ 1” was effective.

Further, the thickness F of the root of the spiral blade part 145a, the thickness f of the tip part, and the pitch p of the screw are set as follows.
“5f ≦ F ≦ p” and “0.3 ≦ (F + f) / 2p ≦
1 and 30 ° ≦ θ ≦ 75 °, the developer stirrability is improved in the same manner as described above, and uneven charging of the developer due to poor stirring and insufficient development due to the presence of uncharged toner. In addition, various problems such as toner scattering, a toner lump falling on a transfer material on which an image is formed, and an image defect occurring are solved.

Hereinafter, embodiments of the developing device according to the present invention will be described.

(Example 1) Stirring time (t1) Replenished toner is supplied from the toner supply port 140d.
The developer is conveyed while being stirred and mixed with the developer by the stirring screw 145, and the toner concentration is detected by a toner concentration sensor provided near the opening 140e. Here, the stirring time until the replenishment toner was completely mixed with the developer and reached a predetermined toner concentration was measured. Alternatively, the mixed state of the black developer and the colored toner (for example, yellow toner) was visually determined.

[0044]

[Table 1]

Table 1 shows that the shape of the stirring screw 145 is set to the following numerical values, and various stirring screws in which the root thickness F of the spiral blade portion 145a is changed are prototyped.
This shows the result of measuring the stirring time t1 until the toner is completely mixed when the toner is mounted in the developing device 14 and the toner is supplied and the developer is mixed.

P = 7 mm, f = 0.6 mm, D = 10 m
m, d = 4 mm, h = 3 mm Length L of the spiral blade part 145a = 200 mm As a result, as shown in Table 1, the thickness F of the root of the spiral blade part with respect to the screw pitch p is set to “0”. .6 ≦
(F / p) ≦ 1, the stirring time t1 is 2
5 to 30 seconds was preferable (claim 1). But,
The stirring screw of “(F / p) ≦ 0.5” was not preferable because the stirring time t1 was 50 seconds or more. In addition, × in the table
The mark indicates that the mixing of the toner and the developer is defective.

[0047]

[Table 2]

Table 2 shows the results of measuring the stirring time t1 until the toner is completely mixed in the same manner as described above, except that the shape of the stirring screw 145 is changed to the one described above, and the following numerical values are set. It is.

P = 14 mm, f = 1 mm, D = 14 m
m, d = 6 mm, h = 4 mm Length of the spiral blade 145a L = 200 mm As a result, as shown in Table 2, the thickness F of the root of the spiral blade relative to the screw pitch p is set to “0”. .4 ≦
(F / p) ≦ 1, the pitch was within the range of “p ≧ 6 mm”, but the stirring time t1 was preferably 25 to 40 seconds (claim 2). However, “(F / p) ≦ 0.3”
The stirring screw t was not preferable when the stirring time t was 70 seconds or more. In addition, the mark x in the table indicates that the mixing of the toner and the developer is defective.

[0050]

[Table 3]

Table 3 shows the results obtained by changing the shape of the stirring screw 145 to the above and setting the following values, and measuring the stirring time t1 until the toner is completely mixed in the same manner as described above. It is.

P = 16 mm, f = 1 mm, D = 14 m
m, d = 6 mm, h = 4 mm Length L of the spiral blade 145a = 250 mm As a result, as shown in Table 3, the thickness F value of the root of the spiral blade is set to “5f ≦ F ≦ p”. However, the stirring time t1 is preferably 25 to 30 seconds (claim 3). That is, when f = 1 mm, F = 5 mm (= 5f) or more, F
= 14 mm (= 14f = p) or less. However, a stirring screw having an F value of 4 mm (= 4f) or less is not preferable if the stirring time t is 60 seconds or more. In addition, the mark x in the table indicates that the mixing of the toner and the developer is defective.

[0053]

[Table 4]

Table 4 shows the results of measuring the stirring time t1 until the toner is completely mixed in the same manner as described above, except that the shape of the stirring screw 145 is changed to that described above and the following numerical values are set. It is.

P = 16 mm, f = 1 mm, D = 16 m
m, d = 6 mm, h = 5 mm Length L of the spiral blade part 145a = 250 mm As a result, as shown in Table 4, the spiral blade part is set to “0.
Although the range of 3 ≦ (F + f) /2p≦0.7 ”was satisfied, the stirring time t1 was preferably 25 to 40 seconds (claim 4). However, a stirring screw having (F + f) / 2p of 0.25 or less or 0.8 or more was not preferable because the stirring time was 50 seconds or more. In addition, the mark x in the table indicates that the mixing of the toner and the developer is defective.

[0056]

[Table 5]

Table 5 shows that the angle of inclination θ of the spiral blade 145a of the stirring screw 145 is 5 to 9
This figure shows the result of measuring the stirring time t1 until the toner is completely mixed in the same manner as described above, with the angle set at 0 °.

P = 16 mm, h = 5 mm, D = 16 m
m, L = 250 mm, d = 6 mm As a result, as shown in Table 5, although the inclination angle θ of the spiral blade was in the range of 30 to 75 °, the stirring time t1 was 20 to
30 seconds was suitable (claim 5). However, the inclination angle θ
Is 25 ° or less, or 80 ° or more stirring screw,
The stirring time required was 40 seconds or more, which was not preferable.

(Example 2) Charge amount rise time (t)
2) The rise time of the charge amount (-μc / g) of the developer was compared. The rise time means that the unmixed carrier and the toner are separately accommodated in the developing device housing 140, and the stirring screw 145 is driven and rotated to charge the developer.

FIG. 6 is a characteristic diagram showing the relationship between the developer stirring time and the charge amount of the developer (-μc / g).

During the rotation of the stirring screw 145, the charge amount of the developer rises, and a time t2 until the charge amount is saturated was measured.

[0062]

[Table 6]

Table 6 shows the charge amount rise time t of the developer.
2 shows the result of measurement. The specifications of the stirring screw 145 are the same as those in Table 1 described above. As a result, as shown in Table 6, the charge amount rising time t2 is
[F / p] of the stirring screw 145 is set to 0.6 or more,
The following range was suitable (claim 1). However, the stirring screw of “(F / p) ≦ 0.5” was not preferable because the charge amount rising time t2 was 60 seconds or more.

[0064]

[Table 7]

Table 7 shows that the shape of the stirring screw 145 was changed to that shown in Table 1 above and set to the same specifications as those in Table 2, and the charging amount rise time t2 of the developer was set in the same manner as described above. It shows the result of the measurement. As a result, Table 7
As shown in (2), the charge amount rising time t2 is preferably such that the (F / p) of the stirring screw 145 is in the range of 0.4 or more and 1 or less (Claim 2). But,
The stirring screw with “(F / p) ≦ 0.3” was not preferable because the charge amount rising time t2 was 55 seconds or more.

[0066]

[Table 8]

Table 8 shows that the shape of the stirring screw 145 was changed to that of Table 2 above and set to the same specifications as in Table 3, and the charging amount rise time t2 of the developer was set in the same manner as described above. It shows the result of the measurement. As a result, Table 8
As shown in the figure, the charging amount rising time t2 is such that the thickness F of the root of the spiral blade portion of the stirring screw 145 is 5 mm.
As described above, those having a range of 14 mm or less were preferable (claim 3). However, a stirring screw having a root thickness F of 4 mm or less was not preferable because the charge amount rising time t2 was 65 seconds or more.

[0068]

[Table 9]

Table 9 shows that the shape of the stirring screw 145 was changed to that shown in Table 3 above, and was set to the same specifications as those in Table 4. Similarly to the above, the rise time t2 of the charge amount of the developer was changed. It shows the result of the measurement. As a result, Table 9
As shown in the figure, the charge amount rising time t2 is preferably such that the spiral blade portion is in the range of “0.3 ≦ (F + f) /2p≦0.7” and the charge amount rising time t2 is 30 to 35 seconds. (Claim 4). However, (F + f) / 2
Stirring screws with p of 0.25 or less or 0.8 or more had an unpreferable charge amount rise time t2 of 50 seconds or more.

[0070]

[Table 10]

Table 10 shows that the inclination angle θ of the spiral blade 145a of the stirring screw 145 is 5 to 5.
The figure shows the result of measuring the rise time t2 of the charge amount of the developer in the same manner as described above, with the angle set at 90 °.

P = 16 mm, h = 5 mm, D = 16 m
m, d = 6 mm, L = 250 mm As a result, as shown in Table 10, the inclination angle θ of the spiral blade portion
Was set in the range of 30 to 75 °, but the stirring time t2 was 30.
It was preferably from 35 to 35 seconds (claim 5). However, a stirring screw having an inclination angle θ of 25 ° or less or 80 ° or more requires a charge amount rising time t2 of 45 seconds or more, which is not preferable.

Example 3 Image Density A comparison result of a running test between the image density obtained by a conventional developing device having a stirring screw and the image density obtained by a developing device having a stirring screw according to the present invention is shown in FIG.
(A) and the characteristic diagram of FIG. 7 (b). In these figures, the horizontal axis represents the number of prints, and the vertical axis represents the image density.

FIG. 7A is a characteristic diagram showing a change in image density by a conventional stirring screw. The specifications of the stirring screw used in this running test are shown below.

P = 14 mm, f = 1 mm, F = 3.5 m
m, D = 14 mm, d = 6 mm, L = 120 mm, rotation speed = 170 rpm As shown in FIG.
The stirring and mixing ability of the developer and the toner is low, and the image density decreases as the number of prints increases.

On the other hand, the stirring screw 1 of the present invention
No. 45 has a high stirring and mixing ability of the developer and the toner as described in Examples 1 and 2, and as shown in FIG.
Even if the number of prints increases, the image density is kept substantially constant. The specifications of the stirring screw 145 of the present invention used in this running test are shown below. The stirring screw 145 satisfies the conditions of claims 1 to 4 of the present invention.

P = 14 mm, f = 1 mm, F = 12 m
m, D = 14 mm, d = 6 mm, L = 120 mm, number of rotations = 170 rpm (Example 4) Charge amount of developer A charge amount of a developer by a developing device having a conventional stirring screw and a stirring screw according to the present invention are provided. 8 (a) and 8 (b) show the results of a running test of the amount of developer charged by the developing device and a running test. In these figures, the horizontal axis represents the number of prints, and the vertical axis represents the charge amount of the developer.

FIG. 8A is a characteristic diagram showing a change in the amount of developer charge by a conventional stirring screw. The specifications of the stirring screw used in this running test are the same as those in Example 3. As shown in FIG. 8A, in the conventional stirring screw, the charge amount when stirring and mixing the developer and the toner decreases as the number of prints increases. In particular, toner scattering starts when the number of prints is about 10,000.

On the other hand, the stirring screw 1 of the present invention
No. 45 has a high stirring and mixing ability of the developer and the toner as described in Examples 1 and 2, and as shown in FIG.
Even if the number of prints increases, the charge amount is kept almost constant,
A stable image can be obtained. The specifications of the stirring screw 145 of the present invention used in the running test are the same as those of the third embodiment, and the stirring screw 145 satisfies the conditions of claims 1 to 6 of the present invention.

(Example 5) Developer charge amount distribution A running charge test was performed on the developer charge amount distribution obtained by the conventional developer provided with the stirring screw and the developer charge amount distribution obtained by the developer provided with the stirring screw according to the present invention. The results of the comparison are shown in the characteristic diagram of FIG.

FIG. 9A shows the initial charge amount distribution of the developer, and FIG. 9B shows the charge amount distribution of the developer by the developing device having the stirring screw of the present invention. The parentheses indicate the distribution of the amount of charge of the developer after copying 36,000 sheets with a conventional developing device equipped with a stirring screw.

<Measurement of Charge Amount Distribution> For measuring the charge amount distribution of the toner, a particle charge amount distribution measuring apparatus E-SPART Analyzer (manufactured by Hosokawa Micron Corporation) was used. This apparatus detects the motion of particles in an air vibration field in an electric field by a laser Doppler method, and simultaneously measures the number, particle size, and charge amount of individual particles based on the data.

<Image Forming Conditions> Konica Colo, a full-color laser printer of non-contact two-component developing system
r Laser Bit KL-2010 (manufactured by Konica Corporation) was improved, and a developer was loaded into the developing device having the configuration shown in FIGS. 3 and 4, and actual printing was performed at a printing rate of 12%. 3
The charge distribution of the developer after printing 6,000 sheets was measured using the above-described particle charge distribution measuring device, and the difference between the stirring screw of the present invention and the conventional stirring screw was compared.

As shown in FIG. 9B, the charge amount distribution of the toner by the stirring screw of the present invention has a sharp charge amount distribution concentrated around -20 μc / g which is almost equal to the initial charge amount distribution. I confirmed that.

On the other hand, in the conventional stirring screw, the distribution of the charge amount is widened, and the frequency of the number of toners is also reduced. If the charge amount of the toner is too large, it is difficult for the toner to fly from the developing sleeve 141 toward the photosensitive drum 10 in the developing area, and it is difficult to perform stable non-contact development. Further, when the charge amount of the toner is small, uncharged toner or weakly charged toner is generated, the toner is scattered from the surface of the developing sleeve 141, and image fogging and defective development occur.

As described above, by using the stirring screw of the present invention, the stirring property of the replenished toner replenished to the developing device 14 is improved, and insufficient development due to running and toner scattering can be eliminated. It is possible to output an image. In addition, problems such as uneven charging of the developer due to poor stirring, insufficient development due to the presence of uncharged toner, toner scattering, and the occurrence of image defects due to the lump of toner falling on the transfer material on which an image is formed are solved. You.

In particular, in color development, a stable stirring amount screw of the present invention can provide an excellent image quality without color turbidity during superposition development of multiple colors due to a stable charge amount distribution.

The developing device of the present invention is not limited to a color image forming apparatus having a plurality of developing units, but can be applied to a monochrome image forming apparatus having one developing device. However, in the case of a color image forming apparatus, the effects such as downsizing of the apparatus and cost reduction are particularly remarkable.

[0089]

According to the agitating screw of the present invention provided in the developing device, (1) the time during which the replenishment toner and the developer are completely stirred and mixed is reduced (2) the rise time of the charge amount of the developer (3) The image density does not decrease even when printing a large number of continuous sheets. (4) There are excellent effects such as the charge amount does not decrease even when printing a large number of continuous sheets.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color printer as an example of an image forming apparatus equipped with a developing device of the present invention.

FIG. 2 is a sectional view of a developing device having a plurality of developing devices.

FIG. 3 is a sectional view of a developing device.

FIG. 4 is a plan sectional view of the developing device.

FIG. 5 is a front view and an AA partial cross-sectional view of a stirring screw.

FIG. 6 is a characteristic diagram illustrating a relationship between a developer stirring time and a charge amount of a developer.

FIG. 7 is a characteristic diagram showing a change in image density during a running test using a conventional stirring screw and the stirring screw of the present invention.

FIG. 8 is a characteristic diagram showing a change in developer charge amount during a running test using a conventional stirring screw and the stirring screw of the present invention.

FIG. 9 is a comparison characteristic diagram of a developer charge amount distribution by a stirring screw of the present invention and a conventional stirring screw.

[Explanation of symbols]

Reference Signs List 10 photoconductor drum (image carrier) 14 developing device 14Y, 14M, 14C, 14K developing device 140 developing device housing 140a partition wall 140b first stirring chamber 140c second stirring chamber 140d toner supply port 141 developer carrier (Developing sleeve) 142 Magnetic field generating means (magnet roll) 143 Developer supply roller (supply roller) 144 Developer layer thickness regulating member 145, 146 Developer stirring screw (stirring screw) 145a Spiral blade 145b Rotating shaft 145c Inclined Surface F Root thickness f Tip thickness p Screw pitch θ Tilt angle

Claims (13)

[Claims] 1. A developing device comprising: a developer carrier for conveying a developer to a developing area of an image carrier; and a stirring screw for stirring and conveying the developer, wherein a helical blade portion of the stirring screw is provided. A developing device characterized in that a root thickness (F) and a pitch (p) of the stirring screw satisfy 0.6 ≦ (F / p) ≦ 1. 2. A developing device comprising: a developer carrier for conveying the developer to a developing area of the image carrier; and a stirring screw for stirring and conveying the developer, wherein a helical blade of the stirring screw is provided. The thickness of the root (F) and the pitch (p) of the stirring screw are 0.4 ≦ (F / p) ≦ 1, p ≧
A developing device having a thickness of 6 mm. 3. A developing device comprising: a developer carrier for conveying the developer to a developing area of the image carrier; and a stirring screw for stirring and transporting the developer, wherein the helical blade portion of the stirring screw is provided. A developing device characterized in that the root thickness (F), the tip thickness (f) of the stirring screw spiral blade and the pitch (p) of the stirring screw satisfy 5f ≦ F ≦ p. 4. A developing device comprising: a developer carrier for conveying the developer to a developing area of the image carrier; and a stirring screw for stirring and conveying the developer, wherein the helical blade portion of the stirring screw is provided. The thickness (F) of the root, the thickness (f) of the tip of the spiral blade of the stirring screw and the pitch (p) of the stirring screw are 0.3 ≦ (F + f) / 2p ≦ 0.
7. A developing device according to claim 7. 5. A developing device comprising: a developer carrier for transporting a developer to a development area of an image carrier; and a stirring screw for stirring the developer and transporting the developer to the developer carrier, wherein the stirring screw rotates A developing device comprising a shaft and a spiral blade provided on the rotation shaft, wherein the blade has an axial spiral angle (θ) of 30 to 75 °. 6. The stirring screw having an outer diameter (D) of 5
The developing device according to claim 1, wherein the thickness is 0 mm or less. 7. The developing device according to claim 1, wherein the developer is a two-component developer including magnetic carrier particles and toner particles. 8. An image forming apparatus comprising: a developing device for forming a developing region in which an image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer for developing the electrostatic latent image are opposed to each other. In the apparatus, the developing device includes a stirring screw for stirring the developer and transporting the developer to the developer carrier, wherein the stirring screw is the stirring screw according to any one of claims 1 to 6. Characteristic image forming apparatus. 9. A bias electric field for superimposing an AC component on a DC component is applied to the developing area, and the developer on the developer carrier flies to an electrostatic latent image on the image carrier, and The image forming apparatus according to claim 8, wherein the latent image is visualized. 10. The image forming apparatus according to claim 8, wherein the developer is a two-component developer including magnetic carrier particles and toner particles. 11. The image forming apparatus according to claim 1, wherein at least two developing devices having different developers are provided around the image bearing member. 12. A bias electric field for superimposing an AC component on a DC component is applied to the developer carrier, and the developer on the developer carrier flies to an electrostatic latent image on an image carrier. 9. The image forming apparatus according to claim 8, wherein the image forming apparatus performs non-contact development for visualizing an electrostatic latent image. 13. The image forming apparatus according to claim 8, wherein the developing device is a reversal developing method in which a developer is attached to a portion of the latent image from which the electric charge has been removed from the uniformly charged surface on the image carrier. Image forming apparatus.