JP2997016B2 - Developing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a developing device such as a copying machine or a printer using a powder developer.

(Prior Art) Conventionally, the developing device has a developing roller composed of a magnet body and a sleeve external to the magnet body, and a developer held on an outer peripheral portion of the sleeve is brought into contact with a photosensitive member. One that visualizes an electrostatic latent image has been proposed. As shown in FIGS. 15 and 20, this developing device fixes the magnet body 23 in a non-rotating state, and inner pole fixed types 21a and 21b around which a cylindrical sleeve 22 rotates in the direction of arrow a. As shown in FIG. 21, the magnet body 23 and the sleeve 22 are roughly divided into an inner pole rotating type 21c in which both rotate in the direction of arrow a '.

In addition, as shown in FIG. 15, the inner-pole fixed type developing device has a plurality of magnetic poles N, S, N,... A single-pole type developing device 21a in which one magnetic pole N is arranged opposite to the region Q and only the developer held by the magnetic pole N is brought into contact with the photoreceptor 20, as shown in FIG. The polarities of the same polarity N ₁ , N ₂ are provided adjacent to the outer peripheral portion of the magnet body 23 facing the development area Q, and the developer held by these two magnetic poles N ₁ , N ₂ is applied to the photoconductor 20 together. It can be classified into the same polarity type developing device 21b in contact.

(Problems to be Solved by the Invention) However, each of these developing devices 21a, 21b, and 21c has the following problems.

I. The first problem with the monopolar developing device 21a is that the developer 26 confined by the magnetic pole N facing the photoconductor 20
As shown in FIG. 16, the toner adhering amount at the peripheral portion (edge portion) 31 of the visualized toner image 30 is smaller than that at the central portion 32 as shown in FIG. And the so-called edge effect is overemphasized. Note that the edge effect is closely related to the developer density at the time of separation from the photoconductor 20, and the edge effect becomes stronger as the developer density in this portion is higher.

Also, as shown in FIG. 17, when the toner image 30 with the edge effect enhanced is fused and fixed on a recording medium 27 such as paper, the toner at the edge portion 31 spreads around, and the adjacent toner images come into contact with each other to improve the image quality. Decrease. In particular, in the case of a dot image,
The halftone dots are crushed, and the image quality is significantly deteriorated.

Further, as shown in FIG.
When an image is formed by superimposing a, 40b, and 40c, the color tone is different between the edge portion 41 and the central portion 42, and the quality of the color image is reduced.

A second problem is that the toner at the leading or trailing edge of the image is scraped off by the magnetic brush to produce a rubbing pattern.

Specifically, the process in which the rear end blurring pattern occurs will be described with reference to FIGS. 22a to 22c.

In the development area Q, the electrostatic latent image portion I ₁ (V _i = −300 V)
Is completed, the non-image portion of electrostatic latent image I ₀ (V ₀ =
−50 V) advances to the development area Q, the carrier Ca at the tip of the magnetic brush, which comes into contact with the non-image portion I ₀ of the electrostatic latent image.
In this case, charges (negative charges) having a polarity opposite to that of the toner To appear on the opposing surface of the photoconductor 20. This is a magnetic brush, carrier Ca
Since toner To adsorbed (positively charged) is moved to the pulled by the sleeve portion of the development bias is applied to the sleeve 22 (V _B = -150 V) (upward in the drawing), electric charge remains in the marks on the It is. As a result, the toner To at the rear end of the image adhered to the photoreceptor 20 becomes the carrier Ca at the tip of the magnetic brush.
The carrier Ca is scraped off by the magnetic brush by the mechanical contact force and the electric attraction force of the carrier Ca, and the scraping marks appear on the image as a flared pattern. A front-end pattern is also generated in the same manner.

The third problem is that, when developing an image in which a high-density image follows a low-density image, the toner at the rear end of the low-density image is scraped off, so-called white spots occur in the lead portion.

The process in which the lead portion white spot occurs will be described with reference to FIGS. 23a to 23c.

When the low-density image electrostatic latent image I ₁ (V _i1 = −300 V) is followed by the high-density image electrostatic contact image I ₂ (V _i2 = −600 V), the electrostatic latent images I ₁ and I in the development area Q ₂ are developed sequentially. At this time, when in contact therewith kept pace with the toner carrier Ca of the magnetic brush that lost toner To develops the electrostatic latent image I ₂ of the high-density image is attached to the low-density image electrostatic latent image I ₁ The electrostatic latent image I ₁ of the low-density image is formed by the electric brushing force generated between the scraping force of the magnetic brush and the electric charge remaining after the toner has been lost.
The toner To attached to the rear end portion of the image is scraped off, and a white spot in the image occurs in the scraping trace.

The fourth problem is that the regulating plate 25 is opposed to the regulating plate 25 to regulate the amount of the developer to be conveyed to the developing area Q while maintaining a minute gap on the outer peripheral surface of the sleeve.
If a foreign substance such as a lump of toner or paper dust is clogged between the developer and the developer 22, the developer 26 is rejected by the foreign substance, and a white streak-like image defect portion appears on the image.

The fifth problem is that the carrier that has lost toner due to development
As shown in FIG. 19, Ca adheres to the photoreceptor 20 due to the sneak electric field E generated at the boundary between the electrostatic latent image portion (-600 V region) and the non-image portion (-50 V region). That's what it means.

B. Unipolar developing device 21b In the unipolar developing device 21b, the unipolar developing device 21a
Similarly to the above, since the density of the developer at the time of separation from the photoreceptor 20 is high, the edge effect is excessively emphasized, the leading end or the trailing end of the image is sharpened, the lead portion becomes blank, and carrier adhesion is reduced. A problem.

However, in the present developing device 21b, two developer stand portions 26a and 26b are formed at a portion facing the photoconductor 20, and the developer is the first developer.
The developer 26 flies from the spike portion 26a toward the second spike portion 26b. At this time, the developer 26 is disturbed in the axial direction of the sleeve 22. That is, the developer is disturbed in the three-dimensional direction.

Therefore, the developer-free portion formed by the toner repelled by the foreign matter caught on the leading end of the regulating portion 25 is erased by the nearby developer, and even if the foreign matter is clogged at the leading end of the regulating portion 25, white streaks appear on the image. No image-deficient portions appear.

C. Inner-Pole-Rotating Developing Device 21c The inner-pole-rotating-type developing device 21c has a problem that the edge effect is excessively emphasized and that carrier adhesion is larger than that of the inner-pole-fixed developing device.

The edge effect is emphasized for the same reason as in the case of the inner-pole fixed developing devices 21a and 21b.

In the case of the inner-pole rotating type developing device 21c, since the spikes of the developer 26 rotate at high speed together with the magnet 23 in the case of the inner-pole rotating type developing device 21c, the centrifugal force acting on the carrier causes the inner-pole fixed type developing device 21c.
This is because the magnetic attraction force to the developer when moving away from the photoconductor 20 changes periodically as the magnetic pole passes.

The leading and trailing edges of the image do not occur for the following reason. This will be described with reference to FIGS. 24a to 24c.

Image of the electrostatic Sezzo image portion I ₁ is completed, the electrostatic latent image non-image portion
When I ₀ advances to the developing area, toner (positive charge) is applied to the sleeve 22 by the magnetic brush in contact with the non-image portion I ₀ of the electrostatic latent image.
The development bias V _B (= -150 V) to the drawn by moving the sleeve side, the photosensitive member opposed surface to the toner and opposite polarity charges in the sleeve 22 (negative charge) will appear. However, the carrier Ca is a magnet
Since moving the sleeve side (upward in the drawing) with the rotation of 23, without electric attraction force acting between the toner To adhering to the carrier Ca and the image portion the electrostatic latent image I _1, also The toner at the leading or trailing edge of the image without being electrically sucked
It does not mean that the To is scraped off and a flared pattern appears on the image.

The reason why the lead portion does not have white spots is as follows. No.
This will be described with reference to FIGS. 25a to 25c.

Carrier Ca lost toner developing low density image electrostatic latent image I ₁ and the high density image electrostatic latent image I _2, as described above, to retreat from the tip of the magnetic plush with the rotation of the magnet body 23, the sleeve Move to the front side. Therefore, the carrier Ca that has lost the toner To contacts the toner To attached to the photoconductor 20,
The toner To is not scraped off. therefore,
No white spots appear on the image.

The white streak does not appear in the image due to foreign matter clogging at the tip of the regulating part because the developer is three-dimensionally disturbed by the rotation of the magnet body 23 and is close to the developer-free part where the developer is removed by the foreign matter. This is because the developer is filled and erased.

The problems of the developing devices 21a, 21b, 21c are summarized in Table 1 below.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and is a sleeve (2) that moves around a fixed magnet body (3).
Developer consisting of carrier and toner on the outer periphery of the toner (6)
And the developer (6) is brought into contact with the photoreceptor (10) to visualize the electrostatic latent image in the developing device. (N ₁ , N ₂ ) are arranged adjacent to each other, and one of these magnetic poles (N ₁ , N ₂ ) is located on the upstream side in the moving direction (direction of arrow a) of the sleeve (2) passing through the photoconductor facing portion. The developer (7) constrained by the magnetic pole (N ₁ ) is brought into contact with the photoconductor (10), and the developer (8) constrained by the other magnetic pole (N ₂ ) is not in contact with the photoconductor (10). It is what it was. Note that a magnetic body (12) or a magnetic field generating means having a polarity different from that of the magnetic pole may be provided near the magnetic pole (N ₂ ) located on the downstream side.

(Operation) According to the above configuration, the developer (6) is transported from the magnetic pole (N ₁ ) toward the magnetic pole (N ₂ ) in the direction of the arrow (a) according to the rotation of the sleeve (2).

Here, since an opposite magnetic field acts between the magnetic pole (N ₁ ) and the magnetic pole (N ₂ ) having the same polarity as the magnetic pole (N ₁ ), the developer (6) is applied to the magnetic pole (N ₁ ) at the opposite portion of the magnetic pole (N ₁ ). N ₁ ), and the photoreceptor (10) is affected by the repulsive magnetic force of the magnetic pole (N ₂ ).
Is formed, and the developer is stirred in the direction opposite to the conveying direction or in the axial direction, that is, in the three-dimensional direction.

Then, the developer (6) forming the spike portion (7) is pushed by the developer (6) sequentially transported from the upstream side, and
From the _one that can no longer be held in the magnetic field (H ₁ ), it sequentially flies to the magnetic pole (N ₂ ). During flight, the developer (6) is not in contact with the photoconductor (10).

In the case where the magnetic material (12) is provided, the developer flying from the upstream spike (7) becomes the magnetic pole (N ₂ ) and the magnetic material (12).
Magnetic field (N ₂ )
The contact between the developer held in the photoconductor (10) and the photoconductor (10) can be reliably prevented, and the developer is prevented from dropping. Further, when the magnetic material (12) is arranged so that a developer chain is formed between the magnetic pole (N ₂ ) and the magnetic material (12), toner scattering generated at the N ₂ pole can be suppressed, and S ₂ It is also possible to prevent toner scattering generated in the developing device after the pole from blowing out to the photoconductor side.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a developing section of a developing device according to the present invention, and a developing roller 1 includes a sleeve 2 and a magnet body 3.

The sleeve 2 is opposed with a predetermined gap with the photoreceptor 10, the bias V _B is applied from the power source 4, it is to be rotated in the direction of arrow a. The regulating plate 5 faces the upper outer peripheral surface of the sleeve 2 with a prescribed regulating gap.

The magnet body 3 has a plurality of magnetic poles extending in the axial direction of the sleeve 2 on the outer peripheral portion. The magnetic pole N _{1 is} located upstream of the portion facing the photoreceptor 10 in the sleeve moving direction, and the same polarity is located downstream. pole N ₂ is arranged. Further, the magnetic pole S ₁ of opposite polarity and which on the upstream side of the magnetic pole N ₁ is, the magnetic pole S ₂ of opposite polarity and which on the downstream side of the magnetic pole N ₂ is is arranged respectively. The magnetic poles are arranged in other regions, but are not shown in the drawings.

Since the magnetic poles S ₁ , N ₁ , N ₂ , and S ₂ are arranged as described above, magnetic fields H ₁ and H ₂ as shown in FIG. Formed and magnetic pole N ₁
The magnetic lines converge the magnetic pole S ₁ on the upstream side, the magnetic force lines of the magnetic poles N ₂ converges to the magnetic pole S ₂ on the downstream side, between the magnetic poles N ₁ and the magnetic pole N _2, the magnetic field H ₁ and the magnetic field H ₂ Have become contradictory.

In the above configuration, the two-component powder developer 6 including the toner and the carrier is transferred to the sleeve 2 by the magnetic force of the magnet body 3.
Are conveyed in the direction of arrow a with the rotation of the sleeve 2, and the amount of conveyance is regulated by the leading end opposing portion of the regulating plate 5.

Developer 6 which has passed through the distal end of the regulating plate 5 is conveyed to the portion facing the pole N ₁ through the opposite portion of the magnetic pole S _1, where the magnetic field lines of the magnetic pole N ₁ is toward the pole S ₁ Due to the formation and the formation of the repulsive magnetic field between the magnetic poles N ₁ and N ₂ , the developer forms the spikes 7 along the lines of magnetic force at the opposing portion of the magnetic pole N ₁ , Contact body 10. If this time is formed an electrostatic latent image on the surface of the photosensitive member 10 is adhered to the electrostatic latent image portion of the toner based on the electrostatic contrast between the potential and the bias V _B of the electrostatic latent image.

Developer 6 of Horitsu portion 7 is pushed to the developer 6 which come sequentially transported to, will fly to the magnetic pole N ₂ from those that are no longer able to hold the magnetic field H ₁ of the magnetic pole N _1. During flight, the developer 6 is not in contact with the photoconductor 10. Therefore, toner fog does not occur in front of the image area.

That is, when the flying developer collides with the surface of the photoconductor 10, as shown in FIGS. 8a to 8c, the electrostatic latent image
Toner To adhering to I ₂ is ejected, this ejected toner To is to produce a toner fogging adhered to the electrostatic latent image bullet image portion I _0, is the developer flying in the developing device Since it does not collide with the photoreceptor 10, toner fogging due to the collision of the flying developer does not occur as described above.

The developer that has flown from the spike 7 is held in the magnetic field H ₂ of the magnetic pole N ₂ and moves in the direction of the arrow a as the sleeve 2 rotates again. Further, the toner adhered to the photoconductor 10 is transferred to a recording medium in a transfer step (not shown), and is further fused and fixed to the storage medium in a fixing step.

Here, the density of the developer 6 that is to fly from the spike portion 7 is low. That is, the density of the developer 6 when it is separated from the photoconductor 10 is low. Therefore, as shown in FIG. 3, a large amount of toner does not adhere to only the edge portion of the electrostatic latent image, and substantially the same amount of toner adheres to the whole, and a toner image (image) having a weak edge effect 9 can be obtained, and even if toner images 9a, 9b, 9c of different colors are overlapped, the overall color tone can be made the same.

Further, the opposing portions of the magnetic poles N _1, as shown in FIG. 5, since magnetic field lines H ₁ being generated from the magnetic pole N ₁ is growing toward the magnetic pole S ₁ on the upstream side, the magnetic brush is the magnetic field lines along becomes sleep state, the developer of the distal end side receives a force in the direction of reverse flow from the magnetic pole N ₁ along the magnetic field lines H ₁ to the magnetic pole S _1.

Further, as shown in Figure 6a, second 6c diagrams that in the magnetic brush in contact with the electrostatic latent image non-image area I _0, electrical toner held on the carrier Ca is the developing bias V _B (= -150V) The carrier Ca moves toward the sleeve side, and a charge having a polarity opposite to that of the toner appears in the photoconductor-facing portion of the carrier Ca. However, since a force in the direction opposite to the magnetic brush transport direction is received as described above,
The carrier Ca at the tip of the magnetic brush is on the sleeve side (upper side in the figure)
Go to Therefore, the electric scraping force of the carrier Ca against the toner is weak, and the leading and trailing edges of the image are not blurred.

Similarly, as shown in 7c view from the 7a view, even if the high-density image electrostatic latent image I ₂ after low-density image electrostatic latent image I ₁ is followed, the toner of the low-density image rear end The lead brush is not scraped off by the supporting brush, and no white spots are generated.

Furthermore, the Horitsu portion 7 is formed in the opposing portions of the magnetic poles N _1,
Since the developer is disturbed in the three-dimensional direction, even if the regulating plate 5
Even if foreign matter is clogged between the sleeve and the sleeve 2, the developer is supplied to the portion of the developer where the foreign matter is not present, and an image without image defects such as white stripes is obtained.

Furthermore, since the density of the developer 6 at the time of leaving the photoconductor 10 is low and the kinetic energy of the developer 6 flying from the spike portion 7 is large, the carrier which has lost the toner may be located at the periphery of the electrostatic latent image. Adherence to the photoreceptor due to the sneak electric field is small, and carrier adhesion to the photoreceptor 10 is reduced.

The developing device of the present invention is not limited to the above embodiment.

That is, although a two-component developer composed of a toner carrier is used as the developer, the present invention can be applied to a developing device using a so-called one-component magnetic developer.

Further, in order to suppress the toner scattering in the magnetic poles N _2, magnetic poles N ₂
With a placed inside of the casing 11, the developer 6 to fly from the magnetic pole N ₁ to the magnetic pole N ₂ in order to prevent the falling from the developing device, further the flying developer does not contact the photosensitive member for, as shown in FIG. 9, the magnetic body 12 opposed to the magnetic pole N ₂ to the casing 11, the magnetic body
In the magnetic field formed between the 12 and the magnetic pole N ₂ may be captured developer.

Further, as shown in FIG. 10, a plurality of developing rollers 13 and 14 similar to the developing roller 1 may be arranged on the side of the photosensitive member 10. This makes it possible to obtain a flat image with a weak edge effect in a high-speed copying machine.

Further, as shown in FIG.
The same developing roller 15 and the monopolar developing roller 16 are continuously arranged, and these two developing rollers 15, 16 are simultaneously driven to form an image having a weak edge effect by the first developing roller 15. Alternatively, an image with an effective edge effect may be formed by the second developing roller 16. In this case, a solid image and a line image can be reproduced while maintaining these features. In addition, as shown in FIG. 12, the arrangement order of the developing rollers 15 and 16 may be reversed.

Then, as shown in FIG. 13, along with the moving direction of the photoconductor 10, four developing devices 17Y, 17M, 17C, 17BX each including yellow, magenta, cyan, and black toners are arranged, First to third developing devices 17Y and 17
The developing roller 1 of the above embodiment may be used for M and 17C, and the conventional developing roller 21 may be used for the fourth developing device 17BK.

In this case, the first to third developing devices 17Y, 17M, 17C
The color image created by the above has a weak edge effect. Therefore, even when these three colors are superimposed, images in all areas including the edge portion are reproduced with the same color tone. Further, only the black image has an edge effect by the fourth developing device 17BK. The reason why the edge effect is applied only to the black image is that the black image generally has many line images. However, if necessary, the fourth developing device 17BK may employ the developing roller of the above-described embodiment similarly to the other developing devices 17Y, 17M, and 17C.

Further, as shown in FIG.
As for BK, a magnetic pole of the same polarity may be arranged adjacent to the opposing portion of the photoconductor 10 so that the developer held by both magnetic poles may be brought into contact with the photoconductor together. In this case, since the developer density at the time of separation between the developer and the photoconductor is high, the black image visualized by the present developing device has an edge effect. In this case, although not shown, other than a method of once transferring the image from the photoconductor 10 to the intermediate transfer body or the recording paper and then developing the next color, the scraping force of the developing device is weak. It is also possible to superimpose toner images sequentially.

(Effects of the Invention) As is clear from the above description, according to the developing device of the present invention, the developer density when separated from the photoconductor is low. Therefore, a large amount of toner does not adhere only to the edge portion of the electrostatic latent image, and an image having a weak edge effect can be obtained. Therefore, even when a halftone image document is developed, individual halftone dots are accurately reproduced, and even in an image forming method in which a plurality of color images are superimposed to form an image, an image having a uniform density can be obtained as a whole. be able to.

Next, in the opposing portion of the upstream magnetic pole, the magnetic lines of force generated from this magnetic pole are formed further toward the upstream magnetic pole, so that the tip of the magnetic brush is laid down and the upstream To receive the force that flows back to the magnetic pole,
The toner scraping effect is weaker than that of a magnetic brush of a conventional developing device which extends substantially linearly. Therefore, the streaking at the leading end of the image and the blurring at the trailing end are reduced, an image having a sharp outline can be obtained, and whiteout of the lead can be prevented.

Subsequently, the developer is three-dimensionally disturbed at the developer spike formed at the opposite part of the magnetic pole, so that even if the foreign matter is clogged between the regulating plate and the sleeve, the developer corresponding to the foreign matter is developed. The portion where no agent is present is erased, and an image without white streaks is obtained.

And that the density of the developer in contact with the photoconductor is low,
In addition, since the kinetic energy of the developer flying from the developer spike is large, the probability that the carrier adheres to the photoconductor due to the wraparound electric field at the peripheral portion of the electrostatic latent image is extremely low, and the carrier adhesion to the photoconductor is reduced. I do.

That is, the developing device according to the present invention can obtain an image having a uniform density without emphasizing the edge effect as compared with the conventional developing device. (C) No white streaks appear on the image even if foreign matter is clogged at the tip of the regulating portion.
(D) There are various advantages such as no carrier adhesion on the photoreceptor or the recording medium.

Further, when a magnetic body is provided in proximity to the downstream magnetic pole, the developer flying from the upstream magnetic pole facing portion is reliably captured by the magnetic field formed between the magnetic pole and the magnetic body, and Contact between the developer held by the magnetic pole and the photoconductor is reliably prevented. In addition, since the flying developer is prevented from dropping, the inside of the image forming apparatus can be kept clean.

[Brief description of the drawings]

1 to 5 relate to the developing device of the present invention, FIG. 1 is a partial cross-sectional view of the developing device, FIG. 2 is a magnetic field distribution diagram, FIGS. FIG. 5 is an explanatory diagram showing the state of the developer and the magnetic field between the sleeve and the photoconductor. FIGS. 6a, 6b, 6c are explanatory views showing the state of development in the development area, while FIGS. 7a, 7b, 7c are diagrams, and FIGS. 8a, 8b, 8c are illustrations. FIGS. 9, 10, 11, 12, 13 and 14 are partial sectional views showing another embodiment of the developing device. FIG. 15 is a partial cross-sectional view of a single-pole fixed inner-pole developing device, and FIG.
FIG. 16 is a cross-sectional view showing the state of toner adhesion on the photoconductor, and FIG.
FIG. 17 is a cross-sectional view showing the state of adhesion of the toner fixed on the recording medium, FIG. 18 is a cross-sectional view of the superimposed toner image, and FIG.
The figure is an explanatory view showing the state of the magnetic brush in the developing area. FIG. 20 is a partial cross-sectional view of the same-polar type inner-electrode fixed developing device, and FIG.
FIG. 21 is a partial cross-sectional view of the inner pole rotating type developing device, and FIGS. 22a, 22b, 22
c, 23a, 23b, 23c, 24a, 24b, 24c, 25a, 25b, 2
FIG. 5c is an explanatory view showing the state of the developer in the development area. 1 ... developing roller, 2 ... sleeve, 3 ... magnet body, 5
... Regulating plate, 6... Developer, 7... Tip, 10... Photoconductor, P... Closest position, N ₁ , N ₂ .

(72) Inventor Hiroshi Murasaki 2-3-13 Azuchicho, Chuo-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Masahiko Matsuura 2-chome Azuchicho, Chuo-ku, Osaka City, Osaka No. 3-13 Osaka Kokusai Building Minolta Camera Co., Ltd. (72) Inventor Susumu Mikawa 2-3-3 Azuchicho, Chuo-ku, Osaka City, Osaka Prefecture Osaka Kokusai Building Minolta Camera Co., Ltd. (56) References JP 63 JP-21682 (JP, A) JP-A-2-19874 (JP, A) JP-A-2-19875 (JP, A) JP-A-61-233760 (JP, A) JP-A-61-233764 (JP, A) ) JP-A-54-76236 (JP, A)

Claims (2)

(57) [Claims] 1. A powder developer comprising a carrier and a toner is held on the outer periphery of a sleeve moving around a fixed magnet body,
In a developing device for developing an electrostatic latent image by bringing the developer into contact with a photoreceptor, magnetic poles of the same polarity are arranged adjacent to a photoreceptor facing portion of the fixed magnet body, and the photoreceptor among the magnetic poles is disposed. The developer confined by one magnetic pole located on the upstream side in the moving direction of the sleeve passing through the opposing portion is brought into contact with the photoconductor, and the developer confined by the other magnetic pole is kept out of contact with the photoconductor. Developing device. 2. The developing device according to claim 1, wherein a magnetic body or a magnetic field generating means having a polarity different from that of the magnetic pole is provided near the magnetic pole located on the downstream side of the magnetic poles.