JPH0258076A - Image forming device - Google Patents

Abstract

PURPOSE:To make plural developing devices in common without phase adjustment by making an included angle of the magnetic poles of magnetic rolls contained in the developing sleeves of developing units disposed parallel equal to an included angle to a photosensitive drum. CONSTITUTION:The fixed magnetic rolls 362-382 contained in the developing sleeves 361-381 which turn clockwise the three developing units 36-38 for respective colors disposed parallel to the photosensitive drum 30 which turns clockwise have magnetic poles of included angles alpha and beta in the clockwise direction including the same-shaped main magnetic pole fixed in the same magnetic force; alpha=36 deg. and beta=34 deg.. Meanwhile, when the peripheral surface of the drum 30 which has the same included angle in the clockwise direction such as alpha=36 deg. and beta=34 deg. is developed, the developing units 36-38 are automatically adjusted in their phase, and a unified one can be used without adjusting phase. By doing similarly with respect to angle gamma when four developing units are used, the same result can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention develops a latent image formed on a photoreceptor drum, which is an image carrier, using a plurality of developing means containing multicolor developers. , relates to an image forming apparatus that obtains color copies by electrophotography.

[Background of the invention]

There are many ways to obtain color images using electrophotography.
A device has been proposed. For example, JP-A-61-10077
As disclosed in Publication No. 0, a latent image is formed and developed on a photoreceptor drum according to the number of separated colors of an original image, and each time the development is performed, the latent image is transferred onto a transfer drum to form a multicolor image on the transfer drum. There is a method of forming a color copy and then transferring it onto recording paper to obtain a color copy. A device using this method requires a transfer drum large enough to transfer one sheet of image onto its circumferential surface in addition to the photoreceptor drum, and the device does not have a large and complicated structure. Inevitable.

For example, as disclosed in Japanese Patent Laid-Open No. 61-149972, a latent image is formed and developed on a photoreceptor drum according to the number of separated colors of the original image, and is transferred onto a transfer material each time it is developed. This is a method of obtaining multicolor copies. With this method, it is difficult to overlay multicolor images with high precision, and it is impossible to obtain high-quality color copies.

Another method is to repeatedly form a latent image on a photoreceptor drum in accordance with the number of separated colors of an original image and develop it with color toner, and then layer color powder on the photoreceptor drum and then transfer it to obtain a color image. The basic process of forming a multicolor image is disclosed in Japanese Patent Application Laid-open Nos. 60-75850 and 60-76766 by the present applicant.
No. 60-95456, No. 60-95458, No. 60-158475, etc.

In a multicolor image forming apparatus that obtains a color image through such superimposition, a plurality of developing units containing different color toners are arranged around the periphery of the photoreceptor drum. The photoreceptor drum is rotated multiple times to develop the latent image on the photoreceptor drum to obtain a color image.

In this case, the length of the photoreceptor drum needs to be at least longer than the length of the original; for example, the maximum recording medium is 84 size (3
64 x 257), the drum needs to have a diameter of about 130 mm, taking into account the allowance that will occur in the image forming process. Furthermore, according to the research of the present applicant, as detailed in the specification of Japanese Patent Application No. 60-296340, the latent image written on the photoreceptor drum by the writing means is transferred to the main transfer layer by overlapping the developed image. Therefore, during image formation, the cleaning means must be separated from the circumferential surface of the photoreceptor drum, and the cleaning means only comes into sliding contact with the circumferential surface of the photoreceptor drum after the transfer process. If the writing device continues to write at this point, the images to be superimposed will shift and the image quality will deteriorate, so the diameter of the photoreceptor drum should be large enough to allow sufficient margin. This is required. The same thing applies to development, and when multiple developing means installed on the peripheral edge of the photoreceptor drum perform development while simultaneously applying a developing bias, there is a difference between the areas developed by a single developing means. This is not desirable. The size of the photosensitive drum is determined based on these conditions, and as mentioned above, a large diameter drum is required.

In a multicolor image forming apparatus in which color images are superimposed on a photoreceptor drum, a conventional developing means in which a conventional magnetic brush is brought into contact with the image carrier to perform development may be used. I can't. The present applicant has made it possible to implement a multicolor image forming apparatus in which toner images are superimposed on an image carrier by using the non-contact developing method disclosed in Japanese Patent Application Laid-Open No. 57-147652.

[Problem that the invention seeks to solve]

In such a multicolor image forming apparatus, as is well known, each developer containing toner of a different color is oriented along the circumferential surface of the photoreceptor drum in its rotating direction, and each developing sleeve is positioned at a predetermined gap or distance from the drum surface. It is set at a position where Dsd can be maintained.

The developing sleeve of each developing device is driven and rotated during the development process of a specific color, but the magnetic roll included in the developing sleeve has different rotation speeds and rotation directions, and there are multiple developing devices. Since the power transmission mechanism becomes complicated, fixed magnetic rolls are generally used, and satisfactory results have been obtained. However, in the case of a fixed magnetic roll, it is necessary to set the magnetic pole of either the N or S pole to the drum surface under specific conditions, such as facing directly or close to directly facing each other. There are problems in that the phase of the magnetic poles must be adjusted, which requires a lot of time and effort, and the main body of the developing device cannot be treated as a common unit.

The present applicant previously proposed in Japanese Patent Application No. 62-331226 that a plurality of developing devices having magnetic rolls in which magnetic poles of equal magnetic force are arranged at equal angles are installed at the same angle on the outside line of the photoreceptor drum. By doing so, we proposed an image forming apparatus that can be used without requiring adjustment of the upper set with a common magnetic roll, but we have further developed this proposal by creating a new magnetic roll with magnetic poles arranged at unequal angles. The object of the present invention is to provide an image forming apparatus that uses a plurality of developing devices in common and can be used without phase adjustment.

[Means for solving problems]

The above object is to provide an image forming apparatus in which development is performed by a plurality of developing devices arranged parallel to each other facing a photoreceptor drum. α clockwise including
, β0. This is achieved by an image forming apparatus having a magnetic pole having an included angle of γ0, and performing development while facing the circumferential surface of the photoreceptor drum having included angles of α, β°, and γ° in the clockwise direction. be done.

[Embodiment 1] A first embodiment in which three developing devices of the present invention are provided at the peripheral edge of a photosensitive drum is shown in FIGS. 1 to 4. Fig. 1 shows the main configuration of a multicolor image forming apparatus, in which A is an image reading system, B is a laser writing system unit, C is an image forming section, and D is a paper feeding section, which is used for the next process. A color image is formed.

In the reading system A, 11 is a document table;
The document placed in the carriage 12 is illuminated by a halogen lamp 13 attached to a carriage 12 that slides in the horizontal direction. The movable mirror unit 15 includes mirrors 16 and 17.
is attached, which also slides in the horizontal direction, and in combination with the mirror 14 attached to the carriage 12 guides the optical image of the document to the lens reading section 20.

The carriage 12 and the movable mirror unit 15 are driven via wires (none of which are shown) connected to a stepping motor, and are slid in the same direction at speeds of V and 1/2V, respectively.

The lens reading section 20 includes a lens 21. prism 22,
First reading board 24, red channel (hereinafter R-ch)
CCD 25, second reading board 26, and cyan channel (hereinafter referred to as C-ch) CCD 27.

The optical image of the original transmitted by the mirrors 14, 16 and 17 is focused by the lens 21, and is focused by the prism 22.
The R-ch image and the C-ch image are separated by a dichroic mirror provided therein. The images are respectively formed on the light receiving surface of the CCD 27.

Said R-ch CCD25 and C-ch CCD27
The image signal output from the image signal processing section is subjected to signal processing. In the signal/processing section, a color signal separated according to the color of the toner is output, and is input to a surface laser writing system unit B, which is an exposure means.

In the laser writing system unit B, a laser beam generated by a semiconductor laser (not shown) is rotated and scanned by a polygon mirror 32 rotated by a drive motor 31, passes through an Fθ lens 33, and has its optical path bent by a mirror 34. The light is projected onto the circumferential surface of the image carrier 30 to which a charge has been applied in advance by a charger 35 serving as a charging means to form a bright line.

On the other hand, when scanning is started, the beam is detected by the index sensor, modulation of the beam by the first color signal is started, and the modulated beam is transferred to the photoreceptor drum 30.
scan the circumferential surface of the Therefore, a latent image corresponding to the first color is formed on the circumferential surface of the photoreceptor drum 30 by main scanning by the laser beam and sub-scanning by the rotation of the photoreceptor drum 30. This latent image is developed by, for example, a developing device 36 loaded with red toner (developing medium) among the developing means, and a toner image is formed on the drum surface. The obtained toner image passes under a cleaning device 51, which is a cleaning means, which is separated from the peripheral surface of the photosensitive drum 30 while being held on the drum surface, and enters the next copy cycle.

That is, the photosensitive drum 30 is charged again by the charger 35, and then the second
The color signal is input to the writing system unit I-B, and writing is performed on the drum surface to form a latent image in the same manner as in the case of the first color signal described above. The latent image is developed by a developer 37 loaded with toner of a second color, for example blue.

This blue toner image is formed in the presence of the previously formed red toner image.

A developing device 38 has black toner, and forms a black toner image on the drum surface based on a control signal generated by a signal processing section. AC and DC biases are applied to the sleeves of each of these developing units 36, 37° 38, and jumping development is performed using the two-component developer, and development is performed without contact with the grounded photoreceptor drum 30. It has become.

The color image thus formed on the circumferential surface of the photoreceptor/drum 30 is transferred to a transfer pole 40 provided as a transfer means as a recording medium fed from the paper feed section by a paper feed belt 411 and a feed roller 42. Transferred to recording paper. The recording paper onto which the toner image has been transferred is separated from the drum surface by a separation pole 43 and transferred to the fixing device 4 via a conveyor belt 44.
5, and the image is fixed.

On the other hand, the photosensitive drum 3 with the recording paper separated from the drum circumferential surface
At 0, the blade 51A of the cleaning device 51 comes into contact and removes the remaining toner, and at the end of the process, the drum is separated from the peripheral surface of the drum again by a ball, and a new color image forming process begins.

Next, to explain the layout of each of the main components mentioned above, as shown in FIG. .

The main body 2 incorporates an image recording system consisting of the writing system B1, image forming section C1, paper feeding section, etc., and the color information from the image reading system A is transmitted through a group of flexible cables connected to the National Sports Festival 1. It is designed to receive signals.

In the main body 2, the photosensitive drum 30 is located approximately in the middle, and facing the right circumferential surface of the main body 2, each of the developing units 36°37.38
are arranged horizontally, while the charger 35 and the cleaning device 51 are arranged on the left peripheral surface.

The photosensitive drum 30, the developing devices 36, 37, and 38, and the cleaning device 51 are all supported members that are removably inserted into the main body 2 without being directly attached to a pair of front and rear substrates fixed to the main body 2. 3 is supported by a bearing or is detachably attached.

As shown in FIG. 3, the support member 3 consists of three panels 3A, 3 of similar shapes fixed to each other via stays etc. and integrated into one body.
B and 3G, and can be easily taken out and attached to the main body 2 by a pair of left and right guide members 4 each consisting of a plurality of poles and rails.

That is, rails 4A1 are provided on the left and right edges of the support member 3.
On the other hand, the rail 4 is located at the position of the main body 2 corresponding to the rail 4A.
C are fixed respectively, and each engages with the rail 4B via a plurality of poles, thereby forming a slidable pair.

Further, a pair of left and right reference pins P are installed near the upper side edges of the back surfaces of the panels 3A and 3B, respectively, and the main body 2
The photoreceptor drums 30 and 30 are suspended by engaging with holes provided in the hanging portions Q derived from the front and rear substrates to which the photosensitive drums 30 are fixed, and are not attached to the support member 3 in this state. The relative positions of the developing device 36, 37, 38, and cleaning device 51 relative to the main body 2 are set.

Therefore, when the handle 5 on the front surface of the panel 3A is pulled, the support member 3 is pulled out to the front of the main body 2 by the rolling action of the pole, using the rail 4B as a relay member.
By pushing in, the reference pin P engages with the hole in the hanging portion Q, and the support member 3 is retracted into the main body 2 in a suspended state.

By holding the support member 3 in a suspended state with respect to the substrate of the main body 2 in this way, the power is transmitted from the motor etc. attached to the main body 2 to the photosensitive drum 30, each developing device, or the cleaning device. Even if the vibrations and shocks that occur are greatly alleviated and absorbed, and slightly transmitted, each piece of equipment will be subject to different vibrations and shocks, so for example, multiple developing units and photoreceptor drums will be relatively different. Since it is held in a stable state, it does not cause any major trouble in image formation.

In particular, by integrally holding the photoreceptor drum 30 and the cleaning device 51 on the support member 3, the blade 5 must be used as a cleaning device for overlapping development image formation.
1A1 Significantly alleviates and absorbs the negative effects of vibrations, shocks, etc. on delicate pressure bonding methods, pressure contact conditions, load conditions, etc. when the second cleaning roller 51B etc. approaches and separates the cleaning blade for processing residual toner, or when pressure is applied. be done. These effects are shown in panel 3A.

The same can be said of the case where the reference pin P on 3B and the hole of the hanging part Q that fits into the main body are replaced with each other and combined. Further, it is sufficient that the panel board is composed of two panels at the front and rear, and it is not necessarily necessary to construct the panel board with three panels as in this embodiment.

The photosensitive drum 30 has a size of 84 mm, which is the largest recording medium, when using the above-mentioned overlapping image forming process.
The circumferential length is required to be one page of A3 size or A3 size with some extra margin, and the outer diameter is at least 130d.
The size of the photosensitive drum is approximately 150 mm to 150 mm, and in this embodiment, a 150 dmm photosensitive drum is rotated at a circumferential speed of 140 mm per second.

- Regarding the compact developing units 36, 37, and 38, as will be described in detail later, the outer diameter of the developing sleeve was reduced to 20 dmm without deteriorating image performance, and the thickness (height) of each developing unit was reduced to approximately 40 mm. As a result, a plurality of three to four developing units are used for one color, that is, developing units 36, 37, and 38 in this embodiment.
can be further stacked and arranged horizontally within a space corresponding to the range of the outer diameter of the photoreceptor drum 30.

Therefore, the support member 3 is a member that is directly attached or fixed to the main body 2, especially the upper laser writing system B1 and the lower transfer pole 40.
Even if the vertical height is limited to the minimum dimension sufficient to cover the photosensitive drum 30 so as not to affect the layout of each member of the transport system including the separation electrode 43,
Needless to say, the cleaning device 39 is fully capable of mounting and accommodating all of the plurality of developing units 36, 37, and 38, thereby forming a recording paper conveyance path in a substantially straight line. This is effective in preventing jams, and even if jams occur, they can be easily disposed of.

Each of the developing units 36, 37, and 38 has the following configuration.

In this embodiment, the developing devices 36, 37, and 38 all have the same structure. The developing device used in the present invention will be explained with reference to a sectional view of the developing device 37 shown in FIG.

370 is a housing, 371 is a developing sleeve, 372 is a magnetic roll, 373 is a developer layer thickness regulating plate, 373A is a fixing member for the layer thickness regulating plate 373, 3768 and 376B
are first and second stirring members, 374 is a supply roller, 37
5 is a scraper, and 377 is a stirring partition plate.

The toner replenished into the device is transferred to the first cartridge that rotates in the direction of the arrow.
The agitating member 376A and the second agitating member 376B, which rotate in the opposite direction so as to overlap with each other, supply the upper developer to the recarrier and the supply roller 374.
is sent to the developing sleeve 371 via.

The first stirring member 376A and the second stirring member 376B
is a screw-shaped member with a left-handed helical angle that rotates in opposite arrow directions, and is a second stirring member 376.
The toner and carrier transported to the back side by the thrust of B are moved to the back side by the stirring partition plate 377 whose upper edge is sloped low.
The developer passes through the toner and carrier sequentially and moves to the side of the first stirring member 376A, and is conveyed to the front side by its thrust, and is triboelectrically charged by the mixing action of the toner and carrier during that time, becoming a homogeneous developer, which rotates in the direction of the arrow in a spongy shape. A layered layer is deposited on the circumferential surface of the developing sleeve 371 by the supply roller.

The surface of the developing sleeve 371 is held by a fixing member 373A extending from the housing 370 and has elasticity;
A layer thickness regulating plate 373 is pressed against the surface near the end, and regulates the layer thickness of the developer to be conveyed, from 100 μm to 50 μm.
This results in the formation of a thin developing layer in the range of 0 μm, preferably 150 μm to 400 μm.

This thin layer of developer adheres to the peripheral surface of a fixed magnetic roll 372 and a developing sleeve 371 that rotates in the direction of the arrow (clockwise) on the outside thereof. The latent image on the drum 30 is developed in a non-contact manner at intervals to form a toner image.

During this non-contact development, a developing bias containing an AC component is applied to the developing sleeve 371 from a power source (not shown),
Only the toner in the developer on the image forming sleeve 371 is selectively transferred and adhered to the surface of the latent image.

The developer that has consumed toner components has a high carrier ratio, is transported by the developing sleeve 371, is peeled off and collected by the scraper 375, and is mixed again with the developer that has a high toner ratio.

The specifications of each component included in the embodiment of the developing device shown in FIG. 2 are as follows.

The developing sleeve 371 is made of a thin cylindrical stainless steel material with an outer diameter of 20 mm, the outer peripheral surface of which has been blasted to a roughness of 3 μm, and rotates at 200 to 300 revolutions per minute, in this embodiment 250 revolutions per minute. is rotated clockwise. The diameter of the developing sleeve is set to 15 to 30 mm, although a small diameter sleeve is required due to the miniaturization of the developing device, due to limitations on the magnetic force of the built-in magnetic roll. We also conducted various experiments regarding the rotation speed of the developing sleeve, and found that when the rotation speed is low, the amount of developer supplied is small and the image density when the latent image is developed is also low.

Regarding a developing sleeve with an outer diameter of 20 mm, the maximum image density increases linearly when the rotation speed is from 0 to 200 rotations per minute, and becomes saturated when the rotation speed is 200 rotations per minute or more. However, when the environmental temperature is low, the maximum image density decreases, so it is necessary to set it with some margin.

As shown in FIG. 2, the magnetic roll 372 rotates S and N alternately in a clockwise direction, each with a center angle α=36°.

L of equal magnetic force arranged at unequal intervals so that β = 34°
Although it is composed of an O-pole magnet, it forms a repulsive magnetic field at the part in contact with the supply roller 374, and the l-pole is omitted to make it easier to peel off the developer, resulting in 9 poles. It is enclosed in a fixed state. The magnetic force of each magnet should be large in order to suppress carrier adhesion, but there is a manufacturing limit depending on the shape of the magnetic roll.
It is maintained at approximately 0 Gauss, but in this embodiment, it is 600 Gauss.

Each of the developing units 36, 37, and 38 is incorporated into the support member 3 so that it can be easily attached to and detached from it by a mounting mechanism as described below.

The case of the developing device 37 will be explained below.
A pair of upper and lower guide pins 51 each having a compression spring externally fitted thereon is installed between a fixed handle 50A and a holding piece 520, and a movable handle 50B slidably fitted to each of the guide pins 51. It is biased to the right.

The movable handle 50B has a pair of upper and lower boss portions 50G.
A pressing lever 54, which is biased counterclockwise by a torsion spring 53, is pivoted to the lower boss portion 50C.

On the other hand, a guide plate 37A on which the developing unit 37 is mounted is fixed to the support member 3, and a "hook-shaped" notch 60 is provided at the side end thereof corresponding to the press lever 54.

When the developing device 37 is attached to the supporting member 3, the pressing lever 54 comes into contact with the linear portion 61 of the notch 60 and is pressed slightly clockwise, and the reaction force pushes the developing device 37. A configuration in which the distance (Dsd) between the image bearing surface and the developing sleeve is maintained at a specified value by pressing in the direction of the photoreceptor drum 30 (for example, a roller provided concentrically with the developing sleeve is brought into contact with the photoreceptor drum to close the gap). (not shown).

On the other hand, in order to remove the developing unit 37 from the support member 3, the movable handle 50B is slid to the left against the action of the compression spring. 54A as movable handle 50
It comes into contact with B and stops.

Therefore, when the fixed handle 50A and the movable handle 50B are grasped and pulled at the position where the boss portion 50C butts against the fixed handle 50A, the pressing lever 54 escapes from the opening of the notch 60 and the developing device 37 is removed. It can be taken out and separated from the support member 3.

Also, when attaching it to the support member 3, please use the current @! 18
37 is placed on the guide plate 37A, and when the bottle 37B attached to the side surface of the developing device 37 is pushed in so as to engage with the groove 3A-2 provided in the panel 3A, the guide pin Movable handle 5 located at the right end of 51
The pressing piece 54 on OB comes into contact with the slope part 63 and slides to the left on the guide bin 51 together with the movable handle 50B due to its slope angle.

When the pressing lever 54 reaches the opening of the notch 60 and the developing device 37 is further pushed in, the movable handle 50B slides to the right due to the action of the compression spring, and the pressing lever 54
comes into sliding contact with the slope portion 62 and is rotated slightly clockwise until it reaches the straight portion 61, thereby obtaining the biased state of the developing device 37 described above. The developing units 36 and 38 are also attached to and detached from the support member 3 by a similar attachment mechanism.

Further, each developing unit 36, 37° 3 is connected to the supporting member 3.
When installing item 8, the dimensions of length, depth, width, or relative position, and the combination of grooves, holes, notches, etc., and protrusions such as dowels, rails, etc., of the mechanical elements must be determined individually or individually. By combining a plurality of components and selecting a fitting mechanism based on the above-mentioned specifications, a fool-proof mechanism is provided that prevents a different type of developing device from being attached by mistake.

For example, the height of the engagement position between the pin 37B and the groove 3A-2 is changed depending on the type of developing device, so that it is possible to prevent a different type of developing device from being attached by mistake.

When the developing units 36, 37, and 38 are mounted in parallel on the support member 3 and stored in the apparatus main body 2, the developing unit 37 has a developing sleeve 371 attached to the photosensitive drum 30 as shown in FIG.
Ds between the drum and the peripheral surface of the drum placed on a horizontal plane passing through the axis of
d, while the developing devices 36 and 38 are connected to the photoreceptor drum 3.
Each developing sleeve 3 is placed at a position on the circumferential surface of the drum with a phase relationship that forms a central angle of σ-36° and β-34° from above to below, that is, clockwise with respect to the horizontal plane passing through the axis of 0.
61 and 381 are arranged to constitute development areas each having a predetermined Dsd.

Therefore, even if the developing devices 36, 37, and 38 commonly use magnetic rolls 362, 372, and 382 whose magnetic poles have the same phase, the developing devices 36, 37, and 38 are
When the magnetic roll 372 of
The magnetic rolls 362 and 382 of Nos. 6 and 38 are
This means that each S pole adjacent to the pole can be made to directly face each other.

That is, the central angles between the developing sleeves 36+, 371.381 as seen from the axis of the photoreceptor drum 30 are α-36° and β-34° clockwise, and each magnetic roll 362.3
The developing units 36, 37, and 38 are installed at each position on the drum circumferential surface under the condition that the central angle between the magnetic poles at 72°382 is equal to α-36° and β-34° clockwise. In this case, each of the magnetic rolls 362, 372, and 382 can be used as a completely common roll including not only the roll body but also the mounting specifications for the developing device.

As a result, the angle between the magnetic poles of the magnetic roll can be determined freely, making it possible to select the magnetic pole position according to the purpose.

[Embodiment 2] A second embodiment in which four developing devices are provided at the peripheral edge of the photosensitive drum will be described with reference to FIGS. 1', 5, and 6. The three developing devices in Example 1 were replaced with four developing devices,
Functional parts that are the same as those in the first embodiment are indicated using the same part numbers.

FIG. 5 shows the arrangement of the magnetic poles of the magnetic rolls 362, 372, 382, and 392 used in common with the developing units 36, 37, 38, and 39, and FIG. This figure shows the arrangement of four developing units 36, 37, 38, and 39.

The photosensitive drum 30 in this embodiment is a cylindrical body having a diameter of 180 um and coated with an organic photoconductive layer (OPC), and rotates clockwise at a circumferential speed of 140 mm per second. The developing units 36, 37, 38, and 39 each contain a two-component developer consisting of yellow-magenta, cyan, and black toners and a magnetic carrier, and perform non-contact development on the latent image on the photosensitive drum 30. The developing sleeve 361 (371, 381, 391) of the developing device 36 (37° 38.39) is 20
) mm cylindrical body, and the magnetic roll 362 (372, 382, 392) fixedly located inside has the magnetic pole array shown in FIG. Here, α=30°, β-28
', with an included angle of γ=28°, the magnetic poles N and S are below the horizontal, and the magnetic poles N3 and S2 are above the horizontal,
Magnetic pole N l+s 3. N3. They are arranged clockwise in the order of S2.

These developing devices 36, 37, 38, 39 are the photosensitive drum 3.
Non-contact development is performed in the arrangement relationship shown in FIG. 6 with respect to 0. In other words, σ=3 in the clockwise direction at a position that is almost symmetrically divided from the horizontal plane of the photoreceptor drum 30.
The developing device 36 is placed in the positional relationship of 0°, β=28°, and γ-28°.
, 37, 38. 39 are installed horizontally. With such a configuration, each magnetic roll 362, 372, 3
82.392 can be used completely in common, including not only the roll body but also the mounting specifications for the developing device.

〔Effect of the invention〕

According to the present invention, it is possible to use a magnetic hole having the same roll body and magnetic pole phase for each developing device arranged in the rotational direction of the photoreceptor drum, thereby reducing the manufacturing cost of the imager. At the same time, by sharing parts, a practically useful image forming apparatus has been provided which is extremely advantageous in terms of service and maintenance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of an image forming apparatus according to the present invention. FIG. 1' is a sectional view of a second embodiment of the image forming apparatus of the present invention. FIG. 2 is a sectional view of a developing device used in the device. FIG. 3 is a perspective view of a support member that houses the developing device. FIG. 4 is a layout diagram of the developing device with respect to the photosensitive drum. FIG. 5 is a diagram showing the magnetic pole arrangement of the magnetic roll of the second embodiment. FIG. 6 is a layout diagram of the developing device of the second embodiment with respect to the photosensitive drum. 1...National polity 2...Main body 3...Supporting member 30...Photosensitive drum 36.37.
38... Developing units 36A, 37A, 38A... Guide plate

Claims (1)

[Claims] In an image forming apparatus in which development is performed by a plurality of developing devices arranged parallel to each other facing a photoconductor drum, the developing devices include main magnetic poles of the same shape fixed with equal magnetic force and enclosed in a developing sleeve. clockwise α°, β°, γ
An image forming apparatus characterized in that the image forming apparatus has a magnetic pole having an included angle of .degree., and performs development while facing a circumferential surface of a photoreceptor drum having an included angle of .alpha., .beta., and .gamma..degree. in the clockwise direction.