JPH0720715A - Development device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a light-weight, small-sized developing device in which developer does not leak during transportation. [Structure] In the developing device 21, the magnet roller 30 is fixed at the first angular displacement position by fitting and fixing the fixing piece 45 in the fixing recess 50 of the housing 40. The first angular displacement position is selected so that the magnetized distribution of the magnet roller is directed toward the inside of the housing 40. Therefore, when the developing device 21 is conveyed, the electrostatically charged powder developer contained in the housing 40 is attracted by the magnetic force. It is held inside the housing 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a developer leakage preventing structure of a developing device which is preferably used in electrophotographic copying machines, laser printers and the like.

[0002]

2. Description of the Related Art Conventionally, in a printing device such as an electrophotographic copying machine or a laser printer, a developing device is removably mounted in the vicinity of a right cylindrical photosensitive drum, and is developed from an opening facing the photosensitive drum. The chargeable toner filled in the developing tank is supplied to the surface of the photosensitive drum via the roller. As a result, the electrostatic latent image formed on the surface of the photoconductor drum is visualized, and an image that can be transferred onto the recording paper is formed on the surface of the photoconductor drum.

However, since such a developing device has the above-mentioned opening portion, a gap between the magnet sleeve and the mounting portion during the transportation of the developing device or the printing apparatus equipped with the developing device until it reaches the user's hand. The developer, which is a powder, spills out from the product, and when the developing device is mounted on the main body of the printing device, the user's hands and clothes may be soiled, or the product may scatter inside the main body of the printing device and interfere with printing. is there. Corresponding to this, Japanese Patent Publication No. 63-9237 and Japanese Patent Laid-Open No. 2-511.
There has been proposed a developing device having a developer leakage prevention structure as shown by reference numeral 81 and the like.

FIG. 7 is a perspective view showing the appearance of a conventional developing device 1 disclosed in Japanese Examined Patent Publication No. 63-9237, and FIG. 8 is a schematic sectional view showing the structure of the developing device 1 shown in FIG. As shown in FIG. 7, the developing device 1 is provided with an opening 16 at the top of the toner hopper portion 2, and when the developing device 1 is attached to the printing device and the printing operation is performed by the printing device, the developing device 1 is filled with toner. A toner container (not shown) is attached.

Further, as shown in FIGS. 7 and 8, the developing device 1 is provided with a compartment 5, and a developer consisting of two components of toner and carrier is sealed in the compartment 5 by a seal member 11. ing. When the developing device 1 is mounted on the main body of the printing apparatus and the printing operation is performed, the sealing member 11 is pulled out in the direction of arrow A shown in FIG. The developer filled in is dropped and supplied into the developing tank 15.

The developer dropped and supplied into the developing tank 15 is
The developer and the toner are agitated by the developer agitating roller 27, and the carrier and the toner are charged to have opposite polarities. The charged developer is attached and conveyed on the magnet sleeve 9 by the magnetization distribution of the magnet 17 of the magnet roller 10 installed in the developing roller 18, and the photosensitive drum on which the electrostatic latent image is formed through the opening 12. 14 Close to the surface. Of the electrostatic latent image, the exposed portion has zero potential,
Only the toner charged to the opposite polarity to the charging portion is attached and supplied to the surface of the photoconductor drum 14 to visualize the electrostatic latent image.

In this way, when only the toner of the developer is consumed and the toner density in the developing tank 15 becomes lower than the predetermined density, the toner hopper 2 is controlled by the control signal from the toner density detector 26. Then, an appropriate amount of toner agitated by the toner agitating roller 3 is supplied into the developing tank 15 by the toner supplying roller 4. Furthermore, the opening 12 is covered with a protection member 13 made of cardboard or the like for protecting the magnet sleeve 9 of the developing roller 18. In this way, in the developing device 1, the developer is enclosed in the compartment 5 during the transportation, and the scattering of the developer from the developing tank 15 during the transportation of the developing device 1 is prevented.

[0008]

However, since the developing device 1 described above is provided with the compartment 5, the mold for molding the housing of the developing device 1 becomes complicated, and the manufacturing cost is increased.
Furthermore, since the developing chamber 1 is provided with the compartment 5, the size of the developing device 1 is increased, and the shape of the developing device 1 having the compartment 5 inside the main body of the printing apparatus hinders the development device 1. In addition, a wasteful space is created, which leads to an increase in size of the printing apparatus.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a light-weight and small-sized developing device without developer leakage.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a developing device detachably attached to the main body of an electrophotographic printing apparatus, which is provided with a magnet sleeve rotatably driven in a circumferential direction of an outer peripheral portion, and has a main pole and a supplementary pole. The magnetized distribution of magnetic powder is attracted onto the magnet sleeve by the magnetized distribution to form a magnetic brush, and the developer is conveyed by the magnet sleeve to expose the developer. A magnet roller to be supplied to the body, a housing to which a component member including the magnet roller is attached, and a housing containing a chargeable powder developer, and a rotation axis of the magnet roller penetrating the housing and protruding outward. A fixing means that is attached by being biased toward the housing side by a spring provided at the end of the rotating shaft, and a fixing piece is provided so as to project toward the housing side. (2) Two fixing recesses are provided on the outer side surface of the mounting portion, and when the fixing piece is fitted in the one fixing recess and is fixed by the biasing force, the magnet roller is displaced by the first angular displacement. The magnet roller is fixed at the second angular displacement position and the first angular displacement position is magnetized by the magnet roller when the fixing piece is fitted in the other fixing recess and is fixed by the biasing force. The distribution is selected so as to be directed toward the inside of the housing, and the second angular displacement position is selected so that the magnetization distribution of the magnet roller is in the optimum direction for supplying an appropriate amount of developer to the photoconductor. It is a developing device.

[0011]

According to the present invention, the developing device is detachably attached to the main body of the electrophotographic printing apparatus. The magnet roller of the developing device has a magnetization distribution composed of a main pole and a complementary pole,
Due to the magnetization distribution, the electrostatically charged powder developer is adsorbed onto the magnet sleeve provided on the outer peripheral portion of the magnet roller. The magnet sleeve is rotationally driven in the circumferential direction of the magnet roller, and conveys the adsorbed developer to the photoconductor of the main body of the printing apparatus and supplies it.

The fixing means, in which the fixing piece is provided so as to project toward the housing side, is attached to the rotary shaft of the magnet roller penetrating through the housing and projecting outward, and the spring is attached to the end of the rotary shaft in the housing direction. Be energized. Two fixing recesses are provided on the outer side surface of the magnet roller mounting portion of the housing, and the fixing piece is fixed to the fixing recess by the biasing force.

When the fixing piece is fitted in the one fixing recess, the magnet roller is fixed at the first angular displacement position, the magnet roller is angularly displaced by the fixing means, and the fixing piece is fixed in the other fixing recess. When is fitted, the magnet roller is fixed at the second angular displacement position. The first angular displacement position is selected so that the magnetized distribution of the magnet roller is directed toward the inside of the housing, and the second angular displaced position is such that the magnetized distribution of the magnet roller is the optimum direction for supplying an appropriate amount of developer to the photoconductor. Chosen to be.

In this way, the magnet roller is the first
When the magnet roller is fixed at the angular displacement position, the magnetized distribution of the magnet roller is fixed toward the inside of the housing, so the electrostatically charged powder developer contained in the housing is held inside the housing by the magnetic force, and the housing is transported. At this time, it is possible to prevent the powder developer from leaking from the housing. When the magnet roller is fixed at the second angular displacement position, the magnetization distribution of the magnet roller is fixed in the optimum direction for supplying an appropriate amount of developer to the photoconductor, so when printing is performed by the printing device,
An appropriate amount of developer can be supplied to the photoreceptor.

Since the developing device holds the developer inside the housing by the magnetic force of the magnet roller, it is not necessary to provide a structure for holding the developer inside the housing.
It is possible to reduce the size of the developing device, and since it is not necessary to complicate the structure of the housing, the manufacturing cost of the developing device can be kept low. Also, the developing device
Since the fixing means for fixing the magnet roller at the first and second angular displacement positions is realized by a simple structure, it is possible to reduce the size of the developing device.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a developing device 21 which is an embodiment of the present invention.
2 is a perspective view showing the external appearance of FIG. 2, and FIG. 2 is a schematic cross-sectional view showing the configuration of the developing device 21. As shown in FIG. 2, the developing device 21 is disposed inside the printing device such as an electrophotographic copying machine or a laser printer in the vicinity of the right cylindrical photosensitive drum 34 and is detachably mounted. As shown in FIGS. 1 and 2, the developing device 21 is provided with an opening 36 in the upper part of the toner hopper portion 22, and when the developing device 21 is attached to the printing device and a printing operation is performed by the printing device, the toner is not supplied. The filled toner container is installed.

Inside the developing tank 35 of the developing device 21, a toner concentration sensor 26, a developer stirring roller 27, a developing roller 28, a doctor 38 and the like are provided. Developing roller 2
8 is a magnet roller 30 and a magnet sleeve 29.
On the circumference of the magnet roller 30, a plurality of magnets 37 having different polarities parallel to the axial direction of the magnet roller 30 are provided.

The magnet roller 30 is mounted so as to be angularly displaceable around the axis, and is in a first angular displacement position when the developing device 21 is conveyed, and in a second angular displacement position when the developing device 21 is mounted on a printing device. Fixed. When the developing device 21 is attached to the printing device and the printing operation is performed by the printing device, the magnet sleeve 29 is rotationally driven counterclockwise around the axis of the magnet roller 30 shown in FIG. 2 by the printing device. An opening 32 is provided at a position where the developing tank 35 faces the photoconductor drum 34 when the developing device 21 is attached to the printing device.

In the developing device 21, a developer in which a toner made of epoxy resin or the like is mixed with a carrier such as iron powder at a ratio of about 4% by weight is built in the developing tank 35 shown in FIGS. 1 and 2. There is. When the developing device 21 is conveyed, the magnet roller 30 is fixed at the first angular displacement position, and the magnetizing distribution is formed toward the inside of the developing tank 35 by the arrangement of the magnet 37 of the magnet roller 30 built in the developing roller 28. To be done. The carrier composed of magnetic particles such as iron powder forms a magnetic brush that moves toward the inside of the developing tank 35 according to the magnetization distribution, and the toner particles are adsorbed by the magnetic brush and held inside the developing tank 35. Further, the toner particles not adsorbed on the magnetic brush are also developed by the wall of the magnetic brush formed in contact with the inner surface of the housing 40 of the developing tank 35 from the surface of the developing roller 28.
Retained inside.

However, since the attraction force of the magnetic brush as described above cannot withstand a large impact such as drop or vibration, the opening 32 is covered with a seal member 33 made of corrugated cardboard as an auxiliary means, The end of the sealing member 33 is sealed with an adhesive tape or the like. As a result, it is possible to more reliably prevent the developer from leaking from the opening 32 and protect the magnet sleeve 29 of the developing roller 28 from damage due to an external force. The seal member 33 is removed when the developing device 21 is attached to the printing device.

When the developing device 21 is mounted in the main body of the printing device and the printing device performs the printing operation, the developer contained in the developing tank 35 is agitated by the developer agitating roller 27 to form a carrier constituting the developer. The particles and the toner particles are charged with electric charges of opposite polarities due to friction. The developer charged by stirring is conveyed toward the developing roller 28. The magnet roller 30 of the developing roller 28 is fixed to the second angular displacement position when it is mounted on the printing apparatus, and the magnetized distribution by the magnet 37 is arranged at the optimum position for supplying the developer to the surface of the photosensitive drum 34. To be done. In the developer conveyed to the developing roller 28, a magnetic brush of carrier particles is formed on the magnet sleeve 29 according to the magnetization distribution formed by the magnet 37, and the toner particles adhere to the magnetic brush composed of the carrier particles. .

In this way, the magnet sleeve 29
The developer adhering to the upper side is conveyed by the magnet sleeve 29 which is rotationally driven, and passes through the doctor 38. The doctor 38 is a developer adhesion amount regulating member whose end surface is arranged in parallel with the axial direction of the magnet sleeve 29 at a predetermined distance from the surface of the magnet sleeve 29.
Since the optimum amount of toner is supplied onto the photosensitive drum 34, the amount of developer adhered onto the magnet sleeve 29 is optimally regulated. Opening 3 by magnet sleeve 29
The developer conveyed to 2 is conveyed close to the surface of the photosensitive drum 34 on which the electrostatic latent image is formed.

The photosensitive drum 34 of the main body of the printing apparatus is made, for example, by forming a thin film of a photoconductive material on a conductive support. The photoconductor drum 34 is uniformly charged in advance to a reference voltage of −340V or less. The exposed surface of the photoconductor drum 34 becomes conductive, so that the potential of the exposed portion is 0 V.
become. The above-mentioned developer is negatively charged to the carrier by triboelectrification and positively charged to the toner, so that the developer is carried when it is carried on the surface of the photoconductor drum 34 by adhering to the magnet sleeve 29. Of the developer, only the toner charged with a positive charge is adsorbed to the charging portion on the surface of the photoconductor drum 34, and the electrostatic latent image on the photoconductor drum 34 is visualized.

In this way, only the toner of the developer is supplied onto the photosensitive drum 34 and consumed. When the toner density of the developer inside the developing tank 35 decreases and becomes lower than the reference density, an appropriate amount of toner is supplied from the toner hopper section 22 via the toner supply roller 24 based on the control signal from the toner density sensor 26. Supplied within. In the toner stirring roller 23, the toner particles are collected by the toner hopper unit 2.
It is provided in order to prevent printing unevenness due to agglomeration inside the container 2 or uneven supply in the axial direction of the developing tank 35.

FIG. 3 is a schematic sectional view showing the magnetization distribution of the magnet roller 30 when the developing device 21 is conveyed. Figure 3
As shown in FIG.
Is covered with a seal member 33 made of cardboard or the like, and an end portion of the seal member 33 is brought into close contact with a housing 40 by a sealing member 39 made of an adhesive tape or the like. A magnet 37 is arranged on the circumference of the magnet roller 30 in parallel with the axial direction. For example, in FIG.
As shown in FIG. 3, one main pole N1 and two auxiliary poles S1 and S2 for assisting the smooth transport of the developer are provided on both sides of the main pole N1. In FIG. 3, a chain double-dashed line R indicates the direction and strength of the magnetic attraction force between the main pole N1 and the complementary poles S1 and S2. As indicated by the two-dot chain line R,
The magnetization distribution by the magnet 37 is directed toward the inside of the developing tank 35, and the developer contained in the developing tank 35 is
A magnetic brush is formed on the magnet sleeve 29 of the magnet roller 30 in accordance with the magnetization distribution indicated by the two-dot chain line R. As a result, the developer contained in the developing tank 35 is held inside the developing tank 35.

FIG. 4 is a side view and a sectional view for explaining the structure in which the magnet roller 30 is fixed at the first angular displacement position. 4A shows the side surface of the mounting portion of the developing roller 28, and FIG. 4B shows the developing roller 2 shown in FIG.
The cross section which looked at the attachment part of No. 8 from the cutting plane line BB direction is shown.
The developing roller 28 has a rotating shaft 43 and a housing 4 of the developing device 21.
0 is mounted on a bearing 42 provided for zero, and in order to prevent the developer from leaking from the gap between the rotary shaft 43 and the bearing 42, a seal member 41 rotates between the developing roller 28 and the bearing 42. Mounted around shaft 43. The magnet roller 30 of the developing roller 28 is the rotary shaft 43.
The rotation shaft 43 rotates and rotates with the rotation of the rotation shaft 43. A pressure spring 44 is attached to the end of the rotary shaft 43, and a fixing member 52 is attached to the developing roller 28 side by an arm 46.

The arm 46 is mounted such that the rotary shaft 43 penetrates through one end thereof, is fixed to the rotary shaft 43 to rotate, and is mounted displaceably in the axial direction of the rotary shaft 43. Further, the arm 46 is pressed toward the developing roller 28 by the pressing spring 44. A fixing member 52 is attached to the other end of the arm 46 so as to penetrate the arm 46.
The fixing piece 45 penetrating the arm 46 and projecting to the developing roller 28 side is fitted into a fixing recess 50 provided on the outer side surface of the mounting portion of the developing roller 28 of the housing 40, so that the developing roller 28
The rotary shaft 43 of is fixed to the first angular displacement position. Fixing member 5
A knob 47 is provided at the end opposite to the second fixing piece 45.

Similarly to the fixing recess 50 for fixing the rotary shaft 43 of the developing roller 28 to the first angular displacement position by fitting the fixing piece 45 on the outer side surface of the mounting portion of the developing roller 28 of the housing 40. And a fixed recess 51 for fixing the rotary shaft 43 of the developer roller 28 to the second angular displacement position. The fixed recess 50 has a groove that is shallower than the fixed recess 51, and the fixing member 52 protrudes to the outside of the developing device 21 by that amount. When the developing device 21 is mounted on the main body of the printing apparatus and the printing operation is performed by the printing apparatus, if the magnetization distribution of the magnet roller 30 is in the position shown by the chain double-dashed line R in FIG. Therefore, as shown in FIGS. 4A and 4B, the fixing piece 45 of the fixing member 52 is provided.
Is fitted into the fixed recess 50, the knob 47 projects outward, the width of the developing device 21 becomes larger than the width of attachment to the main body of the printing apparatus, and the knob 47 is attached to the housing 48 of the main body of the printing apparatus.
The developing device 21 cannot be attached to the main body of the printing apparatus by protruding from the mounting groove 49 provided in the above and contacting the housing 48.

FIG. 5 is a schematic sectional view showing the magnetization distribution of the magnet roller 30 when the developing device 21 is mounted on the main body of the printing apparatus. As shown in FIG. 5, when the developing device 21 is mounted on the main body of the printing apparatus, the seal member 33 and the sealing member 39 are removed from the opening 32. Further, the developing roller 28 is angularly displaced around the axis, and the magnet roller 30 is fixed at a second angular displacement position where an appropriate amount of toner can be supplied to the surface of the photoconductor drum 34 which is arranged in proximity as shown in FIG. It

FIG. 6 is a side view and a sectional view for explaining the structure in which the magnet roller 30 is fixed at the second angular displacement position. 6A shows a side surface of the mounting portion of the developing roller 28, and FIG. 6B shows a cross section of the mounting portion shown in FIG. Magnet roller 30
Is rotated by being fixed to the rotation shaft 43, and is angularly displaced from the first angular displacement position to the second angular displacement position. The fixing piece 45 pulls the knob 47 to the outside of the developing device 21 against the spring force of the pressure spring 44 that presses the arm 46 to which the knob 47 is fixed to the developing roller 28 side, as shown in FIG. ), The rotary shaft 4 of the developing roller 28 is pulled out from the fixed recess 50 shown in FIG.
3 becomes rotatable. While the knob 47 is pulled outside the developing device 21, the knob 47 is rotated around the rotation shaft 43, as shown in FIG.
By fitting the fixing piece 45 into the fixing recess 51 shown in (b), the fixing piece 45 is pressed by the pressure spring 44.
Is fixed in the fixed recess 51. As a result, the magnet roller 30 is fixed at the second angular displacement position, and the magnetization distribution is arranged in the direction of the photosensitive drum 34 as shown in FIG.

The fixed recess 51 is the fixed recess 5 as described above.
Since the groove is deeper than 0, the knob 47 can be fitted into the mounting groove 49 provided on the inner surface of the housing 48 of the printing apparatus main body. In this way, the developing device 21 can be mounted on the main body of the printing apparatus when the magnet roller 30 is fixed at the second angular displacement position.

As described above, according to the present embodiment, in the developing device 21, the magnet roller 30 is fixed at the first angular displacement position during conveyance, and the developer contained in the developing tank 35 is directed to the inside of the developing tank 35. It is held inside the developing tank 35 by the magnetization distribution of the magnet roller 30. Further, the opening 32 for supplying the developer to the surface of the photosensitive drum 34 via the developing roller 28 is covered with a seal member 33, and the end of the seal member 33 is brought into close contact with the housing 40 by a sealing member 39. . As a result, it is possible to prevent the developer from leaking from the developing device 21 at the time of conveyance, so that it is not necessary to provide a compartment as in the conventional case, and the developing device 21 can be made light and compact. Furthermore, since the compartment is not provided, the components inside the printing apparatus main body can be efficiently arranged close to each other, and the printing apparatus main body can be reduced in weight and size. Furthermore, since the developing device 21 does not have a compartment, the mold forming the housing 40 of the developing device 21 does not become complicated, and the manufacturing cost can be kept low.

The magnet roller 30 is fixedly rotated by the rotary shaft 43 of the developing roller 28, and the fixing piece 45 attached to the rotary shaft 43 by the arm 46 is fitted into the fixed recess 50 and the fixed recess 51. By doing so, it is fixed at the first angular displacement position and the second angular displacement position. When the magnet roller 30 is in the first angular displacement position, the fixed recess 5
Since the groove 0 is shallower than the fixed recess 51, the fixing member 52 projects outside the developing device 21, and the knob 47 contacts the housing 48 of the main body of the printing device to mount the developing device 21 on the printing device. To prevent Magnet roller 3
When 0 is in the second angular displacement position, the fixing member 52 is fitted in the fixing recess 51, and the width of the developing device 21 becomes equal to the mounting width of the printing apparatus main body. As a result, the developing device 21 can be attached to the main body of the printing apparatus. In this way, when the magnet roller 30 is in the first angular displacement position, the knob 47 protruding outward of the developing device 21 prevents the developing device 21 from being attached to the main body of the printing device, so that the magnet 37 is attached. It is possible to prevent printing defects due to the printing operation performed while the magnetic distribution is arranged toward the inside of the developing tank 35.

As described above, since the developing device 21 has a simple structure and fixes the magnetized distribution of the magnet roller 30 in an appropriate direction, the developing device 21 can be made lighter and more compact. Manufacturing costs can be kept low.

[0035]

As described above, according to the present invention, the developing device incorporates the electrostatically charged powder developer in the housing, and the magnet roller is moved to the first angular displacement position by the fixing means attached to the rotating shaft of the magnet roller. And the second angular displacement position. The first angular displacement position is selected so that the magnetized distribution of the magnet roller is directed toward the inside of the housing, and the second angular displaced position is such that the magnetized distribution of the magnet roller supplies an appropriate amount of developer to the photoconductor. Since the optimum arrangement is selected, by fixing the magnet roller to the first angular displacement position during the transportation of the developing device, the electrostatically charged powder developer contained in the housing is retained by the magnetic force inside the housing. It is possible to prevent the powder developer from leaking from the housing when the developing device is conveyed. Further, when the developing device is attached to the main body of the printing apparatus and printing is performed, the magnet roller is fixed to the second angular displacement position, so that the photosensitive material can be supplied with an appropriate amount of the powder developer.

Further, since the developing device holds the developer inside the housing by the magnetic force of the magnet roller, it is not necessary to provide a structure for holding the developer inside the housing, and the developing device can be made lightweight and compact. In addition, the manufacturing cost of the developing device can be kept low because it is not necessary to complicate the structure of the housing. Further, in the developing device, since the fixing means for fixing the magnet roller to the predetermined angular displacement position is realized by a simple structure, it is possible to reduce the weight and size of the developing device.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance of a developing device 21 which is an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a configuration of a developing device 21.

FIG. 3 is a magnet roller 30 when the developing device 21 is conveyed.
3 is a schematic cross-sectional view showing the magnetization distribution of FIG.

FIG. 4 is a side view and a sectional view for explaining a structure in which a magnet roller 30 is fixed at a first angular displacement position.

FIG. 5 is a schematic cross-sectional view showing a magnetization distribution of the magnet roller 30 when the developing device 21 is attached to the printing device.

6A and 6B are a side view and a cross-sectional view for explaining a structure in which a magnet roller 30 is fixed at a second angular displacement position.

FIG. 7 is a perspective view showing an appearance of a conventional developing device 1 disclosed in Japanese Examined Patent Publication No. 63-9237.

8 is a schematic cross-sectional view showing the structure of the developing device 1 shown in FIG.

[Explanation of symbols]

 21 developing device 22 toner hopper 23 toner stirring roller 24 toner supply roller 26 toner concentration sensor 27 developer stirring roller 28 developing roller 29 magnet sleeve 30 magnet roller 32, 36 opening 34 photoconductor 35 developing tank 37 magnet 38 doctor

Claims (1)

[Claims] 1. A developing device detachably attached to a main body of an electrophotographic printing apparatus, comprising a magnet sleeve rotatably driven in a circumferential direction of an outer peripheral portion, and having a magnetization distribution composed of a main pole and a complementary pole. A magnet roller that adsorbs a chargeable powder developer on the magnet sleeve by the magnetization distribution to form a magnetic brush, conveys the developer by the magnet sleeve, and supplies the developer to the photoconductor; A housing to which a constituent member including the magnet roller is attached, and a housing containing a chargeable powder developer; and a rotation shaft of the magnet roller penetrating the housing and protruding outward, and provided at the end of the rotation shaft. And a fixing means provided with a fixing piece projecting to the housing side, the fixing member being urged and attached to the housing side by a spring to be mounted on the outer side surface of the magnet roller mounting portion of the housing. , 2
When the fixing piece is fitted into the one fixing recess and is fixed by the biasing force, the magnet roller is fixed at the first angular displacement position, and the other fixing recess is provided. The magnet roller is fixed at the second angular displacement position when the fixing piece is fitted to the and is fixed by the biasing force, and the first angular displacement position is selected so that the magnetization distribution of the magnet roller is directed toward the inside of the housing. The second angular displacement position is selected so that the magnetized distribution of the magnet roller is in an optimum direction for supplying an appropriate amount of developer to the photoconductor.