JP3269316B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image by an electrophotographic method, such as a copying machine, a facsimile, and a printer.

[0002]

2. Description of the Related Art FIG. 20 is a schematic sectional view of a first conventional image forming apparatus.

In FIG. 20, reference numeral 1 denotes a rotating photosensitive drum having a photoconductive layer on a hollow cylindrical conductive substrate, reference numeral 2 denotes a fixed shaft coaxial with the rotation center of the photosensitive drum 1, and reference numeral 3 denotes a scorotron system. A cleaning member 4 made of urethane rubber or the like and having its tip pressed against the surface of the photosensitive drum 1;
Reference numeral 5 denotes a drum housing provided with the photosensitive drum 1, the charger 3, and the cleaning member 4. 6 is an exposure device that irradiates a laser beam according to an image pattern, 7 is a magnetic one-component toner,
Reference numeral 8 denotes a toner hopper, and 9 denotes a transport blade. Numeral 10 has a gear driving unit to which a rotational force is transmitted at one end, and is rotatably installed while maintaining a constant gap (hereinafter referred to as a developing gap) in a portion closest to the photosensitive drum 1 (hereinafter referred to as a developing nip). A developing blade member pressed on the developing electrode member 10, a central axis 12 which is not coaxial with the center of rotation of the developing electrode member 10, and 13 is a plurality of magnetic poles. A fixed magnet integrally formed with the central shaft 12, a developing housing 14 on which the developing electrode member 10 and the developing blade 11 are arranged, and a DC voltage 15 superimposed on the developing electrode member 10 with an AC voltage. This is a developing power supply for applying a predetermined alternating voltage. A DC voltage of -300 V is superimposed on an AC voltage having a peak-to-peak voltage of 1.4 kV. 16
Is a recording paper, 17 is a transfer roller that presses against the photosensitive drum 1 via a member to be transferred, and 18 is a transfer power supply that applies a voltage to the transfer member. 21 is a spring formed of a spring member,
Reference numeral 22 denotes a gap regulating member provided near the both ends of the developing nip and having a constant thickness.

FIG. 21 is a side view of a first conventional image forming apparatus. In FIG. 21, reference numeral 14 denotes an integrated developing housing, 5 denotes a drum housing, 30 denotes a hinge, and 21 denotes a spring. The developing case 14 is connected to the drum case 5 by a hinge 30.
Can be rotated around the center, and the spring 21 is
Is attracted to the drum housing 5, and the developing electrode member 10 and the photosensitive drum 1 are pressed against each other via the gap regulating member 22.

With this configuration, the eccentricity and runout of the photosensitive drum 1 and the developing electrode member 10 are escaped by the rotational movement of the developing case 14 around the hinge 30, and the developing gap is set to 200 μm in thickness of the gap regulating member 22. And constant.

FIG. 3 is an explanatory view of the arrangement of magnetic poles. FIG.
FIG. 3 is a perspective view of an end portion of the fixed shaft 2 and the center shaft 12 (hereinafter, referred to as a shaft end portion).

[0007] In FIGS. 3 and 4, reference numeral 12 denotes a fixed magnet 13.
Central shafts 12 and 23 integrally formed with the developing electrode member 10 are flanges integrally formed with the developing electrode member 10 and coaxially positioning the rotation center of the developing electrode member 10 and the central shaft 12. The developing electrode member 10 rotates with respect to the central axis 12 by sliding between the flange 23 and the central axis 12.

L is an inter-axis reference line connecting the centers of the fixed shaft 2 and the central shaft 12, a and b are magnetic poles for generating magnetic fluxes of N and S poles on the surface of the developing electrode member 10, respectively, and M is a magnetic pole. The magnetic pole center line indicates the direction in which the magnetic flux of the maximum density is generated on the surface of the developing electrode member 10 by a.

Reference numeral 12 denotes a central shaft integrally formed with the fixed magnet 13, and reference numeral 23 denotes a flange integrally formed with the developing electrode member 10 for coaxially positioning the rotation center of the developing electrode member 10 and the central shaft 12. is there. The developing electrode member 10 rotates with respect to the central axis 12 by sliding between the flange 23 and the central axis 12.

Numeral 24 denotes a flange integrally formed with the photosensitive drum 1 and for positioning the rotation axis of the photosensitive drum 1 and the fixed shaft 2 coaxially.
4 rotates by sliding between the fixed shaft 2 and the fixed shaft 2. The fixed shaft 2 is fixed by being fitted into a round hole provided in the drum housing 5.

The center shaft 12 is provided with a D-cut-shaped rotation restricting portion 12d having a flat portion formed on a part of the outer periphery near the side end.
The angle formed by the rotation restricting portion 12d and the magnetic pole center line M is set to a predetermined size. The central shaft 1 is inserted into a regulating hole provided in the developing case 14 having the same shape as the D-cut cross section of the rotation regulating portion.
The set angle of the magnetic pole center line M with respect to the inter-axis reference line L is set by fitting the flat portion of the second rotation restricting portion 12d.

The operation of the image forming apparatus configured as described above will be described below.

First, the surface of the photosensitive drum 1 is uniformly charged to -500 V by the charger 3, and then an electrostatic latent image is formed by the laser beam from the exposure device 6.

On the other hand, a toner layer having a predetermined amount of toner and a predetermined amount of charge is formed on the developing electrode member 10 by the developing blade 11. This toner adheres to an image portion on the photosensitive drum 1 by an electric field generated in a developing gap by the developing power supply 15 to form a toner image.

On the other hand, the recording paper 16 is conveyed to a pressure contact portion (hereinafter referred to as a transfer nip) between the photosensitive drum 1 and the transfer roller 17 by a conveying means (not shown). And transfer power 1
The toner image on the photosensitive drum 1 is transferred onto the recording paper 16 by the electric field force generated by the transfer nip 8.

The recording paper 16 carrying the toner image on its surface is
The toner image is conveyed to a fixing unit (not shown), and the toner image is fixed to the surface by a fixing unit such as heat and pressure to form a final image.

On the other hand, the toner remaining on the photosensitive drum 1 without being transferred to the recording paper 16 in the transfer nip reaches the pressure contact portion with the cleaning member 4 with the rotation of the photosensitive drum 1 and is removed. Thereafter, the above-described steps after charging are repeated.

In the developing nip, an alternating electric field is formed by the developing power supply 15, and the toner repeats reciprocating motion in the developing nip due to the alternating electric field force. The voltage is applied such that the electric field formed in the image portion of the electrostatic latent image is in the opposite direction to the electric field formed in the non-image portion. At the end of the development, the electric field force and the magnetic force of the fixed magnet 13 are balanced so that the toner adheres toward the developing electrode in the non-image area and toward the photosensitive drum 1 in the image area. The electric field force is determined by the voltage of the developing power supply 15 and the size of the developing gap, and the magnetic force is determined by the strength of the magnetic pole, the distance (coaxiality) between the magnetic pole and the outer peripheral surface of the developing electrode member 10, and the set angle of the magnetic pole.

With the above arrangement, the resultant force of the electric field force and the magnetic force acts on the toner in the developing nip, and selectively adheres to only the image portion of the electrostatic latent image to form a toner image corresponding to the image pattern. You.

As an image forming apparatus, there is one proposed by the present inventor in Japanese Patent Application No. 4-241590. FIG.
2 is a schematic sectional view of such a second conventional image forming apparatus.

In FIG. 22, 1 is a rotating photosensitive drum having a photoconductive layer on a hollow cylindrical conductive substrate, 2 is a fixed shaft coaxial with the rotation center of the photosensitive drum 1, and 25 is a fixed shaft. A stationary magnet formed integrally with 2, a scorotron charger 3, and a cleaning member 4 made of urethane rubber or the like and having its tip pressed against the surface of the photosensitive drum 1. 6
Is an exposure device that irradiates laser light according to the image pattern,
Reference numeral 7 denotes a magnetic one-component toner, 8 denotes a toner hopper, and 9 denotes a transport blade. Reference numeral 10 denotes a photosensitive drum which has a gear driving unit to which a rotational force is transmitted at one end, and maintains a constant gap (hereinafter referred to as a developing gap) in a portion closest to the photosensitive drum 1 (hereinafter referred to as a developing nip). The developing electrode member 12 is a hollow cylindrical conductor rotating in a direction opposite to that of the developing electrode member 12.
A fixed shaft 1 which has a plurality of magnetic poles and is formed integrally with the center shaft
Reference numerals 3 and 26 denote toner reservoirs, and 27 denotes a scraper formed of a plate-like member such as phosphor bronze and having its tip pressed against the developing electrode member 10. Reference numeral 14 denotes a developing housing in which the developing electrode member 10 and the scraper 27, the toner reservoir 26, and the toner hopper 8 are disposed. Reference numeral 15 denotes a developing power supply for applying a predetermined alternating voltage obtained by superimposing a DC voltage on an AC voltage to the developing electrode member 10. .
A DC voltage of -300 V is superimposed on an AC voltage having a peak-to-peak voltage of 1.4 kV. 16 is a recording paper, 17 is a transfer roller that presses against the photosensitive drum 1 via a transfer member, 1
Reference numeral 8 denotes a transfer power supply for applying a voltage to the transfer member. Reference numeral 21 denotes a spring formed of a spring member, and reference numeral 22 denotes a gap regulating member provided near both ends of the developing nip and having a certain thickness.

FIG. 23 is a side view of a second conventional image forming apparatus. In FIG. 23, 14 is a developing case, 5 is a drum case, 30 is a hinge, and 21 is a spring. Developing case 1
Reference numeral 4 denotes a rotatable movement about the hinge 30 with respect to the drum housing 5, and a spring 21 connects the developing housing 14 to the drum housing 5.
The developing electrode member 10 and the photosensitive drum 1 are pressed against each other via the gap regulating member 22.

With this configuration, the eccentricity and the deflection of the photosensitive drum 1 and the developing electrode member 10 are escaped by the rotational movement of the developing casing 14 about the hinge 30, and the developing gap is set to 200 μm in thickness of the gap regulating member 22. And constant.

Next, a configuration for forming a magnetic field will be described. FIG. 7 shows the setting positions of the photosensitive drum 1, the developing electrode member 10, the fixed magnet 13, and the fixed magnet 25. In the fixed magnet 25 in the photosensitive drum 1, the magnetic pole c is an S pole, and the magnetic pole d
Is the N pole. In the fixed magnet 13 in the developing electrode member 10, the magnetic pole a is an N pole and the magnetic pole b is an S pole. Magnetic pole c
Means that the maximum magnetic flux density is 620 to 700 G and the set angle B = 35 on the upstream side in the rotation direction of the photosensitive drum 1 from the inter-axis reference line L.
゜, the magnetic pole d was set at 440 to 530 G and B ′ = 5 °. The magnetic pole a has a set angle A = 20 ° at 550 to 630 G, and the magnetic pole b has A ′ = 20 ° at 380 to 470 G. The magnetic flux density shown here is measured independently on each surface of the photosensitive drum 1 and the developing electrode member 10.

The fixed magnet 13 is formed integrally with the center shaft 12. The central axis 12 is set coaxially with the developing electrode member 10 via the flange 23. Further, the developing electrode member 10 rotates with respect to the central axis 12 as the flange 23 and the central axis 12 slide.

The center shaft 12 is provided with a D cut-shaped rotation restricting portion 12d in which a flat portion is formed on a part of the outer periphery near the side end.
The angle formed by the rotation restricting portion 12d and the magnetic pole center line M is set to a predetermined size. Then, by inserting the D-cut portion of the rotation restricting portion 12d into the D-cut mounting hole of the rotation restricting portion provided in the developing case 14, the set angle of the magnetic pole center line M with respect to the inter-axis reference line L (hereinafter, referred to as a reference angle). Set angle A
Described).

On the other hand, the fixed magnet 25 is formed integrally with the fixed shaft 2. The fixed shaft 2 is set coaxially with the photosensitive drum 1 via a flange 24. Further, the photosensitive drum 1 rotates with respect to the fixed shaft 2 as the flange 24 and the fixed shaft 2 slide.

The fixed shaft 2 is provided with a D-shaped rotation restricting portion 2d having a flat portion formed on a part of the outer periphery near the side end, and an angle formed by the rotation restricting portion 2d and the magnetic pole center line N is set to a predetermined value. It is set to. Then, by inserting the D-cut portion of the rotation restricting portion 2d into the fixed shaft restricting hole having the same shape as the D-cut cross section of the rotation restricting portion 2d provided in the developing housing 14, the axis reference line of the magnetic pole center line N is inserted. A set angle for L (hereinafter referred to as set angle B) is set. With this configuration, a magnetic field is formed in the developing nip portion of the photosensitive drum 1.

With the above configuration, the developing electrode member 10
A magnetic field is formed in the developing nip portion of the photosensitive drum 1 opposite to the developing nip. Since this magnetic field makes the two magnetic fields face each other at a short distance, the form of the magnetic field is determined by a balance of many parameters. For this reason, the influence of each parameter is very large as compared with the case where the parameter exists alone.

The operation of the image forming apparatus configured as described above will be described below.

First, the surface of the photosensitive drum 1 is uniformly charged to -450 V by the charger 3, and then an electrostatic latent image is formed by the exposure device 6. Thereafter, the toner is developed in the developing nip, and a toner image is formed on the surface of the photosensitive drum 1.

The recording paper 16 carrying the toner image on its surface is
The toner image is conveyed to a fixing unit (not shown), and the toner image is fixed to the surface by a fixing unit such as heat and pressure to form a final image.

On the other hand, the developer remaining on the photosensitive drum 1 without being transferred to the recording paper 16 in the transfer nip reaches the pressure contact portion with the cleaning member 4 with the rotation of the photosensitive drum 1 and is removed. . Thereafter, the above-described steps after charging are repeated.

Next, the process of developing an electrostatic latent image with toner will be described. First, the toner in the toner hopper 8 is supplied into the toner reservoir 26 with the rotation of the transport blade 9.

The toner supplied into the toner reservoir 26 is
Due to the magnetic force of the fixed magnet 25, the toner adheres to the entire surface of the photosensitive drum 1 irrespective of the electrostatic latent image. Next, as the photosensitive drum 1 rotates, the toner is conveyed to the vicinity of the development nip while receiving a magnetic force on the surface of the photosensitive drum 1.

The amount of toner conveyed into the developing nip is determined by the balance of the magnetic force between the fixed magnet 13 and the fixed magnet 25. In the developing nip, an alternating electric field is formed by the developing power supply 15, and the toner repeats reciprocating motion in the developing nip due to the alternating electric field force. The DC voltage superimposed on the AC voltage is applied such that the electric field formed in the image portion of the electrostatic latent image is in the opposite direction to the electric field formed in the non-image portion. At the end of the development, the toner is transferred in the direction of the developing electrode in the non-image area and the photosensitive drum 1 in the image area.
The electric field force and the magnetic force of the fixed magnet 13 and the fixed magnet 25 are balanced so as to adhere in the direction.

The electric field force is determined by the voltage of the developing power supply 15 and the size of the developing gap. The magnetic force is determined by the strength of the magnetic pole, the coaxiality between the fixed magnet 13 and the outer peripheral surface of the developing electrode member 10, and the fixed magnet 25 and the photosensitive member. Coaxiality with drum 1 outer peripheral surface,
Distance between fixed magnet 13 and fixed magnet 25, fixed magnets 13, B
Are determined by the set positions of all the magnetic poles. In particular, since two fixed magnets, a total of four poles, are opposed to each other, a change in one parameter greatly affects the entire magnetic field.

With the above arrangement, the resultant force of the electric field force and the magnetic force acts on the toner during the reciprocating motion, and selectively adheres only to the image portion of the electrostatic latent image to form a toner image corresponding to the image pattern. Is done.

On the other hand, the toner in the non-image area is
Receives the magnetic force and the electric field force, and adheres to the developing electrode member 10.
Collected in 6. The collected toner is in a scraper 2
The toner is scraped off from the surface of the developing electrode member 10 by the magnetic force 7, and again adheres to the surface of the photosensitive drum 1 under the action of the magnetic force to be used for the next image formation.

In this type of developing method, all the charge patterns on the photosensitive drum 1 are visualized immediately above the photosensitive drum 1 having the maximum S / N ratio between the image portion and the non-image portion, and the development of the non-image portion is performed. The agent can be effectively removed, and a high-resolution image can be obtained.

[0041]

However, in the above-mentioned conventional structure, the eccentricity and the deflection of the photosensitive drum 1 and the developing electrode member 10 are escaped by the rotational movement about the hinge 30 of the developing housing 14. In addition, the set angle formed by the magnetic poles of the fixed magnet 13 and the fixed magnet 25 with a line connecting the developing electrode member 10 and the center of the axis of the photosensitive drum 1 (hereinafter referred to as an inter-axis reference line L) changes.

FIG. 19 schematically shows a situation in which the rotational movement of the developing case 14 changes the set angle of the fixed magnet. FIG.
In FIG. 9, first, the photosensitive member center 0, the developing electrode member 10 center Q, the inter-axis reference line L, and the magnetic pole center line M are arranged as indicated by the solid lines. In this state, the distance between the axis of the photosensitive drum 1 and the axis of the developing electrode member 10 changes due to the eccentricity and the deflection of the photosensitive drum 1 and the developing electrode member 10. At this time, the rotation of the developing case 14 about the hinge P causes the center Q to be displaced to Q 'and the inter-axis reference line L to be displaced to L' as shown by the broken line in the figure. Then, the magnetic pole center line M is displaced to M ′.

At this time, the angle θ formed by L and M is the angle θ ′ formed by L ′ and M ′. The relationship of θ′−θ = δ1 + δ2 holds between these angles. That is, the set angle of the magnetic pole with respect to the inter-axis reference line changes by (δ1 + δ2). This is because the developing electrode member 10 and the fixed magnet 13 are displaced not by a translational motion but by a rotational motion with respect to the inter-axis reference line L.

As described above, since the magnetic pole position deviates from the set position, a change in image density and fogging of toner on the non-image portion occur in accordance with the rotation cycle of the photosensitive drum 1 and the developing electrode member 10. There was a problem that it occurred.

In particular, as shown in FIG. 22, when a fixed magnet is included in both the photosensitive drum 1 and the developing electrode member 10, the relative positions of the magnetic poles are more important together with the balance between the two fixed magnets. When the fixed magnet 25 and the fixed magnet 13 are moved or rotated with respect to a predetermined position and a set direction, the magnetic field generated in the developing nip changes greatly, and greatly affects image quality.

Accordingly, the relative angle of the magnetic pole with respect to the reference line between the axes changes due to the rotation of the developing case 14 about the hinge as the photosensitive drum 1 and the developing electrode member 10 having eccentricity and runout rotate. There has been a problem that image quality changes such as a change in image density corresponding to the rotation cycle of the photosensitive drum 1 and the developing electrode member 10 and a fog on a non-image portion cause a great decrease in image quality.

The developing electrode member 10 and the fixed magnet 13
Are separately provided on the developing housing 14 and the photosensitive drum 1 and the fixed magnet 25 are separately provided on the drum housing 5. Therefore, the developing electrode member and the fixed magnet A for the photosensitive drum 1 and the fixed magnet 25 are separately provided. Position accuracy cannot be guaranteed, and the image quality is greatly reduced.

In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of forming a high-quality image by generating a predetermined magnetic field in a developing nip accurately and stably. I do.

[0049]

SUMMARY OF THE INVENTION According to the present invention, there is provided a magnetic developer, a rotatable image holding member carrying a charge pattern on a surface thereof, and a rotatable image holding member which faces the image holding member with a gap therebetween. And a movably provided developing electrode member, pressing means for pressing at least the developing electrode member against the image carrier, gap regulating means interposed in the gap to regulate the developing electrode member to a fixed size, and a rotation center of the developing electrode member. A central axis coaxially disposed with respect to the first axis; a first magnetic flux generating unit formed integrally with the central axis to generate a magnetic flux on the surface of the developing electrode member; an image holding member; and a developing electrode member. And a central shaft guide provided on the mounting member for guiding the first magnetic flux generating means so as to be able to translate in one direction together with the developing electrode member while regulating the rotation of the central axis of the developing electrode member. Means and an electric field applied to the opposing portion between the image carrier and the developing electrode. Formation to those provided with the electric field generating means.

[0050]

According to the above construction of the present invention, the magnetic flux generating means is rotated while maintaining the gap between the image forming member and the developing electrode member, and the coaxiality of the magnetic flux generating means, the developing electrode member and the image carrier constant. The translation can be performed while maintaining a predetermined angle instead of the movement. Therefore, even if the image bearing member and the developing electrode member rotate with eccentricity and run-out, and the inter-axis distance between both members changes, the set angle of the magnetic pole with respect to the inter-axis reference line of the magnetic flux generating means does not change. Therefore, a predetermined magnetic field can be stably formed in the developing nip. Therefore,
A predetermined magnetic force can be reliably applied to the developer conveyed to the developing nip, thereby preventing a decrease in image quality such as a change in image density or fogging on a non-image portion.

Further, since the image carrier and the fixed shaft / magnetic flux generating means inside the image carrier and the developing electrode member and the central axis / magnetic flux generating means inside the image carrier are arranged on an integral disposing member, their relative positions and The set angle can be easily and accurately arranged.

[0052]

【Example】

(Embodiment 1) An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an image forming apparatus according to a first embodiment of the present invention, and FIG. 2 is a side view of a developing section thereof.
Here, the developing section refers to the vicinity where the photosensitive drum and the developing electrode member are disposed.

1 and 2, reference numeral 1 denotes a rotating photosensitive drum having a photoconductive layer on a hollow cylindrical conductive substrate, 2 denotes a fixed shaft coaxial with the rotation center of the photosensitive drum 1, and 3 denotes a rotating shaft. The scorotron charger 4 is a cleaning member formed of urethane rubber or the like and having its tip pressed against the surface of the photosensitive drum 1. 6 is an exposure device that irradiates a laser beam according to an image pattern, 7 is a magnetic one-component toner, 8 is a toner hopper,
9 is a conveying blade. Numeral 10 has a gear driving unit to which a rotational force is transmitted at one end, and is rotatably installed while maintaining a constant gap (hereinafter referred to as a developing gap) in a portion closest to the photosensitive drum 1 (hereinafter referred to as a developing nip). A developing blade member pressed on the developing electrode member 10, a central axis 12 which is not coaxial with the center of rotation of the developing electrode member 10, and 13 is a plurality of magnetic poles. Fixed magnet integrally formed with the central shaft 12, 15
A developing power supply for applying a predetermined alternating voltage obtained by superimposing a DC voltage on an AC voltage to the developing electrode member 10. A DC voltage of -300 V is superimposed on an AC voltage having a peak-to-peak voltage of 1.4 kV. Reference numeral 16 denotes a recording paper, reference numeral 17 denotes a transfer roller which presses the photosensitive drum 1 through a transfer target member, and reference numeral 18 denotes a transfer power supply for applying a voltage to the transfer member. Reference numeral 41 denotes an integrated developing housing in which the photosensitive drum 1, the developing electrode member 10, and the developing blade 11 are arranged, 42 denotes a pressing member formed of a spring member,
Reference numeral 43 denotes a long hole-shaped center axis regulating hole provided in the developing case 41. Reference numeral 22 denotes a gap regulating member provided near the both ends of the developing nip and having a constant thickness. Pressing member 4
Numeral 2 presses the central shaft 12 to bring the developing electrode member 10 and the photosensitive drum 1 into pressure contact with each other via the gap regulating member 22.

FIG. 3 is an explanatory view of the magnetic pole arrangement in this embodiment. FIG. 4 shows the fixed shaft 2 and the central shaft 12 in this embodiment.
It is a perspective view of the end part.

3 and 4, reference numeral 12 denotes a fixed magnet 13
Central shafts 12 and 23 integrally formed with the developing electrode member 10 are flanges integrally formed with the developing electrode member 10 and coaxially positioning the rotation center of the developing electrode member 10 and the central shaft 12. The developing electrode member 10 rotates with respect to the central axis 12 by sliding between the flange 23 and the central axis 12.

L is an inter-axis reference line connecting the centers of the fixed axis 2 and the center axis 12, a and b are magnetic poles for generating magnetic fluxes of N and S poles on the surface of the developing electrode member 10, respectively, and M is a magnetic pole. The magnetic pole center line indicates the direction in which the magnetic flux of the maximum density is generated on the surface of the developing electrode member 10 by a.

The center shaft 12 has a D-shaped rotation restricting portion 12d having a flat portion formed on a part of the outer periphery near the side end.
The angle formed by the rotation restricting portion 12d and the magnetic pole center line M is set to a predetermined size. A central shaft regulating hole 43 provided in the developing case 41 having the same shape as the D-cut cross section of the rotation regulating portion.
The error of the set angle (hereinafter referred to as set angle A) of the magnetic pole center line M with respect to the inter-axis reference line L is set within a range of ± 3 ° You have set. When the set angle A is determined, A 'is automatically determined.

Reference numeral 2 denotes a fixed shaft fixed to the drum housing;
Is a flange integrally formed with the photosensitive drum 1 and coaxially positioning the rotation center of the photosensitive drum 1 and the fixed shaft 2. The photosensitive drum 1 is formed by sliding the flange 24 and the fixed shaft 2. Rotate. The fixed shaft 2 is fixed by fitting it into a hole provided in the drum housing.

With these configurations, a magnetic field is formed in the developing nip portion of the developing electrode member 10. The operation of the image forming apparatus configured as described above will be described below. This operation is divided into an overall image forming process and a developing process for visualizing the electrostatic latent image.

First, the image forming process will be described. The surface of the photosensitive drum 1 is uniformly charged to −500 V by the charger 3, and then an electrostatic latent image is formed by the laser beam of the exposure device 6. Then, an electric field generated in the developing gap by the developing power supply 15 adheres to the electrostatic latent image on the photosensitive drum 1 to form a toner image.

On the other hand, the recording paper 16 is conveyed by a conveying means (not shown) to a pressure contact portion (hereinafter referred to as a transfer nip) between the photosensitive drum 1 and the transfer roller 17. And transfer power 1
The toner image on the photosensitive drum 1 is transferred onto the recording paper 16 by the electric field force generated by the transfer nip 8.

The recording paper 16 carrying the toner image on its surface is
The toner image is conveyed to a fixing unit (not shown), and the toner image is fixed to the surface by a fixing unit such as heat and pressure to form a final image.

On the other hand, the toner remaining on the photosensitive drum 1 without being transferred to the recording paper 16 in the transfer nip reaches the pressure contact portion with the cleaning member 4 with the rotation of the photosensitive drum 1 and is removed. Thereafter, the above-described steps after charging are repeated.

Next, the developing step will be described. First, a toner layer having a predetermined amount of toner and a predetermined amount of charge is formed on the developing electrode member 10 by the developing blade 11. In the developing nip, an alternating electric field is formed by the developing power supply 15,
The toner repeats reciprocating motion in the developing nip due to the alternating electric field force. The electric field formed in the image portion of the electrostatic latent image is
A voltage is applied so as to be in the opposite direction to the electric field formed on the non-image portion. At the end of development, the toner
The electric field force and the magnetic force of the fixed magnet 13 are balanced so as to adhere to the developing electrode in the non-image area and toward the photosensitive drum 1 in the image area. The electric field force is determined by the voltage of the developing power supply 15 and the size of the developing gap, and the magnetic force is determined by the strength of the magnetic pole, the distance (coaxiality) between the magnetic pole and the outer peripheral surface of the developing electrode member 10, and the set angle of the magnetic pole.

With the above configuration, the resultant force of the electric field force and the magnetic force acts on the toner in the developing nip, and selectively adheres to only the image portion of the electrostatic latent image to form a toner image corresponding to the image pattern. You.

In this embodiment, by disposing the photosensitive drum 1 and the developing electrode member 10 in the integral developing housing 41, the developing electrode member 10 and the photosensitive drum 1 can be arranged with high precision. In addition, the D-shaped rotation restricting portion 12d provided on the central shaft 12 is provided with a central shaft restricting hole 43 provided on the developing housing 41 having the same width as the D cut of the rotation restricting portion 12d.
Has been inserted. With this configuration, the developing electrode member 10
Is pressed against the photosensitive drum 1 via the gap regulating member 22 to keep the size of the developing gap constant and to maintain the coaxiality of the central axis 12 integral with the developing electrode member 10 and the fixed magnet 13. Even if the photosensitive drum 1 and the developing electrode member 10 are eccentric or run out, the center axis 12
And the fixed magnet 13 translates, so that the set angle A does not change. Therefore, a stable magnetic field is reliably formed in the developing nip, and a high-quality image can be obtained.

In the developing step used in this embodiment, when the size of the developing gap changes, the electric field intensity in the developing gap changes. Accordingly, when the developing electrode member 10 is fixed to the developing case 41 together with the central shaft 12 and the developing gap is defined by the distance between the fixed shaft 2 and the developing shaft, the developing gap is degraded due to the deflection and eccentricity of the photosensitive drum 1 and the developing electrode member 10. Fluctuates, the electric field intensity changes, and the image quality deteriorates.

When the distance (coaxiality) between the fixed magnet 13 and the developing electrode member 10 changes, the intensity of the magnetic field on the surface of the developing electrode member 10 changes. For this reason, the coaxiality of the fixed magnet 13 and the developing electrode member 10 is important. Therefore, the central axis 1
2 is fixed to the developing case 41 independently of the developing electrode member 10 so that only the developing electrode member 10 is movable, the photosensitive drum 1, the developing electrode member 10 and the fixed magnet 13 And the magnetic force of the developing nip changes, thereby deteriorating the image quality.

In this embodiment, the fixed shaft 2 extends over the entire width of the photosensitive drum 1 in the longitudinal direction. However, the fixed shaft 2 may be configured to support only both ends of the photosensitive drum 1.

Further, in this embodiment, a D-cut shape is provided in which one rotation regulating surface is provided at the end of the central shaft 12, but two or more rotation regulating surfaces may be provided.

The fixed magnet 13 in the developing electrode member 10
May be composed of two or more poles.

(Embodiment 2) A second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a sectional view of an image forming apparatus according to a second embodiment of the present invention, and FIG. FIG.

In this embodiment, differences from the first embodiment will be described with reference to FIGS. 2 is a photosensitive drum 1
25 is a fixed shaft that is non-rotating and coaxial with the center of rotation of
The fixed magnet is formed integrally with the fixed magnet. Reference numeral 10 denotes a photoreceptor which has a gear driving unit to which a rotational force is transmitted at one end, and which keeps a constant gap (hereinafter referred to as a developing gap) at a portion closest to the photoreceptor drum 1 (hereinafter referred to as a developing nip). A developing electrode member, which is a hollow cylindrical conductor rotating in the opposite direction to the drum 1; a gap regulating member 22 provided near both ends of the developing nip and having a constant thickness; and 12 a rotating center of the developing electrode member 10; A central shaft which is not coaxial and does not rotate; 13 is a fixed magnet integrally formed with the central shaft 12; 26 is a toner reservoir; 27 is a scraper formed of a plate-like member such as phosphor bronze and having its tip pressed against the developing electrode member 10 It is. 41 is a photosensitive drum 1, a developing electrode member 10, and a scraper 2
7, a developing case in which the toner reservoir 26 and the toner hopper 8 are disposed. Reference numeral 4 denotes a cleaning member formed of urethane rubber or the like and having a tip pressed against the surface of the photosensitive drum 1, and reference numeral 15 denotes a developing power supply for applying a predetermined alternating voltage obtained by superimposing a DC voltage on an AC voltage to the developing electrode member 10. A DC voltage of -250 V is superimposed on an AC voltage having a peak-to-peak voltage of 1.4 kV. The photosensitive drum 1 and the developing electrode member 10 are brought into pressure contact with each other via a gap regulating member 22, so that the developing gap is kept constant at 200 μm.

The other components and the overall image forming process are the same as in the first embodiment. Next, a configuration for forming a magnetic field in the present embodiment will be described. FIG. 7 shows a photosensitive drum 1, a developing electrode member 10, a fixed magnet 13, and a fixed magnet 2.
5 shows the setting position. Fixed magnet 25 in photoconductor drum 1
, The magnetic pole c is an S pole and the magnetic pole d is an N pole. In the fixed magnet 13 in the developing electrode member 10, the magnetic pole a is N
The pole and the magnetic pole b are S poles. The magnetic pole c has a maximum magnetic flux density of 6 on the upstream side in the rotation direction of the photosensitive drum 1 from the inter-axis reference line L.
20-700G, set angle B = 35 °, magnetic pole d is 440-
At 530 G, B ′ was set to 5 °. Magnetic pole a is 550-6
30G, set angle A = 20 °, magnetic pole b is 380-470G
And A ′ = 20 °. The magnetic flux density shown here is measured independently on each surface of the photosensitive drum 1 and the developing electrode member 10.

With the above configuration, the developing electrode member 10
A magnetic field is formed in the developing nip portion of the photosensitive drum 1 opposite to the developing nip. Since this magnetic field makes the two magnetic fields face each other at a short distance, the form of the magnetic field is determined by a balance of many parameters. For this reason, the influence of each parameter is much greater than in the case where it is present alone.

FIG. 8 is a perspective view of the shaft end. 7 and 8
, The fixed magnet 13 is formed integrally with the center shaft 12. The central axis 12 is set coaxially with the developing electrode member 10 via the flange 23. Further, the developing electrode member 1
Numeral 0 rotates with respect to the central axis 12 by sliding the flange 23 and the central axis 12.

The center shaft 12 is provided with a D-cut-shaped rotation restricting portion 12d having a flat portion formed on a part of the outer periphery near the side end.
The angle formed by the rotation restricting portion 12d and the magnetic pole center line M1 is set to a predetermined size. Then, by inserting the D cut portion of the rotation restricting portion 12d into the center shaft restricting hole 43 having substantially the same dimension as the D cut width of the rotation restricting portion provided in the developing case 41, the axis of the center line M1 of the magnetic pole a is formed. The error of the set angle A with respect to the inter-base line L is set within a range of ± 3 °.
With this configuration, a magnetic field is formed on the surface of the developing electrode member 10.

On the other hand, the fixed magnet 25 is formed integrally with the fixed shaft 2. The fixed shaft 2 is set coaxially with the photosensitive drum 1 via a flange 24. Further, the photosensitive drum 1 rotates with respect to the fixed shaft 2 as the flange 24 and the fixed shaft 2 slide.

The fixed shaft 2 is provided with a D-shaped rotation restricting portion 2d in which a flat portion is formed on a part of the outer periphery near the side end, and an angle formed by the rotation restricting portion 2d and the magnetic pole center line M2 is a predetermined angle. It is set to. Then, by inserting the D cut portion of the rotation restricting portion 2d into the fixed shaft restricting hole 44 having the same shape as the D cut cross section of the rotation restricting portion B provided in the developing case 41, the axis of the center line N of the magnetic pole c is formed. The error of the set angle B with respect to the reference line L is set within a range of ± 3 °. With this configuration, a magnetic field is formed in the developing nip portion of the photosensitive drum 1.

Next, the process of developing an electrostatic latent image with toner will be described. First, the toner in the toner hopper 8 is supplied into the toner reservoir 26 with the rotation of the transport blade 9.

The toner supplied into the toner reservoir 26 is
Due to the magnetic force of the fixed magnet 25, the toner adheres to the entire surface of the photosensitive drum 1 irrespective of the electrostatic latent image. Next, as the photosensitive drum 1 rotates, the toner is conveyed to the vicinity of the development nip while receiving a magnetic force on the surface of the photosensitive drum 1.

The amount of toner conveyed into the developing nip is determined by the balance of the magnetic force between the fixed magnet 13 and the fixed magnet 25. In the developing nip, an alternating electric field is formed by the developing power supply 15, and the toner repeats reciprocating motion in the developing nip due to the alternating electric field force. The DC voltage superimposed on the AC voltage is applied such that the electric field formed in the image portion of the electrostatic latent image is in the opposite direction to the electric field formed in the non-image portion. At the end of the development, the toner is transferred in the direction of the developing electrode in the non-image area and the photosensitive drum 1 in the image area.
The electric field force and the magnetic force of the fixed magnet 13 and the fixed magnet 25 are balanced so as to adhere in the direction.

The electric field force is determined by the voltage of the developing power supply 15 and the size of the developing gap. The magnetic force is determined by the strength of the magnetic pole, the coaxiality between the fixed magnet 13 and the developing electrode member 10, the fixed magnet 25 and the photosensitive drum 1 , The distance between the fixed magnet 13 and the fixed magnet 25, and the set positions of the magnetic poles a to d. In particular, since two fixed magnets, a total of four poles, are opposed to each other, a change in one parameter greatly affects the entire magnetic field.

With the above configuration, the resultant force of the electric field force and the magnetic force acts on the toner during the reciprocating movement, and selectively adheres only to the image portion of the electrostatic latent image to form a toner image corresponding to the image pattern. Is done.

On the other hand, the toner in the non-image area is
Is applied to the developing electrode member 10 by receiving the magnetic force and the electric field force, and is collected in the toner reservoir 26 as the developing electrode member 10 rotates. The collected toner is in a scraper 2
The toner is scraped off from the surface of the developing electrode member 10 by the magnetic force 7, and again adheres to the surface of the photosensitive drum 1 under the action of the magnetic force to be used for the next image formation.

In this type of developing method, all the charge patterns on the photosensitive drum 1 are visualized immediately above the photosensitive drum 1 having the maximum S / N ratio between the image portion and the non-image portion, and the toner in the non-image portion is Can be effectively removed, and a high-resolution image can be obtained.

In the structure of this embodiment, the developing gap is kept constant by pressing the photosensitive drum 1 and the developing electrode member 10 through the gap regulating member 22. For this reason, when the photosensitive drum 1 and the developing electrode member 10 having a runout or eccentricity rotate, the axial interval between the fixed shaft 2 and the central shaft 12 must be changed. At this time, the central shaft 12 translates while sliding on the inner surface of the central shaft regulating hole 43. Since the D-shaped rotation restricting portion of the central shaft 12 is inserted into the elongated central hole restricting hole 43 of the same width, the central shaft 1
The movement of 2 and fixed magnet 13 is limited to translational movement.

FIG. 9 shows that the developing gap is changed in the developing step of this embodiment, the fixed magnet 13 is displaced independently of the rotation center of the developing electrode member 10 (coaxiality is changed), and the set angle of the fixed magnet 25 is changed. FIG. 9 is a diagram showing a change in image quality that occurs when a set angle B of the fixed magnet 13 is displaced. The horizontal axis is the displacement angle of the fixed magnet 25, and the vertical axis is the fixed magnet 1
3 is the displacement angle. The origin of the set centrality is set as the origin, and the sign of the displacement angle is set to the positive sign on the upstream side in the rotation direction of the photosensitive drum 1 or the developing electrode member 10. The solid line indicates that the development gap is 2
In this case, the fixed magnet 13 is arranged coaxially with the center of rotation of the developing electrode member 10. The broken line indicates the case where the developing gap is 250 μm, and the dashed line indicates the case where the fixed magnet 13 is displaced in the direction of the photosensitive drum 1 by 0.25 mm from the rotation center of the developing electrode member 10.

The curves in the drawing represent contour lines of image density or fog. The image density was 1.35 or less as low density. In the lower right direction, the image density is 1.35 or less. Further, in a region above and to the left of the upper left broken line, the adhesion of the developer to the non-image portion, so-called "fogging" occurs. The broken line shows only the boundary where fogging occurs, and the dashed line shows only the boundary where the image density becomes 1.35.

From the results shown in FIG. 9, it is understood that the coaxiality between the fixed magnet 13 and the developing electrode member 10 is important. It is considered that this is because the magnetic field of the developing nip changes due to a change in the distance between the magnetic pole position and the developing electrode member 10 and the fixed magnet 25. Therefore, the central axis 12 is
When only the developing electrode member 10 is movable and fixed to the developing frame independently of the photosensitive drum 1, the developing electrode member 1
The developing electrode member 10 and the fixed magnet 13
, The balance between the magnetic force and the electric field force of the developing nip is lost, and the image quality is reduced.

From the results shown in FIG. 9, it is understood that the size of the developing gap is important. This is considered to be mainly due to the change in the electric field strength due to the change in the distance between the electrodes. Therefore, when the developing electrode member 10 is fixed to the developing frame together with the center shaft 12 and the developing gap is defined by the distance between the fixed shaft 2 and the developing shaft, the developing gap fluctuates due to deflection and eccentricity of the photosensitive drum 1 and the developing electrode member 10. However, the balance between the electric field force and the magnetic force is lost, and the image quality is reduced.

According to the above configuration of this embodiment, the fixed shaft 2
Is provided in the integral developing case 41 on which the developing electrode member 10 is disposed, so that the center position of the fixed shaft 2 and the set angle of the fixed magnet 25 can be set. It can be set reliably.

Further, the D-shaped rotation restricting portion provided on the central shaft 12 is inserted into the central shaft restricting hole 43 which is a long hole provided in the developing case 41 having the same width as the D-cut portion of the rotation restricting portion. are doing. With this configuration, the developing electrode member 10 is pressed against the photosensitive drum 1 via the gap regulating member 22 to keep the size of the developing gap constant, and
While maintaining the coaxiality of the central axis 12 integrated with the fixed magnet 13 and the eccentricity and runout of the photosensitive drum 1 and the developing electrode member 10, the central axis 12 and the fixed magnet Since 13 is translated, the set angle does not change. Therefore, a stable magnetic field is reliably formed in the developing nip, and a high-quality image can be obtained.

(Embodiment 3) Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 10 is a block diagram of an image forming apparatus according to the third embodiment of the present invention. Other configurations and the developing process are the same as those of the second embodiment.

The present embodiment is different from the second embodiment in that, first, the center line in the longitudinal direction of the elongated hole-shaped center axis regulating hole 43 provided in the developing case 41 is aligned with the photosensitive drum 1. The second point is that the rotation center and the plane including the rotation center of the developing electrode member 10 are provided in parallel with each other, and the second point is that the pressure contact position of the cleaning member 4 is provided on the center axis reference line L. With this configuration, the acting direction of the resultant force of the pressing force by the cleaning member 4 and the pressing force by the pressing member 42 is the same as the inter-axis reference line L.

The second embodiment of the present invention has the following problems. The first is the displacement of the inter-axis reference line L. In FIG. 6, when the fixed magnet 13 translates, the set angle with respect to the inter-axis reference line L is constant. However, since the center axis 12 of the center axis regulating hole 43 is not on the same straight line as being inclined with respect to the original position of the center axis reference line L, the center axis reference line L itself, which is to be a reference with the movement of the center axis 12, is It will be displaced. Therefore, due to the translation of the fixed magnet 13, the set position of the developing nip and the magnetic pole is shifted. For this reason, the magnetic field generated in the development nip changes, and the image quality deteriorates.

Second, there is the problem of the deflection of the fixed shaft 2.
The pressing member 42 is connected to the developing electrode member 10 and the gap regulating member 2.
2, the photosensitive drum 1 is pressed at both ends, and the cleaning member 4 is pressing the photosensitive drum 1 from another direction.
As a result of this resultant force, the fixed shaft 2 receives bending moments at four points of both ends and the flange 24 of the photosensitive drum 1 as shown in FIG. For this reason, the fixed shaft 2 and the fixed magnet 25 are deformed as shown by the broken line in FIG.
The distance (coaxiality) between the photosensitive drum 1 and the surface of the photosensitive drum 1 changes in the longitudinal direction of the drum.

According to the configuration of this embodiment, while the center shaft 12 slides on the inner wall of the center shaft regulating hole 43 while the center shaft 12 slides on the rotation restricting portion 12d, the center shaft 12 and the fixed magnet 13 maintain the set angle and maintain the reference angle between the shafts. The translation can be performed on the line L. As a result, the developing electrode member 10 is pressed against the photosensitive drum 1 via the gap regulating member 22 to keep the size of the developing gap constant, and the central shaft 12 integrated with the developing electrode member 10 and the fixed magnet 13.
Even if the photosensitive drum 1 and the developing electrode member 10 have eccentricity and runout, the center axis 12 and the fixed magnet 13 translate on the inter-axis reference line L while maintaining the coaxiality of The set angle for L does not change at all.

Further, by arranging the cleaning member 4 on the photosensitive drum 1 on the reference line L between the axes, the direction of action of the resultant force of the pressing force by the cleaning member 4 and the pressing force by the pressing member 42 is determined by the reference between the axes. It is in the same direction as line L. As a result, the force by which the flange 24 of the photosensitive drum 1 presses the fixed shaft 2 is canceled. Therefore, the deflection of the fixed shaft 2 and the fixed magnet 25 described above is suppressed, and the fixed magnet 2
5 and the photosensitive drum 1 can be kept constant.

With the above configuration, a predetermined magnetic field is always formed in the developing nip, and a high-quality image can be obtained.

In this embodiment, the photosensitive drum 1
The developing electrode member 10 and the cleaning member 4
I thought. In addition, when the pressing force of the transfer roller, the charging roller, and the like is large, the resultant force of all these may be minimized.

(Embodiment 4) FIG. 12 is a side view of a developing section of an image forming apparatus according to a fourth embodiment of the present invention, and FIG. 13 is a sectional view of a shaft end portion according to the fourth embodiment of the present invention. It is a perspective view.

Referring to FIGS. 12 and 13, points different from the third embodiment of the present invention will be described. Reference numeral 51 denotes a cylindrical pin that protrudes from the central shaft 12 and is fixed. 52 denotes a cylindrical pin that protrudes from the fixed shaft 2 and is fixed. Reference numerals 53 and 54 denote central shaft regulating holes 43 provided in the developing case 41, and 53 is referred to as a guide portion and 54 is referred to as an angle regulating portion. 55 and 56 are developing housings 4
In the fixed shaft regulating hole 44 provided in 1, the 55 is referred to as a positioning portion, and the 56 is referred to as an angle regulating portion. Angle regulating parts 54 and 56
Are formed in parallel with the inter-axis reference line.

The fixed shaft 2 is inserted into the positioning portion 55, the pin 52 is inserted into the angle regulating portion 56, and the outer peripheral surface of the pin 52 contacts the inner wall of the angle regulating portion 56 and is fixed to the developing case 41. Further, the pin 51 is inserted into the angle restricting portion 54. The center shaft 12 and the pin 51 are integrally formed with the guide portion 53.
And it moves while sliding on the inner wall surface of the angle regulating section 54.
The inner wall surfaces of the guide portion 53 and the angle regulating portion 54 are the reference line L
Are fixed in parallel with the fixed magnet 13.
Move while maintaining the size of at a predetermined angle.

The other components and the developing process are the same as in the third embodiment of the present invention. The third embodiment has the following problems.

First, there is an error in the set angle of the magnetic pole. 8 and 10, the angle of the fixed shaft 2 or the center shaft 12 is fixed to the developing housing 41 and the D-cut surfaces 2d and 12d. For this reason, the angle regulating surface is small, and the length for setting the angle is short. Therefore, even a slight error appears as an error in the set angle of a large magnetic pole. Since the outer diameter of the center shaft 12 is smaller than that of the fixed shaft 2, the error of the set angle is further increased.

In particular, the center shaft 12 translates by sliding on the inner surface of the center shaft regulating hole 43. In order to suppress this frictional resistance, a certain clearance is required between the center shaft 12 and the inner surface of the center shaft regulating hole 43. Because of this clearance, the angle of the D-cut surface cannot be completely regulated, causing a large set angle error.

Further, in this type of image forming apparatus,
Usually, since the diameter of the photosensitive drum 1 is larger than that of the developing electrode member 10, the fixed magnet 25 is set to be larger than the fixed magnet 13. Therefore, when the magnitude of the set angle B changes by 1 °, the amount of change of the magnetic flux formed in the developing nip is larger than when the magnitude of the set angle A changes by 1 °, and the magnitude of the set angle B Must be accurately set by the pin 52.

Second, there is the problem of wear of the angle regulating surface. The D-cut surface 12 d of the central shaft 12 slides on the inner surface of the central shaft regulating hole 43 while regulating the rotation of the central shaft 12. For this reason, when a large external force such as a rotational driving force acts, abrasion occurs on the surface that regulates the angle. This wear causes a change in the set angle of the central shaft 12 and the fixed magnet 13.

According to the structure of this embodiment, the photosensitive drum 1
Since the rotation of the fixed magnet 25 with respect to the center of rotation is restricted by the pin 52 protruding from the outer periphery of the fixed shaft 2,
The length of the portion for setting the angle can be increased. For this reason,
Even if an error occurs, a change in the set angle can be suppressed, and the size of the set angle B can be set with high accuracy. Similarly, since the rotation of the fixed magnet 13 with respect to the rotation center of the developing electrode member 10 is regulated by the pin 51 protruding from the outer periphery of the center shaft 12, the magnitude of the set angle A can be set with high accuracy. In particular, the angle regulating portion 54 of the central shaft regulating hole 43
The set angle A can be set with high precision even if there is a certain clearance between the pin and the pin 51.

Since the surface for regulating the angle of the central shaft 12 and the guide surface for translation are different, the external force acting on the central shaft 12 is received by the guide portion 53 other than the angle regulating portion 54 and acts on the angle regulating portion 54. The force is only a force that regulates the rotation of the center shaft 12, and the slide is performed with a low load. Therefore, a change in the set angle of the fixed magnet 13 due to wear can be prevented.

With the above configuration, the magnitudes of the set angle B and the set angle A can be set with high precision, and a predetermined magnetic field can be reliably formed in the developing nip.

(Embodiment 5) FIG. 14 is a side view of a developing section of an image forming apparatus according to a fifth embodiment of the present invention.

The point that this embodiment is different from the third and fourth embodiments will be described. First, the fixed shaft regulating hole is extended in the direction of the central shaft 12 to provide a biaxial regulating hole 61 integrated with the guide portion 53 of the central shaft regulating hole 43, and the rotation regulating surface of the fixed shaft 2 and the central shaft 1 are formed.
The two guide surfaces are coplanar. Further, the distance between the center of the fixed shaft 2 and the D-cut surface is set equal to the radius of the center shaft 12.

The fixed shaft 2 is fixed to the developing case 41 as in the third embodiment. Further, by pressing the center shaft 12 by the pressing member 42, the developing electrode member 10 is pressed against the photosensitive drum 1 via the gap regulating member 22. The fixed shaft 2 is provided with a D-shaped rotation restricting portion 2d, and the rotation of the fixed shaft 2 is restricted by contacting the inner wall of the biaxial restricting hole 61. The rotation of the central shaft 12 is restricted by the pin 51 abutting on the inner wall of the angle restricting portion 54. Furthermore, the central axis 12
Designates a plane that specifies the angle of the fixed shaft 2 as a sliding surface during movement. Other configurations and development steps are the same as in the third and fourth embodiments.

In this embodiment, since the biaxial regulating hole 61 is provided, and the rotation regulating surface of the fixed shaft 2 and the central shaft regulating surface are on the same plane, the moving direction of the central shaft 12 is reliably regulated on the inter-axis reference line. it can. Therefore, the fixed magnet 25 and the fixed magnet 1
3 ensures that a constant magnetic flux is formed in the developing nip.

(Embodiment 6) FIG. 15 is a sectional view of a flange 23 of an image forming apparatus according to a sixth embodiment of the present invention.

This embodiment is different from the fourth embodiment in that an electrode regulating member 62 having a sliding groove having substantially the same width as the outer diameter of the projecting portion outside the flange 23 of the developing electrode member 10 is provided. The point where the protrusion of the flange 23 is inserted into the electrode regulating member 62 and the pressing member 4
2 to press the developing electrode member 10 to the gap regulating member 2.
2, the clearance between the central shaft 12 and the central shaft regulating hole 43 is increased, and the position of the central shaft 12 is determined by the developing electrode member 10.
Other components and the developing process are the same as those of the fourth embodiment of the present invention.

The fifth embodiment of the present invention has a problem of the deflection of the central shaft 12. The central shaft 12 receives bending moments from four points of the pressing of the pressing members 42 at both ends and the flange 23 of the developing electrode member 10 pressing the gap regulating member 22. Further, a resultant force in a direction perpendicular to the rotation axis such as a meshing force of the developing electrode member 10 from the gear driving portion and a pressing force of the scraper 27 acts on the developing electrode member 10. With this external force,
The center shaft 12 receives bending moments from the four points of the flange 23 and the center shaft regulating hole 43 at both ends. For this reason, the center axis 12 and the fixed magnet 13 are deformed as shown by a broken line in FIG. 11, and the distance (coaxiality) between the fixed magnet 13 and the surface of the developing electrode member 10 changes in the longitudinal direction of the developing electrode member 10. The magnetic field at the development nip will change.

However, in this embodiment, the bending moment from four points of the pressing member 42 and the flange 23 can be eliminated by pressing the pressing member 42 against the flange 23 integrated with the developing electrode member 10. Also,
Since the flange 23 is inserted so as to slide in the sliding groove of the electrode regulating member 62, the flange 23 and the sliding portion can support an external force. Therefore, it is possible to prevent a bending moment from acting on the central shaft 12 and the fixed magnet 13, and to prevent the central shaft 12 and the fixed magnet 13 from bending.

With the above configuration, the distance between the developing electrode member 10 and the fixed magnet 13 can be kept constant, a predetermined magnetic field can be constantly formed in the developing nip, and a high-quality image can be obtained.

(Embodiment 7) FIG. 16 is an inner view of a developing case 41 of an image forming apparatus according to a seventh embodiment of the present invention, and FIG. It is sectional drawing in a perpendicular surface.

The present embodiment is different from the sixth embodiment in that a ring 63 is inserted into a projecting portion of the developing electrode member 10 outside the flange 23, and the flange 23 and the developing electrode member 10 slide on the inner surface of the ring 63. The developing case 41, a point where the ring 63 is inserted into the developing groove 41, and a point where the ring 63 is inserted into the developing groove 41. Is that the developing member 10 is pressed against the photosensitive drum 1 via the gap regulating member 22.

The other components and the developing process are the same as in the sixth embodiment of the present invention. The sixth embodiment of the present invention has the following problems.

First, there was certainty in pressing. By pressing the pressing member 42 against the flange 23 integrated with the developing electrode member 10, the pressing member 42, which is a spring, is pressing the rotating part. For this reason, the spring material of the pressing member 42 is involved in the rotation of the flange 23. Therefore, the developing electrode member 10 is connected to the photosensitive drum 1 via the gap regulating member 22.
Therefore, the developing gap is opened.

Second, the developing electrode member 10 is moved by the rotation of the flange 23. Rotating flange 23
Is inserted into the sliding groove, the sliding groove and the flange 2
When the frictional force of No. 3 overcomes the pressing force of the pressing member 42,
The flange 23 rolls in the sliding groove. As a result, the developing electrode moves to open a developing gap between the developing electrode and the photosensitive drum 1, and the position of the fixed magnet 13 also shifts.

Third, since the sliding groove for guiding the developing electrode is provided in the electrode regulating member 62, which is a separate member from the developing housing 41 in which the rotation shaft regulating hole of the central shaft 12 is provided, the sliding groove is formed. And the setting position of the rotation shaft regulating hole tends to have an error. Therefore, when the developing electrode moves, the set angles of the central axis 12 and the fixed magnet 13 change.

However, in the structure of this embodiment, the ring 63 is inserted into the flange 23, the flange 23 and the developing electrode are rubbed against the inner surface of the ring 63 and rotated, and the pressing member 42 is pressed against the non-rotating ring 63. Therefore, it is possible to prevent the spring material of the pressing member 42 from being involved. further,
Since the non-rotating ring 63 is inserted into the sliding groove 64, it is possible to prevent the developing electrode member 10 and the fixed magnet 13 from moving due to friction with the sliding groove 64. Further, since the sliding groove 64 for guiding the developing electrode is provided in the integral developing case 41, the positional relationship between the center shaft regulating hole 43 and the sliding groove 64 can be set with high accuracy. With these configurations, a predetermined magnetic field is always formed in the developing nip, and a high-quality image can be obtained.

(Embodiment 8) FIG. 18 is a side view of a developing section of an image forming apparatus according to an eighth embodiment of the present invention.

The present embodiment differs from the fourth embodiment in that a pin 51 protruding from the center shaft 12 and fixed is slidably inserted into a rotation preventing hole 72 of the fixed shaft 2. .
Other components and the developing process are the same as those of the fourth embodiment of the present invention.

According to the configuration of this embodiment, the set angles of the magnetic poles of the fixed magnet 13 and the fixed magnet 25 are set to
Thus, the magnetic field of the developing nip can be obtained more accurately and stably.

In the above-described embodiment of the present invention, the photosensitive drum 1 and the developing electrode member 10 are constituted by hollow cylindrical members. However, the photosensitive drum 1 and the developing electrode member 10 may be constituted by a belt-like elastic body or the like. It is not something to be done.

In the present embodiment, the fixed shaft 2 is arranged coaxially with the rotation center of the photosensitive drum 1. However, the photosensitive drum 1 has a structure in which the flange 24 is slid. If the magnetic field on the surface of the photosensitive drum 1 is similarly formed by the fixed magnet 25, the fixed magnet 2
The arrangement position of 5 may be anywhere within the photosensitive drum 1 and is not limited to the configuration using the fixed shaft 2 as in the present embodiment.

The developing method includes a method in which a coaxial fixed magnet is provided on the photosensitive drum or the developing electrode member, and the photosensitive drum and the developing electrode member are pressed through the gap regulating member 22 to maintain the developing gap. Can be used. It is not limited to the developing method described in the present embodiment.

[0137]

As described above, according to the present invention, while maintaining the gap between the image forming member and the developing electrode member, and the coaxiality of the magnetic flux generating means, the developing electrode member and the image holding member constant, the magnetic flux generating means Can be translated while maintaining a predetermined angle instead of rotating. For this reason, a predetermined magnetic field can be accurately and stably formed in the development nip, and a predetermined magnetic force is applied to the developer without fail, so that a high-quality image with a low image density can be stably formed.

By this effect, the photosensitive drum 1
In addition, since the allowable width for the dimensional accuracy of the constituent members such as the developing electrode member can be set wide, the cost of parts can be reduced and the manufacturing process can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a side view of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is an explanatory view of a magnetic pole arrangement in the first embodiment of the present invention.

FIG. 4 is a perspective view of a shaft end according to the first embodiment of the present invention.

FIG. 5 is a sectional view of an image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a side view of an image forming apparatus according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram of a magnetic pole arrangement in a second embodiment of the present invention.

FIG. 8 is a perspective view of a shaft end according to a second embodiment of the present invention.

FIG. 9 is a correlation diagram between the displacement angle of the magnetic flux generating means and the image quality.

FIG. 10 is a side view of an image forming apparatus according to a third embodiment of the present invention.

FIG. 11 is an explanatory view of deflection caused by four-point bending.

FIG. 12 is a side view of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 13 is a perspective view of a shaft end according to a fourth embodiment of the present invention.

FIG. 14 is a side view of an image forming apparatus according to a fifth embodiment of the present invention.

FIG. 15 is a sectional view of a flange portion according to a sixth embodiment of the present invention.

FIG. 16 is an inner view of a flange portion according to a seventh embodiment of the present invention.

FIG. 17 is a sectional view of a flange portion according to a seventh embodiment of the present invention.

FIG. 18 is a side view of an image forming apparatus according to an eighth embodiment of the present invention.

FIG. 19 is an explanatory diagram of a conventional problem.

FIG. 20 is a sectional view of an image forming apparatus of a first conventional example.

FIG. 21 is a side view of a first conventional image forming apparatus.

FIG. 22 is a sectional view of a second conventional image forming apparatus.

FIG. 23 is a side view of an image forming apparatus of a second conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2 fixed shaft 4 cleaning member 10 developing electrode member 12 center shaft 13 fixed magnet 15 developing power supply 41 developing housing 42 pressing member 43 center shaft regulating hole 22 gap regulating member 12d rotation regulating section

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroshi Komagine 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Katsutoshi Ogawa 1006 Odaka, Kadoma, Kadoma, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-2-29763 (JP, A) JP-A-6-51558 (JP, A) JP-A-2-181165 (JP, A) JP-A-4-188175 (JP, A) JP-A-62-15577 (JP, A) JP-A-64-88480 (JP, A) JP-A-64-88479 (JP, A) JP-A-62-251773 (JP, A) (JP, U) Japanese Utility Model 2-140547 (JP, U) Japanese Utility Model Utility Model 57-82355 (JP, U) Japanese Utility Model Utility Model 5-45728 (JP, U) Japanese Utility Model Utility Model 1-59269 (JP, U) 63-146867 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03 G 15/08-15/095

Claims (9)

(57) [Claims] (1) Carry a charge pattern on the surface, rotatable
An image carrier,A fixed shaft disposed coaxially with the rotation center of the image holding member, The image carrier is opposed to the image carrier with a gap therebetween, and is rotatable and movable.
A developing electrode member movably provided, and the gapToA gap regulating means for regulating the size of the developing electrode member to a fixed size;WhenCentral axis arranged coaxially
When,A developing electrode member integrally formed with the developing electrode member;
The first for coaxially positioning the center of rotation and the central axis
A flange, The image carrier is integrally formed and is rotating.
Second flange for coaxially positioning the core and the fixed shaft
When, The developing electrode member is formed integrally with the central shaft,
A first magnetic flux generating means for generating a magnetic flux on a surface, and an image holder, and an integrated
An arrangement member, provided on the arrangement member, and a center axis of the developing electrode member;
The first magnetic flux generating means is connected to the developing electrode while regulating rotation.
With the membersA plane including the fixed axis and the central axis;
In parallelTranslateableWhenCenter axis guide means,At least the developing electrode member is fixed to the image holding member.
A pressing hand that presses in parallel with a plane including a fixed axis and the central axis.
Steps and Being disposed on a plane including the central axis and the fixed axis,
Press-contact the image carrier, and transfer the remaining transfer on the image carrier.
A cleaning member for cleaning the developer; With
Image forming apparatus. 2. The image forming apparatus according to claim 1, further comprising a second magnetic flux generating unit formed integrally with said fixed shaft and generating a magnetic flux on a surface of said image holding member. 3. The rotation of the center shaft is regulated by a D-cut shape.
By rotation regulation part Claim 1 or Claim
Item 3. The image forming apparatus according to Item 2. 4. The restriction of rotation of the central axis is determined by the central axis.
A rotation preventing member protruding from the center shaft and the fixed shaft.
A center axis regulation provided on the disposing member in parallel with the plane including
3. The method according to claim 1, wherein the hole is formed.
Image forming apparatus. 5. The anti-rotation member protruding from the center axis is provided at the front.
Characterized in that it protrudes from the outer periphery of the developing electrode member.
The image forming apparatus according to claim 4. 6. A guide surface of said center axis guide means is fixed to said fixed surface.
Claims characterized by being coplanar with a shaft rotation regulating surface.
An image forming apparatus according to claim 1. 7. An outer diameter of a projection outside the first flange.
Provide an electrode regulating part with a sliding groove of approximately the same width as Insert the protrusion of the first flange into the electrode regulating member
And presses the pressing member against the protrusion of the first flange.
And a clearance between the central axis and the central axis guiding means.
6. The method according to claim 1, wherein
An image forming apparatus according to any of the preceding claims. 8. The developing electrode member according to claim 1, wherein
Insert and hold the ring on the outside protrusion of this first flange
And A sliding groove having substantially the same width as the outer diameter of the ring is provided on the mounting member.
And inserting the ring into the sliding groove, and pressing the pressing member.
Presses on said ring.
An image forming apparatus according to claim 5. 9. comprises a rotation regulating hole profile and the shape of the fixed shaft is the rotation preventing member, wherein said rotation preventing member is provided so as to slidably inserted into the rotation limiting hole The image forming apparatus according to claim 4 .