JPS5924421B2 - Electrostatic latent image developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an electrostatic latent image developing device used in an electrophotographic copying machine, etc. In particular, the present invention is a method for magnetically developing an electrostatic latent image carried on the surface of an electrostatic latent image carrier that is moved in one direction. The present invention relates to an electrostatic latent image developing device for developing using an agent.

Conventionally, as an electrostatic latent image developing device using a magnetic developer,
For example, as described in Japanese Patent Application Laid-Open No. 52-17831, a multipolar magnet is fixed inside a rotatable non-magnetic developing sleeve, and the developer supplied onto the developing sleeve is regulated by a doctor blade. However, there is a rotating sleeve type in which a magnetic brush is formed on the outer peripheral surface of the developing sleeve, and the electrostatic latent image formed on the photoreceptor is developed by this magnetic brush, or as disclosed in Japanese Patent Laid-Open No. 52-67336. As described, a magnetic brush is formed on the outer circumferential surface of the developing sleeve with developer by the action of an alternating magnetic field of a magnetic roller rotating within a fixed non-magnetic developing sleeve, and this magnetic brush causes the magnetic brush to form a magnetic brush on the photoreceptor. A rotary magnet type is known, which develops an electrostatic latent image formed on the surface.

However, since the developer used in these developing devices is very fine, the developer tends to aggregate and clump due to moisture and mutual electrostatic attraction, and it is difficult to control the amount of developer on the developing sleeve. If the developer gets clogged near the doctor blade or at the inlet of the developing gap, it may interfere with the smooth conveyance of the developer, causing fog in the developed image and deteriorating the quality of the developed image. . In addition, in both the sleeve rotating type and magnet rotating type developing devices, the developing method is to lightly rub a magnetic brush formed on the developing sleeve on the electrostatic latent image on the photoreceptor, and the density of the developed image is determined by the developing device. It is approximately proportional to the moving speed of the developer above. That is, in order to obtain sufficient developed image density,
It is necessary to increase the moving speed of the developer moving on the developing sleeve. However, when only the moving speed of the developer is increased, the relative moving speed between the surface of the photoreceptor and the developer changes significantly, and various adverse effects are exerted on the developed image.
Therefore, there is a certain limit to improving the density of a developed image in the developing device. The present invention has been made in view of the current situation, and it is possible to prevent clogging of the developer on the developing sleeve, and to improve the density of the developed image without increasing the moving speed of the developer. The object of the present invention is to provide an electrolatent image developing device.

Embodiments of the electrostatic latent image developing device according to the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, an electrostatic latent image developing device 10 according to the present invention generally includes a developing sleeve 11 installed in a developing section, a magnetic roller 12 built into the developing sleeve 11, and a developer stirring device 20. It consists of

The developing sleeve 11 is made of a non-magnetic conductive material such as aluminum and is formed into a cylindrical shape, and is rotated counterclockwise by 10 mm.
/Sec in the counterclockwise direction in proximity to the photoreceptor drum 1 which is rotatable at a circumferential speed of approximately 30 rpm. p. m. It is installed so that it can rotate. The magnetic roller 12 has an N pole and an S pole around it.
The developing sleeve 11 is a roll-shaped material whose poles are sequentially magnetized.
2000r. in the same direction. p. m. It can be rotated by That is, when the diameter of the developing sleeve 11 is 31 mm, the developer is applied at a rate of approximately 10 CfL/S in the clockwise direction along the circumferential surface of the developing sleeve 11 based on the rotational drive of the magnetic roller 12.
Obtain a moving speed of ec, and obtain a moving speed of about 5 (-Ffl/S1) in the counterclockwise direction based on the rotational drive of the developing sleeve 11, which is the same as the rotational speed (peripheral speed) of the developing sleeve 11.
As a result, about 5C in the clockwise direction! It will move at a speed of n/Sec. Further, first and second developer scraping plates 14a and 14b made of an elastic non-magnetic material, such as an appropriate synthetic resin material or thin metal flakes, are provided on the outer circumferential surface of the developing sleeve 11 located below the developing sleeve 11. They are attached to the support shaft 14 so that their respective tips are pressed against each other in the forward direction opposite to the rotational direction and in the reverse direction following the rotational direction.

The developer is moved to a position A where it is affected by the magnetic force of the magnetic roller 12 by the bucket 31 of the developer stirring device 20, which will be explained in detail below.
From this position A, the developing sleeve 11 is conveyed and supplied in a clockwise direction at a speed of about 5 CWL/Sec, with the amount of conveyance being regulated by the doctor blade 13 (the doctor blade 13 is not necessarily required). The electrostatic latent image, which has been previously formed on the surface of the photosensitive drum 1 by known means, is rubbed in the developing gap, and the electrostatic latent image is developed into a toner image.

At this time, the developer moving along the circumferential surface of the developing sleeve 11 is rotated on its own axis by the formation of an alternating magnetic field based on the rotation of the magnetic roller 12, causing the entire developer to turbulently move. Therefore, the fluidity of the developer on the developing sleeve 11 is improved, and the developer is not clogged near the doctor blade 13 or on the entrance side of the developing gap, and is smoothly transported. Note that the moving direction of the developer is the direction in which the developer is packed into the portion, but the developing sleeve 11
Because the turbulence includes a motion component in the direction opposite to the moving direction, no developer clogging occurs. Furthermore, the turbulence increases the frequency of contact between the surface of the photoreceptor and the developer in the development gap, and the density of the developed image during development of the electrostatic latent image is not improved. What is important here is that although a high-frequency alternating magnetic field is formed due to the rotation of the magnetic roller 12, the moving speed of the developer along the circumferential surface of the developing sleeve 11 is high due to the rotation of the developing sleeve 11. This is something that has not been standardized. For this reason,
Since the density of the developed image is improved while the relative moving speed between the developer and the surface of the photoreceptor is not substantially changed, there is no adverse effect on the developed image. On the other hand, the developer that is not supplied onto the developing sleeve 11 may contain components that have an adverse effect on the development of the electrostatic latent image, such as impurities such as dust mixed into the developer and developer that has been solidified and touched. If
Many of these components are not affected by the moving force caused by the rotation of the magnetic roller 12, and are moved by the rotation of the developing sleeve 11 in a direction opposite to the moving direction of the developer, that is, in a counterclockwise direction. , the developer is scraped off from the peripheral surface of the developing sleeve 11 by the first developer scraping plate 14a in the forward direction, and falls downward under its own weight. Therefore, these components are not transported to the development gap. It should be noted that some of the developer scraped off by the first developer scraping plate 14a is excessively supplied to the circumferential surface of the developing sleeve 11, and is hardly affected by the moving force based on the rotation of the magnetic roller 12, so that the developer does not react. Also included is developer material that moves in a clockwise direction. On the other hand, the developer after the electrostatic latent image is scraped off from the circumferential surface of the developing sleeve 11 by the second developer scraping plate 14b in the opposite direction, and is allowed to fall downward under its own weight, thereby being developed. It is returned to the tank 21. On the other hand, the developing sleeve 11
A roll 15 is rotatably installed above the surface of the photosensitive drum 1 with a small gap therebetween to prevent toner powder smoke from leaking into the machine body.

This roll 15 has slightly larger diameter rollers 1 provided at both ends.
6 contacts both ends of the photoreceptor drum 1, rotates in synchronization with the drum 1, and also positions the developing sleeve 11 with respect to the photoreceptor drum 1. The developer stirring device 20 is as shown in FIGS. 1, 2, and 3. , a rotating shaft 22, a pair of rotating disks 29a and 29b1 that are rotationally driven integrally with the rotating shaft 22; a pair of rotating disks 29;
a and 29b, a plurality of buckets 31 having a U-shaped cross section, and a coil spring 2 wound around the rotating shaft 22.
8. A plurality of stirring plates 32 arranged in parallel at the bottom of the bucket 31
has. The rotating shaft 22 has one end rotatably supported on the side plate 17a of the developing device 10 via a bearing 23, and the other end rotatably supported on a bearing 25b provided at the end of the cylinder 24. It is connected to rotational drive means by a gear 26 fixed to. The cylinder 24 has three openings 24a, 24b, and 24c on its outer periphery, and is fixed to a fixed bearing 27 attached to another side plate 17b so that the rotating shaft 24
2, and both ends rotatably support the rotating shaft 22 via bearings 25a and 25b. The opening 24a is formed upward on the outside of the side plate 17b, that is, the outside of the developer tank 21 of the developing device 10, and stores new toner (supplemented developer) or developer recovered by cleaning the surface of the photoreceptor drum 1. is now being accepted in a timely manner. Other openings 24b and 24c are formed in the developer tank 21 of the developer device 10 at both ends thereof, upward and downward. The number of openings may be increased as appropriate. Further, the rotating shaft 2
A coil spring 28 is spirally wound around the cylinder 24 over the entire length thereof, and both ends of the coil spring 28 are fixed to the rotating shaft 22. The coil spring 28 rotates integrally with the rotating shaft 22 as it is rotationally driven in the clockwise direction in FIG. 1, and rotates in the axial direction, that is, to the left in FIG. move it to
The rotating disk 29a is fixed to one end of the rotating shaft 22,
Another rotary disk 29b is rotatably mounted on the fixed bearing 27 via a bush 30 made of sintered metal or the like. The bucket 31 is connected to these rotating disks 29a, 29b.
It spans the outer periphery at equal intervals. The stirring plate 32 has bent pieces 33 as shown in FIG. It is fixed at an appropriate inclination angle with respect to the rotating shaft 22. This stirring plate 32 has a rotation shaft 22 that rotates clockwise in FIG.
When the bucket 31 rotates together with the developer 9b, the developer is stirred in the rotational direction outside the cylinder 24 and moved in the axial direction, that is, in the right direction in FIG. 2, at a preset inclination angle. Note that the stirring plate 32 has a notch 34 formed in the bent piece 33 as shown in FIG.
A large number of items are attached at a constant angle of inclination by screwing them to the corners. In the agitating device 20 having the above configuration, the developer is fed into the opening 24 of the cylinder 24.
A is newly replenished from a, and is moved to the left in FIG. 2 while being stirred in the rotational direction within the cylinder 24 by the coil spring 28 rotating in synchronization with the rotating shaft 22, and released from the cylinder 24 through the opening 24c. The stirring plate 32, which rotates in synchronization with the rotating shaft 22, stirs and stirs the cylinder 24 in the rotational direction while moving it to the right, while a portion is scooped up by the bucket 31, and the first Convey and feed to point A in the figure.

Then, the developer is magnetically attracted onto the developing sleeve 11 by the magnetic action of the magnetic roller 12, moves clockwise on the developing sleeve 11 as described above, and is deposited on the electrostatic surface of the photoreceptor drum 1. Develop the image. The developer that has not been scooped up into the bucket 31 is stirred by the stirring plate 32, moves to the right, and enters the cylinder 24 again through the opening 24b. Note that the developer tank 21 does not always accommodate the amount of developer up to the level shown by the two-dot chain line B in FIG. FIG. 5 shows another embodiment of the electrostatic latent image developing device 10 according to the present invention, which differs from the one in FIG. The only difference is that a sealing plate 18 made of Mylar or the like is provided so that its tip lightly contacts the surface of the photosensitive drum 1, and the other configurations are the same.

Although there is a problem in that the eddy current and the rotational driving torque of the magnetic roller 12 slightly increase due to the high-speed rotation of the magnetic roller 12 described above, members close to the magnetic roller 12, such as the first and second developer scrapers, Removing plates 14a, 14b
This problem can be effectively solved by making the first doctor blade 13 a non-magnetic, non-conductive member.

However, the developing sleeve 11 must be made of a conductive material due to the principle of development, and therefore it is preferable to make the developing sleeve 11 as thin as possible to increase the planar electrical resistance. Furthermore, it is not possible to reduce the generation of eddy current by using a non-conductive material such as synthetic resin as the base material of the photosensitive drum 1. In this case, a conductive layer such as metal vapor deposition may be provided on the resin surface to provide grounding, and the vapor deposited film is extremely thin and eddy current is unlikely to occur. As is clear from the above description, in the electrostatic latent image developing device according to the present invention, the developing sleeve and the magnetic roller are rotationally driven in the developing gap in a direction opposite to the moving direction of the surface of the electrostatic latent image carrier. In addition, since the moving speed of the developer based on one rotation of the magnetic roller is set to be higher than the rotating speed of the developing sleeve, the direction of developer movement is opposite to the direction of developer movement with respect to the developer on the developing sleeve. A turbulence containing a motion component in the direction occurs.

Therefore, clogging of the developer on the developing sleeve cannot be prevented, and the density of the developed image cannot be improved without increasing the moving speed of the developer. Furthermore, even if the developer supplied onto the developing sleeve does not contain any components that adversely affect the development of the electrostatic latent image, most of them will move in the opposite direction to the direction in which the developer moves. , and the components moved in the opposite direction in this way are not scraped off from the circumferential surface of the developing sleeve by the first developer scraping member.
It does not reach the development gap, that is, it is not used for developing the electrostatic latent image, and the adverse effects of stiff components are reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the electrostatic latent image developing device according to the present invention, FIG. 2 is a sectional view taken along the line -- in FIG. 4 is a perspective view of the stirring plate, FIG. 4 is a plan view showing how the cap body is attached, and FIG. 5 is a sectional view showing another embodiment. DESCRIPTION OF SYMBOLS 1...Photosensitive drum, 10...Electrostatic latent image developing device, 11...Developing sleeve, 12...
. . . Magnetic roller, 14a . . . First developer scraping plate, 14b. ．． ．． ．． ．． ．． Second developer scraping plate, 20...Developer stirring device, 21...
・Developer tank.

Claims (1)

[Scope of Claims] 1. An electrostatic latent image developing device for developing an electrostatic latent image carried on the surface of an electrostatic latent image carrier that is moved in one direction using a magnetic developer, comprising: A developing sleeve made of a non-magnetic material is rotatably provided facing the surface of the electrostatic latent image carrier; a magnetic roller that magnetically attracts the developer; a means for rotating the developing sleeve and the magnetic roller in a direction opposite to the moving direction of the surface of the electrostatic latent image carrier in the developing gap; While the first sleeve is in pressure contact with the developing sleeve, the first
and a second developer scraping member also installed in the opposite direction, and the moving speed of the magnetic developer along the circumferential surface of the developing sleeve based on the rotational drive of the magnetic roller. An electrostatic latent image developing device characterized in that the rotational drive speed of each of the developing sleeve and the magnetic roller is set so that the rotational speed of the developing sleeve is higher than the rotational speed of the developing sleeve. 2 The tips of the first and second developer scraping members are pressed against the peripheral surface located below the developing sleeve, and the first and second developer scraping members remove the peripheral surface of the developing sleeve. 2. The electrostatic latent image developing device according to claim 1, wherein the magnetic developer scraped off from the surface falls downward under its own weight.