JP2966885B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device provided with a developer carrier having a ferromagnetic layer provided on a conductive substrate and finely magnetizing the ferromagnetic layer. .

Conventionally, a fine stripe-shaped magnetization is applied to a ferromagnetic layer constituting a developing roller, and a magnetic attraction force is applied to a toner layer regulating member having magnetism and elasticity to form a thin toner layer.
A developing device of a type in which development is performed by attaching the toner to a latent image carrier is conventionally known. In this case, the pitch of the magnetized pattern is conventionally determined by the ratio between the linear speed of the developer carrier and the linear speed of the latent image carrier so that the stripe pattern caused by this pitch becomes less noticeable on the developed image. Has been determined based on

Problems to be Solved by the Invention The developing device described in the related art enables fine image formation with a simple configuration and has a small driving torque. However, when the developing roller is to be rotated at a small linear velocity ratio, a stripe pattern resulting from the magnetization pitch becomes conspicuous on the image. On the other hand, when the number of magnetized poles is increased, the pitch of the stripes becomes narrower, and the image itself does not matter.

However, in this method, the magnetic field around the developing roller is concentrated only very close to the roller surface, and the magnetic field acting on the periphery becomes extremely weak. (The outer radius of the magnetized layer is r, from the center of the roller to a point outside the roller. Where R is the distance and k is the number of sets of magnetization, the magnetic field strength H decreases in proportion to (r / R) raised to the power of (k + 1). Insufficient power to suck the member. For this reason, the frictional force of the toner is reduced, and the chance of the toner coming into contact with another member is reduced.

As a result, the charge amount of the toner decreases, the image becomes hard, and unnecessary toner adhesion to the background occurs, and the resolution also decreases. Further, when a magnetic toner is used as the toner, the toner is not sufficiently supplied to the roller, and unevenness due to insufficient toner supply occurs when developing a solid black image.

Therefore, the present invention solves the above-mentioned problems in the prior art,
It is an object of the present invention to provide a developing device having improved image quality without unevenness without increasing the number of fine magnetized poles and without increasing the linear velocity ratio. A third object of the present invention is to provide a developing device capable of more completely achieving the above object.

Means for Solving the Problems In order to solve the above problems, the present invention is directed to a developing method in which a ferromagnetic layer is provided on a conductive substrate and the ferromagnetic layer is finely magnetized. On the toner carrier, a toner thin layer is formed by a toner layer regulating member having magnetism and elasticity, and the amount of toner adhering to the latent image carrier carrying the electrostatic image is controlled by developing amount adjusting means, A developing device for developing the toner image by rotating the developer carrier so that the thin toner layer adheres to the latent image carrier, wherein the finely magnetized pattern includes the latent image carrier and the developer carrier. A magnetic field detecting means for detecting a magnetic field intensity in the vicinity of the developer carrier which periodically changes due to the rotation of the developer carrier, wherein the magnetic field detector has a periodicity in a direction perpendicular to the direction extending in a line of contact with the developer carrier. And based on the signal detected by the magnetic field detecting means. The toner amount adhesion adjustment having the same repetition frequency as the periodic change repetition frequency, and having a phase having a predetermined relationship for correcting the periodic variation of the toner adhesion amount with respect to the phase of the periodic change. A signal is output to control the developing amount adjusting means. In addition to the above, the invention is characterized in that the magnetic field detecting means is located near the contact line portion and inside the latent image carrier. According to a third aspect of the present invention, in addition to the first aspect, the magnetic field detecting means is attached to the developing device main body.

According to the present invention, the magnetic field intensity is detected by the magnetic field detecting means, and the signal has the same repetition frequency as the frequency of the periodic change of the magnetic field. A toner amount adhesion adjustment signal having a phase (the same phase in this case) having a predetermined relationship for correcting the periodic variation of the amount of adhesion is generated, and the toner amount control means is controlled by this. It is possible to correct the influence of the toner adhesion on the latent image carrier due to the change in the thin layer forming condition of the toner layer regulating member based on the change. Further, when the toner is a magnetic toner, the toner particles are strongly attracted to the magnetic pole portion, and even if the layer thickness is regulated by the toner layer regulating member, the toner adhered to the developer carrier periodically changes. In this case, a toner amount adhesion adjustment signal having a phase (in this case, a phase having a difference) having a fixed relationship with the phase of the periodic change is generated, so that the toner adhesion to the latent image carrier is made uniform. Can be done.

According to the second aspect of the present invention, since the magnetic field detecting means is provided on the inner peripheral side of the latent image carrier at the contact portion between the latent image carrier and the developer carrier, the periodic change of the toner layer in the developing area can be directly detected. Can be detected.

According to the third aspect of the present invention, since the magnetic field detection means is attached to the developing device main body, the attachment accuracy is improved.

Embodiment FIG. 1 is an explanatory view showing an embodiment of the present invention.

A developing device is provided to face a belt-shaped photoconductor 1 used in an image forming apparatus such as a copying machine.

A developing roller 3 as a developer carrier, a toner replenishing member 4, a toner agitator 5, and a toner thin layer forming blade 6 as a toner layer regulating member are provided in a main body case 2 of the developing device.
Etc. are provided.

The toner in the main body case 2 agitated by the toner agitator 5 is supplied to the developing roller 3 by the toner replenishing member 4, thinned by the toner thin layer forming blade 6, and then adhered to the electrostatic image of the photoconductor 1. , And development is performed.

The developing roller 3 is a multipolar magnetized developing roller in which a ferromagnetic layer 3b is provided on a conductive substrate 3a and finely magnetized on the ferromagnetic layer 3b. Contact rotation. The finely magnetized pattern extends in the direction of the line of contact between the photoreceptor 1 and the developing roller 3 and is periodically arranged in a direction perpendicular to the direction of contact.

The toner thin layer forming blade 6 is a plate member having magnetism and elasticity, and is attracted by the magnetic field of the developing roller 3 to thin the toner. Therefore, a stripe pattern is generated in a thin layer corresponding to the strength of the magnetic field. Further, when the toner is a magnetic toner, the toner is strongly attracted to the magnetic pole portion, so that the toner is not completely and uniformly thinned even by the toner thin layer forming blade 6, and a stripe pattern corresponding to the magnetic field intensity is generated.

In order to reduce the influence of such a stripe pattern on an image, first, the intensity of a magnetic field on the developing roller 3 is detected. It is installed on the inner peripheral side of the photoconductor 1 in a development area which is a contact portion with the photoconductor 1. It is of course possible to use a magnet diode or the like instead of the Hall element 7.

The periodic change of the magnetic field detected by the Hall element 7 is input to a phase comparator 9 via an absolute value calculation circuit or a square calculation circuit 8, and a developing amount adjusting means 10 such as a developing bias.
Is compared with the phase of the output transmitted from the voltage-controlled oscillation circuit (VCO) 11. If necessary, the output of the Hall element 7 may be input to the phase comparator 9 via a low-pass filter (LPF).

The output of the phase comparator 9 becomes the control voltage of the VCO 11 by taking the difference from the DC voltage for phase setting. However, the frequency of the output of the VCO 11 is the same as the frequency of the fluctuation of the magnetic field intensity caused by the rotation of the developing roller 3.

The output of the VCO 11 is guided to the developing amount adjusting means 10 as a control voltage synthesized with the DC component. In this example, a bias voltage is applied in synchronization with the periodic fluctuation of the magnetic field strength in the developing region and with a constant phase difference. As a result, the periodic fluctuation of the toner adhesion amount due to the magnetization pitch is corrected.

In a laser printer or the like, if the distance between the development area and a writing position (not shown) is determined, VC
The output of O11 may be used as a writing system adjustment signal such as a laser diode and an LED array bias voltage (not shown).

In the embodiment shown in FIG. 1, the Hall element 7 is connected to the photosensitive member 1 in the vicinity of the developing portion, which is the contact portion between the photosensitive member 1 and the developing roller 3.
Since the Hall element 7 is close to the developing unit, the fluctuation of the toner layer in the developing area can be directly detected.

The embodiment shown in FIGS. 2 and 3 shows a case where the Hall element 7 is provided integrally with the main body case 2 of the developing device. Since the positional relationship between the development area and the detection position is predetermined, the same operation as in the embodiment shown in FIG. 1 can be performed in this case, too. Can be improved.

The embodiment shown in FIGS. 4 and 5 shows an example in which the Hall element 7 is mounted on the main body side of the image forming apparatus to which the developing device is mounted. Although the Hall element 7 is independent of the developing device, when the developing device is set in the image forming apparatus of the image forming apparatus, the developing roller 3 and the Hall element 7, the magnetic field detection position by the Hall element 7, and the developing area are different. The positional relationship is determined, and detection by the Hall element 7 and control based on the detection can be performed. In this embodiment, since the Hall element 7 is provided independently of the developing device, the developing device can be replaced without replacing the Hall element 7.

In the embodiment shown in FIGS. 3 to 5, the photosensitive member 1 has a drum shape, but may have a belt shape as shown in FIG.

In a developing device that performs development using an AC superimposed bias in non-contact development, it is desirable to supply an adjustment signal to a DC bias that determines the overall tendency of the development bias.

Effects As described above, according to the present invention, in the first aspect of the present invention, the linear velocity between the developer carrier and the latent image carrier can be increased without increasing the number of poles of fine magnetization applied to the developer carrier. Without increasing the ratio, it is possible to correct the effect of the change in the thin layer forming conditions due to the periodic change in the magnetic field strength, to almost eliminate the pattern of fine magnetization from the formed image, and in addition to improving the image quality, The manufacturing process of the developer carrier can be simplified, the quality can be stabilized, and the cost can be reduced. Further, the driving torque required for the developer carrier can be reduced to drive the image forming unit of the image forming apparatus. It is also possible to reduce the size and speed of the means.

According to the second aspect of the present invention, in addition to the above-described effects, a change in the toner layer in the development area can be directly detected and fed back to the development characteristics, so that the adjustment accuracy can be improved.

According to the third aspect of the present invention, in addition to the effect of the first aspect of the present invention, the adjustment accuracy can be improved by improving the installation accuracy of the magnetic field detecting means.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention, FIGS. 2 to 5 are explanatory views of another embodiment, and FIGS. 2 and 3 show a case where a hall element is provided integrally with a developing device main body. 4 and 5
The figure shows a case where the Hall element is provided on the image forming apparatus side on which the developing device is mounted. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor (latent image carrier) 2 ... Body case (developing device main body) 3 ... Developing roller (developer carrier) 3a ... Conductive substrate 3b ... Ferromagnetic layer 6 ... Toner Thin layer forming blade (toner layer regulating member) 7 Hall element (magnetic field detecting means) 9 Phase comparator 10 Development amount adjusting means

Continued on the front page (72) Inventor Toshihiro Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Masako Mizusawa 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Inside Ricoh (72) Inventor Kenji Karashima 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/08-15/09

Claims (3)

(57) [Claims] A ferromagnetic material layer is provided on a conductive substrate, and the ferromagnetic material layer is finely magnetized. On a developer carrier, a toner layer regulating member having magnetism and elasticity is used. Forming a layer, while controlling the amount of toner adhering to the latent image carrier carrying the electrostatic image by the developing amount adjusting means, and rotating the developer carrier to apply the thin toner layer to the latent image carrier. In a developing device for performing development by attaching, the finely magnetized pattern extends in a contact line direction between the latent image carrier and the developer carrier and has periodicity in a direction orthogonal to the direction. A magnetic field detecting means for detecting a magnetic field intensity in the vicinity of the developer carrier, which periodically changes due to the rotation of the developer carrier, and repeating the periodic change based on a signal detected by the magnetic field detecting means. Has the same repetition frequency as the frequency Outputting a toner amount adhesion adjustment signal having a phase having a predetermined relationship for correcting the periodic variation of the toner adhesion amount with respect to the phase of the periodic change, and controlling the developing amount adjusting means. Developing device. 2. The developing device according to claim 1, wherein said magnetic field detecting means is provided near said contact line portion and on an inner peripheral side of said latent image carrier. 3. The developing device according to claim 1, wherein said magnetic field detecting means is attached to a developing device main body.