JPH041683A - Developing device - Google Patents

Abstract

PURPOSE:To uniformize toner sticking by detecting the intensity of a magnetic field, generating an adjusting signal for sticking amount of toner which is an integral multiple of the frequency of periodic variation of the magnetic field and also has a phase in constant relation with it, and controlling a toner amount control means. CONSTITUTION:The periodic variation of the magnetic field generated by a hole stop 7 is inputted to a phase comparator 9 through an absolute value arithmetic circuit or square-law arithmetic circuit 8 and compared with the phase of the output of the voltage-controlled oscillation circuit (VDO) 11 of a development quantity adjusting means 10 for a developing bias, etc. The difference of the output of the phase comparator 9 from a DC voltage for phase setting is calculated to obtain the control voltage for the VCO 11. Here, when the output frequency of the VCO 11 is an integral multiple of the frequency of variation in the magnetic field intensity caused by the rotation of a developing roller 3, the output of the VCO 11 is properly frequency-divided and sent to the phase comparator 9. The output of the VCO 11 is led to the development adjusting means 10 as the control voltage obtained by superposing the DC component. Consequently, the periodic variation in toner sticking quantity due to a magnetization pitch is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a developing device comprising a developer carrier in which a ferromagnetic layer is provided on a conductive substrate and the ferromagnetic layer is finely magnetized. Regarding equipment.

Conventional technology The ferromagnetic layer constituting the developing roller is magnetized in fine stripes, and a thin toner layer is formed by applying magnetic attraction to a toner layer regulating member that has magnetism and elasticity. 2. Description of the Related Art A developing device that performs development by attaching toner to a latent image carrier is conventionally known. In this case, the pitch of the magnetized pattern is conventionally adjusted to the ratio of the linear velocity of the developer carrier and the linear velocity of the latent image carrier so that the stripe pattern caused by this pitch becomes less noticeable on the developed image. It is determined based on

Problems to be Solved by the Invention The developing device described in the prior art has a simple configuration, enables fine image formation, and has a small driving torque.

However, when attempting to rotate the developing roller at a small linear speed ratio, a striped pattern resulting from the magnetization pitch becomes noticeable on the image. On the other hand, when the number of magnetized poles is increased, the pitch of the stripes becomes narrower, and this itself becomes unnoticeable on the image.

However, with this method, the magnetic field around the developing roller is concentrated only in the vicinity of the roller surface, and the magnetic field acting on the surrounding area becomes extremely weak. When the distance between R1 and the number of magnetized pairs is k, the strength of the magnetic field H becomes weaker in proportion to the (k+1) power of (r/R)], a toner layer regulating member having magnetism and elasticity. This results in a lack of suction power. Therefore, the force that rubs the toner is reduced, and the chances of the toner coming into contact with other members are reduced.

As a result, the amount of charge of the toner decreases, the image becomes high contrast, unnecessary toner adhesion to the background portion occurs, and the resolution also decreases. Further, when magnetic toner is used as the toner, toner is not replenished to the roller properly, and when a solid black image is developed, unevenness occurs due to insufficient toner replenishment.

Therefore, the present invention solves the above-mentioned problems in the prior art, and the invention of claim 1 provides development that improves image quality without unevenness without increasing the number of finely magnetized poles or increasing the linear speed ratio. An object of the present invention is to provide a developing device, and an object of the invention according to claim 2 or 3 is to provide a developing device that can more completely achieve the above object.

Means for Solving the Problems In order to solve the above problems, the invention of claim 1 provides a development method in which a ferromagnetic layer is provided on a conductive substrate and the ferromagnetic layer is finely magnetized. A thin toner layer is formed on the agent carrier 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 a development amount adjusting means. A developing device that performs development by rotating the developer carrier to attach the toner thin layer to the latent image carrier, wherein the finely magnetized pattern is formed between the latent image carrier and the developer carrier. A magnetic field detecting means for detecting a magnetic field strength near the developer side carrier which changes periodically due to the rotation of the developer carrier, the magnetic field detecting means extending in the direction of the contact line with the developer carrier and having periodicity in the direction orthogonal thereto. and based on the signal detected by the magnetic field detection means,
A toner amount adhesion adjustment signal having a phase that is an integral multiple of the repetition frequency of the periodic change and has a constant relationship with the phase of the periodic change is output to control the development amount adjustment means. The invention of claim 2 is characterized in that, in addition to the above, the magnetic field detection means is provided near the contact line portion and on the side of the latent image carrier.The invention of claim 3 is the invention of claim 1. In addition, the magnetic field detection means is attached to the main body of the developing device.

According to the invention of claim 1, the intensity of the magnetic field is detected by the magnetic field detection means, and this signal is used to detect a phase that is in a constant relationship with the frequency of the periodic change of the magnetic field (in this case, the same phase). ) is generated to control the toner amount control means, so that the toner on the latent image carrier is controlled by changes in the thin layer forming conditions of the toner layer regulating member based on periodic changes in magnetic field strength. The effects of adhesion can be corrected. In addition, when the toner is magnetic, the toner particles are strongly attracted to the magnetic pole part, and even if the layer thickness is controlled by the toner layer regulating member, periodic changes in the toner adhering to the developer carrier occur. Even in this case, toner adhesion on the latent image carrier can be made uniform by generating a toner amount adhesion adjustment signal with a phase that has a certain relationship with the phase of this periodic change (in this case, a phase with a difference). can be done.

According to the second aspect of the invention, since the magnetic field detection means is provided on the latent image carrier side of the contact portion between the latent image carrier and the developer carrier,
Periodic changes in the toner layer in the development area can be directly detected.

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

L-Sh-j FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

A developing device is disposed opposite to a belt-shaped photoreceptor 1 used in an image forming apparatus such as a copying machine.

Inside the main body case 2 of the developing device, there are a developing roller 3 as a developer carrier, a toner replenishing member 4, and a toner agitator 5.
, a toner thin layer forming blade 6, which is a toner layer regulating member, and the like are provided.

The toner in the main body case 2 stirred by the toner agitator 5 is supplied to the developing roller 3 by the toner replenishing member 4, and after being made into a thin layer by the toner thin layer forming blade 6, it is attached to the electrostatic charge image on the photoreceptor 1. , development will be performed.

The developing roller 3 is a multi-polar magnetized developing roller in which a ferromagnetic layer 3b is provided on a conductive substrate 3a and finely magnetized. Contact rotation in the direction. The finely magnetized pattern extends in the direction of the contact line between the photoreceptor 1 and the developing roller 3, and is arranged with periodicity in a direction perpendicular to this.

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

In order to alleviate the influence of such a stripe pattern on the image, the strength of the magnetic field on the developing roller 3 is first detected.
is installed on the photoreceptor 1 side of the developing area, which is the contact area between the developing roller 3 and the photoreceptor 1. Of course, it is also possible to use a magnet diode or the like instead of the Hall element 7.

The periodic change in the magnetic field detected by the Hall element 7 is
The signal is inputted to the phase comparator 9 via the absolute value calculation circuit or the square calculation circuit 8, and is compared with the phase of the output transmitted from the voltage controlled oscillation circuit (VCO) 11 of the development amount adjustment means 10 such as the development bias. Note that, 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 8 becomes the control voltage of the VCO II by taking the difference from the DC voltage for phase setting. However, VCOII
When the frequency of the output of the VCO is an integral multiple of the frequency of the fluctuation in magnetic field strength caused by the rotation of the developing roller 3, the VCO
The output of II is appropriately frequency-divided before reaching phase comparator 9.

The output of VCOII is led to the development amount adjusting means 10 as a control voltage combined with a DC component.

In this example, a bias voltage is applied that is synchronized with periodic fluctuations in the strength of the magnetic field in the development area and has a constant phase difference. As a result, periodic fluctuations in the amount of toner adhesion caused by the magnetization pitch are corrected.

In addition, in a laser printer, etc., if the distance between the development area 9N and the writing position (not shown) is determined, the V
A laser diode and LED (not shown) output the COII.
It may also be a write system adjustment signal such as an array bias voltage.

In the embodiment shown in FIG. 1, the Hall element 7 is installed on the side of the photoreceptor 1 near the developing section, which is the contact area between the photoreceptor 1 and the developing roller 3. Therefore, fluctuations in the toner layer in the development area can be directly detected.

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

The embodiment shown in FIGS. 4 and 5 shows an example in which the Hall element 7 is attached to the main body side of the image forming apparatus to which the developing device is attached. Although the Hall element 7 is independent from the developing device, when the developing device is set in the image forming device of the image forming apparatus, the developing roller 3, the Hall element 7, and the Hall element 7
The positional relationship between the magnetic field detection position and the development area is determined by
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 from the developing device, the developing device can be replaced without replacing the Hall element 7.

In the embodiments shown in FIGS. 3 to 5, the photoreceptor 1 is drum-shaped, but it may be belt-shaped as shown in FIG.

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

Effects As described above, according to the present invention, in the invention of claim 1, the number of finely magnetized poles applied to the developer carrier is not increased, and the line between the developer carrier and the latent image carrier is Without increasing the speed ratio, it is possible to correct the effects of changes in thin layer formation conditions due to periodic changes in magnetic field strength, and to eliminate most of the fine magnetization patterns from the formed image, which not only improves image quality. ,
The manufacturing process of the developer carrier can be simplified, the quality can be stabilized, and the cost can be reduced.Furthermore, by reducing the driving torque required for the developer carrier, the drive of the image forming section of the image forming apparatus can be improved. It is also possible to make the means smaller and faster.

In addition to the above-mentioned effects, in the invention of claim 2, since changes in the toner layer in the development area can be directly detected and fed back to the development characteristics, adjustment accuracy can be improved.

In the invention of claim 3, in addition to the effect of the invention of claim 1, the adjustment accuracy can be improved by improving the installation accuracy of the magnetic field detection means.

[Brief explanation of the drawing]

Fig. 1 is a detailed explanatory diagram of the present invention, Figs. 2 to 5 are explanatory diagrams of other embodiments, and Figs. 2 and 3 show a case where the Hall element is integrally provided in the main body of the developing device. , FIG. 4, and FIG. 5 show the case where the Hall element is provided on the side of the image forming apparatus to which the developing device is installed. Fig. 1 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, 191 ．． Hall element (magnetic field detection means) 9...
...Phase comparator 10...Development amount adjustment means Fig. Fig. Fig. Fig.

Claims (3)

[Claims] (1) A thin toner layer is formed on a developer carrier in which a ferromagnetic layer is provided on a conductive substrate and the ferromagnetic layer is finely magnetized using a toner layer regulating member having magnetism and elasticity. The thin layer of toner is deposited on the latent image carrier by rotating the developer carrier while controlling the amount of toner attached to the latent image carrier carrying the electrostatic charge image using a development amount adjusting means. In a developing device that performs development using a magnet, the finely magnetized pattern extends in the direction of a contact line between the latent image carrier and the developer carrier and has periodicity in a direction perpendicular thereto, A magnetic field detection means is provided for detecting the magnetic field strength near the developer carrier which periodically changes due to the rotation of the developer carrier, and the repetition frequency of the periodic change is determined based on the signal detected by the magnetic field detector. A developing device configured to output a toner amount adhesion adjustment signal having a phase that is an integral multiple and has a constant relationship with the phase of the periodic change to control the development amount adjustment means. (2) The developing device according to claim 1, wherein the magnetic field detection means is provided near the contact line portion and on the side of the latent image carrier. (3) The developing device according to claim 1, wherein the magnetic field detection means is attached to a main body of the developing device.