JP2001134093A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and inexpensively detect toner carrying amount or toner electrification amount on a developer carrier and to obtain stable image quality on the basis of the detected result in a developing device provided with the developer carrier so as to be opposed to an image carrier on which an electrostatic latent image is formed and performing development by transferring toner to the latent image from a toner thin layer formed on the developer carrier. SOLUTION: This developing device is provided with a layer forming member 3 in press-contact with the developer carrier 2, and the member 3 is provided with a conductive member (leaf spring 3b) opposed to the developer carrier 2. Developing bias voltage is applied to the sleeve 2a of the developer carrier and a current flowing from the sleeve 2a to the member 3 is detected by a toner state detection means 6. When the toner carrying amount on the sleeve changes, a resistance value or the capacitance of a capacitor formed by the leaf spring and the sleeve is changed, and the current value detected by the means 6 is fluctuated. Thus, a toner state is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device which is used in an electrophotographic apparatus or an electrostatic recording apparatus and visualizes an electrostatic latent image formed on an image carrier by attaching toner.

[0002]

2. Description of the Related Art Various types of developing devices for selectively transferring toner to an electrostatic latent image formed on an image carrier and visualizing the toner have been proposed according to the type of developer used. I have. Among them, as a developing device using a magnetic one-component developer, for example, there is one having a configuration shown in FIG. The developing device includes a housing 101 for housing a magnetic one-component developer.
And a developing roller 102 (developer supporting member) provided to face the image carrier 100 on which the electrostatic latent image is formed, and a layer which is pressed against the developing roller 102 and regulates the amount of the developer adhered on the developing roll. And a forming member 103. The main part of the developing roll 102 is constituted by a magnet roll 102b provided with a plurality of magnetic poles in a circumferential direction, and a cylindrical sleeve 102a which rotates around the magnet roll independently of the magnet roll. As the layer forming member 103, an elastic member 103a such as rubber is generally used in a portion that comes into contact with the developing roll 102.

In such a developing device, the one-component magnetic developer housed in the housing 101 is held on the surface of the sleeve 102a by the magnetic force of the magnet roll 102b and passes through the space between the sleeve 102a and the layer forming member 103. Is rubbed against the surface of the developing roll 102 to form a thin layer of developer (toner). Then, the developer is frictionally charged by the rubbing between the developer and the surface of the developing roll 102, so that a charge is applied.

[0004] The developer thinned by the layer forming member 103 is rotated by the rotation of the sleeve 102a to form the image carrier 100.
And the developing roller 102 are conveyed to a developing area facing the developing roller 102. Between the image carrier 100 and the developing roll 102, a DC superimposed AC voltage or DC voltage is applied from a power supply device 104, and a developer having an electric charge due to an electric field generated in the developing area causes the electrostatic charge of the image carrier 100 to be reduced. The development is performed by flying to the latent image.

The above-described one-component developing apparatus is often used for low-speed small-sized copiers and printers, taking advantage of the fact that it can be easily miniaturized. It is being used, and further improvement in performance is required.

[0006]

In the conventional developing device as described above, there are the following items that are desired to be improved. In a developing device provided with a layer forming member that is pressed against a developing roll and rubs and rubs toner, the layer thickness of the toner layer formed on the developing roll, that is, the amount of toner transported on the developing roll becomes unstable. Easy to be. In particular, when the developing operation is repeated over a long period of time, the surface of the developing roll is worn due to the layer forming member being pressed against the developing roll, and the amount of toner conveyed on the developing roll is reduced. Sometimes. Further, by repeatedly rubbing the toner on the surface of the developing roll, the toner is subjected to mechanical stress, and external additives attached to the toner surface are buried in the toner. Easy to occur. Even when such toner deterioration occurs, the amount of toner conveyed on the developing roll decreases,
As a result, the charge amount of the toner decreases.

As described above, when the amount of toner transported on the developing roll or the amount of charged toner decreases, the amount of transfer of the toner to the electrostatic latent image decreases, causing a decrease in density and uneven development. The developed image will be degraded.

To solve such a problem, Japanese Patent Application Laid-Open No. H5-25-2
Japanese Patent No. 89483 discloses a developing device provided with an optical toner layer detector close to and opposed to a developing roll on the upstream side of a developing area. In this developing device, the amount of toner transported on the developing roll is detected, and the pressure and the like of the layer forming member are adjusted based on the detected value. In this way, an attempt is made to control the toner conveyance amount on the developing roll to be substantially constant. However, when the toner layer detector is provided so as to face the developing roll, the manufacturing cost increases and the size of the developing device increases,
This is contrary to the recent demand for miniaturization.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to detect the amount of toner transported on a developer carrier or the amount of charge of toner with high accuracy and low cost.
An object of the present invention is to provide a one-component developing device that maintains stable image quality based on this.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 is provided so as to face an image carrier having a surface on which a latent image due to a difference in electrostatic potential is formed. A developer carrying member whose peripheral surface moves around; a layer forming member that is pressed against the peripheral surface of the developer carrying member to form a thin layer of developer; and the developer carrying member and the image carrying member. A power supply device for applying a developing bias voltage between the image bearing member and the developer carrying member in a developing region opposed to each other,
In a developing device for selectively transferring the thinned forging agent to the image carrier to visualize the latent image, the layer forming member has a portion made of a conductive material, A toner state detecting unit that measures a current value flowing from the developer carrier to the conductive portion of the layer forming member to detect a toner transport amount on the developer carrier or a charge amount of the toner on the developer carrier; A developing device is provided.

The portion of the layer forming member made of a conductive material is made of a material such as a metal having a negligible electric resistance. The member made of such a conductive material is referred to as a high resistance member. They may be used in combination. For example, it is possible to adopt a structure in which a high-resistance member is used for a portion directly pressed against the developer carrier, and a conductive material such as a metal is disposed behind the high-resistance member to support the high-resistance member.

In such a developing device, the toner supplied to the developer carrier is triboelectrically charged by the layer forming member and forms a substantially uniform toner layer on the peripheral surface of the developer carrier. Then, it is transported to a position facing the image carrier,
Here, the image is transferred to an electrostatic latent image on the image carrier, and the electrostatic latent image is made a visible image.

On the other hand, a developing bias voltage is applied to the developer carrier, so that a small amount of current flows through the toner layer on the peripheral surface to the conductive portion of the layer forming member. This current value varies according to the toner amount because the resistance value varies depending on the amount of toner on the peripheral surface of the developer carrying member. By detecting this current value, the current value on the peripheral surface of the developer carrying member is It is possible to detect a change in the toner conveyance amount. That is, the amount of toner transport on the peripheral surface of the developer carrier is varied in advance, and the amount of toner transport is measured by other means, and the amount of current flowing through the layer forming member at this time is measured and corresponded. . This makes it possible to know the relationship between the fluctuation of the toner transport amount and the amount of current flowing to the layer forming member. Then, when the amount of current to the layer forming member is detected at a predetermined time when an image is formed using the developing device, the amount of toner transport on the peripheral surface of the developer carrying member is determined from a relationship that has been investigated in advance. Can be detected.

On the other hand, the amount of charge of the toner conveyed on the developer carrying member is determined by the amount of charge already existing up to the pressing position of the layer forming member and the amount of charge applied by rubbing of the layer forming member. It will be combined. By detecting the amount of the charge that moves to the conductive portion of the layer forming member via the toner layer, it is possible to detect a change in the charge amount of the toner.

According to a second aspect of the present invention, the conductive portion of the layer forming member is a plate-shaped member disposed so as to face the developer carrier, and the developing bias voltage includes an alternating current. The conductive plate member and the developer carrier function as a capacitor, and an alternating current is generated from the developer carrier to the layer forming member. This current fluctuates due to a change in the capacitance of the capacitor due to a change in the amount of toner transport on the peripheral surface of the developer carrier. Therefore, the change in the value of the current flowing through the layer forming member is a combination of the change in the resistance value and the change in the capacitance of the capacitor, and the change in the toner conveyance amount can be detected more remarkably.

When a change in the amount of current is detected, whether the change is due to a change in the toner transport amount or a change in the toner charge amount is determined based on the relationship between time and the change rate. . In other words, the change in the amount of charge of the toner is often due to a change in humidity and the like, and fluctuates in a relatively short period of time. It is gradually generated by use, and can be determined by taking these factors into consideration. Further, it is conceivable that the decrease in the charge amount due to the deterioration of the toner is caused by the use for a long time. In this case, the fluctuation of the current value when only the DC bias voltage is applied to the developer carrier and the AC bias voltage By comparing the fluctuation of the current value when applying
It is possible to determine that the toner transport amount has decreased.

According to a third aspect of the present invention, in the developing device according to the first aspect, the current value is measured when a portion of the image carrier having no image is opposed to the developer carrier. It is assumed that it is set to perform.

In this developing device, the amount of current flowing through the layer forming member when the non-image portion of the image carrier faces the developer carrier, that is, when the development of the electrostatic latent image is not performed. Detect. During the development, the charged toner is transferred to the image carrier, and the amount of current detected may be affected by the amount of transfer of the toner. An accurate current value can be obtained by detecting the current when the body is facing the image portion without an image.

According to a fourth aspect of the present invention, in the developing device according to the first or second aspect, the pressing force of the layer forming member is adjusted according to a current value detected by the toner state detecting means. It has a layer thickness adjusting means.

In this developing device, the current value flowing to the layer forming member is detected by the toner state detecting means, and based on the detected current value, it is determined that the amount of toner transported on the developer carrier is small. The pressing force of the layer forming member against the developer carrier is reduced. As a result, the amount of toner passing through the layer forming member increases, and it is possible to control the amount of toner conveyed on the developer carrying member to be substantially constant at all times. When it is determined by the toner state detecting means that the toner transport amount on the developer carrying member is large, the pressure contact force of the layer forming member is increased, and the toner transport amount is adjusted so as to decrease.

According to a fifth aspect of the present invention, in the developing device according to the first or second aspect, the image carrier is transferred from the developer carrier in accordance with a current value detected by the toner state detecting means. It has a developing toner amount adjusting means for adjusting the amount of toner transferred to the body.

As the developing toner amount adjusting means, for example, means for changing the voltage of the DC component or the AC component of the developing bias voltage can be employed. Further, when a member having a photoreceptor layer on the surface is used as the image carrier, a signal for changing a charging voltage is output to a charging device that performs uniform charging before image light irradiation. Well,
Other means that can adjust the amount of developed toner can also be employed.

In such a developing apparatus, the current value flowing to the layer forming member is detected by the toner state detecting means, and when it is determined based on this that the amount of toner transported on the developer carrying member is small, generally, the image carrying amount is reduced. The amount of toner transferred to the electrostatic latent image in the region facing the body decreases, and the density of the developed image decreases. On the other hand, the operation of the developing toner amount adjusting means is adjusted so that the amount of toner transferred to the image carrier is increased, and the decrease in density due to the decrease in the amount of toner transport is complemented, so that a substantially constant developing density is maintained. Is done. On the other hand, if the toner state detecting means determines that the amount of toner transported on the developer carrying member is large, the developing toner amount adjusting means operates so as to reduce the developing toner amount, and excessive toner is transferred to the image carrying member. Metastasis is prevented.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a developing device according to an embodiment of the present invention. The developing device 10 is provided at a position opposing an image carrier 50 on the surface of which a latent image is formed due to a difference in electrostatic potential. The developing device 10 accommodates toner in the housing 1 and has an image in the housing. A developer carrier 2 (developing roll) that is closely opposed to the carrier 50 and adheres and conveys a developer (magnetic toner) on the surface, and a toner layer is formed by regulating the toner on the developer carrier 2. A layer forming member 3 and a stirring and supplying member 4 for stirring the toner and supplying the toner to the developer carrier 2
A power supply device 5 for applying a developing bias voltage between the image carrier 50 and the developer carrier 2;
And a toner state detecting means 6 for measuring a current value flowing through the layer forming member 3 to detect a toner transport amount on the developer carrying member or a charge amount of toner on the developer carrying member.

The image carrier 50 is a photoconductive drum having a surface layer made of a negatively charged organic photoreceptor on its surface, and after being uniformly charged by charging means (not shown),
By irradiating image light, a latent image due to a difference in electrostatic potential can be formed. The surface potential when an electrostatic latent image is formed can be, for example, -100 V in the image portion exposed portion and -500 V in the background portion (non-exposed portion).

The developer carrier 2 is provided so as to face the image carrier 50, and is capable of transporting the toner adhered to the surface by rotating. The developer carrier 2 has a close position A to the image carrier 50. The gap is set to be approximately 200 μm to 350 μm in the (development region).

The developer carrier 2 is supported by a cylindrical developing sleeve 2a which is driven to rotate around an axis, and is fixed so as not to rotate inside the developing sleeve 2a.
A main part is constituted by a magnet roll 2b in which a plurality of magnets are arranged along the peripheral surface. The plurality of magnets form a magnetic pattern in which S poles and N poles are arranged along the peripheral surface. According to this magnetic pattern, the magnetic toner can be attracted onto the surface of the developing sleeve 2a. Has become. On the other hand, the developing sleeve 2a is made of a resin sleeve such as phenol, a metal sleeve such as aluminum or stainless steel, an aluminum oxide layer or metal plating on the surface, or a metal sleeve having a resin-based coating film such as acrylic, epoxy, or polyester. Is used.

A DC bias AC voltage is applied as a developing bias voltage from the power supply 5 to the developing sleeve 2a of the developer carrier, and in the developing area A where the developing sleeve 2a and the image carrier 50 are close to each other, the image carrier is An alternating electric field is generated between a grounded electrode under the photoreceptor layer on the surface. The developing bias voltage has, for example, a frequency of an AC component of 2.2 KHz and a peak-to-peak voltage of 1800.
V and the DC component can be -300V.

The layer forming member 3 is formed by bonding a pressing member 3a made of silicone rubber having a thickness of about 0.2 mm in which conductive powder is dispersed to a stainless leaf spring 3b having a thickness of about 0.5 mm. The one end of the leaf spring 3b is fixedly supported by the housing 1, and is pressed against the developing sleeve 2a in a state where the pressing member 3a faces upstream in the rotation direction of the developing sleeve 2a.

The pressing force of the pressing member 3a is 0.5 N / c.
m, and the position of being pressed against the developing sleeve 2a is at a central angle of about 10 ° downstream from the attracting magnetic pole (N pole) of the magnet roll 11 that attracts the magnetic toner supplied from the stirring and supplying member 4. It is a position of 20 °. The pressing member 3a may be made of urethane rubber or the like instead of silicone rubber.

The leaf spring 3b of the layer forming member 3 is grounded via the toner state detecting means 6 so that the current flowing from the developing sleeve 2a to the layer forming member 3 is detected by the toner state detecting means 6. Has become.

The toner state detecting means 6 stores an ammeter for measuring a current value and information on a relationship between the current value detected by the ammeter and the state of the toner on the developer carrier. Means for determining the state of the toner on the developer carrier by comparing the detected current value with the information stored in the storage means. Then, a signal corresponding to the determined result can be output to a display means or the like.

The magnetic toner used in the developing device 10 contains at least a binder resin, a magnetic powder, and a colorant.
Its average particle size is in the range of 3 to 10 μm. Further, an external additive is appropriately added. As the binder resin, a stainless steel-n-butyl acrylate-based or polyester-based resin or the like is used. Ferrite, magnetite, etc. are used as the magnetic powder. A release agent may be added. As the release agent, paraffin having 8 or more carbon atoms, paraffin wax, paraffin latex, microcrystalline wax, or the like, or polypropylene or the like can be used. Further, as the external additive, SiO ₂ , Ti
O ₂ , Al ₂ O ₃ , MgO, CuO, ZnO, SnO
₂ , CeO ₂ , Fe ₂ O ₃ , BaO, CaO, K ₂ O,
Na ₂ O, ZrO ₂ , CaO · SiO ₂ , CaCO ₃ ,
K ₂ O (TiO ₂ ) _n , MgCO ₃ , Al ₂ O ₃ .2S
TiO ₂ , BaSO ₄ , MgSO _{4 and the} like can be used, and preferably, SiO ₂ , TiO ₂ , and Al ₂ O ₃ are used. One of these may be used, or two or more of them may be used in combination. The fine particles may be untreated, may be subjected to a hydrophobic treatment with a hydrophobic agent such as a silane coupling agent, or may be subjected to a surface treatment with a quaternary ammonium salt or silicone oil.

In the developing device of the above embodiment, binder resin: styrene-n-butyl acrylate copolymer 45 parts by weight Magnetic powder: magnetite 45 parts by weight Negative charge control agent 6 parts by weight Polypropylene wax 3 parts by weight Polyethylene wax A toner having a volume average particle diameter of 7 μm using 1 part by weight as a material is used, and 1.0 part by weight of hydrophobic silica having a diameter of 12 nm and 1.0 part by weight of titania are used as external additives with respect to 100 parts by weight of the toner. ing.

The image carrier 5 by such a developing device 10
The development of the electrostatic latent image on 0 is performed as follows. The magnetic toner contained in the housing 1 is supplied to the surface of the rotating developing sleeve 2 a by the stirring and supplying member 4, and is conveyed to the pressure-contact position of the layer forming member 3 by the rotation of the developing sleeve. Then, the surface of the developing sleeve 2a is rubbed by the pressing member 3a, whereby the toner is thinned and an appropriate charge is applied to the toner. The thinned toner is further transported to the developing area A by the rotation of the developing sleeve 2a, and the developer carrier 2 and the image carrier 50 are rotated.
Many toner particles having electric charge fly and reciprocate in an alternating electric field generated in a gap between the toner particles. In addition, the toner particles collide with each other due to the reciprocating motion, and the whole becomes cloud-like. The toner cloud is attracted to the latent image portion (exposure portion) on the image carrier 50 by the DC component of the bias voltage, and this electrostatic latent image is visualized.

On the other hand, a time period during which the above-described developing process is repeated, that is, a period from when the development of one electrostatic latent image is completed to when the development of the next electrostatic latent image is started. Then, the state of the toner on the developer carrier is detected. Note that this toner state detection does not need to be performed each time the electrostatic latent image is developed, and is performed each time a predetermined number of developments are performed.
What is necessary is just to perform at the timing set arbitrarily.

The detection of the toner state is performed as follows. A developing bias voltage is applied to the developing sleeve 2a from the power supply device 5, and a current is generated to the leaf spring 3b through the toner layer on the developing sleeve 2a and the high-resistance conductive pressure contact member 3a. This current is detected by an ammeter included in the toner state detecting means 6. Further, the developing bias voltage includes an AC component, and there is a current generated by a capacitor effect due to the development sleeve 2a and the plate spring 3b facing each other, and this current value is also detected.

On the other hand, the pressing force of the layer forming member 3 against the developing sleeve 2a is changed to change the toner conveyance amount on the developing sleeve 2a, and in each case, the current value flowing from the developing sleeve 2a to the leaf spring 3b and The toner conveyance amount on the developing sleeve 2a is measured in advance. Then, the relationship between the toner conveyance amount on the developing sleeve 2a and the current value is stored in the storage unit of the toner state detection unit 6.

FIG. 2 shows an example of the relationship between the toner transport amount and the current value measured as described above. The current detected by the toner state detecting means 6 in accordance with the variation of the toner transport amount. It can be seen that the values are different. Then, when the good development is performed, the toner layer on the developing sleeve 2a it has been previously investigated a ^{16g / m 2 ~20g / m 2} . Therefore, when the current value is detected before or after the development process, this value is, for example, as shown in FIG.
The toner state at that time can be determined by comparing with the information stored in the storage unit.

The relationship between the amount of toner transported and the current value from the developing sleeve 2a to the layer forming member 3b may be affected by changes in the environment such as temperature or humidity. It is desirable to investigate in advance the relationship between the amount and the current value. A temperature / humidity detecting means is provided, and an appropriate one is selected from a plurality of correspondences stored in advance according to the detected value, and the toner conveyance amount is determined from the current value, so that accurate determination is possible. Becomes

Although the developing device of the embodiment described above applies a DC superimposed AC voltage as a developing bias voltage, it may apply a DC voltage. In this case, since the capacitor effect does not occur due to the developing sleeve and the leaf spring, only the current generated through the toner layer and the pressure contact member is detected.

FIG. 3 is a schematic structural view showing a developing device according to an embodiment of the present invention. The developing device 20 includes a developer carrier 12, a layer forming member 13, a stirring and supplying member 14, a power supply device 15, and a toner state detecting unit 16 similar to the developing device 10 shown in FIG. 1. In addition, the leaf spring 13b of the layer forming member
And a layer thickness adjusting means 18 for deforming the leaf spring 13b in accordance with the current value detected by the toner state detecting means 16.
Is provided.

The layer thickness adjusting means 18 drives the operating member 18a, the tip of which is in contact with a leaf spring, and is supported so as to be able to move forward and backward, and slowly rotates the operating member 18a forward or backward by rotation of a motor. And a driving unit 18b. The driving unit 18b includes a driving unit 18b based on a signal corresponding to the current value detected by the toner state detection unit 16.
A driving current is supplied so as to drive the motor of a predetermined amount. When the operating member 18a is retracted, the pressing force of the leaf spring 13b against the developing sleeve 12a decreases, and the amount of toner transport on the developing sleeve 12a increases. Therefore, when the toner state detecting means 16 detects that the toner conveyance amount on the developing sleeve 12a is reduced, the pressing force of the layer forming member 13 is reduced so as to compensate for the reduced amount, and the toner on the developing sleeve 12a is reduced. The transport amount can be maintained at an appropriate value.

FIG. 4 is a diagram showing the relationship between the current value detected by the toner state detecting means 16 and the amount of displacement of the operating member 18a generated based on the detected value. In the case of ３０30 μA, the amount of toner transported on the developing sleeve 12 a is a value appropriate for development, and the layer thickness adjusting means 18 is not activated. When the detected current is lower than 23 μA, the toner transport amount is excessive, the resistance value increases, and the capacitance of the capacitor decreases. Therefore, the operation member 18a is advanced, and the pressing force of the layer forming member 13 is increased to reduce the toner conveyance amount. On the other hand, if the detected current is 3
When it exceeds 0 μA, the operation member 18a is set back so as to reduce the pressing force of the layer forming member 13 and increase the toner conveyance amount.

Therefore, when the toner transport amount decreases due to other factors such as abrasion of the peripheral surface of the developing sleeve 12a, and this is detected by the toner state detecting means 16, the layer thickness is determined based on the relationship shown in FIG. Adjusting means 18
Is operated, the amount of toner transport on the developing sleeve 12a can be maintained at an appropriate value.

Although the developing device 20 of the above-described embodiment uses a magnetic toner, in a developing device using a non-magnetic toner, a bias voltage is applied to a supply roll for supplying the toner to a developing sleeve. The amount of toner transport on the developing sleeve can be controlled by adjusting.

FIG. 5 is a schematic structural view showing a developing device according to an embodiment of the present invention. This developing device 30 also has the same configuration as the developing device shown in FIG. 1, and in addition, varies the amount of developing toner transferred from the developer carrier 22 to the electrostatic latent image on the image carrier 50. And a developing toner amount control means 27 for controlling the amount of toner to be developed.

The developing toner amount control means 27 is a control device for adjusting the developing bias voltage applied to the developing sleeve 22a according to the current value detected by the toner state detecting means 26. This is because, when the toner state detecting means 26 detects a decrease in the amount of toner transported on the developing sleeve 22a, the voltage of the DC component is increased so that the transfer amount to the electrostatic latent image is reduced even if the amount of toner transported decreases. Are controlled to be substantially the same. When a large amount of toner transport on the developing sleeve 22a is detected, the DC component of the developing bias voltage is reduced so that excessive toner does not transfer to the electrostatic latent image.

FIG. 6 is a diagram showing the relationship between the current value detected by the toner state detecting means 26 and the DC component of the developing bias voltage controlled based on the detected value. When the detected current value is in the range of 23 μA to 30 μA,
The amount of toner transported on the developing sleeve 22a has an appropriate value for development, and the developing bias voltage is set so as not to fluctuate. Then, the detected current value is 30 μA
When the value exceeds the threshold value, the amount of developing toner tends to decrease because the amount of toner transported on the developing sleeve 22a decreases. However, the DC component of the developing bias voltage is increased to compensate for this. On the other hand, when the detected current value is lower than 23 μA, the toner conveyance amount on the developing sleeve 22a is too large, and the DC component of the developing bias voltage is reduced so that excessive toner does not transfer to the electrostatic latent image. It is set to reduce. By adjusting the DC component of the developing bias voltage in this manner, the electrostatic latent image on the image carrier 50 is always developed at a substantially constant density.

The developing device of the above embodiment employs a control device for adjusting the DC component of the developing bias voltage as the developing toner amount control means. In addition, the developing device controls the AC component applied to the developing sleeve. Means for changing the peak-to-peak voltage value, frequency, duty ratio, and the like, and means for changing the potential of the photoreceptor to change the effective electric field involved in development can also be adopted. It is possible to control the amount of developed toner.

FIG. 7 shows the same layer thickness adjusting means 38 as used in the developing device shown in FIG. 3 and the same amount of developing toner control means 39 as used in the developing device shown in FIG. It is provided. Thus, the developing sleeve 3
It is also possible to supplement the variation of the toner transport amount on 2a with the above two means, and it is possible to perform more accurate and stable control.

[0052]

As described above, according to the developing device of the present invention, the toner value is measured by measuring the current value flowing from the developer carrier to the layer forming member by the developing bias voltage applied to the developer carrier. The transport amount or the toner charge amount is detected. This makes it possible to accurately detect the state of the toner on the developer carrying member while being inexpensive and space-saving. A toner carrying amount control unit that varies a toner carrying amount in accordance with an output value of the toner state detecting unit; and / or a developing toner in accordance with an output value of the toner state detecting unit on the developer carrier. By having the developing toner amount control means for varying the amount, the amount of toner developed on the electrostatic latent image on the image carrier can be changed in any environment.
In addition, it is possible to stably maintain the image even when used continuously for a long period of time, and it is possible to obtain a developing performance free from image defects such as a decrease in image density.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a one-component developing device according to an embodiment of the present invention described in claim 1, 2 or 3.

FIG. 2 is a diagram illustrating a relationship between an output current value of a toner state detecting unit in the developing device illustrated in FIG. 1 and a toner conveyance amount on a developing sleeve.

FIG. 3 is a schematic configuration diagram showing a one-component developing device according to an embodiment of the present invention.

4 is a diagram illustrating a relationship between an output current value of a toner state detecting unit in the developing device illustrated in FIG. 3 and a set adjustment value of a pressing force of a layer forming member.

FIG. 5 is a schematic configuration diagram showing a one-component developing apparatus according to an embodiment of the present invention.

6 is a diagram illustrating a relationship between an output current value of a toner state detecting unit in the developing device illustrated in FIG. 5 and a set DC component adjustment value of a developing bias voltage.

FIG. 7 is a schematic configuration diagram showing a one-component developing apparatus according to another embodiment of the invention described in claim 4 or 5;

FIG. 8 is a schematic configuration diagram illustrating an example of a conventional one-component developing device.

[Explanation of symbols]

 1, 11, 21, 31 Housing 2, 12, 22, 32 Developer carrier 2a, 12a, 22a, 32a Developing sleeve 2b, 12b, 22b, 32b Magnet roll 3, 13, 23, 33 Layer forming member 4, 14 , 24, 34 Stirring supply member 5, 15, 25, 35 Power supply device 6, 16, 26, 36 Toner state detecting means 10, 20, 30, 40 Developing device 17, 37 Driving power supply 18, 38 Layer thickness adjusting means 18a, 38a operating member 18b, 38b driving unit 27, 39 developing toner amount adjusting means 50 image carrier

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Miyata 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Hiroyuki Miyamoto 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.F-term ( Reference) 2H073 AA01 BA03 BA04 BA12 BA25 CA02 2H077 AD06 AD13 AD17 AD36 AE03 DA24 DA42 DA57 DA81 DB25 EA13 FA19 FA21 FA22 FA23 FA25 GA03

Claims (5)

[Claims] A developer carrier having a surface on which a latent image formed by a difference in electrostatic potential is formed, the developer carrier having a circumferential surface moving around the image carrier; A layer forming member that is pressed against a surface to form a thin layer of toner; and a power supply device that applies a developing bias voltage between the developer carrier and the image carrier. A developing device for selectively transferring the thinned toner to the image carrier in a developing region opposed to a developer carrier to visualize the latent image, wherein the layer forming member is made of a conductive material And measuring a current value flowing from the developer carrier to the conductive portion of the layer forming member to transfer the toner on the developer carrier or charge the toner on the developer carrier. A toner state detecting means for detecting the amount. The developing device. 2. The method according to claim 1, wherein the conductive portion of the layer forming member includes a plate-shaped member arranged so as to face the developer carrier, and the developing bias voltage includes an alternating current. Item 2. The developing device according to Item 1. 3. The apparatus according to claim 1, wherein the measurement of the current value is performed so as to be performed when a portion of the image bearing member having no image faces the developer bearing member. Developing device. 4. The apparatus according to claim 1, further comprising a layer thickness adjusting unit that adjusts a pressing force of the layer forming member according to a current value detected by the toner state detecting unit. Developing device. 5. A developing toner amount adjusting means for adjusting an amount of toner transferred from the developer carrier to the image carrier according to a current value detected by the toner state detecting means. The developing device according to claim 1.