JPH1078693A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain an image of high quality by always keeping the layer thickness of toner on a developer carrier constant, in accordance with the lapse of time and environmental conditions, in an image forming device using a one- component developer. SOLUTION: The image forming device is constituted so that the potential difference between a developing roller 2 and a lower supplying roller 4b can be arbitrarily set by a device for varying the potential difference. When the charge quantity of the toner is large in a low humidity environment and attracting force to the developing roller 2 is great as well, the potential difference between the roller 2 and the lower supplying roller 4b is set so as to form an electric field where the toner is hardly stuck to the roller 2. Further, when the charge quantity of the toner is small in a high humidity environment and the attracting force to the roller 2 is small as well, the potential difference between the roller 2 and the lower supplying roller 4b is set so as to form the electric field where the toner is easily stuck to the roller 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a developing device that is used to develop a latent image on a latent image carrier by charging a one-component developer externally added with an auxiliary agent as needed to a desired polarity.

[0002]

2. Description of the Related Art In an image forming apparatus for forming a latent image on an image carrier and visualizing the latent image with a developer, a one-component developer is used in view of miniaturization, cost reduction and high reliability of the developing device. Are advantageous. In particular, when performing colorization, it is advantageous to use a non-magnetic one-component developer rather than a magnetic one-component developer in that transparency is higher. As a developing device using a one-component developer, a developer carrier that carries the one-component developer on its surface and transports the developer along a predetermined circulation path including a development area, and stores the one-component developer. There is known a storage device having a reservoir and developer supply means for contacting the developer carrier and supplying the one-component developer stored in the developer reservoir to the developer carrier. (See, for example, JP-A-60-229057 and JP-A-61-42672).

Here, for example, in a developing system using a non-magnetic one-component developer (hereinafter, referred to as toner), the amount of toner adhering on the developer carrier is 0.6 to 0.6 on the image carrier.
1.0 mg / cm ² toner adhesion amount, 0.5 to 0.5 on transfer paper
It is desirable that a toner adhesion amount of about 0.7 mg / cm ² can be obtained. The amount of toner adhered on the image carrier and the transfer paper depends not only on the amount of toner adhered on the developer carrier but also on the relative speed between the image carrier and the developer carrier in the development area. However, according to this type of developing device that has been put to practical use, the toner adhering amount on the developer carrying member is less than 0.2 since the toner amount on the developer carrying member is as small as one layer. a ~0.5mg / cm ^2, in order to obtain a desired toner adhesion amount of the above image carrier choice sets the speed of the developer carrying member in two to four times the speed of the image bearing member Needed. When the rotation of the developer carrier is set high in order to cover the insufficient amount of toner attached on the developer carrier in this way, not only is it difficult to increase the image forming speed, but also the A phenomenon called “toner trailing edge” in which the density of the trailing edge of the image increases when developed is also caused. This phenomenon is not a big problem in black and white images, but in color images, the color is transmitted through the toner and the color is visually perceived. Had been lost.

In order to prevent the phenomenon of “toner trailing edge” and to obtain a desired amount of toner adhering on the image carrier or the like, the speed of the developer carrier must be reduced. It is necessary to approach the speed, that is, to approach the constant speed development, and to increase the amount of toner adhered on the developer carrying member as compared with the related art. Specifically, in order to secure a sufficient amount of toner adhered on the image carrier or the transfer paper by substantially constant speed development, the amount of toner adhered on the developer carrier is determined by:
At least 0.8mg / cm ² by contact development method with good development efficiency,
At least 1.0 mg / cm ^{2 by} non-contact development method with poor development efficiency
Need to be In order to obtain such a toner adhesion amount on the developer carrying member, it is necessary to make the thickness of two or more layers, that is, a multilayer toner layer.

In view of the above, the present applicant has previously used, as a developer carrying member, a developer carrying member comprising a dielectric portion whose surface is regularly or irregularly distributed over a small area and a grounded conductive portion. At a contact portion between the developer carrier and the developer supply member rotating at a position where the developer carrier is in contact with the surface thereof, the one-component developer is frictionally charged, and the dielectric portion is charged with the developer supply member and the one-component developer. The developer is frictionally charged to form a number of minute closed electric fields in the vicinity of the surface of the developer carrying member, and the one-component developer is transferred from the developer supply member to the developer carrying member by the minute closed electric field to form a developer. A developing device in which a multi-layer is supported on a carrier has been proposed (for example, see Japanese Patent Application Laid-Open No. 4-127177).
issue). According to the developing device according to this proposal, a one-component developer is transferred from the developer supply member to the developer carrier by a minute closed electric field formed on the developer carrier to form a multilayer on the developer carrier. Thus, a multi-layer toner layer having a stable charge amount can be formed on the developer carrying member, and the system can be stabilized and the image quality can be improved.

However, in the one-component developing apparatus having the above-described structure, the developer supply member and the developer carrier are arranged in the same direction, for example, as shown in FIG. Are rotated in the counterclockwise direction, a part of the one-component developer injected into the developer carrier 2 from the developer reservoir 6 is partially removed by the developer supply member 4 and the developer. There is a possibility that the developer may be immediately conveyed onto the developer carrier 2 without passing through the region where the carrier 2 comes into contact, and the developer regulating member 3 may form a developer layer. When the developer is conveyed in this way, the frictional charging is insufficient, and the developer layer is formed thick on the developer carrier 2, which may cause uneven development and scattering of the developer. There was a problem that there was.

The developer supply member 4 and the developer carrier 2 are different from each other, for example, as shown in FIG. 10, the developer supply member 4 is clockwise, and the developer carrier 2 is counterclockwise. When the developer storage unit 6 is rotating in the
The one-component developer supplied to the developer carrier 2 from below passes under the developer supply member 4 and reaches a region where the developer supply member 4 and the developer carrier 2 come into contact with each other. Since the developer is conveyed, the developer carried on the developer carrier 2 is uniformly charged. However, in this case, only the seal mechanism 10 for blocking the developer conveyed under the developer carrier 2 from scattering between the developer carrier 2 and the developing device wall is required. Instead of this sealing mechanism 10
However, there is a problem in that the mechanism for securely blocking the developer becomes complicated because of the increased burden on the developer.

Further, when a large amount of developer is consumed by solid development, a sufficient amount of developer cannot be obtained by a single developer supply operation, and the developer carrier must pass through the developer supply region several times. Thus, the desired layer thickness and charge amount could not be obtained.

[0009] The above problem is not limited to the above-described developing device in which the one-component developer is transferred from the developer supply member to the developer carrier by the minute closed electric field formed on the developer carrier. Was likely to occur.

In order to solve such a problem, the present applicant has disclosed in Japanese Patent Application No. 8-53907, for example, that the developer carrier is brought into contact with or close to the developer reservoir from the developer reservoir side. A developing device having a first developer supply member and a second developer supply member which rotate so as to move the developer on the developer storage side to the developer carrier via the mutually facing regions, respectively. Is disclosed. According to this developing device, uniform charge and uniform thickness of the developer layer on the developer carrier can be achieved, and the sealing mechanism can be simplified.

[0011]

However, if the charge amount of the toner fluctuates due to the amount of moisture in the atmosphere during image formation in the developing device having the above-described structure, the toner attraction to the developer carrier changes, and The layer thickness varies. Accordingly, there is a problem that the amount of the developing toner changes depending on the humidity condition, and the image density changes. Also, there is a problem that the toner layer thickness becomes thin even when the toner in the developing device is reduced and the toner end is approached.

The present invention has been made in view of the above problems, and has as its object to maintain a constant toner layer thickness on a developer carrying member at all times according to aging and environmental conditions, thereby achieving high quality. An image forming apparatus capable of maintaining an image is provided.

[0013]

In order to achieve the above object, according to the present invention, a one-component developer to which an auxiliary agent is externally added as needed is charged to a desired polarity and supported. A developer carrier that is transported to a development area facing the latent image carrier,
The developer carrier comes into contact with or approaches from the developer reservoir side, and rotates to move the developer on the developer reservoir side to the developer carrier side via the mutually facing regions. One developer supply member, a second developer supply member provided downstream of the first developer supply member in the developer carrier transport direction, the first developer supply member, and the developing device. A potential difference forming means for forming a potential difference between the developer carrying member and a developer regulating member for regulating the developer carried on the developer carrying member and conveyed to the developing area to a predetermined layer thickness. An image forming apparatus provided with a developing device for developing a latent image on the latent image carrier using the developer on the developer carrier regulated by the developer regulating member; Potential difference that changes the potential difference between the developer supply member and the developer carrier In which it characterized in that a variable means.

In this image forming apparatus, the potential difference between the first developer supply member provided upstream of the two developer supply members in the direction in which the developer carrier is transported and the developer carrier is determined. The amount of the developer carried on the developer carrier can be adjusted by changing the potential difference. For example, in a low humidity environment, when the charge amount of the developer is high and the attracting force to the developer carrier is high, the developer carrier is formed so that the developer forms an electric field that is difficult to adhere to the developer carrier. The potential difference between the body and the first developer supply member is changed. When the amount of charge of the developer is high in a low-humidity environment and the attraction force to the developer carrier is high, the developer carrier is formed so as to form an electric field in which the developer does not easily adhere to the developer carrier. The potential difference between the body and the first developer supply member is changed. Even if a large amount of uncharged developer adheres to the surface of the developer carrier due to the change in the potential difference, the friction between the second developer supply member and the developer carrier is limited by the friction. After being charged and uniformly charged, it is used for development.

According to a second aspect of the present invention, a one-component developer externally supplemented with an auxiliary agent is charged to a desired polarity and supported, and is conveyed to a development area opposed to the latent image carrier. The carrier and the developer carrier come into contact with or approach each other from the developer reservoir side, and the developer on the developer reservoir side is moved to the developer carrier side via the mutually facing regions. A first developer supply member rotating in the direction of rotation, a second developer supply member provided downstream of the first developer supply member in the developer carrier conveying direction, and the first developer supply member. A potential difference forming means for forming a potential difference between the member and the second developer supply member; and regulating the developer carried on the developer carrier and transported to the development area to a predetermined layer thickness. A developer regulating member, and the developer regulated by the developer regulating member. An image forming apparatus including a developing device that develops a latent image on a latent image carrier using a developer on a developer carrier, wherein the first developer supply member and the second developer supply member Characterized in that a potential difference varying means for changing the potential difference is provided.

In this image forming apparatus, the potential difference between the first developer supply member and the second developer supply member is changed by the potential difference varying means, and the first developer supply member is connected to the second developer supply member. By increasing or decreasing the amount of the developer charged to a desired polarity between the developer supply member and the first developer supply member or the second developer supply member, the developer carrier It is possible to adjust the amount of the developer carried on the substrate.

According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, a latent image forming means for forming a latent image for detection on the latent image carrier, and developing the latent image for detection with the developing device The image forming apparatus further includes an adhesion amount detection unit configured to detect an amount of the developer adhered to a developed image formed by the apparatus, and a control unit configured to control the potential difference varying unit based on a detection result of the detection unit. Things.

In this image forming apparatus, a latent image for detection is formed on the latent image carrier by the latent image forming means, and the latent image for detection is developed by the developing device. The amount of developer attached is detected by the attached amount detecting means, and the potential difference varying means is controlled by the control means based on the detection result of the detecting means. Thereby, the amount of the developer carried on the developer carrier can be automatically adjusted.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, an adhesion amount detecting means for detecting an amount of the developer adhered on the developer carrying member, and based on a detection result of the detecting means. And control means for controlling the potential difference varying means.

In this image forming apparatus, the amount of developer adhering to the developer carrier is detected by the adhering amount detecting means, and the potential difference varying means is controlled by the control means based on the detection result of the detecting means. Control. Thereby, the amount of the developer carried on the developer carrier can be automatically adjusted.

According to a fifth aspect of the present invention, in the image forming apparatus of the first or second aspect, the developer amount detecting means for detecting the amount of the developer in the developing device, and based on a detection result of the detecting means, A control means for controlling the potential difference varying means is provided.

In this image forming apparatus, the amount of developer in the developing device is detected by the developer amount detecting means, and the potential difference varying means is controlled by the control means based on the detection result of the detecting means. I do. Thereby, the amount of the developer carried on the developer carrying member is adjusted.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the humidity detecting means for detecting humidity at the time of image formation and the potential difference varying means are controlled based on a detection result of the detecting means. Control means for performing the control.

In this image forming apparatus, the humidity at the time of image formation is detected by the humidity detecting means, and the control means controls the potential difference varying means based on the detection result of the detecting means. Thereby, the amount of the developer carried on the developer carrying member is adjusted.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) as an image forming apparatus will be described below. [Embodiment 1] FIG. 1 is a schematic diagram of a copying machine according to the present embodiment, and FIG. 2 is a schematic configuration diagram of a non-magnetic one-component developing device used in the copying machine. 1, in this copying machine, a charging device 21 charges a photosensitive drum 1 serving as a latent image carrier rotating in a direction indicated by an arrow in the figure, and then writes an electrostatic latent image by an exposure device 22. Thereafter, development is performed by the developing device 23 to form a toner image on the photosensitive drum 1. Thereafter, the toner image is transferred onto transfer paper as a transfer material by the transfer / transport member 24, and the toner image on the transfer paper is fixed to the transfer paper by the heat or pressure of the fixing device 25. The transfer sheet on which the toner image has been fixed is discharged onto a discharge tray 26. Then, the transfer residual toner on the photosensitive drum 1 is scraped off by the cleaning device 27 and used again for image formation.

In FIG. 2, inside the developing device 23, a toner hopper 6 as a toner storage is formed. The developing roller 2 as a developer carrier that rotates in the direction of the arrow in the drawing has a surface in which a grounded conductive portion and a dielectric portion made of a dielectric material are regularly distributed over a small area. In the portion, a minute electric field called a microfield is formed between the toner and the conductive portion in which charges of the opposite polarity are accumulated. The first developer is supplied to the developing roller 2 on the hopper 6 side and below the position where the developing roller 2 is pivotally supported, in the direction of gravity so as to be parallel to and contact with the developing roller 2. A lower supply roller 4b as a member is provided. The surfaces of the lower supply roller 4b that come into contact with each other in the contact area with the developing roller 2 move in opposite directions. Further, the developing roller 2 is located on the hopper 6 side with respect to the developing roller 2 and above the position where the developing roller 2 is pivotally supported.
An upper supply roller 4a as a second developer supply member is provided so as to contact on the downstream side in the rotation direction. The surfaces of the upper supply roller 4a that contact each other move in the same direction in the contact area with the development roller 2. The upper and lower supply rollers 4a and 4b are formed of a medium-resistance elastic member. During development, a developing bias is applied to the developing roller 2 so that the upper and lower supply rollers 4a and 4b can supply toner to the developing roller 2 in a normal environment, for example, in an environment of 20 ° C. and 50%. Each set potential is applied. (Hereinafter, margin)

An elastic layer-thinning blade 3 as a developer regulating member is in contact with the developing roller 2 in a surface contact from the trailing direction with respect to the rotation of the developing roller 2.

The toner 7 in the hopper 6 is sent to the developing roller 2 side by the agitator 5 and moves as shown by a white arrow in FIG. 3, and is taken in from between the upper supply roller 4a and the lower supply roller 4b. It is. Upper supply roller 4
a is the dielectric portion of the developing roller 2 and the upper and lower supply rollers 4a,
The frictional charging of the toner 7 in the area between 4b and the adjustment of the amount of the toner 7 attached is performed by rotating the developing roller 2 in contact with the developing roller 2. The charged toner 7 is carried on the developing roller 2 in multiple layers by a minute closed electric field on the developing roller 2. Then, the free end of the thinning blade 3 comes into contact with the developing roller 2 with respect to the rotation of the developing roller 2, and is conveyed to the developing area with an appropriate toner layer thickness. Then, development is performed by transferring the toner 7 to the photosensitive drum 1 on which the latent image is written by the exposure device 22. Further, the upper supply roller 4a is
It also has a function of returning uncharged toner that has entered between a and the thinning blade 3 back into the toner hopper. On the other hand, the lower supply roller 4b conveys the uncharged toner in the toner hopper onto the developing roller, scrapes off the toner on the developing roller 2 at a contact portion with the developing roller 2, and further transfers the toner under the developing roller 2 Is sent back into the hopper.

In this embodiment, the developing roller 2
The potential difference between the lower supply roller 4b and the lower supply roller 4b can be arbitrarily set by a potential difference variable device (not shown), for example, a supply bias power supply that applies a bias to the lower supply roller 4b. Further, for example, a density setting panel (not shown) is provided on the upper surface of the copying machine, and the operator can set the image density with the density setting panel. When the charge amount of the toner is high and the attraction force to the developing roller 2 is high in a low humidity environment, the operator sets the density using the density setting panel so as to be lower than the density at the time of normal image formation. . Then, based on this setting, a potential difference is applied between the developing roller 2 and the lower supply roller 4b so as to form an electric field in which the toner is less likely to adhere to the developing roller 2 as compared with normal image formation. As described above, the potential difference is changed by the potential difference varying device. For example, when a negatively charged toner is used as the toner 7, the potential difference of the lower supply roller with respect to the developing roller 2 is changed so as to be a positive value compared with the normal image formation. On the other hand, when the amount of charge of the toner is low and the attraction force to the developing roller 2 is low in a high humidity environment, the operator sets the density using the density setting panel so as to be higher than the density during normal image formation. I do. Then, based on this setting, a potential difference is applied between the developing roller 2 and the lower supply roller 4b so as to form an electric field in which the toner is more likely to adhere to the developing roller 2 than during normal image formation. As described above, the potential difference is changed by the potential difference varying device. For example, when a negatively charged toner is used as the toner, the potential difference of the lower supply roller 4b with respect to the developing roller 2 is changed so as to be a negative value compared with the normal image formation. As a result, even when there are many uncharged toners in a high humidity environment, the toner layer can be sufficiently adhered to the developing roller surface. Then, prior to the regulation by the thinning blade 3, the toner adhering to the developing roller surface is conveyed between the upper supply roller 4a and the developing roller 2 and regulated. For this reason, even when a large amount of uncharged toner adheres to the surface of the developing roller due to the change in the potential difference, the toner is frictionally charged during the above-described regulation and uniformly charged, and is then conveyed to the developing area. As described above, according to the present embodiment, the potential difference between the developing roller 2 and the lower supply roller 4b can be arbitrarily set using the potential difference variable device according to the environment. By performing appropriate control, constant image formation can always be performed satisfactorily.

Second Embodiment Next, another embodiment will be described with reference to FIG. In the present embodiment, a configuration basically similar to that of the first embodiment is provided. In this embodiment, a configuration is employed in which the potential difference between the upper supply roller 4a and the lower supply roller 4b is variable. In the illustrated example, a voltage applying means capable of applying an arbitrary voltage is provided independently to the upper supply roller 4a and the lower supply roller 4b, and the potential difference between the upper supply roller 4a and the lower supply roller 4b becomes variable. It is configured as follows. In this apparatus, the potential difference between the upper supply roller 4a and the lower supply roller 4b is changed based on the density setting by the density setting panel. In this apparatus, when the attraction force of the toner to the developing roller 2 is high and the amount of toner adhering to the developing roller is apt to increase, the operator sets the density setting panel so that the density becomes lower than that in normal image formation. Set the density with. Then, based on this setting, the lower supply roller 4 positioned upstream in the rotation direction of the developing roller 2 between the two supply rollers.
To form an electric field where toner tends to adhere toward b,
The potential difference between the upper supply roller 4a and the lower supply roller 4b is changed by the voltage applying means. For example, when a negatively charged toner is used as the toner 7,
The potential difference is changed so that the potential difference of the lower supply roller 4b with respect to the upper supply roller 4a becomes a positive value as compared with the normal image formation. As a result, the flow of the toner transported to the regulation area by the blade 3 on the downstream side in the rotation direction of the developing roller 2 is weakened, and the thickness of the toner layer on the developing roller is reduced. On the other hand, if the toner has a low adsorption force to the developing roller 2 and the amount of toner attached to the developing roller 2 is likely to be insufficient, the operator operates the density setting panel so that the density becomes higher than the density at the time of normal image formation. Set the density. Then, based on this setting, the voltage applying means is used by the voltage applying means so as to form an electric field between the two supply rollers and the upper supply roller 4b located on the downstream side in the rotation direction of the developing roller 2 so that the toner easily adheres. The potential difference between the upper supply roller 4a and the lower supply roller 4b is changed. For example, when a negatively charged toner is used as the toner 7, the lower supply roller 4b with respect to the upper supply roller 4a is used.
The potential difference is changed so that the potential difference becomes a negative value compared with the normal image formation. As a result, the flow of the toner being conveyed to the regulation area is increased, and the thickness of the toner layer on the developing roller 2 is increased. As described above, according to the present embodiment, the potential difference between the upper supply roller 4a and the lower supply roller 4b can be arbitrarily set by using the voltage applying means according to the environment. By performing such control, constant image formation can always be performed satisfactorily.

In the above-described embodiment, the upper supply roller 4a and the lower supply roller 4b are provided with voltage applying means capable of independently applying an arbitrary voltage to the upper supply roller 4a and the lower supply roller 4b. Has been described, the potential difference between the upper supply roller 4a and the lower supply roller 4b is fixed, and only the other potential can be set arbitrarily.
A configuration may be adopted in which the potential difference between the lower supply roller 4b and the lower supply roller 4b is variable. However, the upper supply roller 4a and the lower supply roller 4
When a configuration in which voltage applying means capable of applying an arbitrary voltage independently to each other is provided is adopted, the potential difference between the developing roller 2 and the lower supply roller 4 can be arbitrarily set as a result. The effect of controlling the toner amount by the change in the potential difference can also be exerted. Therefore, the upper supply roller 4a
Alternatively, the toner amount can be controlled in a wider range as compared with the case where the configuration in which the potential of only the lower supply roller 4b can be arbitrarily set is adopted.

[Embodiment 3] Next, still another embodiment will be described. This embodiment basically has the same configuration as the first embodiment. In the present embodiment, a fixed latent image pattern is formed on the photosensitive drum 1,
A configuration is adopted in which the amount of toner adhered by development is detected, and the amount of toner adhered to the developing roller 2 is controlled so that the desired amount of toner adheres. Hereinafter, this configuration will be described. As a technique for forming a fixed latent image pattern on the photosensitive drum 1 and detecting the amount of toner adhered to the latent image pattern by development, conventionally known techniques for forming a detection pattern for toner replenishment control, development, and detection are known. Can be adopted. Reference numeral 28 in FIG. 1 denotes an optical sensor that detects the light reflectance of the detection pattern. The optical sensor 28 detects the reflectance of the light of the detection pattern formed on the photoconductor 1 at the end of the image forming operation, for example, and detects the light of the background portion of the photoconductor drum where no toner is attached. The reflectance is detected, and the change in the ratio between the two reflectances is regarded as the change in the amount of toner attached on the detection pattern. The potential difference between the developing roller 2 and the lower supply roller 4b is changed by the potential difference varying device based on the change in the amount of toner attached, and the amount of toner attached to the developing roller 2 is controlled.
Specifically, the output signal of the optical sensor 28 is sent to a main control unit (not shown), and the ratio of the reflectance of the detection pattern to the reflectance of the background portion is higher than the upper limit of a predetermined range. For example, it is determined that the toner adhesion amount is larger than usual, and the potential difference between the developing roller 2 and the lower supply roller 4b is set so as to form an electric field in which the toner does not easily adhere to the developing roller 2. If the ratio of the reflectance of the detection pattern to the reflectance of the background portion is lower than the lower limit of the predetermined range, it is determined that the toner adhesion amount is smaller than usual, and the toner is The potential difference between the developing roller 2 and the lower supply roller 4b is set so as to form an electric field that easily adheres to the roller 2. By such control, the amount of toner adhered to the developing roller 2 is automatically adjusted. As described above, according to the present embodiment, the amount of toner attached to the detection pattern on the photosensitive drum is detected by the optical sensor, and the potential difference between the developing roller 2 and the lower supply roller 4b is determined based on the detection result. By adjusting the amount, the amount of toner on the surface of the developing roller can be automatically kept constant. Therefore, a constant high-quality image can always be obtained, and the operability is improved.

In the above embodiment, an example in which the amount of toner on the surface of the developing roller is adjusted by adjusting the potential difference between the developing roller 2 and the lower supply roller 4b has been described. The upper supply roller 4a
The toner amount on the surface of the developing roller may be adjusted by adjusting the potential difference between the developing roller and the lower supply roller 4b. Alternatively, both the potential difference between the developing roller 2 and the lower supply roller 4b and the potential difference between the upper supply roller 4a and the lower supply roller may be adjusted.

Embodiment 4 Next, still another embodiment will be described with reference to FIG. This embodiment basically has the same configuration as the first embodiment. Further, in this embodiment, an adhesion amount detecting means for detecting the amount of toner adhesion on the surface of the developing roller is provided, and the amount of toner adhering to the developing roller 2 is controlled based on the detection result of the adhesion amount detecting means. Such a configuration is adopted. Less than,
This configuration will be described.

In the example shown in the figure, an optical sensor as the adhesion amount detecting means is provided on a portion above the developing roller 2 before passing through a portion of the developing roller 2 facing the photosensitive drum 1, that is, before passing through a developing area for developing. 2a is provided. During the image forming operation, for example, the optical sensor 2a detects the reflectance of light on the surface of the developing roller 2 to which the toner is attached, and determines the change in the reflectance as the change in the amount of toner attached to the surface of the developing roller 2. Catch. Then, the potential difference between the developing roller 2 and the lower supply roller 4b is changed by the potential difference variable device based on the change in the toner adhesion amount,
The amount of toner to be attached to the developing roller 2 is controlled. Specifically, an output signal of the optical sensor 2a is sent to a main control unit (not shown), and if the detected reflectance is higher than the upper limit of a predetermined range, the toner adhesion amount is larger than usual. After the determination, the potential difference between the developing roller 2 and the lower supply roller 4b is set so as to form an electric field in which the toner does not easily adhere to the developing roller 2. Also, if the detected reflectance is a value lower than the lower limit of the predetermined range,
When it is determined that the toner adhesion amount is smaller than usual, the potential difference between the developing roller 2 and the lower supply roller 4b is set so as to form an electric field where the toner easily adheres to the developing roller 2. By such control, the amount of toner adhered to the developing roller 2 is automatically adjusted.

The optical sensor 2 serves as an adhesion amount detecting means for detecting the amount of toner adhered to the surface of the developing roller 2.
Instead of a, a surface voltmeter 2b for detecting the surface potential of the surface of the developing roller 2 may be used. FIG. 6 is an enlarged view around a developing roller of a developing device using a surface voltmeter as the adhesion amount detecting means. In this developing device, a non-contact type surface voltmeter 2b is provided in a portion above the developing roller 2 before passing through the developing area. During the image forming operation, for example, the surface potential of the toner layer on the developing roller 2 is detected by the optical sensor 2a, and the change in the difference between the surface potential and the bias applied to the developing roller 2 is detected. This is regarded as a change in the amount of toner adhesion. The potential difference between the developing roller 2 and the lower supply roller 4b is changed by the potential difference varying device based on the change in the amount of toner attached, and the amount of toner attached to the developing roller 2 is controlled. Specifically, the output signal of the surface voltmeter 2b is sent to a main control unit (not shown), and if the difference between the detected surface potential and the potential applied to the developing roller 2 is larger than the upper limit of a predetermined range. It is determined that the toner adhesion amount is larger than usual, and the potential difference between the developing roller 2 and the lower supply roller 4b is set so as to form an electric field where the toner does not easily adhere to the developing roller 2. If the difference between the detected surface potential and the potential applied to the developing roller 2 is smaller than the lower limit of the predetermined range, it is determined that the toner adhesion amount is smaller than usual, and the toner is transferred to the developing roller 2. The potential difference between the developing roller 2 and the lower supply roller 4b is set so as to form an electric field that is easily adhered. By such control, the amount of toner adhered to the developing roller 2 is automatically adjusted.

As described above, according to the present embodiment,
The amount of toner adhering to the surface of the developing roller 2 is detected by the optical sensor 2a or the surface voltmeter 2b as the adhering amount detecting means, and the potential difference between the developing roller 2 and the lower supply roller 4b is adjusted based on the detection result. The toner amount on the developing roller surface can be automatically kept constant. Therefore, a constant high-quality image can always be obtained, and the operability is improved.

In the above embodiment, only the example in which the toner amount on the developing roller surface is adjusted by adjusting the potential difference between the developing roller 2 and the lower supply roller 4b has been described. Alternatively, the amount of toner on the surface of the developing roller may be adjusted by adjusting the potential difference between the upper supply roller 4a and the lower supply roller 4b.
Alternatively, both the potential difference between the developing roller 2 and the lower supply roller 4b and the potential difference between the upper supply roller 4a and the lower supply roller may be adjusted.

Embodiment 5 Next, still another embodiment will be described with reference to FIG. This embodiment basically has the same configuration as the first embodiment. Further, in the present embodiment, a toner amount detecting means for detecting the amount of toner in the toner hopper 6 for storing the toner is provided. The configuration is such that the toner is sufficiently supplied to the surface. Hereinafter, this configuration will be described.

In the illustrated apparatus, a piezoelectric sensor 6a is provided below the toner hopper 6 as the toner amount detecting means. An agitator 5 is provided above the piezoelectric sensor 6a.
Therefore, the toner does not stay in this portion. Then, when the toner is consumed by the image formation and approaches the toner end, a signal of the toner end is output to the main control unit by the piezoelectric sensor 6a. When the toner end signal is output continuously two or more times, the potential difference between the developing roller 2 and the lower supply roller 4b is set so as to form an electric field in which the toner easily adheres to the developing roller 2. I do. When the toner end signal is continuously output three or more times after performing this setting, the developing roller 2 and the lower supply roller 4b are so formed as to form an electric field in which the toner is more likely to adhere to the developing roller 2. Is set. By such control, the amount of toner adhered to the developing roller 2 is automatically adjusted.

The piezoelectric sensor 6 serves as a toner amount detecting means for detecting the amount of toner in the toner hopper 6.
Instead of a, a torque sensor (not shown) may be provided on the shaft 5 a of the agitator 5 as a stirring means for stirring the toner in the toner hopper 6. When the toner is consumed by the image formation and the driving torque of the agitator 5 becomes a predetermined value, for example, 0.02 Nm or less, the developing roller 2 and the developing roller 2 are so formed as to form an electric field in which the toner easily adheres to the developing roller 2. The potential difference with the lower supply roller 4b is set. Then, after the setting, the driving torque further decreases, for example, when the driving torque becomes 0.01 Nm or less, the developing roller 2 and the lower supply roller are formed such that an electric field in which the toner easily adheres to the developing roller 2 is formed. 4b is set. By such control, the developing roller 2
Automatically adjusts the amount of toner attached to the

As described above, according to the present embodiment,
The toner end in the toner hopper is detected by the piezoelectric sensor 6a or the torque sensor as the toner amount detecting means, and the potential difference between the developing roller 2 and the lower supply roller 4b is adjusted based on the detection result. As a result, even if the toner in the toner hopper decreases and approaches the toner end, the amount of toner to be automatically attached to the surface of the developing roller can be kept constant. Therefore, a constant high-quality image can always be obtained, and the operability is improved. (Hereinafter, margin)

In the above embodiment, only the example in which the toner amount on the developing roller surface is adjusted by adjusting the potential difference between the developing roller 2 and the lower supply roller 4b has been described. Alternatively, the amount of toner on the surface of the developing roller may be adjusted by adjusting the potential difference between the upper supply roller 4a and the lower supply roller 4b.
Alternatively, both the potential difference between the developing roller 2 and the lower supply roller 4b and the potential difference between the upper supply roller 4a and the lower supply roller may be adjusted.

[Embodiment 6] Next, still another embodiment will be described. This embodiment basically has the same configuration as the first embodiment. In the present embodiment, a humidity sensor (not shown) as humidity detecting means for detecting humidity is provided in the copying machine as the image forming apparatus shown in FIG. Then, based on the detection result of the humidity sensor, the potential difference between the developing roller 2 and the lower supply roller 4b is changed by the potential difference variable device, and the amount of toner adhering to the developing roller 2 is controlled. Specifically, the output signal of the humidity sensor is sent to a main control unit (not shown), and when the humidity in the copying machine is higher than the upper limit of a predetermined range and the attraction force to the developing roller 2 is low, the toner is The potential difference between the developing roller 2 and the lower supply roller 4b is set so as to form an electric field that easily adheres to the roller 2. On the other hand, when the humidity in the copying machine is lower than the lower limit of the predetermined range and the attraction force to the developing roller 2 is high, the developing roller 2 is formed so as to form an electric field in which the toner hardly adheres to the developing roller 2. The potential difference between the lower supply roller 4b and the lower supply roller 4b is set. By such control, the amount of toner adhered to the developing roller 2 is automatically adjusted.

As described above, according to the present embodiment, the humidity at the time of image formation is detected by the humidity sensor as the humidity detecting means, and the potential difference between the developing roller 2 and the lower supply roller 4b is determined based on the detection result. , The amount of toner on the surface of the developing roller can be automatically kept constant. Therefore, a constant high-quality image can always be obtained, and the operability is improved.

In the above embodiment, only an example in which the toner amount on the surface of the developing roller is adjusted by adjusting the potential difference between the developing roller 2 and the lower supply roller 4b has been described. Alternatively, the amount of toner on the surface of the developing roller may be adjusted by adjusting the potential difference between the upper supply roller 4a and the lower supply roller 4b.
Alternatively, both the potential difference between the developing roller 2 and the lower supply roller 4b and the potential difference between the upper supply roller 4a and the lower supply roller may be adjusted.

[0047]

【Example】

[Embodiment 1] In the copying machine shown in FIG. 1, the photosensitive member 1 was rotated clockwise at a speed of 200 mm / sec. The developing device of FIG. 2 is used as a developing device of the copying machine.
The developing roller 2 was rotated counterclockwise at about 210 mm / sec. The shortest interval t between the upper and lower supply rollers 4a, 4b was set to 1.5 mm. The potential difference between the developing roller 2 and the lower supply roller 4b can be set arbitrarily. Other specific development component characteristics and development conditions are as follows. As shown in Table 1, the potential difference of the lower supply roller with respect to the development roller 2 (hereinafter, referred to as control potential difference) is adjusted according to humidity to form an image. Was done. 1. Specific development part characteristics and development conditions (1) Thinning blade 3 ・ Material Urethane rubber ・ Thickness 2mm ・ Blade length to free end 11mm ・ Blade penetration into roller 0.6mm ・ Blade abutment to free end Projection amount up to 0.5
mm (2) Developing Roller 2 (Preparation Method) FIG. 8 is a schematic diagram.・ Knurled type, roller diameter is 20mm, pitch 0.3mm, depth 0.1mm, groove width 0.2mm on aluminum core
To perform iris knurling at an angle of 45 degrees. -Dielectric layer coat is epoxy modified silicone resin (Toray SR
2115) and dried at 50 ° C. for about 90 minutes. Cut the roller surface to expose the aluminum surface 51 and the dielectric surface 52 at a ratio of 3: 7. (3) Lower supply roller 4a Material: polyurethane sponge roller with carbon kneading Roller: diameter 13 mm Sponge thickness: diameter 3 mm Biting: 0.5 mm Ratio of linear speed to developing roller: 0.5 times speed (reverse rotation) ( 4) Upper supply roller 4b ・ Material: Polyurethane sponge roller kneaded with carbon ・ Roller: Diameter 13mm Sponge thickness: Diameter 3mm ・ Decrease: 1mm ・ Linear speed ratio to developing roller: 0.8 times speed (forward rotation) (5) Development Gap ・ 150μm (Photoconductor used drum type) Developing bias ・ DC -750V (6) Photoconductor drum 1 ・ Photoconductor type: OPC ・ Surface potential: background part -850V, writing part (image part)
-100V (7) Toner 7-Negatively charged toner using non-magnetic styrene acrylic-based + polyester-based resin, volume average particle diameter: 10 µm-External additive: hydrophobic silica fine powder 0.7 wt% added (hereinafter, blank)

[0048]

[Table 1]

According to the first embodiment, a good image was always obtained regardless of the humidity environment in which the image was formed. Further, even when a large amount of uncharged toner adheres to the surface of the developing roller due to the setting of the potential difference under the high humidity environment, the unstable toner does not mix with the toner layer and does not cause problems such as background contamination. Was. [Embodiment 2] The same developing device and developing parts as those in Embodiment 1 are used, but as shown in FIG. 4, the upper supply roller 4a and the lower supply roller 4b are independently provided with voltage applying means. Then, as shown in Table 2, image formation was performed by adjusting the potential applied to each of the upper supply roller 4a and the lower supply roller 4b according to the humidity. (Hereinafter, margin)

[0050]

[Table 2]

According to the second embodiment, by varying the potentials of the two supply rollers 4a and 4b, the amount of toner adhered varies in the range of 0.5 to 2.0 mg / cm2 depending on the environment. Was adjusted to 1.2 mg / cm 2 which is suitable for normal image formation by adjusting the above potential. [Embodiment 3] A developing device and a developing part similar to those in Embodiment 1 are used, but as shown in the schematic configuration diagram of the copying machine in FIG.
An optical sensor 28 is provided below the image sensor 3. At the end of the image forming operation, a pattern for detection is written on the photoreceptor 1 by the exposure device 22 and developed by the developing device 23. The light reflectance is detected. Then, the above-mentioned electric potential difference varying device is controlled by a main control unit (not shown), and the control electric potential difference is set as shown in Table 3 according to the ratio of the reflectance of the pattern to the reflectance of the background portion of the photoreceptor (hereinafter referred to as the reflectance ratio). The image was formed while changing.

[0052]

[Table 3]

According to Example 3, a substantially constant image density was obtained from a low humidity environment of 10 ° C. and 10% to a high humidity environment of 30 ° C. and 90%. [Embodiment 4] The same developing device and developing parts as those in Embodiment 1 are used, but as shown in the schematic configuration diagram of the developing device in FIG. An optical sensor 2 a is provided above the roller 2. During the image forming operation, the sensor detects the light reflectance of the toner layer on the developing roller. As described above, the developing roller 2 is formed by providing a groove in an aluminum cored bar and coating the groove with a transparent resin as a dielectric material. That is, the grounded conductive portion 51 shown in FIG. 8 is formed of a metal having good reflectivity, and the dielectric portion 52 is formed of a transparent resin coated on the surface of the metal. For this reason, the optical sensor 2a is used regardless of whether black toner or color toner such as magenta or cyan is used.
Has a good correlation between the reflectance detected and the toner adhesion amount. Here, the potential difference varying device was controlled by a main control unit (not shown), and an image was formed while changing the control potential difference as shown in Table 4 according to the reflectance detected by the optical sensor 2a. (Hereinafter, margin)

[0054]

[Table 4]

According to Example 4, a substantially constant image density was obtained from a low humidity environment at 10 ° C. and 10% to a high humidity environment at 30 ° C. and 90%.

[Embodiment 5] A developing device and a developing part similar to those in Embodiment 1 are used, but as shown in a schematic configuration diagram of a developing device in FIG. A non-contact type surface voltmeter 2 b is provided above the developing roller 2.
Is provided. Then, during the image forming operation, the surface potential of the toner layer on the developing roller is detected by the surface potential meter. At this time, the toner adhesion amount is almost appropriate when the value of the change in the surface potential by the toner layer with respect to the potential applied to the developing roller 2 is in the range of 60 to 100V. Here, the potential difference varying device was controlled by a main control unit (not shown), and image formation was performed while changing the control potential difference as shown in Table 5 according to the change in the surface potential. (Hereinafter, margin)

[0057]

[Table 5]

According to Example 5, a substantially constant image density was obtained from a low humidity environment at 10 ° C. and 10% to a high humidity environment at 30 ° C. and 90%.

[Embodiment 6] The same developing device and developing parts as those in Embodiment 1 are used, but as shown in FIG.
Is provided below the piezoelectric sensor 6a. When the toner is consumed during the image forming operation and the toner end signal is output twice consecutively by the piezoelectric sensor 6a, the control potential difference set at that time is further increased by -100 V (not shown). Image formation was performed while controlling the potential difference varying device by the main control unit. If the piezoelectric sensor 6a outputs the toner end signal three times consecutively after this setting, the control potential difference is further reduced by -100.
Image formation was performed while controlling the potential difference varying device by a main controller (not shown) so that V was applied. As a result, the toner in the toner hopper 6 becomes about 10 g,
Immediately before the toner layer could not be completely formed on the developing roller, an image could be formed with the toner layer thickness being substantially constant, and the image did not become thin near the toner end.

[Embodiment 7] The same developing device and developing parts as those in Embodiment 1 are used, but a torque sensor is provided on the shaft of the agitator 5 for stirring the toner in the toner hopper 6. During the image forming operation, the toner is consumed, and the driving torque of the agitator is set to 0.02 Nm by the torque sensor.
When the following condition was detected, image formation was performed while controlling the potential difference variable device by a main control unit (not shown) so as to apply -100 V to the control potential difference set at that time. After this setting, the drive torque of the agitator is set to 0.0 by the torque sensor.
When it was detected that the potential became 1 Nm or less, image formation was performed while controlling the above-mentioned potential difference varying device by a main controller (not shown) so as to further apply -100 V to the control potential difference. As a result, the toner in the toner hopper 6 becomes 10 g.
Until the toner layer could not be completely formed on the developing roller, an image could be formed with the thickness of the toner layer substantially constant, and the image did not become thin near the toner end. . [Embodiment 8] A developing device and a developing component similar to those in Embodiment 2 are used, but a humidity sensor is provided in the copying machine. Then, as shown in Table 2 used in the description of the second embodiment, image formation was performed by adjusting the potentials respectively applied to the upper supply roller 4a and the lower supply roller 4b by the main controller in accordance with the humidity. . As a result, the low humidity environment of 10 ° C.
An almost constant image density could be obtained up to a high humidity environment of 90 ° C.

[0061]

According to the first and third to sixth aspects of the present invention, the developer carried on the developer carrier by changing the potential difference between the first developer supply member and the developer carrier. The amount of the toner can be adjusted, so that the thickness of the toner layer on the developer carrier is always kept constant according to the time and environmental conditions,
There is an excellent effect that a high quality image can be maintained. Further, even when a large amount of uncharged toner adheres to the surface of the developer carrying member due to the change in the potential difference, only the uniformly charged toner is used for development, so that good image quality can always be maintained. This has the effect.

According to the second to sixth aspects of the present invention, the potential difference between the first developer supply member and the second developer supply member is changed to change the potential difference of the developer carried on the developer carrier. Since the amount can be adjusted, there is an excellent effect that the toner layer thickness on the developer carrying member is always kept constant according to aging and environmental conditions, and a high-quality image can be maintained. .

In particular, according to the third aspect of the present invention, the potential difference varying means is controlled by the control means based on the detection result of the developer adhesion amount of the detection visual image detected by the adhesion amount detecting means. This makes it possible to automatically adjust the amount of the developer carried on the developer carrying member, so that the thickness of the toner layer on the developer carrying member is always kept constant according to the time and environmental conditions. There is an excellent effect that quality images can be maintained and operability is improved.

According to the fourth aspect of the present invention, the control means controls the potential difference varying means on the basis of the result of detection of the amount of developer adhering on the developer carrier detected by the adhering amount detecting means. As a result, the amount of the developer carried on the developer carrier can be automatically adjusted, so that the thickness of the toner layer on the developer carrier is always kept constant according to aging and environmental conditions, and high quality is achieved. In addition to this, there is an excellent effect that a proper image can be maintained and operability is improved.

According to the fifth aspect of the present invention, the potential difference varying means is controlled by the control means based on the result of detection of the developer amount in the developing device detected by the developer amount detection means. Since the amount of the developer carried on the developer carrier can be automatically adjusted,
There is an excellent effect that the toner layer thickness on the developer carrying member is always kept constant according to aging and environmental conditions, and a high quality image can be maintained, and operability is improved.

Further, according to the invention of claim 6, by controlling the potential difference varying means by the control means based on the humidity detection result at the time of image formation detected by the humidity detecting means, the developer carrying Since the amount of the developer carried on the body can be automatically adjusted, the toner layer thickness on the developer carrier is always kept constant according to the time and environmental conditions, and a high quality image is maintained. And the operability is improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic copying machine according to an embodiment.

FIG. 2 is a schematic configuration diagram of a developing device in FIG.

FIG. 3 is an enlarged view around a developing roller of the developing device.

FIG. 4 is a schematic configuration diagram of a developing device according to another embodiment.

FIG. 5 is a schematic configuration diagram of a developing device according to another embodiment.

FIG. 6 is an enlarged view around a developing roller of a developing device according to another embodiment.

FIG. 7 is a schematic configuration diagram of a developing device according to another embodiment.

FIG. 8 is an explanatory diagram of a developing roller of the copying machine used in the embodiment.

FIG. 9 is an explanatory view of a developing device of a copying machine according to a conventional example.

FIG. 10 is an explanatory diagram of a developing device of a copying machine according to another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Developing roller 3 Thinning blade 4a Upper supply roller 4b Lower supply roller 5 Agitator 6 Toner hopper 28 Optical sensor 2a Optical sensor 2b Surface potentiometer 6a Piezoelectric sensor

Claims (6)

[Claims] A developer carrying member for carrying a one-component developer externally supplemented with an auxiliary agent as required, charged to a desired polarity, and transporting the developer to a developing area opposed to the latent image carrier; A first rotating member is brought into contact with or close to the developer carrier from the developer reservoir side, and rotates so as to move the developer on the developer reservoir side to the developer carrier via the mutually facing regions. Developer supply member, a second developer supply member provided downstream of the first developer supply member in the direction of transport of the developer carrier, the first developer supply member, and the developer A potential difference forming means for forming a potential difference between the developer carrying member and a developer regulating member for regulating the developer carried on the developer carrying member and conveyed to the developing region to a predetermined layer thickness; Using the developer on the developer carrier regulated by the developer regulating member. An image forming apparatus including a developing device that develops a latent image on a latent image carrier, wherein a potential difference varying unit that changes a potential difference between the first developer supply member and the developer carrier is provided. Characteristic image forming apparatus. 2. A developer carrying member for carrying a one-component developer externally supplemented with an auxiliary agent as required, charged to a desired polarity, and transporting the developer to a developing region facing the latent image carrying member. A first rotating member is brought into contact with or close to the developer carrier from the developer reservoir side, and rotates so as to move the developer on the developer reservoir side to the developer carrier via the mutually facing regions. A second developer supply member provided downstream of the first developer supply member in the developer carrier transport direction with respect to the first developer supply member, the first developer supply member, and the second developer supply member. A potential difference forming means for forming a potential difference between the developer supply member and a developer regulating member for regulating the developer carried on the developer carrier and conveyed to the developing area to a predetermined layer thickness; And developing on the developer carrier regulated by the developer regulating member An image forming apparatus provided with a developing device for developing a latent image on a latent image carrier using: a potential difference variable for changing a potential difference between the first developer supply member and the second developer supply member. An image forming apparatus comprising: 3. The image forming apparatus according to claim 1, wherein said latent image forming means forms a latent image for detection on the latent image carrier, and said latent image for detection is developed by said developing device. An amount-of-adhesion detecting means for detecting the amount of developer attached to the formed visual image,
An image forming apparatus comprising: a control unit that controls the potential difference varying unit based on a detection result of the detection unit. 4. An image forming apparatus according to claim 1, wherein said amount detecting means detects an amount of developer adhered on said developer carrying member, and said electric potential difference varying means based on a detection result of said detecting means. An image forming apparatus comprising a control unit for controlling the image forming apparatus. 5. The image forming apparatus according to claim 1, wherein a developer amount detecting means for detecting a developer amount in said developing device, and said potential difference varying means is controlled based on a detection result of said detecting means. An image forming apparatus, comprising: 6. An image forming apparatus according to claim 1, further comprising humidity detecting means for detecting humidity at the time of image formation, and control means for controlling said potential difference varying means based on a detection result of said detecting means. An image forming apparatus characterized in that: