JPH11174855A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of an image after being developed by accurately detecting the concentration of a liquid developer to adjust the concn. of a toner. SOLUTION: A coating roller 42 coats a developing bent 43 with a liquid developer having high viscosity to form a thin layer of the liquid developer on the developing bent 43. A concentration control part 47 uses a concentration sensor 46 to detect the concn. of the developer on the belt 43 and controls the concn. of the developer in accordance with the detected concn. of the developer. The belt 43 brings the developer on the belt 43 into contact with a photoreceptor 1 in which an electrostatic latent image is formed on the surface to develop the electrostatic latent image on the photoreceptor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing apparatus for visualizing an electrostatic latent image by bringing a thin layer of a liquid developer into contact with the electrostatic latent image on the surface of a photoreceptor, and more particularly, to the stability of image density. .

[0002]

2. Description of the Related Art A toner in a liquid developer is transferred to an electrostatic latent image on a photoreceptor to form a toner image on the photoreceptor, and the toner image on the photoreceptor is transferred to a recording material to form an image. There are the following methods for detecting the toner concentration in the forming apparatus. (1) A test pattern image is formed by developing a test pattern using the toner in the liquid developer, and the formed test pattern image is read by an optical sensor to detect the toner concentration in the liquid developer using the result. I do.
(2) A sensor having a light emitting element and a light receiving element is immersed in the liquid developer, and the concentration of the liquid developer is detected from the light transmittance of the liquid developer. (3) The liquid developer is circulated through a transparent pipe, the liquid developer circulating in the pipe is sandwiched between sensors having a light emitting element and a light receiving element, and the liquid developer concentration is determined based on the light transmittance of the liquid developer. Is detected.

As an apparatus using the above method, there is, for example, a concentration detecting apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 6-27823.
A light-emitting element and a light-receiving element corresponding to each color are provided, and light optimal for detecting the toner density of the color from the light-emitting element corresponding to each color is applied to the liquid developer or the density measurement pattern, and the reflected light or The density is detected based on the transmitted light.

[0004]

However, a test pattern is developed by using a toner in a liquid developer to form a test pattern image, and the formed test pattern image is read by an optical sensor and the result is used as a liquid. In the method of detecting the toner density in the developer, the density of the test pattern changes due to the deterioration of the photoreceptor and the difference in transfer conditions such as the type and thickness of paper, and the accuracy is not very high.

Further, a method of detecting a concentration of a liquid developer from the transmittance of light of the liquid developer by immersing a sensor having a light emitting element and a light receiving element in the liquid developer, and a method of detecting the concentration of the liquid developer through a transparent pipe In a method of detecting the concentration of the liquid developer from the light transmittance of the liquid developer by sandwiching the liquid developer circulating in a pipe with a sensor having a light emitting element and a light receiving element, When the toner density of the toner is high, light hardly passes through, and the S / N ratio deteriorates.

[0006] In order to prevent light from being transmitted between the light emitting element and the light receiving element and thereby deteriorating the S / N ratio, the distance between the light emitting element and the light receiving element is reduced, or the pipe is made thinner. As a result, the liquid developer having high viscosity may not be able to pass.

The present invention has been made to solve such a problem, and has as its object to improve the image quality after development by accurately detecting the density of a liquid developer and adjusting the toner density. .

[0008]

According to the present invention, there is provided a developing apparatus comprising: applying a high-viscosity liquid developer in which toner is dispersed in an insulating liquid to a developer carrier; A thin layer was formed, the concentration of the liquid developer on the developer carrier was detected, and the concentration of the liquid developer was controlled in accordance with the detected concentration of the liquid developer to form an electrostatic latent image on the surface. A thin layer of liquid developer formed on the developer carrier is brought into contact with the photoconductor, and the liquid developer on the developer carrier is transferred to an electrostatic latent image on the photoconductor to transfer the electrostatic latent image on the photoconductor. The image is developed so that the image density is stable.

Further, the developer carrying member is made of a member having a high light reflectance, and a reflection type photo sensor is provided opposite to the surface of the developer carrying member coated with the liquid developer. , The concentration of the liquid developer on the developer carrier is detected based on the signal from the developer.

Further, the developer carrier is made of a transparent member, and the transmission degree of light of the liquid developer on the developer carrier is detected using a transmission type photosensor, and based on the detected transmission degree. The concentration of the liquid developer on the developer carrier is detected.

Further, the developer carrying member is made of a member having a high light reflectance, and a reflective type member is provided in the vicinity of the supporting member of the developer carrying member so as to face the surface of the developer carrying member coated with the liquid developer. A photo sensor is provided, and the concentration of the liquid developer on the developer carrier is detected based on a signal from the reflection type photo sensor.

Further, the photosensor is provided upstream of the developing position of the developer carrier.

Furthermore, the light emitting surface and the light receiving surface of the photosensor are cleaned to prevent dust from accumulating on the light emitting surface and the light receiving surface of the photosensor, thereby preventing the detection accuracy from being deteriorated.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A developing apparatus according to the present invention can be used for forming an image in an analog copier, an analog color copier, a digital copier, a digital color copier, a printer, a color printer, a facsimile machine or a color facsimile machine. Used in an apparatus, an electrostatic latent image formed on a photoreceptor is visualized using a high-viscosity liquid developer.

The developing device of the present invention includes, for example, a drawing roller, a coating roller, a developing belt, a density sensor, a density control unit, and a belt cleaning blade. The pumping roller pumps up a highly viscous liquid developer in which toner is dispersed in an insulating liquid from a developer tank. The application roller applies the liquid developer pumped up by the pumping roller to the developing belt to form a thin layer of the liquid developer having a uniform layer pressure on the developing belt. The developing belt is made of, for example, a member having a high reflectance, and rotates while maintaining a constant tension to transfer a liquid developer having a thin layer formed on the surface thereof to an electrostatic latent image on the photoconductor, and A toner image is formed thereon. The density sensor includes, for example, a reflection-type photosensor, and outputs a signal indicating the intensity of light transmitted through the liquid developer and reflected by the developing belt. The density control unit detects the toner density in the liquid developer based on a signal from the density sensor, and controls the toner density in the liquid developer based on the detected toner density.

Since the toner concentration in the liquid developer on the developing belt is detected as described above, even when the toner concentration is high, it is possible to prevent light from being unable to pass through the liquid developer, and to accurately detect the liquid. The toner concentration in the developer can be detected.

Here, a developing roller may be used instead of the developing belt, and a transmission type photo sensor may be used instead of a reflection type photo sensor as the density sensor. When a transmission type photosensor is used as the density sensor, a member having high transmittance may be used for the developing belt.

[0018]

FIG. 1 is a block diagram showing an embodiment of an image forming apparatus using a developing device 4 of the present invention. As shown in the figure, the image forming apparatus includes a photosensitive member 1, a charging roller 2, a pre-wetting device 3, a developing device 4, and a set roller (hereinafter referred to as "S
R ". 5, a transfer roller 6, a quenching lamp (hereinafter referred to as "QL") 7, and a cleaning blade 8. The photoconductor 1 is uniformly charged by the charging roller 2. The pre-wet device 3 is, for example, a thin and uniform oil on the surface of the photoconductor 1 in order to prevent toner from adhering to the background portion of the electrostatic latent image formed on the surface of the photoconductor 1 during development. Apply to. The photoreceptor 1 then forms an electrostatic latent image on the surface by writing light based on an image signal from a host device (not shown).

The developing device 4 includes, for example, a drawing roller 41, a coating roller 42, a developing belt 43, a driving roller 44, tension rollers 45a to 45d, a density sensor 46, a density control unit 47, a toner replenishing device 48, and a toner charger 49.
And a belt cleaning blade 50. The pumping roller 41 pumps a high-viscosity liquid developer 90 in which toner is dispersed in an insulating liquid from a developer tank 91. The application roller 42 applies the liquid developer 90 pumped by the pumping roller 41 to the developing belt 43 to form a thin layer of the liquid developer 90 on the developing belt 43 with a uniform layer pressure. Developing belt 4
Numeral 3 is a member made of a material having a high reflectance, for example,
4 and the tension rollers 45a to 45d rotate while maintaining a constant tension to transfer the liquid developer 90 having a thin layer formed on the surface to an electrostatic latent image on the photoconductor 1,
A visible toner image is formed on the photoconductor 1.

The density sensor 46 is located downstream of the coating roller 42 and upstream of the developing position of the electrostatic latent image on the photosensitive member 1 and, for example, as shown in FIG. And a reflection-type photosensor having: The light emitting element 461 irradiates the developing belt 43 via a thin layer of the liquid developer 90. The light receiving element 462 receives light transmitted through the liquid developer 90 and reflected by the developing belt 43, and outputs a signal indicating the intensity of the light. The signal output from the light receiving element 462 is amplified by the amplifier 465 and input to the density controller 47. Since the signal from the light receiving element 462 is small and easily affected by noise, the light receiving element 462 and the amplifier 465 are preferably provided as close as possible. Here, since a reflection type photo sensor is used as the density sensor 46, the density sensor 46 is provided so as to face the tension roller 45a supporting the development belt 43, so that the development can be performed in a portion where the development belt 43 is less blurred. The reflected light from the belt 43 can be incident, and the detection accuracy can be improved. The density controller 47 detects the toner density in the liquid developer 90 based on the signal from the density sensor 46 and controls the toner density in the liquid developer 90 using the toner replenishing device 48 based on the detected toner density. I do. The toner replenishing device 48 replenishes toner to the liquid developer 90 under the control of the density controller 47.

The toner charger 49 includes a developing belt 43
The liquid developer 90 in the form of a liquid is electrolyzed, and the liquid developer 90 having a thin layer is further divided into two layers of a portion having a higher toner concentration and a portion having a lower toner concentration. This has the same effect as performing pre-wetting, and has a greater effect than when only the pre-wetting device 3 is used. After the developing belt 43 develops the electrostatic latent image on the photoconductor 1 using the liquid developer 90, the belt cleaning blade 50
3 scrapes off the liquid developer 90 remaining on the developing belt 4
Clean 3

The SR 5 applies an electric charge to the toner image, which is a visible image on the photoconductor 1, so that the toner is firmly attached to the photoconductor 1, so that the image is transferred from the photoconductor 1 to the recording paper 80. The image is prevented from being disturbed by contact with the recording paper 80 during transfer. The transfer roller 6 applies a high voltage to transfer the toner image on the photoconductor 1 to the recording paper 80. QL7
Discharges the charge of the electrostatic latent image on the photoconductor 1 after transferring the image to the recording paper 80. The cleaning blade 8 scrapes off the toner remaining on the photoconductor 1 after transferring the image to the recording paper 80.

The operation of the developing device 4 having the above configuration will be described with reference to the flowchart of FIG.

After the application roller 42 applies the liquid developer 90 to the developing belt 43 to form a thin layer of the liquid developer 90 on the surface of the developing belt 43 (step S1), the liquid developer 90 on the developing belt 43 is formed. Passes through the photo sensor which is the density sensor 46 (step S2), the density control unit 47
Detects the transmittance of the liquid developer 90 on the developing belt 43 based on the signal from the density sensor 46 (step S3).
Here, since the thickness of the layer of the liquid developer 90 on the developing belt 43 is uniform and constant, the transmittance becomes worse as the concentration of the liquid developer 90 is higher. When the concentration of the liquid developer 90 is detected by immersing the photo sensor in the developer, light cannot be transmitted if the concentration of the liquid developer 90 is high.
Since the liquid developer 90 on the developing belt 43 is made thinner, it can transmit light even when the concentration becomes high.

The density controller 47 detects the density of the liquid developer 90 based on the detected transmittance of the liquid developer 90 (step S4). If the detected density is lower than the predetermined density of the liquid developer 90 (step S5), the density controller 47 controls the toner replenishing device 48 to replenish the toner to the liquid developer 90, and The density is increased (step S6). Thereby, the concentration of the liquid developer 90 can be kept within a certain range, and a good image can be formed.

Here, in the above embodiment, the density sensor 46
Although a reflection type photo sensor is used as the above, a transmission type photo sensor as shown in FIG. 4 may be used instead of the reflection type photo sensor. When a transmission type photo sensor is used as the density sensor 46, the light from the light emitting element 461 passes through the liquid developer 90 and the developing belt 43, and
Since the light enters the developing belt 62, the developing belt 43 is formed of a member having high transparency.

Further, as shown in FIG.
As a member for cleaning a transparent glass window 466 covering the light emitting element 461 and the light receiving element 462 of
For example, a felt 467 impregnated with a cleaning agent is provided beside the transparent window 466, and the density sensor 46
8 around the window 4 of the density sensor 46.
66 may be cleaned. As a result, it is possible to prevent dust and the like from accumulating in the window portion of the density sensor 46, and prevent the detection accuracy from deteriorating.

FIG. 5 shows the case of the density sensor 46 using the reflection type photo sensor. However, the density sensor 46 using the transmission type photo sensor also impregnates the cleaning agent as shown in FIG. Felt 467
Is provided beside the transparent window 466, and the density sensor 46 is
It is preferable that the window 466 of the density sensor 46 be cleaned by rotating about the center 68.

When a transmission type photo sensor is used as the density sensor 46, even if the developing belt 43 is slightly moved up and down, the density detecting accuracy is not affected. For example, as shown in FIG. May be provided in a portion not supported by the tension roller 45 or the like.

In the above embodiment, the case where the developing belt 43 is used as the developer carrier has been described. However, a developing roller may be used instead of the developing belt 43.

[0031]

As described above, according to the present invention, a liquid developer is applied to a developer carrier to form a thin layer of the liquid developer on the developer carrier, and the liquid developer on the developer carrier is formed. Since the concentration of the liquid developer is detected and the concentration of the liquid developer is controlled in accordance with the detected concentration of the liquid developer, the mobility of the liquid developer can be kept within a predetermined range.

Further, since the concentration of the liquid developer on the developer carrier is detected, light can pass through the liquid developer even when the concentration of the liquid developer becomes high, and the concentration of the high-concentration liquid developer can be increased. Can be detected.

Further, since the concentration of the liquid developer thinned on the developer carrier is detected, it is not necessary to newly thin the liquid developer, and the apparatus configuration can be simplified. it can.

Further, a reflection type photo sensor is provided opposite to the surface of the developer carrying member on which the liquid developer has been applied, and the liquid developer on the developer carrying member is determined based on a signal from the reflection type photo sensor. Since the concentration is detected, the concentration of the liquid developer on the developer carrier can be detected with a simple configuration.

Further, the degree of transmission of the liquid developer on the developer carrier is detected using a transmission type photosensor, and the concentration of the liquid developer on the developer carrier is detected based on the detected degree of transmission. Therefore, it is possible to detect the concentration of the liquid developer on the developer carrier with a simple configuration, and particularly to accurately detect the concentration of the liquid developer even when the concentration of the liquid developer becomes high. it can.

In addition, a reflection type photo sensor is provided in the vicinity of the support member of the developer carrying member so as to face the surface of the developer carrying member coated with the liquid developer, and based on a signal from the reflection type photo sensor. Since the concentration of the liquid developer on the developer carrier is detected, it is possible to prevent the occurrence of a detection error due to blurring of the developer carrier.

Furthermore, since the photosensor is provided upstream of the developing position of the developer carrier, the concentration of the liquid developer before development can be accurately detected.

Further, since the light emitting surface and the light receiving surface of the photo sensor are cleaned, it is possible to prevent the accuracy of the photo sensor from being deteriorated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image forming apparatus using a developing device of the present invention.

FIG. 2 is a configuration diagram of a density sensor using a reflection type photosensor.

FIG. 3 is a flowchart illustrating an operation of the developing device.

FIG. 4 is a configuration diagram of a density sensor using a transmission type photosensor.

FIG. 5 is a perspective view of a density sensor using a reflection type photo sensor.

FIG. 6 is a perspective view of a density sensor using a transmission type photosensor.

FIG. 7 is a configuration diagram of a developing device when a transmission type photosensor is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 3 Pre-wet device 4 Developing device 42 Application roller 43 Developing belt 46 Density sensor 461 Light emitting element 462 Light receiving element 466 Window 467 Felt 47 Concentration control unit 48 Toner replenishing device 49 Toner charger

Claims (6)

[Claims] 1. A liquid developer having a high viscosity in which toner is dispersed in an insulating liquid is applied to a developer carrier to form a thin layer of the liquid developer on the developer carrier, and an electrostatic latent image is formed. A thin layer of liquid developer formed on a developer carrier is brought into contact with the photoconductor formed on the surface, and the liquid developer on the developer carrier is transferred to an electrostatic latent image on the photoconductor to form a photoreceptor on the photoconductor. Detecting the concentration of the liquid developer on the developer carrier and controlling the concentration of the liquid developer according to the detected concentration of the liquid developer. Developing device. 2. The reflection-type photosensor, wherein the developer-carrying member is made of a member having a high light reflectance, and a reflection-type photosensor is provided opposite to the surface of the developer-carrying member on which the liquid developer is applied. 2. The developing device according to claim 1, wherein a concentration of the liquid developer on the developer carrier is detected based on a signal from the developing device. 3. The developer carrier is made of a transparent member, and detects the degree of light transmission of the liquid developer on the developer carrier using a transmission type photosensor, and based on the detected degree of transmission. 2. The developing device according to claim 1, wherein the concentration of the liquid developer on the developer carrier is detected. 4. The developer carrying member is made of a member having a high light reflectance, and a reflection type member is provided in the vicinity of a surface of the developer carrying member on which a liquid developer is applied in the vicinity of a supporting member of the developer carrying member. 2. The developing device according to claim 1, further comprising a photosensor for detecting a concentration of the liquid developer on the developer carrier based on a signal from the reflection type photosensor. 5. The developing device according to claim 2, wherein the photosensor is provided upstream of a developing position of the developer carrier. 6. The developing device according to claim 2, wherein the light emitting surface and the light receiving surface of the photo sensor are cleaned.