JPH05204229A - Image forming device - Google Patents

Abstract

PURPOSE:To make it possible to output a stable image in the case temperature and humidity change by controlling an electrifier according to the result of the detection of a sensor which detects the temperature of developer, and varying the potential of the electrification of the surface of a photosensitive body. CONSTITUTION:In developer tanks 17, the liquid temperature sensor 25 as developer temperature detecting means are provided in their holding color developers. Each of the liquid temperature sensors 25 is connected to a grid bias control circuit 30 as an electrifier control means. The grid bias control circuit 30 is connected to the grid of a scorotron electrifier 14. A photosensitive sheet 11 is electrified by the scorotron electrifier 14. The grid bias of the scorotron electrifier 14 is controlled by means of a grid bias control circuit 30 by the use of a bias value corrected by the developer temperature detected by the liquid temperature sensor 25 provided in the developer of each developer tank 17. Therefore, in the case the temperatures of the developers change, it is made possible to output a stable image by means of the simple constitution and without increasing an amounts of evaporations of the developers.

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,
In particular, the present invention relates to a wet electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in a wet electrophotographic image forming apparatus, it has been known that the image density of an output image changes when the temperature of a developing solution changes. Specifically, when the temperature of the developer rises, the viscosity of the dispersion medium that disperses the toner, which is the charged colored particles, in the components of the developer decreases, and the viscous resistance received when the toner moves decreases. As a result, the mobility of the toner becomes high, and as a result, the image density becomes high as a whole even if the electrostatic latent image formed on the surface of the photoconductive photoconductor does not change. On the contrary, when the temperature of the developing solution is lowered, the viscosity of the dispersion medium is increased to decrease the mobility of the toner and the image density is lowered as a whole.

In order to solve such a problem, a conventional wet electrophotographic image forming apparatus is provided with a temperature sensor and a heater in the liquid developer, and when the temperature becomes lower than a set temperature, the heater is used. The temperature was controlled by heating it to the set temperature.

[0004]

However, when control is performed such that the temperature of the developing solution is raised to a set temperature by heating with a heater, the set temperature is the maximum temperature in the temperature range that guarantees the operation of the apparatus, or the maximum temperature. Therefore, the temperature of the developing solution is maintained at about 35 to 40 degrees. in this case,
There is a problem that the amount of evaporation of the developer increases. Further, in order to solve such a problem, it is possible to provide a cooling device to cool and keep it constant, but this is not realistic because the device becomes complicated and large.

The present invention has been made to solve the above-mentioned problems, and is characterized by having a charger control means for changing the charging potential of the photoconductive photosensitive member according to the temperature of the developing solution. An object of the present invention is to provide an image forming apparatus having a simple structure and capable of outputting a stable image with respect to a temperature change of the developing solution without increasing the evaporation amount of the developing solution. is there.

[0006]

In order to achieve this object, an image forming apparatus of the present invention uses a developing solution temperature detecting means for detecting the temperature of a developing solution and a detection result of the developing solution temperature detecting means. And a charger control means for controlling the charging means so that the charging potential of the surface of the photoconductive photoreceptor changes.

[0007]

The image forming apparatus of the present invention having the above structure is
The developing solution temperature detecting means detects the temperature of the developing solution, and the charging device controlling means controls the charging means so that the charging potential of the surface of the photoconductive photoreceptor changes according to the detection result of the developing solution temperature detecting means. ..

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, the overall configuration of the image forming apparatus of this embodiment will be described with reference to FIG.

At the upper right corner of the housing 27, a photoconductor sheet 11 which is a photoconductive photoconductor is held in a roll shape.
A paper discharge tray 23 is installed on the outer left side, and a drum 10 is installed in the center rotatably by a drive device (not shown). Around the drum 10 is a photosensitive sheet cutter 1
2, transport roller 13, peeling claw 20, drying device 21, transport belt 22, scorotron charger 1 as a charging means
4, an exposure scanning device 15, which is an exposing means, a pre-wetting device 31, a drum cleaner 18, and a charge eliminating device 19 are provided.

Below the drum 10, four developing solution tanks 17 for holding developing solutions of respective colors of yellow, magenta, cyan and black are installed, and each developing solution tank 1
In FIG. 7, a developing electrode 16 is connected to a driving device (not shown) inside and is installed so as to be vertically movable. The four developing solution tanks 17 are connected to a driving device (not shown) and joined to the rails 24 so as to be movable left and right. The developing solution tank 17 is provided with a solution temperature sensor 25 as a developing solution temperature detecting means in each of the developing solutions of the respective colors held therein. The liquid temperature sensor 25 is connected to a grid bias control circuit 30 which is charging device control means, and the grid bias control circuit 30 is connected to the grid of the scorotron charger 14.

A temperature sensor 2 is provided near the drum 10.
8 and a humidity sensor 29 are provided. Temperature sensor 28
The humidity sensor 29 is connected to the exposure scanning device 15, and is configured to send the temperature / humidity data 100 to the exposure scanning device 15.

Next, the operation of the entire image forming apparatus of this embodiment will be described.

Photoreceptor sheet 11 held in roll form
After being cut into a predetermined size by the photoconductor sheet cutter 12, the sheet is conveyed by the conveying roller 13 and wound around the drum 10 rotating counterclockwise in the drawing. The wound photoreceptor sheet 11 follows the rotation of the drum 10,
Go through each process of electrophotography.

First, the photoconductor sheet 11 is charged by the scorotron charger 14. The grid bias of the scorotron charger 14 is controlled by the grid bias control circuit 30 with a bias value corrected by the developing solution temperature detected by the solution temperature sensor 25 installed in the developing solution in the developing solution tank 17. .. The exposure scanning device 15 performs pulse width modulation according to the image data 104 sent from an external device such as a scanner, and the temperature sensor 2
8. The exposure intensity is controlled by the temperature / humidity data 100 from the humidity sensor 29 to expose the photoconductor sheet 11 to form an electrostatic latent image on the surface of the photoconductor sheet 11.

Photoconductor sheet 11 on which an electrostatic latent image is formed
Is pre-wet by pressing the sponge soaked with the dispersion medium of the developing solution by the pre-wetting device 31. During this time, the developing solution tank 17 is moved along the rail 24 by a driving device (not shown) until the developing solution tank containing the yellow developing solution is positioned directly below the drum 10, and the developing electrode 16 is driven by a driving device (not shown). It is moved upward to a position having a slight clearance with the drum 10. Then, when the front end of the photosensitive sheet 11 reaches the position facing the developing electrode 16, the yellow developing solution is supplied to the gap between the developing electrode 16 and the photosensitive sheet 11, and a visible yellow single color is formed on the photosensitive sheet 11. An image is formed. Then, the surface of the photoreceptor sheet 11 is discharged by the discharging device 19 using a corotron. This process is magenta,
By doing the same for cyan and black,
A full-color image is formed on the photoconductor sheet 11. The photoreceptor sheet 11 on which the image is formed is peeled from the drum 10 by the peeling claw 20 and is conveyed to the drying device 21 by the conveying belt 22. Then, the photoconductor sheet 11 is dried and fixed by the drying device 21, and then the paper discharge tray 2
Then, the entire process of image formation is completed. On the other hand, while the photoconductor sheet 11 is being dried, the drum cleaner 18 cleans the drum by pressing a sponge soaked with a dispersion medium of the developing solution against the drum.

Next, the configuration and operation of the grid bias control circuit 30 will be described with reference to FIGS. 2 and 3.

The liquid temperature is measured by the liquid temperature sensor 25 installed in the developing liquid in the developing tank 17, and the measured liquid temperature data is sent to the grid bias control circuit 30. Inside the grid bias control circuit 30, the liquid temperature data is converted into a digital signal by the A / D conversion circuit 32 and then sent to the ROM table 33. Also, RO
The drawing condition data 200 is also sent to the M table 33 from an apparatus controller (not shown). The drawing condition data 20
0 is a color to be output, or data such as whether to output darker or lighter than the standard. The ROM table 33 is
Possessing multiple tables, the drawing condition data 2
The table is switched by 00 to convert the liquid temperature data into a grid bias value. ROM table 33
Is given by experimentally measuring the image density when the grid bias and the developer temperature are changed in advance and obtaining the relationship between the grid bias and the developer temperature at which the image density becomes a constant value. FIG. 3 shows an example of the table thus obtained.

When the temperature of the developing solution rises, the viscosity of the dispersion medium in which the toner, which is the charged colored particles, is dispersed in the components of the developing solution is lowered, and the viscous resistance received when the toner is moved is lowered. Then, the mobility of the toner becomes high. As a result, the image density is generally high, even though the electrostatic latent image formed on the surface of the photoconductive photoreceptor remains unchanged. Therefore, when the temperature of the developer rises, the grid bias is lowered to lower the charging potential of the photoconductive photoconductor, whereby the image density can be kept constant. When the temperature of the developer decreases, the image density can be kept constant by raising the grid bias. The value of the grid bias is D / A converted by the D / A conversion circuit 34 and sent to the voltage control circuit 35. Voltage control circuit 35
Controls the voltage of the grid 36 so that the grid bias value is obtained.

Next, the configuration and operation of the exposure scanning device 15 will be described with reference to FIGS.

Image data 104, which is digital data transmitted from an external device, is converted into analog data 105 by the D / A conversion circuit 40 and sent to the modulation comparator 42. On the other hand, the triangular wave 106 from the triangular wave generation circuit 41 is also sent to the modulation comparator 42. In the modulation comparator 42, as shown in FIG.
6 and analog-converted image data 105 are compared,
When (value of image data 105) ≦ (value of triangular wave 106), an ON signal is sent to the current drive circuit 43, and when (value of image data 105)> (value of triangular wave 106), an OFF signal is sent to the current drive circuit 43. In the current drive circuit 43, the laser drive current 108 is turned on / off according to the on / off signal 107.
The semiconductor laser element 53 emits a laser beam 111 according to the laser driving current 108. As described above, a method of controlling the on / off timing of the semiconductor laser according to the image data 104 is generally called a pulse width modulation method.

When the present invention is applied to an image forming apparatus adopting a pulse width modulation method as in this embodiment, gradation is expressed by the area ratio of white and black even in a halftone image. By controlling the grid bias according to the temperature of the solution to keep the image density of black and white constant against changes in the temperature of the developer, even if the temperature of the developer changes, the overall image density including the halftone There is an effect that an image with stable image density can be output in the range.

When the power is turned on, the current drive circuit 43 drives the semiconductor laser element 53 so that the laser exposure intensity reaches the set initial value. The laser beam 111 emitted from the semiconductor laser element 53 is reflected by the polygon mirror 65 rotated by the motor 66, and the reflected laser beam is bound by the fθ lens 67 onto the photosensitive sheet 11 wound around the drum 10. Image. On the other hand, a monitor diode 54 is arranged beside the drum 10, and the laser beam 111 emitted from the semiconductor laser element 53 is also received by the monitor diode 54, and the laser beam 111 is an electric signal 109.
Is converted to. Electrical signal 109 proportional to this exposure intensity
Is amplified by the amplifier circuit 51, and the peak detection circuit 52 causes the electric signal 11 corresponding to the peak laser exposure intensity.
0 is sent to the correction comparator 47.

On the other hand, the temperature / humidity data 100 sent from the temperature sensor 28 and the humidity sensor 29 is converted into a digital signal by the A / D conversion circuit 44 and then sent to the ROM table 45. The ROM table 45 stores a conversion table for converting temperature / humidity data into laser exposure intensity. The conversion table must be obtained in advance by experiments.

As an example, a graph of a conversion table in the case of a titanium oxide photoconductor is shown in FIG. Photoreceptors such as titanium oxide and zinc oxide have high hygroscopicity, and their sensitivity is affected by absolute humidity, and the sensitivity decreases as absolute humidity increases. And it is hardly affected by temperature. Therefore, when such a photoconductor is used, the environment sensor does not need a temperature sensor and may be an absolute humidity sensor, and the conversion table is sufficient if conversion from absolute humidity to laser exposure intensity is possible.
In the case of titanium oxide and zinc oxide, there are some cases where this conversion can be expressed by a linear equation, and in this case, an arithmetic circuit can be used instead of the ROM table.

The exposure intensity signal converted by the ROM table 45 is converted into an analog signal 1 by the D / A conversion circuit 46.
It is converted into 01 and sent to the correction comparator 47.
The analog signal 101 becomes the reference signal, and the correction comparator 47 compares the reference signal with the electric signal 110 corresponding to the laser exposure intensity. And the comparison result is U
If the laser exposure intensity is greater than the reference signal, the U / D counter 49 sends the clock signal to the clock circuit 4.
The clock signal of 8 decrements the count value by 1, and if it is smaller than the reference signal, the U / D counter 49 increments the count value by 1 by the clock signal of the clock circuit 48. The D / A conversion circuit 50 converts the count value of the U / D counter 49 into an analog signal 103 and sends it to the current drive circuit 43. The current drive circuit 43 corrects the laser exposure intensity at the peak, and the corrected laser The semiconductor laser element 53 is turned on according to the exposure intensity.

The present invention is not limited to the embodiments described in detail above, and various modifications can be made without departing from the spirit of the invention.

For example, in this embodiment, the photosensitive sheet 11 is wound around the drum and an image is directly formed on the photosensitive sheet 11 without performing the transfer process. It is also possible to output an image by using a body drum and providing a transfer process to plain paper.

In the present embodiment, an example of pulse width modulation using a semiconductor laser device as the exposure method is given.
It is also possible to change the exposure to a halftone dot using a gas laser and an acousto-optic device or a dither method.

[0030]

As is apparent from the above description, the image forming apparatus of the present invention has the charger control means for changing the charging potential of the photoconductive photoconductor according to the temperature of the developing solution. Therefore, with a simple configuration, it is possible to output a stable image with respect to the temperature change of the developing solution without increasing the evaporation amount of the developing solution.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an entire image forming apparatus.

FIG. 2 is a block diagram of a grid bias control circuit.

FIG. 3 is a conversion graph from a developer temperature to a grid bias.

FIG. 4 is a block diagram of an exposure scanning device.

FIG. 5 is a graph illustrating pulse width modulation of the exposure scanning device.

FIG. 6 is a schematic diagram showing a configuration of an optical system of the exposure scanning device.

FIG. 7 is a conversion graph from absolute humidity to exposure intensity.

[Explanation of symbols]

 11 Photoconductor Sheet 14 Scorotron Charger 15 Exposure Scanning Device 17 Developer Tank 25 Liquid Temperature Sensor 28 Temperature Sensor 29 Humidity Sensor 30 Grid Bias Control Circuit 43 Current Drive Circuit 53 Semiconductor Laser Device

Claims (1)

[Claims] 1. An electrostatic latent image is formed by charging the surface of a photoconductive photoconductor by a charging unit, and exposing the charged photoconductive photoconductor according to image data input by an exposing unit. A wet electrophotographic image forming apparatus for forming a visible image by contacting a developing solution with the photoconductive photoreceptor on which an electrostatic latent image has been formed, wherein the developing solution detects the temperature of the developing solution. A temperature detecting means, and a charger control means for controlling the charging means so that the charging potential of the photoconductive photoconductor changes according to the detection result of the developing solution temperature detecting means. Image forming apparatus.