JPS6122361A - Automatic image density contoller of dry electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To irradiate light whose quantity is large enough to transmit the background of an original image and supplement toner as much as image area to a developing device by detecting the quantity of original reflected light while the original is scanned by specific distance from the front end. CONSTITUTION:A photodiode 30 detects the quantity of light from a lamp 7 which is reflected by a reference reflecting plate 5 and an arithmetic control circuit 31 performs control as that the detected value coincides with the set value of a light emission quantity setting means 34. When the left end of the original 6 is colored in thin black, the detected value of the diode 30 becomes smaller than usual which a scanning system moves by 10mm., so the quantity of light emission of the lamp 7 is increased through the operation of a light emission quantity adjusting circuit 17 to obtain a copy image similar to the normal original. The output of the diode 30 proportional to the image area of the original is integrated by a circuit 31 and compared by a density setting means 34 to supplement toner as much as the image area to the developing device 19 through the rotation of a motor 33, thereby obtainng faithful image density.

Description

[Detailed description of the invention] The present invention utilizes a two-component developer for slit exposure-1-"
The present invention relates to an automatic image density control device that keeps image density constant at all times in a dry type electrophotographic copying machine that performs copying.

'' In a dry electrophotographic copying machine that uses a two-component developer to make copies by slit exposure, the area occupied by the original image (
When copying an original with a large (ratio of the total surface area of the original to the area occupied by the image) (original with a large black background), the amount of toner consumed is large, so immediately replenish only the amount of toner that matches this amount of consumption. There is a need.

However, in conventional methods, the toner concentration in the developer is detected by measuring the inductance, capacitance, viscosity, etc. of the developer, and the amount of toner replenishment is controlled based on the detected concentration value. In this method, the toner power generation is detected with a time delay with respect to a change in the difference between the toner consumption amount and the replenishment amount, so the responsiveness of the 1-toner depth control is not good.

In order to improve this, the invention described in Japanese Patent Application Laid-Open No. 49-79247-3 (Japanese Patent Application No. 120931-1982) was proposed. A half mirror is inserted to block the image, and the light reflected by the half mirror is applied to a photoelectric conversion element.The image area of the document is determined from the output of the photoelectric conversion element, and toner is applied in accordance with this image area. It was supposed to be replenished.

However, in a copying machine equipped with such an automatic developer toner replenishment device, if the background of the original is dark or colored in a young color, the amount of light emitted by the exposure lamp may be reduced. Since there is no function to remove the background without changing it, the background of the copy remains dark and the contrast is low, making it difficult to view.
, and the amount of toner consumed is large.

The present invention provides an automatic image density control i! of a dry type electrophotographic copying machine that overcomes these difficulties. In a dry type electrophotographic copying machine that performs copying by slit exposure using a two-component developer, an illumination means for illuminating a document, a light emission amount adjustment means for adjusting the light emission amount of the illumination means, A light amount detection means for detecting the amount of reflected light from the document and a toner replenishment means for replenishing toner to a developing device are provided, and the light amount detection means detects the amount of light while scanning within a predetermined distance from the leading edge of the document at the start of copying. control means for controlling the amount of light emitted by the illumination means so that the amount of light reflected from the original document becomes the amount of light after the background, and controlling the amount of toner replenishment in response to the deviation of the detected value from the light amount detection means with respect to a reference value; By forming
irradiating the photoreceptor with an amount of light that is sufficient to penetrate the background of the original image;
Further, toner can be supplied to the developing device from the toner supplying means in accordance with the area occupied by the image, which has a large effect on toner consumption.

EMBODIMENT OF THE INVENTION An embodiment of the present invention illustrated in FIG. 1 will be described below.

Reference numeral 1 denotes a dry type electrophotographic copying machine with a moving slit exposure mirror, in which a platen glass 3 is fixedly stretched above a casing 2, and a platen cover 4 is attached above the glass 3 so as to be openable and closable.

Further, a reference reflector 5 is provided above the left edge of the platen glass 3.
are fixed integrally, and the reference reflector plate 5 also serves as a registration shimming guide.

Roughly in the copy Ifil, the platen glass 3
A lamp carriage (not shown) is provided below so as to be movable left and right, and the exposure lamp 7 is mounted on the same lamp carriage.
A reflector 8 surrounding the lamp 7 and a reflector 8
Corresponding to the opposite reflector 9 and both reflectors 8 and 9
A first mirror 10 located midway down is attached integrally with the first mirror 90, and a second mirror 10 and a third mirror 12 below the second mirror 11 are integrally attached to the left of the first mirror 90. It is attached to a mirror carriage (not shown), and when the exposure lamp 7 and the first mirror 10 are moved left and right by an optical system drive device (not shown),
The second and third mirrors 11, 12 are moved left and right at half the speed of movement of the lamp 7 and the first mirror 10.

Furthermore, a lens 14 is disposed to the right of the third mirror 12, and a fourth mirror 13 is disposed further to the right of the third mirror 12, and the light projected from the exposure lamp 7 and diffusely reflected by the document 6 on the platen glass 3 is 1, 2nd, 3rd mirror 10.11.1
2, passes through the lens 14, is sequentially reflected by the fourth mirror 13, and is then projected onto the exposure area 16 on the drum-shaped photoreceptor 15.

Furthermore, the exposure lamp 7 is provided with a light emission amount adjustment circuit 17 that changes the voltage applied to the exposure lamp 7 so that the light emission amount of the exposure lamp 70 can be adjusted.

Further, a charger 18,
Dry two-component developer 19, static elimination lamp 18 for pre-transfer processing
, a transfer device 21, a peeling device 22, a pre-cleaning charger 23, a cleaning device 24, and a pre-charging eraser lamp 25 are sequentially arranged clockwise in FIG.

Further, a paper tray 26 is arranged on the right side of the developing device 19, and the paper 27 stored in the tray 26 is transferred to the paper feeder 2.
After being sent to the drum-shaped photoreceptor 15 by 8 and transferred,
The image is sent to a fixing device 29 and fixed.

Furthermore, a photodiode 30 as a sensor for detecting the amount of light is disposed at a position adjacent to the optical axis of the exposure system at a position closer to the fourth mirror 13 than the lens 14, and the output end of the photodiode 30 is connected to an arithmetic control circuit 31. It is connected.

Furthermore, the dry two-component developing device 19 is provided with a toner dispenser 32, which is rotated by a stepping motor 33.

Further, the arithmetic control circuit 31 is provided with a light emission amount setting means 34 and a density setting means 35, so that the light emission amount M of the exposure lamp 7 and the density standard value of the copy can be set as appropriate. ing.

Further, the arithmetic control circuit 31 provides a control signal to the light emitting amount adjustment circuit 11 so that the difference between the light emitting amount reference value and the detected value of the light reflected by the reference reflector 5 becomes O, and If the detection value of the photodiode 30 during scanning within a range of 10M from the left end is below a certain threshold (
(If the background of original 6 is dark or lightly colored)
, further increasing the light emission amount of the exposure lamp 7 and applying a correction control signal to the light emission amount adjustment circuit 17 so that the detection value of the photodiode 30 becomes the same as the detection value of the normal background original 6; The difference between the concentration reference value and the detected value from the photodiode 30 is determined, and a control signal is given to the stepping motor 33 to rotate the stepping motor 33 at an appropriate number of rotations in accordance with the difference.

Since the embodiment shown in FIG. 1 is configured as described above, after operating the light emission amount setting means 34 and the density setting means 35 respectively to set appropriate light emission amount reference values and density reference values, When the copying machine 1 is operated after placing the original 6 on the platen glass 3F and closing the platen cover 4, the exposure lamp 7 is turned on and the reference reflector 5 is illuminated, and the light is reflected by the same reflector 5. The amount of reflected light is determined by the photodiode 30
The calculation control circuit 31 controls the light emission amount adjustment circuit 1 so that the detected value of the photodiode 30 matches the light emission reference value detected by the light emission amount setting means 34.
A control signal is sent to the exposure lamp 7, and the voltage applied to the exposure lamp 7 is adjusted. Therefore, even if the light emitting capacity of the exposure lamp 7 is reduced or the reflectance of the lefters 8 and 9 is reduced due to being contaminated with toner or the like, the light emission amount adjustment circuit 17 operates to compensate for these fluctuations. The amount of light irradiated onto the document 6 is maintained at a predetermined set light weight.

Further, when the left edge of the original 6 is dark black or lightly colored, the exposure lamp 7, the reflectors 8 and 9, and the first mirror 10 move 108 from the left edge of the original 6 to the right edge. Since the detected value of the photodiode 30 becomes lower than the detected value of the photodiode 30 when scanning the original 6 with a normal background and becomes below a certain threshold, the arithmetic control circuit 31 operates and the control circuit 31 emits light. A correction control signal is sent to the hi adjustment circuit 17, the voltage applied to the exposure lamp 7 is increased, and the amount of light emitted from the exposure lamp 7 is adjusted to the original 6.
This is increased to compensate for the decrease in the reflectance of the background part -〇-, 8-8-, and the exposed part 16 of the photoreceptor 15 receives reflected light with an amount of light comparable to that of the background part of the normal original 6. is irradiated. Therefore, the background of the original 6 is light or lightly colored, and a copy similar to that of the ordinary original [6] with a white background is obtained.

Furthermore, when the exposure optical system starts scanning, the band-shaped irradiated portion of the original 6 moves from the left to the right, and the band-shaped image of the original 6 is continuously exposed to the exposure area 16 of the drum-shaped photoreceptor 15. The latent images are successively developed by the developing device 19 to form a toner image, which is transferred onto the paper 27 by the transfer device 21 and then fixed by the fixing device 29.

In this case, in the developing device 19, toner is consumed in proportion to the area occupied by the image of the original 6, but when the image of the original 6 is scanned by the exposure optical system, part of the light reflected from the original 6 is consumed. The photodiode 30 is irradiated with an output proportional to the area occupied by the image of the band-shaped portion of the document 6, and the arithmetic control circuit 31
The output from the photodiode 30 is integrated and stored in the same logic control circuit 31, and the difference between the density reference value set by the density setting means 35 and the integrated value is determined. A number of pulses proportional to the difference is applied to the stepping motor 33, and the stepping motor 33 is rotated by an amount corresponding to the number of pulses, so that an amount of toner proportional to the image occupation area of the original WA 6 is dispensed from the toner dispenser 32. The developing device 19 is replenished, and as a result, the responsiveness of toner concentration-based control is good.

Further, since the photodiode 30 is located adjacent to the fourth mirror 13 from the lens 14 and located off the optical axis 1-, a part of the light beam reflected from the band-shaped portion of the original 6 is blocked by the fort diode 30. However, the light 6 to the photoreceptor 15
There is little adverse effect on the distribution, and the image quality of copies does not deteriorate.

Moreover, since the light from the exposure lamp 7 is effectively used for exposure, there is no need to use the exposure lamp 7 with a large amount of light emission.
A cooler for forcibly cooling the area around the exposure lamp 7 is not necessarily required, and the cost is reduced.

In the embodiment shown in FIG. 1, the fort diode 30 is placed adjacent to the fourth mirror 13 from the lens 14 and removed laterally from the optical axis so as to have less influence on the light intensity distribution to the photoreceptor 15. However, as shown in FIGS. 2 and 3, in order to make the light amount distribution on the photoreceptor 15 constant, a light amount distribution correction sulin h36 is arranged adjacent to the exposure area 16 of the photoreceptor 15, If the fort diode 30 is placed at the center in the longitudinal direction of this slit 36, adjacent to the window 37 of the slit 1-36, and on the surface facing the fourth mirror 13, the fort diode 30 can be arranged in the reflected light beam. There is no adverse effect on the light amount distribution on the photoreceptor 15 due to the installation.

According to the present invention, even if the background of the original is dark black or colored in a light color, it is possible to copy a copy with the background missing, similar to an original with a white background, and toner consumption can be reduced. Since toner can be replenished to the developing device in accordance with the area occupied by the image of the original, which has a large impact, copies with a clear background and image density that is faithful to the image density of the original can be obtained, and the responsiveness of toner density control is improved. In good condition.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal sectional side view illustrating an embodiment of an automatic image density control device for a dry type electrophotographic copying machine according to the present invention, and FIG. 3
The figure is a partial perspective view. 1... Slit exposure mirror moving dry type electrophotographic copying machine,
2... Casing, 3... Platen glass, 4 Platen cover, 5... W quasi-reflector, 6... Original, 7 Exposure lamp, 8... Reflector-19... Opposing reflector-110 ...First mirror, 11...Second mirror, 12...Third mirror, 13...Fourth mirror, 14
...Lens, 15...Drum-shaped photoreceptor, 16...
Exposure area, 17... Light emission amount adjustment circuit, 18... Charger, 19... Developing device, 20... Static elimination lamp for transfer pretreatment, 21... Transfer device, 22... Peeling device , 23...
Charger for static elimination before cleaning, 24...Cleaning device, 25...Eraser lamp for pre-charging treatment, 26
... paper tray, 27 ... paper, 28 ... paper feeder, 29 ... fixing device, 30 ... photodiode,
31... Arithmetic control circuit, 32... i-ner dispenser, 33... stepping motor, 34...
Light emission amount setting means, 35...Density setting means, 36...
Light intensity distribution correction slit, 37...window.

Claims (1)

[Claims] In a dry type electrophotographic copying machine that performs copying by slit exposure using a two-component developer, an illumination means for illuminating a document, a light emission amount adjustment means for adjusting the light emission amount of the illumination means,
a light amount detection means for detecting the amount of reflected light from the document; a toner replenishing means for replenishing toner to a developing device; control means for controlling the amount of light emitted by the illumination means so that the amount of light reflected from the document becomes the amount of light passing through the background, and controlling the amount of toner replenishment in response to the deviation of the detected value from the light amount detection means with respect to a reference value. An automatic image density control device characterized by: