JPS61158354A - Development control device - Google Patents

Abstract

PURPOSE:To obtain a device allowed to start copying operation only when toner in a developing unit is uniformly dispersed by detecting the mixing state of toner with carrier, driving an agitating means independently, and starting the copying operation after checking the uniform mixing. CONSTITUTION:When large variance is generated in toner concentration between the end part and the center part of the developing unit, a concentration difference detecting circuit 19 outputs a high level signal. Consequently, a copying stop circuit 20 outputs a signal to inhibit copying operation, rotates an agitation screw in the developing unit independently and starts a counter 21, a developer is agitated and the counter 21 counts up the number of times of agitation. When the counted value of the counter 21 reaches a fixed value, a reference pattern image is formed again to detect the variance of picture density. When the agitation is sufficiently performed and the toner is uniformly distributed, the circuit 19 outputs a density difference signal of a low level. Consequently, the circuit 20 stops the rotation of the agitation screw and a copying stop releasing circuit 25 actuates a copying availability display unit 24 and resets the counter 23 simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a development control device in a dry type electrophotographic machine.

(Prior art) Since dry-type electrophotographic machines use a developer consisting of two components, toner and carrier, the quality of the copied image is easily affected by the agitation state of the developer. When copying, there is a problem that an imbalance occurs in the amount of toner consumed in the developing unit, and when a large size original is subsequently copied, the image density becomes uneven and a copying error occurs.

(Objective) In view of the above-mentioned circumstances, it is an object of the present invention to provide a development control device that can perform a copying operation only when the toner in the development unit is uniformly diffused.

That is, the present invention is characterized by detecting the mixed state of toner and carrier and independently operating the stirring means,
The key point is that the copying operation can be started after confirming that the mixture has been uniformly mixed.

(Structure) Therefore, details of the present invention will be explained below based on illustrated embodiments.

FIG. 2 shows an embodiment of a dry electrophotographic apparatus to which the present invention is applied, in which reference numeral 1 denotes a contact glass on which an original is placed, an exposure lamp 2, mirrors 3 to 6, and It is configured to be scanned by an exposure optical system consisting of a lens 7 and to form an image of an original placed on the top of a contact glass l on a photoreceptor drum 8. Reference numeral 10 denotes a standard pattern plate for detecting image density, which is provided at the bottom of the original scale 9 at the end of the contact glass l, and has a uniform optical density over the entire width of the contact glass 1, and is scanned by the exposure optical systems 2 to 7. It is configured to form a latent image on the photoreceptor drum 8 in response to the received light. Reference numeral 11 denotes a developing unit disposed close to the photoreceptor drum 8, which is provided with a toner tank lla at the top, receives toner replenishment from a toner replenishing roller llb, and uniformly mixes toner and carrier with a stirring screw 11c. The developing sleeve llc is configured to supply toner to the photosensitive drum 8 via the developing sleeve llc. 1
Reference numeral 2 denotes an image sensor group provided downstream of the developing unit 11, which includes image density sensors 12a, 12b, 12c, and 12 consisting of a light emitting element and a light receiving element as shown in FIG.
2d, 12c°, 12b°, 12a.

are arranged in a line in the axial direction of the photoreceptor drum 8. Reference numeral 13 denotes a control device that operates the toner supply roller drive circuit 14 and stirring screw drive circuit 15 based on signals from the image density sensor group 12. In addition, the reference numeral 16. and 17 and 18 respectively indicate a paper feed cassette, a fixing unit (22) and an eraser unit provided around the photosensitive drum 8.

FIG. 1 shows an embodiment of the above-mentioned control device 13, in which reference numeral 19 denotes a density difference detection circuit for detecting a difference in standard pattern images formed on the photosensitive drum 8;
an image density sensor 12a disposed on the photoreceptor drum 8;
12a', 12b, 12b', 12c, 12c'', 1
The signal from 2d is input, and the maximum level and minimum level of the input signals are compared, and a density difference signal proportional to the difference is output. 20
is a copying operation stop circuit which outputs a signal when the concentration difference signal exceeds a set level, and outputs a signal to the stirring screw drive circuit 15.
The stirring screw 11c is driven through the stirring screw 11c, while the counter 21 is operated to count the number of times of stirring. Reference numeral 23 denotes a copy stop release circuit, which activates the copy enable indicator 24 and resets the counter 21 at the same time when the concentration difference signal after the stirring process is lower than a set value.

25 is a toner concentration detection circuit, and 3 is located in the center.
image density sensors 12d, 12c, 12c'
It is configured to average the signals from the toner replenishment roller drive circuit 14, compare the set level, and output a signal to the toner replenishment roller drive circuit 14 when the set level is lower than the set level.

Next, the operation of the apparatus configured as described above will be explained.

In order to copy a minimum size manuscript, for example, 85,
When the plate feed cassette is inserted into the main body of the electrophotographic apparatus, the power is turned on, and the copy switch is pressed, the exposure optical systems 3 to 7 scan the standard pattern plate 10, and the photosensitive drum 8
A latent image 26 (FIG. 3) is formed completely in the axial direction. As the photoreceptor drum 8 rotates, this latent image 26 is
11, the toner is developed and visualized in accordance with the toner concentration and distribution state within the developing unit 11, and converted into a standard pattern image 27. Needless to say, the optical density distribution in the longitudinal direction of this standard pattern image 27 reflects the toner density distribution within the developing unit 11. The standard pattern image is moved to one image source sensor group 12, and the image density across the axial direction of the photosensitive drum 8 is detected. At this point, the developer is uniformly diffused in the axial direction of the photoreceptor drum 8, so each image density sensor outputs an image signal of the same level, and the density difference detection circuit 19 does not output a signal.

If you copy small-sized originals continuously in this way,
A large amount of toner is consumed only in the axial center of the developing tank, and the toner concentration becomes uneven in the axial direction. In such a state, when the copying paper is replaced with, for example, A3 size paper in order to copy a large-sized original, and the copy switch is subsequently pressed, a standard pattern image is formed on the photoreceptor drum 8.

As described above, in the previous copying operation, the toner in the center was consumed and there was a large variation in toner density between the edges and the center, so the density difference detection circuit 19 outputs a high level signal. The copy stop circuit 20 receives this high level signal and outputs a signal to prohibit the copying operation by the copy switch, while independently rotating the stirring screw lie in the developing unit 11 and starting the counter 21. The developer in the developing unit 11 is stirred, and the counter 21 counts the number of times the developer is stirred. counter 2
When the count value of 1 reaches a certain value, a standard pattern image is formed again to detect variations in image density. When the developer is sufficiently stirred by the rotation of the stirring screw 11c and the toner is uniformly distributed, the density difference detection circuit 19 outputs a low level density difference signal. The copying stop circuit 20 stops the rotation of the stirring screw 11c upon receiving this low level concentration difference signal, and also stops the copying stop canceling circuit 2.
3 activates the copy-ready indicator 24 and at the same time the counter 2
Reset 1. By pressing the copy switch at this point, high quality copies with uniform image density can be obtained regardless of the copy size history.

On the other hand, if unevenness in toner density still remains in the axial direction of the photoreceptor drum 8 even after the detection of the toner density difference, the abnormality difference detection circuit 19 outputs a high level signal and copies the data by pressing the copy button. The operation is continued to be prohibited, and at the same time, the stirring screw 11c is rotated to continue stirring until the unevenness of the toner concentration is reduced to the set level. In addition, if the number of times of such stirring exceeds a certain value.

The counter 21 determines that an abnormality has occurred in the stirring mechanism or the like of the developing unit 11, lights up the abnormal state indicator 22, and prompts the operator to check.

Further, the toner density detector 25 calculates the average value of the signals from the three image density sensors 12c, 12d, and 12c' arranged in the center, compares it with a set level, and determines when the signal falls below the set level. The toner supply roller ttb is driven to supply toner to the developing tank.

In this embodiment, the standard pattern image is formed in a continuous straight line, but the same effect can be obtained even if the standard pattern image is formed discretely only in the portion facing the image density sensor. Also,
In this embodiment, the number of rotations of the stirring screw is counted, but the rotation duration time may also be measured.

(Effects) As described above, according to the present invention, a standard pattern image is formed in the axial direction of the photoreceptor drum to detect the difference in toner density in the axial direction, and when this exceeds a set level, the copying operation is prohibited. On the other hand, since the agitation mechanism is driven, the copying operation can be performed with the toner uniformly agitated in the axial direction of the photoreceptor drum regardless of the history of the copying operation, thereby preventing copy errors from occurring. be able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention;
FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIG. 3 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing the relationship between a standard pattern image and an image density sensor in the same apparatus as above. 8... Photosensitive drum 10... Standard pattern plate 11... Development unit flb... Toner supply roller 11c... Stirring screws 12a-d, 12a' to 12c'-...・Image density sensor

Claims (1)

[Claims] means for forming a standard pattern image in the axial direction of the photoreceptor drum and detecting the toner density difference in the axial direction; when the density difference exceeds a set level, the copying operation is prohibited, while driving the agitation mechanism of the developing unit; A development control device consisting of circuit means for controlling