JPS5942551A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an always optimum image density irrespectively of whether the size of an original is a prescribed standard size or not, by detecting the size of the original and setting the region for detecting the image density in accordance with the detected size. CONSTITUTION:Scales 20a and 20b are disposed on the outside of an original plate 17 in parallel with the sides and bottom thereof, and indices 21a and 21b are provided slidably thereto. The detection of image density in the region A corresponding to the entire area of an original placed on the plate 17 is accomplished first by sliding the indices 21a and 21b until the indices coincide with the end edge of the original. Since the indices 21a and 21b of the scales 20a and 20b are interlocked to a detection element 13, the element 13 is informed by CON of the fact that the region to be detected is the region A and the density of only the region A, that is, the density of only the original, is detected. Signal processing is accomplished in accordance with said input information and an electrostatic charger 2, a lamp 3 and a developing device 7 are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus that detects image density and assigns image forming conditions for exposure amount, charge amount, and q.

Generally, this divine device has an L-shaped structure as shown in Figure 1. Reference numeral 1 denotes a photoreceptor, a charger 2 (which is uniformly charged, and a photoreceptor 3), a reflector 5a.

51), 5c, 5(+) A reflected image of the original 4 is exposed by a series of optical systems including lens 6 to form an electrostatic latent image. This electrostatic latent image is converted into a toner image by developer 7. A transfer material P is supplied in response to the rotation of the photoreceptor 10.The toner image is transferred onto the transfer material Pj- by the transfer charger 8.After this, the transfer material P is separated and charged. After being electrostatically separated, the fuser IO
It is then transported out. On the other hand, the toner remaining on the photoreceptor 1 is removed by the cleaner 11, and the series of copying processes is completed.

This copying apparatus is provided with a device that detects the image exposure amount, that is, the document density, in order to automatically adjust the image density at tV and a. An example of this device, as shown in FIG. 1, consists of a reflecting mirror 12 that can be moved on the optical path, and a sensing element 1 (for example, an inno-hincer) that reads the reflected image, that is, the original image. It is. This detection device +
'+' means that before starting a series of copying processes, the original image is exposed once, and at this time, the reflected image 12 is in the optical path -H, and the detection element 13 reads the density of the original image. Appropriate trust treatment for the corresponding human resources 1-J
(For example, by calculating the average density of the original, the light from the original illumination rack can be applied to the developing device 7.) to increase the contrast. Control the phenomenon bias by 1ilJ. After this,
The reflecting mirror 12 moves out of the optical path to perform heavy image exposure, and obtains a subject image through the series of processes described above.

In conventional copying machines, if the original is smaller than a predetermined size such as A3, A4, etc., the sensing element 13 is activated as shown in FIG. The area is within area 14, but since the original is smaller than the predetermined size, area 15 becomes the actual area of this original.

Therefore, the remaining diagonally shaded portion 1G will be read extra. Therefore, since the area other than the original is generally a white surface, the average density of the original 1 m detected by the detection element 13 is different from the average density of the actual original.

Since signal processing is performed using an average density different from that of the actual original, there is a drawback that desired density and contrast cannot be obtained.

The present invention was proposed in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide an image forming apparatus that can always obtain an appropriate image density regardless of whether the document size is a standard predetermined size or not. do.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments with reference to the drawings. FIG. 3 is a plan view of a document table of a copying machine to which the first embodiment of the present invention is applied. A document 18, which is an object to be copied, is placed on a document table 17 with one corner aligned with one reference point.

In order to specify the size of the original 18, scales 20a and 20b are disposed outside the original table 17 in parallel on the sides and bottom thereof. In the scales 20a and 201, indicators 2ta and 211] are respectively disposed so as to be slidable in the longitudinal direction thereof. FIG. 4 is a schematic configuration diagram in which indicators 21a and 21b and control means CON (hereinafter referred to as CON) are interlocked. The sensing element 13 is configured to scan in the direction of arrow 1, and is interlocked with CON. This CON and the arithmetic circuit 27 are connected.

This arithmetic circuit 27 performs functions such as integration and average value calculation. CON is connected to the rack via the electric σP circuit 28:
connected to the sea urchin. Furthermore, CON is a high-voltage tosynth IIV
The charging device 2 and the developing device 7 are connected to each other through a T.

Next, the operation of this embodiment will be explained. The area for automatic image density adjustment is area A corresponding to the entire area of the document 18 as shown in FIG.
and 2 (] I) by sliding the indicators 2]a and 21)],
2'' of the edge portions 18a and 181) of the original 18; 1a and 21
131). CON reads the size into the region. The sensing element 13 is informed by COH that the area to be detected is area A). So scale 20
a and 201) (7) 4 effect F21.1 and 211] and the detection element 13 are interlocked, so Fig.
-a: When you press the button, the optical system first scans once as described above with reference to FIG. The density of only the area A that should be detected, that is, the density of only the document J8, is detected by the controller, and the charger 2, lamp 3, and developer 7 are controlled by performing signal processing based on the human power information. Here,
The detection element 13 detects the image density of the area A, and this signal is transmitted to the arithmetic circuit 27 via CON. At this time C
When ON, signals other than the width and height of the document 18 are excluded,
It is output to the arithmetic circuit 27.

The arithmetic circuit 27 calculates the average value of image density, etc.
Output to ON. Based on the result of this calculation, CON controls the voltage, current bias conditions, etc. applied to the charger 2 and developer 7 via the power supply circuit 28 and the high voltage transformer HVT to adjust the image density. No fogging phenomenon occurs.

Next, a second embodiment of the present invention will be described. A schematic configuration diagram is shown in FIG. 5, which is mostly the same as the embodiment shown in FIG. 4, but has the following points: a part of the upper surface of one end of the sensing element 3 is located in the longitudinal direction of the sensing element 13. The shutter 29 is provided so as to be slidable in the direction of the arrow 29a.

FIG. 6 is a plan view of the shack 29 disposed on the detection element 13, showing the rack 29c and the pinion 2 meshing with the rack 29c.
9cl, index 211) and rack 29
c is connected. This shutter 29 is the scale 20b
Where 7 guy 2 is connected to the index 21b of
Reference numeral 9 corresponds to the index 21b and covers the detection element 13 other than the area A of the original 18. In other words, the detection range of the detection element 13 is mechanically controlled. CON controls the scanning width of the sensing element 13 in the direction of the arrow 13a, that is, the width from the reference point 19 to the position of the index 21a.

Therefore, the detection area of the detection element 13 is not area A)
0 Next, an embodiment of the present invention will be described. FIG. 7 is a partial side view of the document table 17 of a copying machine to which the third embodiment of the present invention is applied. .

A feeder 22 is provided on the document table 17 and also serves as a pressure plate. This feeder 22 has a structure in which a rectangular flat plate extends over the document table 17 in a downward-hanging manner.Transport belts 2 and 3 are provided above the document table 17 and inside the feeder 22. This conveyor belt 23 carries the original 18 to position B in FIG.
It is to be removed completely. A reflective optical sensor 24 consisting of a light emitting element 24a and a light receiving element 241 is provided at the entrance of the feeder 22. The length of the original 18 is detected based on the time it takes for the original 18 to pass below the sensor 2.1. On the other hand, as shown in FIG. 8, a side plate guide 26 that is slidable in a direction perpendicular to the direction in which the document 18 is carried in is provided on the human log guide plate 25 provided near the carry-in port of the feeder 22. This side plate guy 1526 is
By sliding the document 180 in accordance with the width of the document 180, the width of the document 18 is detected while preventing the document 18 from being carried in diagonally. As a result, the vertical width and horizontal width of the original 18, that is, the size of the original 18 can be detected. Therefore, the area A in which the concentration should be detected by the detection element 13 is specified. Then, a) applied voltages to the charger 2, lamp 3, and developer 7 are controlled, and an appropriate image density can be obtained. sensor 2
4 and the control circuitry connected to side plate 26 is constructed similarly to the embodiment of FIGS. 4 and 5.

As described above, the present invention specifies the size of the document, and by providing a means for automatically or manually detecting the density within the specified area, it is possible to determine whether the document is a predetermined standard size or a cup. Always be sure to maintain the same image density and achieve the desired effect.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic configuration diagram of a copying device, FIG. 2 is a plan view of a document table of the copying device, and FIG. 3 is a first and second embodiment of the present invention. FIG. 4 is a schematic configuration diagram of the first embodiment of the present invention, and FIG. 5 is a schematic diagram of the second embodiment of the present invention (11). Figure 6 constitutes the embodiment of Figure 5/Explanatory diagram of Kinotar 29, Figure 7
The figure shows a document table I7 to which the third embodiment of the present invention is applied.
8 is a side view of the original h to which the embodiment of FIG. 7 is applied.
It is a perspective view of nine units 17. . 2... Charger, : U... Lamp, 7... Developing device, 13... Detection element, 17... Original table, ] 8 ...Original f height, 24...Sensor 26...Side plate guide, A...Area, CON...1lilJ If: 11 means. 1st Figure 1b 2nd Figure 7? jS3 figure

Claims (1)

[Scope of Claims] In an image forming apparatus having means for detecting the density of an original using a detection element and adjusting the density of a copied image according to the detected density of the original, there is provided a means for detecting the size of the original; , Set the image density detection area corresponding to the original size V: 1
An image forming apparatus characterized in that the image forming apparatus has an illuminating means.