JPH0650409B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as an electrophotographic apparatus, an electrostatic recording apparatus, etc., in particular, an electrophotographic photosensitive member is rotated by a predetermined amount after a copying operation start switch is turned on and before a normal copying operation is started. The present invention relates to an image forming apparatus.

This type of image forming apparatus has an image density adjusting mechanism in order to obtain a high quality image. Conventionally, as one of the image density adjusting mechanisms, a light receiving element measures the amount of light transmitted through the lens in the vicinity of an imaging lens in an optical system for projecting a document image on a photoconductor, and this measured value is immediately read by a document illumination lamp. There is a method in which the lighting voltage is controlled by feedback so that the measured value becomes a set value. Since this mechanism measures the reflected light from the original surface during copy scanning, it has the advantage that the speed of copying operation (hereinafter abbreviated as copy) does not decrease, but it has the following drawbacks. Since the amount of light reflected from the surface of the original is measured every second to feed back, for example, if there is a lot of black in a document such as a photograph, the characters and the like next to it are overexposed. When a book is spread and copied, the black part on the periphery is detected, and the characters are skipped. When the original platen is opened and copied, there is no light reflected from the edge, so the image is detected as a black original and detected. This development is more remarkable as the original is smaller. Since the amount of light reflected from the original is measured, special adjustment is required to establish a correspondence between the sensitivity of the photoconductor and the amount of illumination light.
Due to the difference in the spectral characteristics between the light receiving element and the photoconductor, the image density adjustment may be incorrect depending on the color of the original. A change in the sensitivity of the photoconductor causes an error in the image density adjustment.

Therefore, as an image density adjusting mechanism for compensating for the above-mentioned drawbacks, a document exposure scan is performed only to measure the average brightness of the document before the copying operation, and after determining the illuminance correction amount of the document illumination lamp, the copy is performed. There is one that moves to the operation and uniformly illuminates the entire surface of the original with the illuminance determined above. However,
This mechanism requires a document exposure run for one measurement prior to the copy operation, so the copy speed is reduced.
In particular, there is a drawback that the copy speed is reduced to about 1/2 when obtaining one copy from a large number of originals.

The present invention has been proposed in view of the above, and an object of the present invention is to obtain an image forming apparatus including an image density adjusting mechanism capable of performing accurate image density adjustment without reducing copy speed.

The present invention which achieves the above-mentioned object, means for forming an electrostatic latent image corresponding to an original image on an electrophotographic photosensitive member, detection means for detecting the density of the original, and image formation in response to a signal from the detection means. An image forming apparatus having control means for controlling conditions, wherein a copy button is operated to instruct the start of a copying process so that the photoconductor is preceded by the copying process each time the copying process is instructed. And a photoconductor on which a pre-rotation step for stabilizing the characteristics of the photoconductor is performed and a light source for illuminating the document, relative to the document setting table, and
With the start of rotation of the photoconductor in the pre-rotation step, from the home position located at the end of the original placing table on the original placing side, which is the same position as in the actual copying step, from the scanning distance during the actual copying step. Also, the original that is moved to the original density measurement start position, which is a short distance, and after the pre-rotation step, returns to the home position and waits while being lit to form an electrostatic latent image for measuring the original density. The density of the document is detected by measuring the potential of the electrostatic latent image formed by turning on the light source of the scanning unit and the light source of the document scanning unit, and prior to the copying process performed after the pre-rotation process. And a calculation means for forming a predetermined latent image on the basis of the detection result of the density detection means, and after the calculation by the calculation means, the original scanning device for copying. It is to start the scan.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a very schematic structure of an image forming apparatus of the present invention of an optical system moving type, in which a pre-exposure lamp 2 and a front exposure lamp 2 are provided around a photoconductor 1 which is rotatably supported in an arrow direction. The image forming process equipment such as the discharging charger 3, the primary charging device 4, the secondary charging simultaneous exposure device 5, the blank exposure lamp 6, the whole surface exposure lamp 7, the developing device 8, the transfer charging device 9 and the cleaning blade 10 is a photoconductor. They are sequentially arranged in the direction of rotation 1. Document placing table 1
1 and the photoconductor 1 are movable mirrors 12 and 13, an in-mirror lens 14, and a fixed mirror 15 for scanning a document.
An optical system consisting of and is provided. The movable mirror 12 is mounted integrally with the original exposure lamp 16 on a support (not shown), and reciprocates in parallel with the original table 11 in the direction of the arrow a at the same speed V as the rotational speed of the photoconductor 1. Movable mirror 13
Moves reciprocally in parallel with the document table 11 and in the same direction as the movable mirror 12 at a speed V / 2.

The image forming apparatus having the above structure is disclosed in, for example, Japanese Patent Publication No. Sho 42-2391.
Copying is performed by the NP process disclosed in JP-A-0. In this case, the image density adjustment is performed on the original to be copied as follows. The image density adjusting operation will be described below with reference to the flow chart of FIG. 2 and the time chart of FIG. It should be noted that FIG.
7 to 9, F indicates movement of the optical system for detecting the original density, and G indicates preliminary movement of the optical system for detecting the original density.

a) Set the document O on the document table 11 and turn on the copy button.

b) At the same time when the pre-rotation of the photosensitive member 1 is started, the scanning means having the document illuminating means, which is an optical system, moves the home position B from the home position B to the document setting table 11 at a predetermined position A in the predetermined minimum document area or less. Go to and stop here.
That is, this movement is completed during the previous rotation.

c) After a predetermined time T1 (see FIG. 3) has passed since the copy button was turned on (corresponding to the end of the previous rotation), the optical system is moved from position A in FIG. ) Position B in the direction of arrow a, and the original exposure lamp 16 is turned on at the reference lighting voltage V ₀ , and the original exposure light from the original exposure lamp 16 is moved by the movable mirrors 12, 13, the in-mirror lens 14, and the fixed mirror. The surface of the photoconductor that has passed through the electrostatic latent image forming processes 2 to 6 is rotated through the arrow 15 to expose the surface of the photoconductor, and a latent image corresponding to the original image is formed on the surface of the photoconductor.

d) The surface potential of the photoconductor formed according to the original density pattern is detected by the potential sensor 17 at the position after the whole surface exposure by the whole surface exposure lamp 7.

e) The detection output of the potential sensor 17 is amplified by the amplification circuit 18 and input to the arithmetic control circuit 19.

f) The arithmetic control circuit 19 A / D-converts the input analog signal into a digital signal and detects the minimum surface potential value V ₁ which is the background of the document during the detection output. Then, the lighting voltage V ₀ ′ of the document exposure lamp 16 is determined by calculation so that the background of the document does not become fogged, that is, the minimum surface potential value V ₁ becomes zero or a negative potential.

g) The lighting voltage V ₀ ′ determined above is applied to the original exposure lamp 1
The ramp regulator 20 is controlled by the output of the arithmetic control circuit 19 so as to be applied to No.

h) The original exposure lamp 16 is turned on based on the above-mentioned lighting voltage V ₀ ′, moves from the position B in FIG. 1 (b) in the direction of arrow b, and starts the normal copying operation. And after the copying operation is completed,
When copying one sheet, the optical system returns to the position B in FIG. 1 (b), and the photoconductor 1 is rotated backward to complete all the operations. If the original is replaced and the copy button is turned on, the above operation is repeated.

In the above example, the lighting voltage of the original exposure lamp is controlled to adjust the image density, but the developing bias voltage may be controlled to adjust the image density as shown in FIG.
In the example of FIG. 4, after the detection signal supplied from the amplifier circuit 18 is A / D converted by the arithmetic control circuit 19, the arithmetic control circuit 19 further integrates the A / D conversion value to determine the background density of the document. An average value V ₂ is set, and a developing bias voltage V ₂ ′ is determined by comparing the developing bias value such that the background of the document is not fogged with a stored control value and a correction coefficient. The determined developing bias voltage V ₂ ′ is applied to the developing sleeve 8a.
The developing bias power source 21 is controlled by the output of the arithmetic control circuit 19 so as to be applied to the developing bias power source 21.

Since the minimum value detection in the example of FIG. 1 detects only the white background of the document, it may be difficult to reproduce the high density portion. Therefore, various known methods such as comparison means and average value may be adopted. Good. Therefore, when the original is a solid area such as a photograph, it is more effective to reproduce the solid area by detecting the integral value (average value) in the example of FIG.

Further, although the example of FIG. 1 illustrates an outline of the image forming apparatus of the optical system moving type, even in the image forming apparatus of the document placing table moving type, the document placing table is the optical system in the example of FIG. Similarly, the image density can be adjusted in the same manner as in the example of FIG. 1 by reciprocating within the range of the planned minimum original area before the start of the normal copying operation. Further, this image density adjustment can be performed by detecting the minimum value of the photosensitive member surface potential or the integrated value of the photosensitive member surface potential, and controlling the lighting voltage of the document exposure lamp or the developing bias voltage based on the detected value. preferable.

As described above, according to the above-described embodiment, the optical system does not have to scan the entire length of the original document to be copied in order to detect the density of the original document. Therefore, it is possible to shorten the time until the first copied image is obtained. It will be possible.

Next, another embodiment will be described.

FIG. 5 is a time chart for copying the same document on a plurality of sheets. The image density is adjusted in the same manner as in the example of FIG. 1 at the time of the first copy of the first sheet immediately after the copy button is turned on.
The image density is not adjusted after the first copy. This is because once the image density is adjusted, the conditions do not change unless the document is converted. It is determined that the image density adjustment is not performed from the time of copying the second sheet, for example, in accordance with a signal from the continuous copy number setting button, the previous step associated with the previous rotation is performed, and then the automatic density detection mode is selected. However, the preliminary operation of the optical system is forcibly stopped. At the same time, the image forming conditions of the exposure lamp system which has been carried out previously can be stored in memory and recalled from the tailing part, and the normal copying can be carried out under the same conditions as the preceding process. This continuous copying may be stopped according to the number of sheets for which copying is completed. Further, the image forming speed is improved even if the operation sequence of the image forming apparatus is created by another method.

FIG. 6 shows an example of an image forming apparatus provided with an automatic document loading device, and the same parts as those in FIG. 1 are designated by the same reference numerals. The automatic document loading device installed on the document placing table 11 feeds one by one from a plurality of loaded documents. More specifically, a document feeding belt 24 stretched in parallel with the document placing table 11 and a document feeding device for feeding the document O between the document placing table and the document feeding belt in a main body case 23 having a document receiving portion 22 on the upper surface. A feed roller 25, a document discharge roller 26 that sends the document to the document receiving portion 22, and the like are provided. 27 is a cassette containing the transfer paper P, 28 is a manual paper feed guide whose shaft 29 is rotatable, 30 is a cassette paper feed roller, 31 is a manual paper feed roller, 32 is a registration roller, and 33 is a transfer paper feed. Rollers, 34 is a fixing device, 35 is a transfer paper discharge roller, and 36 is a cleaning erasing device.

Next, the image density adjusting operation in this image forming apparatus
The time chart diagram (when two originals are copied to each one) will be described. When a copy button (not shown) is turned on, automatic document loading starts and at the same time, the photoconductor 1
Usually starts rotation before the copying operation, and during rotation, the optical system starts moving from the position B toward the position A indicated by a chain line. The optical system stops when it reaches the position A indicated by a chain line (a position which is equal to or larger than the planned minimum original area). After that, upon receipt of the signal of completion of automatic document loading, the movement of position A → position B → position C is followed by latent image formation of c) and the image density adjustment through steps d) to h), and then shifts to the normal copying operation. To do. When the copy of the first document is completed, the optical system is moved back from the position C to the position B at the same time as the second document is automatically fed onto the document placing table 11, and the trailing end (the sixth end) is performed.
Immediately after reaching the solid line position B), it moves forward to the position indicated by the chain line A and stops. This ends during document loading. And
Upon receiving the automatic loading completion signal for the second original, the optical system moves from the position A to the same B, and the latent image formation of c) and the steps d) to h) are repeated as described above to obtain two sheets. The image density adjustment is performed on the eye original and the normal copying operation is started, and the above operation is repeated every time the original is exchanged after the density detection mode continues.

The embodiment of the present invention shown in FIG. 7 is an example characterized by performing a preliminary operation for detecting the density of a document during the pre-rotation (detailed later) of the photoconductor. In the examples, an inventive arrangement unrelated to the pre-rotation is disclosed.

This is particularly effective when there is a mechanism for continuously or manually feeding the original, and is also effective in the initial state of automatically feeding the original as follows. That is, the image forming apparatus is characterized by performing a preliminary operation for detecting the image density of the document while the document is loaded in a predetermined position.
As a result, the preliminary operation necessary for detecting the document density can be performed without delaying the image formation, and higher-speed image formation can be achieved. Further, regarding the image density, the optical system does not have to scan the entire length of the document to be copied in order to detect the density of the document as in the above-described embodiment, so the time until the first copied image is obtained should be shortened. Is possible.

FIG. 8 is a time chart showing a modified example of the image density adjusting operation in the case of the automatic document loading of the embodiment of FIG.
After the first document is exposed, the optical system is stopped at the forward end, and the second document is automatically loaded again after the time set in the timer has elapsed. Is started, and the operation steps of d) to h) are executed in the middle of the backward movement by using, for example, a document automatic loading completion signal.

In the embodiment of FIG. 8, as in FIG. 7, the preliminary operation movement G for density detection is performed during automatic document loading, so the time required for image formation can be shortened. Further, in this example, when moving the detection distance ▲ ▼ for density detection, the preliminary operation movement G is made ahead of time, and the movement speed can be stabilized before reaching the position A, so that it is stable during the concentration detection movement F that is continuously performed. The density can be detected at the specified speed. Therefore, the detection result can be made more stable. In the figure, point H is a point where the time when the optical system moves to the position H and the time when the loading of the original is completed coincides. It is sufficient to set the above-mentioned consistency by setting a time or using a sensor or the like so as to match this position.

FIG. 9 is a time chart showing another modified example. When the second original is automatically loaded, the optical system is returned to the position A indicated by the chain line in FIG. 6 and temporarily stopped, and, for example, the automatic original loading completion signal is used. Then, the operation steps d) to h) are executed.

To further elaborate the embodiment of FIG. 9, in the description,
The optical system is located in advance on the side of the point where the document scanning is finished. When the document is loaded, the optical system starts to move and stops at a predetermined position, and then the optical system is moved to detect the document density according to the document loading completion signal. An image forming apparatus is disclosed which is characterized by carrying out. This can minimize the movement of the optical system and improve the image forming speed when the automatic density detection is performed on continuous originals. This is effective for a device that is placed at a position and continuously feeds automatic documents. This is also effective for automatic document feeding of the first sheet. By adopting this, the movement of the optical member can be used effectively and minimized, so that the durability of the member due to the movement of the optical member can be improved, the control thereof can be simplified, and the image formation can be performed quickly. be able to.

The term "pre-rotation" in each of the above-mentioned embodiments means that 1) the photoconductor rotates at the same time as the copy button to recover the fatigue of the photoconductor, and 2) one or more revolutions of the photoconductor at the same time as the copy button and the blank exposure or The deterioration recovery process due to charging is performed, 3) the pre-exposure lights up as the photoconductor rotates at the same time as the copy button, and the photoconductor makes one or more revolutions. Static elimination, primary and secondary charging, blank exposure, overall exposure, etc. are activated and the photosensitive member becomes 1
It means rotating more than once, etc., but the case of 4) is preferable because the photoconductor is normalized.

This pre-rotation is indispensable for obtaining a stable image during image formation, and is most suitable for observing the density of the original by observing the potential of the photoconductor.

The main feature of the present invention is that the time during this pre-rotation is efficiently used as a part of the time required for automatic density detection to eliminate time loss and enable high-speed image formation. It should be noted that this pre-rotation may be finished before the automatic density detection is started, not immediately before it is started.

As described above, in the above example, the image density is adjusted by making at least the preparation during the pre-image forming process such as pre-rotation and document loading. Therefore, the copy speed is not reduced at all. Further, since the original image is exposed on the photoconductor and the image density is adjusted based on the surface potential formed on the photoconductor, the above-mentioned disadvantages in the conventional image density adjustment are eliminated. Regarding the image density adjustment, the optical system does not have to scan the entire length of the document to be copied in order to detect the density of the document, so that it is possible to shorten the time until the first copied image is obtained.

In addition to the illustrated example in which the lighting voltage of the original exposure lamp and the developing bias voltage are controlled to adjust the image density, the lighting voltage of the primary charging device, the secondary charging simultaneous exposure device, the full exposure lamp and the image forming conditions One or two of the above may be controlled.

As described above, the present invention enables high-speed image formation, and makes it possible to obtain an image based on information corresponding to a document in an appropriate state.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the image forming apparatus of the present invention. FIG. 1 (a) is a diagram at the start of image density adjustment, FIG. 1 (b) is a diagram at the start of copying, and FIG. 1 is a flow chart of the image density adjustment process according to the example, FIG. 3 is a time chart of the image density adjustment in the case of manually loading an original, and FIG. 4 is a main part of the image density adjustment by controlling the developing bias voltage. Block diagram, FIG. 5 is a time chart of image density adjustment when two or more copies are made from the same document, FIG. 6 is a front view of an image forming apparatus equipped with an automatic document loading device, and FIG. Time charts of image density adjustment in the image forming apparatus, FIGS. 8, and 9 are timing charts showing modified examples of the image density adjustment. Reference numeral 1 is a photoconductor, 11 is a document table, and 12 to 16 are optical systems.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-56-89752 (JP, A) JP-A-53-63021 (JP, A) JP-A-57-120964 (JP, A) JP-A-54- 2134 (JP, A) JP-A-56-27175 (JP, A) Actually developed Shou 53-9842 (JP, U)

Claims (1)

[Claims] 1. A means for forming an electrostatic latent image corresponding to an original image on an electrophotographic photosensitive member, a detecting means for detecting the density of the original, and an image forming condition controlled according to a signal from the detecting means. In the image forming apparatus having the control means, by operating the copy button to instruct the start of the copying process, the photoconductor is rotated prior to the copying process each time the copying process is instructed. The photoconductor that undergoes the pre-rotation process to stabilize the characteristics of the body and the light source for document illumination are moved relative to the document setting table, and the actual rotation of the photoconductor is started in the pre-rotation process. Move from the home position, which is located at the same position as the copy process, at the end of the platen side of the document platen, to the document density measurement start position, which is a distance shorter than the scanning distance during this actual copy process. ,the above After the rotation process, the light source of the document scanning means for returning to the home position and standing by while lighting for forming an electrostatic latent image for measuring the document density, and the light source of the document scanning means are formed. By measuring the potential of the electrostatic latent image, a predetermined latent image is formed based on the density detection means for detecting the density of the original document and the detection result by the density detection means prior to the copying step performed after the pre-rotation step. An image forming apparatus, comprising: a calculating unit for forming an image; and after the calculation by the calculating unit, scanning of the document scanning unit is started for copying.