JPS6026375A - Automatic image density controlling device - Google Patents

Abstract

PURPOSE:To reduce toner consumption by controlling turning on and off of light emitting elements in accordance with the region detected with a sensor at the time of preliminary scanning of a photosensitive drum for measuring an original density. CONSTITUTION:A photosensitive drum 1 is scanned preliminarily to detect the surface potential corresponding to a latent image on the drum 1 with a sensor 42 and the density of an original is measured. In this case, a large number of light emitting elements BL for blank exposure are controlled with a controller 44 and the elements corresponding to the region detected with the sensor 42 are turned off, and the elements BL corresponding to the other regions are turned on to illuminate the drum 1. As a result, a latent image is not formed on the area other than the necessary area, and toner consumption can be reduced at the time of detection of the image density.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an automatic image density adjustment device for a copying machine.

[Prior art]

Generally, this type of automatic image shading adjustment device performs a scan (hereinafter referred to as a preliminary scan) to measure the density of a pre-crimped original before performing a scan for copying using an optical system (hereinafter referred to as a copy scan). The density of the original is measured by detecting the surface potential of the electrostatic latent image formed on the surface of the photoreceptor through the 1u scan, and a voltage corresponding to the density of the original is applied to the exposure lamp to increase the amount of light. is designed to be adjusted.

However, such automatic image density e, 1lrl
In the machine, toner is deposited on the electrostatic latent image formed by preliminary scanning, which is not the original scanning for copying, in the same way as the electrostatic latent image formed by copying scanning. There was a drawback that toner was wasted.

[Purpose of the invention]

This invention was made by paying attention to the above-mentioned drawback, and when performing preliminary scanning, the sensor at position 111 on the front side of the photoreceptor,
7. The purpose of the present invention is to provide an automatic image density adjustment device that can reduce toner consumption by including a light-emitting element that irradiates light to a position other than the area where surface potential and image brightness are detected by an autosensor or the like. do.

[Explanation of Examples]

This invention will be explained below based on an embodiment shown in FIGS. 1 to 4.

First, a copying machine to which this invention is applied will be explained. 1st
In the figure, 100 is the main body of the copying machine, 200 is an external additional device connected to the main body 100, and in this embodiment, an automatic document feeder (hereinafter referred to as F) is connected to the main body 100. As shown in FIG. 2, copy start signals CPEXA, D, and F start signals DFE are mainly used.

and document size data signal PSD. The copy start signal CPE is a copy enable signal, which is generated when an original is set in A, D, or F.

Also, the A, D, F start signals DFE are A, D, F
The operation enable signal is a signal generated when the copying machine main body 100 is ready for copying operation. Therefore, for example, during wait-up after turning on the power switch or when there is no paper in the cassette, the A, D, and F start signals DFE are not generated t7. The document size data signal PSD is a signal generated when A, D, and F detect the document size. Therefore, if it is possible to detect documents of four different sizes, for example A, D, and F, two signal lines SL, SL, as shown in FIG.

It is sufficient to provide

In addition, in the main body 100 of the copying machine, there is a photoconductor drum whose 1i:1 surface is formed by a photoconductor.
Rotate in the direction of ・)). Reference numeral 2 denotes a high-voltage charger that charges the photoreceptor drum 1, and the photoreceptor drum 1 charged by the high-voltage charger 2 receives light from an illumination lamp 3 that scans an original document through a platen glass 4, and a reflection mirror. 5
, 6.7.8 and the lens 9, and the photoreceptor drum 1 is imaged at the exposure point A) and exposed.
As a result, an electrostatic latent image is formed on the photoreceptor drum 1.

10.11 is a reversal sensor, and as mentioned above, the illumination lamp 3
, reflector 5, 6.7.8. When scanning an original by moving the optical system such as the lens 9 in the direction of the arrow (→) in the figure, the optical system is reversed when it is moved to the position 1a of the reversal sensor 10 or 11. Further, one of the reversing sensors 10 and 11 is provided at a reversing position when the document is in a small size (for example, B5 or A4. ) is provided in the reverse position.

Reference numeral 12 denotes a developing device that applies toner to the electrostatic latent image using a developing roller 13 to make it visible. Reference numeral 14 denotes a cassette containing a large number of transfer papers. Reference numeral 15 feeds the transfer papers one by one from the cassette 14. Paper feed roller 16 is the paper feed roller 45
Registration rollers that feed the transfer paper fed by
The registration roller 16 starts rotating at a timing such that the leading edge of the visible image formed on the photosensitive drum 1 and the leading edge of the transfer paper are aligned. In this embodiment, the illumination lamp 3 is the registration sensor 17.
When the registration sensor 17 detects the illumination lamp 3, the registration roller 16 starts rotating. 18 is a transfer charger that transfers the visible image onto the transfer paper; 19 is a separation roller that separates the transfer paper from the photoreceptor drum 1; 20 is a transport unit that transports the transfer paper separated from the photoreceptor drum 1; The transfer paper is transported by a conveyor belt 20
A is conveyed while being sucked onto the upper surface of the paper by a suction fan 20b. Reference numeral 21 denotes a part of the cleaner, which is equipped with a cleaner brush 21a for removing and cleaning residual toner from the photosensitive drum 1 after transfer. 22 is the cleaner brush 2
This eraser removes the surface potential of the photosensitive drum 1 cleaned in step 1a to approximately 0. 23 is constant: X + instrument, 1
The image forming apparatus includes a fixing roller 23a for fixing an image on the transfer paper conveyed from the transport section 20, and a web motor 23b for winding a web for cleaning the fixing roller 23a. Reference numeral 24 designates a paper discharge roller for discharging the transfer sheet after nine copies from the fixing device 23 to a paper discharge tray 25, and 26 a heat exhaust fan for dissipating the heat of the illumination lamp 3. A main motor 27 drives the photosensitive drum 1, the optical system, the paper feed roller 15, the conveyance section 20, the fixing device 23, etc., and the drive system, all using a chain (not shown). I am doing it. 28 is a power transformer.

On the other hand, in 15 people, I)-, F 22o;
t AF original detection sensor 31 detects the original stacked on the tray 29; A, D for each copy of the original from the top;
, F.20.0. The pickup rollers 32a and 32b that feed the sheets one by one are a pair of separating belts that move in the direction of the arrow ((-) in the figure.
The document fed by is inserted between the pair of separation belts and conveyed.

33 is the separation bell) K inserted between 328 and 32b.
(AF timing sensor that detects the leading edge of the paper; 34 is the separation bell) a document detection sensor that detects the leading edge of the document fed from 32a and 32b; 35 is a presser roller;
6 is a conveying roller, and 37 is a full-surface belt. The full-face belt 37 is bridged between a drive roller 38 and a turn roller 39, and operates as the drive roller 38 rotates. 40
Reference numeral 418 and 41b indicate an entrance sensor that detects the leading edge of the document that has passed through the transport roller 36, and a discharge roller 418 and 41b.

The shell thickness device described above is provided with an automatic image density adjustment device shown in FIG.

This will be explained below based on FIG. 4. 42 is photosensitive drum 1
This is a surface potential sensor for detecting the surface potential of the image forming apparatus, and is located between the exposure window A and the developing roller 13, as shown in FIG. Generally, the surface potential of the photoreceptor tram 1 is as shown in FIG. That is, Vo is the maximum potential (saturation potential) that can be charged by the high voltage charger 2.
In this embodiment, after charging to the highest surface potential (1), exposure is performed at exposure point A after dark decay over a predetermined period of time. As a result, the surface potential decreases to Ve, and a contrast between bright and dark areas is formed. At this time, the surface potential Ve changes depending on the brightness of the original. That is, when the original is light, the surface potential Ve decreases, and conversely, when the original is dark, the surface potential Ve increases. Therefore, by detecting this surface potential Ve, it is possible to measure the density of the original. Reference numeral 43 denotes a concentration measuring circuit connected to the surface potential sensor 42, and this concentration measuring circuit is a peak hold circuit PH consisting of FET T I + T t and an operational amplifier OP as shown in FIG.
As shown in FIG. 7, it is reset by inputting Ceratoid No. d to the gate of 'vETT, as shown in FIG. Concentration measurement is started upon input. 45 corresponds to the output from the concentration measuring circuit 43,
That is, it is a lamp regulator that appropriately supplies a predetermined lamp lighting voltage VLINT to the illumination lamp 3 according to the density of the original. Further, the predetermined lamp lighting voltage V LI
Nφ was calculated using the graph in FIG.

For example, the original density is light. In this case, the lamp lighting voltage becomes V Ll, which is a dark value. If so, it becomes VL2. BL applies light to the parts of the photoreceptor drum 1 that do not require toner attachment! A plurality of blank exposure lamps BL, to BL6 are arranged on the photosensitive drum 1 as shown in FIG. 1'0. Moreover, FIG. 9i1 shows an enlarged side view of this blank exposure lamp BL. These blank exposure lamps BL, ~BL, are connected to the control device 4.
In other words, the blank exposure lamps BL, to BL6, which are designed to blink in response to a blinking signal from 4, are all turned on during rotation of the photoreceptor drum 1 except when an original is being scanned. The surface charge of the photoreceptor drum 11 is erased to prevent excess toner from adhering to the photoreceptor drum 1, and during reduction copying, the light from the illumination lamp 3 covers the entire surface of the drum. Blank exposure lamp BL is used for non-image areas that are not irradiated.
and blank exposure lamp BL,,BL according to the reduced size.
s is turned on even when the optical system is moving forward, and by irradiating this portion with light, it is possible to suppress adhesion of excess toner as much as possible. Furthermore, during preliminary scanning, the potential sensor 42 turns off only the blank exposure lamp BL4 that irradiates light to the portion B of the photoreceptor drum 1 where the surface potential is detected, and irradiates light to the position other than the portion B. Other blank exposure lamps BL, , BL, , BL3,
BL6 is designed to be lit. As a result, the electric charge in the portion of the electrostatic latent image formed by preliminary scanning that is unnecessary for density measurement is removed without affecting the potential of the portion necessary for density measurement, and excess toner is removed. is prevented.

Next, the operation of this embodiment will be explained based on the flowcharts shown in FIGS. 11 and 12.

First, the operations of A, D, and F 200 will be explained. 11th
) In step A1, the AF document detection sensor 30 detects the document stacked on the document tray 29, and
When the A, D, and F start switches (not shown) are pressed, the A, D, and F start lamps (not shown) light up, the pickup solenoid (not shown) is energized, and the pickup roller 31 descends. After a predetermined time has elapsed, the AF motor (not shown) is driven and starts rotating, and the uppermost document is fed into A, D, and F200. In step A2, the pickup roller 2
The document fed by 1 is transferred to the pair of separating bells)
32a.

32b and transported. Also, at this time -AF
When the timing sensor 33 detects the rear end of the document, the pickup solenoid is de-energized and the pickup roller 31 moves upward.

Then, it is determined whether the DF document sender 34 has detected the leading edge of the document conveyed from the separation bells 32a and 32b, and if it has been detected, steps A, D, and A are performed in step A3.
It is determined whether or not the F start signal DFE is being sent out, and if it is being sent out, the copy start is reset. After this, in step A4, the peak bold circuit PH of the concentration measuring circuit 43 shown in FIG. 6 is reset, and the D
It is determined again whether or not the FRP sensor 34 has detected the leading edge of the document. If detected, the process proceeds to step A5; if not, the process jumps to step A12. In step A5, a presser solenoid (not shown) is energized and the presser roller 35 moves upward to press the document. Then, after a predetermined period of time has elapsed, the DF motor (not shown) and the clutch (not shown) are turned on, and the presser roller 35, conveyance roller 36, belt drive roller 38, turn roller 39, and ejection roller 41a are turned on. , 41b rotate.

As a result, the document starts to be transported at a faster speed than when it is transported by the separation bells 32a and 32b. In step 86, when the population sensor 40 detects the leading edge of the document that has passed the conveyance roller 36, a clock pulse generated from a clock generator (l\1 not shown) synchronized with the rotation of the I)F motor is activated. Start counting. At the same time, the presser solenoid is de-energized and the presser roller 35 moves upward. Then, the reset of the peak hold circuit PH of the concentration measurement circuit 43 is turned off. In step AI, a concentration measurement signal is manually input to the concentration measurement circuit 43, and concentration measurement is started. In step 88, when the population sensor 40 detects the trailing edge of the document, feeding of the next document to be fed to the AF destination is started. Please note that this manuscript is DF
It is waiting at the location of the original document sensor 34. Further, the signal that was manually input to the concentration measurement circuit 43 is turned off. In step A9, when the number of pulses generated from the clock generator reaches a predetermined value, a clutch (not shown) of the DF motor is activated.
At the same time, the brake (not shown) is energized. Then, in step A10, the main body 100 of the copying machine
A copy start signal CPE is sent out. Note that the power to the brakes is cut off after a certain period of time.

In step A11, it is determined whether or not a document is placed on the document tray 29. If the document is placed trf, the process goes to step A2; if it is not placed, the process returns to step A3, and the same operation is performed thereafter. repeat. Then, in step A12, first, when the DF paper ejection operation is started, counting of clock pulses generated by the clock generator is started. Thereafter, when the number of pulses reaches a predetermined value, the DF paper ejection operation is stopped and the A, D, and F start lamps are turned off.

Next, based on the flowchart shown in FIG.
The automatic image density adjustment operation will be explained together with the copying operation of 0.

In step B1, an F start signal DFE is sent to A, D, and F20Q. and,
When a document is placed on A, D, and F 200 and copying is started, a copy start signal CPE is sent.

Based on this, the main body 1oo starts a series of copying operations, but at this time, A, D, F start are first set so as not to cause the A, D, F 200fA operation. This is to prohibit the operations of A, D, and F200 until the copy is reversed. Next, the optical system starts moving forward for density measurement, but at this time, in preparation for density measurement, the peak hold circuit P of the density measurement circuit 43 shown in FIG.
H is reset.

In step B2, A, D, ' as shown in FIG.
By the document size data signal sent from F200,
It is determined whether the size of the original is large or small, and when one of the reversing sensors 10, 11 detects the illumination lamp 3 depending on the size of the original, the optical system starts reversing.

After this, concentration measurement is started; first, the illumination lamp 3 is turned on at a predetermined standard brightness.

That is, as shown in the time chart of FIG. 7, the illumination lamp 3 is turned on at the standard lamp lighting voltage VLo. This is because the shading of the original is always measured at a constant brightness. Then, in step B3, concentration measurement is started after the time T1 has elapsed.

At this time, six blank exposure lamps BL, -BL are used.

Of these, only the blank exposure lamp BL is turned off, and the other blank exposure lamps BL, BL2, BL, BL,
, BL6 lights up. As a result, the static 11! formed on the photoreceptor drum 1 by the preliminary scanning! Charges in parts of the latent image that are unnecessary for density measurement are removed without affecting the potential of parts necessary for density measurement. Step B4
Then, when the time T2 has elapsed since the start of the concentration measurement, the concentration measurement is stopped. This is for measuring the shaded area in FIG. Further, in the figure, +α indicates a distance difference between the exposure point A shown in FIG. 1 and the measurement of the surface potential. By the above preliminary scanning, an electrostatic latent image is formed on the photosensitive drum 1 in the shaded area shown in FIG. Note that the arrow in the figure indicates the scanning direction.

In step B5, when the optical system finishes the preliminary scan and returns to the home position HP, a home position sensor (not shown) detects this and immediately starts moving forward again for copy scanning. At this time, the density measuring circuit 43 outputs an output corresponding to the highest density measured by performing the preliminary scan, and is held by the peak hold circuit PH, and the graph shown in Figure @8 is output according to this output. The lamp lighting voltage VINT calculated by is supplied to the illumination lamp 3 from the lamp regulator 45. Also, paper feeding is performed at the same time as this copying scan starts, and step B6
Thereafter, a series of well-known copying operations are performed. As a result, an image with a stable density is always obtained regardless of the density of the original, and during preliminary scanning, charges other than the portion B necessary for density measurement of the electrostatic latent image formed on the photoreceptor drum 1. is removed from the photoreceptor drum 1, and no toner adheres to that portion B.

In the above embodiment, six blank exposure lamps BL, -BL are used as light emitting elements, but the number is not limited to six, and any other desired number may be used.

Further, although a well-known microcomputer was used as the control device Ft44, this invention is particularly applicable to 1 (1) in the above embodiment.
1 (This is not specified. It is also possible to measure the light and shade by inserting a photosensor into the optical path near the center in the axial direction of the drum during preliminary scanning.

〔Effect of the invention〕

As described above, the automatic image density adjustment device d of the present invention measures 6 degrees of the document by preliminary scanning, and lights the illumination lamp at a predetermined 1 (L pressure) to copy the document. An automatic image density adjustment device configured to perform scanning, including a front handle (a light-emitting element that irradiates light to a position of the photoreceptor excluding a portion detected by a surface potential sensor when performing 1fff scanning). As a result, the electrostatic latent image in the area that is important for density measurement is removed, and toner is not attached to that area, which has the effect of significantly reducing toner consumption.

[Brief explanation of the drawing]

Fig. 1 is an explanatory side view of the main parts of a ladle copying machine to which the present invention can be applied, Fig. 2 is a diagram showing the connection relationship between the main body and A, D, and F, and Fig. 3 is the same as shown in Fig. 2. FIG. 4 is a diagram showing the overall configuration of an embodiment of the present invention. FIG. 5 is a diagram showing the surface potential of the photosensitive drum. FIG. A circuit diagram showing a concentration measuring circuit, FIG. 7 is a time chart of an embodiment of the present invention,
FIG. 8 is a diagram showing the relationship between document density and lamp lighting voltage in this embodiment, FIG. 9 is an enlarged side view of the blank exposure lamp, and FIG. 10 is an explanatory side view showing the arrangement of the blank exposure lamp (7). Figure 11 shows A in one embodiment of this invention.
, D, and F; FIG. 12 is a flowchart showing the main body's copying operation and automatic image density adjustment operation; FIG. 13 is a diagram showing the movement of the optical system and the scanning portion during preliminary scanning of the original; fP; Figure 14 is the preliminary ω1
FIG. 3 is a diagram showing a portion where an electrostatic latent image is formed on a photoreceptor drum in one scan. 1...Photosensitive drum 3...Illumination lamp 42...Surface potential sensor 43...Concentration measuring circuit 44... ... Control device 45 ... Lamp regulator BL ... Blank exposure lamp

Claims (1)

[Claims] An automatic image density adjustment device w that performs a preliminary scan when measuring the density of a document includes a light-emitting element that irradiates light to a position of the photoconductor other than a portion detected by the sensor when performing the preliminary scan. An automatic image density adjustment device characterized by comprising: