JPH0241028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to toner concentration measurement in electrostatographic reproduction machines.

In an electrostatographic original copying machine, a charged latent image is formed on a photoconductive material and then developed with a developer mixture. Upon separation of the copy paper from the photoconductive material, transfer of the developed image to the copy paper occurs and the image is then fused. A common type of developer mixture currently used in such copying machines consists of a carrier material, such as magnetic beads, coated with a colored powdery substance called toner. The toner is attracted to the charged latent image, which develops the image and then transfers the developed image to the copy paper when the copy paper is separated from the photoconductive material. The toner is then fused to the copy paper to form the final copy.

It is clear from the process outlined above that as toner is used in a copier to form an image on copy paper, the toner is depleted and the developer mixture must be periodically replenished with the toner. be. It is clear that the concentration of toner particles in the developer mixture is important for good development of the latent image since low toner concentrations result in a faintly developed image and high toner concentrations result in a dark developed image.

The present invention provides an electrostatic photoconductor of the type in which the surface of the photoconductor has a first area for receiving an original image of a first dimension and a second area for receiving an original image of a second size smaller than the first dimension. An object of the present invention is to accurately measure toner concentration in a photocopying machine without interrupting the copying cycle.

To accomplish this objective, the present invention provides that toner is applied to a first area of the photoconductor surface that is not included in the second area during a copying cycle for copying an original image of a second dimension. A test area is formed and the toner density in this test area is measured.

For toner concentration measurements, it has been found that using the area of the photoconductor that receives the original image (image area) as the test area provides a significant advantage in accuracy. Some reasons for this are that as the photoconductor ages with frequency of use, toner tends to build up in the image area, and that the photoconductor surface characteristics in the image area change with frequency of use. As a result, the development process is affected and the image area is subject to electrostatic degradation with frequency of use. As a result of these factors, the image area is dark compared to the photoconductor area not used for copying. It has been found that these deterioration factors hardly appear in the density test when the test area is provided outside the image area. However, in the apparatus of the present invention, in which the test area is located within the image area, a thin film of toner,
Any results due to aging, frequency of use, etc. will appear in the quality test. As a result, the absolute amount of toner in the developer mixture can be adjusted as the photoconductor changes and the bias voltage of the developer process can be varied to provide a factor that compensates for these effects. Such results cannot be obtained if the test is not performed within the image area.

a Overview Figure 1 shows a typical transfer type electrostatographic copying machine. Copy paper is guided by paper path guide means 1
2 along the paper bin 10 or paper bin 11
The transfer station 13A is placed directly above the transfer corona 13. At the station, the image is transferred to copy paper. The copy paper is fed between fuser rolls 15 and 16 where the image is fused to the copy paper. The sheets are fed along a paper path 17 and fed to a movable deflection device and from the deflection device into one of the collator bins 19.

To generate an image on photoconductor surface 26,
The original to be copied is placed on the glass plate 50. The image of the original document is transferred to the photoconductor surface 26 through an optical system module 25 that produces an image of the original document on the photoconductor surface 26 at an exposure station. As drum 20 continues to rotate in direction A, developer device 23 develops the image, which is then transferred to copy paper. As the photoconductor continues to rotate, the image area of the photoconductor moves beneath a pre-cleaning corona 22 and erase lamp 24 which discharge any remaining charged areas on the photoconductor. The photoconductor passes through a development station (also a cleaning station in this example) until the area reaches a charging corona 21 where the photoconductor 26 is charged again before receiving another image at an exposure station 27. Keep rotating.

FIG. 2 is a perspective view of the optical system, showing an original glass 50 on which an original to be copied is placed. Irradiation lamp 40 is provided within reflector 41 .
Sample beams 42 and 43 are generated from a lamp 40 and directed from a dichroic mirror 44 to an original glass 50 where light streaks 45
is generated. Rays of light 42 and 43 are deflected from the original placed on the original glass to a reflective surface 46, from the reflective surface 46 to a reflective surface 47, from the reflective surface 47 to a reflective surface 48, and reflected from the reflective surface 48. From surface 48 through lens 9 to another reflective surface 49
deflected to Finally, the light beam is deflected from the mirror 49 through the aperture 51 in the wall 52 to the photoconductor 26, producing a light streak 45'. In this way, the copy information contained in the light streaks 45 of the glass plate 50 is generated on the photoconductor 26 as light streaks 45'. The entire length of the original placed on the original glass 50 is the lamp 40.
and is scanned by the movement of the reflecting mirrors 44, 46, 47 and 48. The light line 45' is the drum 2
By moving the light streak 45 across the document at the same speed that it is moved across the photoconductor 26 by the rotation of
A 1:1 copy of the original document is generated on photoconductor 26.

FIG. 3 is a perspective view showing various parts of the paper path. Here, the copy sheet 31 is the copy sheet 31.
The trailing edge 31A of the sheet is the guide means 12 for the paper path.
It is shown in the following condition. The copy sheet is being imaged at transfer station 13A, and rolls 15 and 16 are fusing the image to the sheet. The leading edge 31B of the copy sheet is leaving the copier and is being fed to collator 19, which is shown in simplified form.

Once the image is transferred to the copy paper, the photoconductor 2
6 reaches below the cleaning corona 22 before applying a charge to the photoconductor surface in order to erase the charge remaining on the photoconductor surface. Photoconductor 2
6 continues to rotate until the photoconductor is below the erase lamp 24' of the housing 24. The erasing light is directed across the photoconductor 26 to discharge any areas remaining on the photoconductor surface that are not erased by the pre-cleaning corona 22. After passing under the erase lamp 24', the photoconductor continues to rotate through the cleaning station 23 of the developer/cleaner, where any residual toner not transferred to the copy paper is removed for the next copy cycle. removed from the photoconductor before starting.

In the next copy cycle, the charging corona 21
uniformly charges the photoconductor 26 such that the image of the original is exposed at the exposure station 27 shown in FIG.
variably removed when imaged onto the photoconductor.

If a toner concentration control cycle is executed and the developer needs to be refilled with toner, a signal is issued to the replenisher 35 which is operative to hold a supply of toner and deposit a metered amount of toner into the developer. It will be done. In this way, the amount of toner in the developer mixture is replenished. IBM Technical for any suitable replenisher mechanism
The supply device described in Volume 17, Issue 12, pages 3516 and 3517 of Disclosure Bulletin can be used.

b. Test Cycle FIG. 3 shows a housing 32 with the toner concentration control and sensing device shown in FIGS. 4 and 6. When it is desired to detect the toner concentration of the developer mixture, the photoconductor is connected to the charging corona 21.
The photoconductor is normally charged, but no document image is formed on the charged photoconductor at the exposure station. Instead, in this cycle the erase lamp 24' is used to discharge any charge that has been charged by the charging corona 21 to provide a reference test area of toner-free photoconductor. It's on. However, erase lamp 24' is momentarily shut off to create a toned sample area.
If the erase lamp 24' consists of an array of light emitting diodes (hereinafter referred to as LEDs), the array is split so that only a few LEDs are turned off and therefore only small "patches" of charged parts are left. remains on the photoconductor at the end of this cycle. If a fluorescent tube is used as the erase lamp 24'', a charged streak is placed on the photoconductor at the end of the cycle by momentarily reducing the energization of the fluorescent tube to a low potential. bring forth

Whether a charged area is formed in the form of a streak or a patch, the charged test area reaches the developer device 23 as it rotates, where the toner is applied to form a toned sample test area. is deposited over the charged area. This test cycle does not require a copy sheet to be present at transfer station 13A, and thus this developed test area is A until it reaches toner density control housing 32.
Rotate in the direction of. Referring to FIG. 4, at this point the LED or other suitable light source 33 is
It is energized to produce light that is reflected from the toned sample test area 30 and onto the photo sensor 34. It will be appreciated that the toned image can be transferred to copy paper if desired. The reflectance of the developed and transferred streaks (or patches) is then detected by placing a sensor in the paper path. The principles of this apparatus are also found to work well in electrophotographic reproduction machines where the photosensitive paper or image is exposed directly onto the copy paper without the use of a transfer station.

FIG. 5 is an exploded view of photoconductor 26, with the image area indicated at 28. Developed patch 30
is formed within image area 28. FIG. 2 shows an apparatus for producing patch 30. FIG. As mentioned above, erase lamp 24' is momentarily cut off to generate a charging streak. Although the line 45' mentioned above as the light beam produces an image on the photoconductor 26, during the test cycle the line or line 45'
5' is assumed to be used to define the charging streak produced by momentarily cutting off the erase lamp 24'. Assume also that the light from document lamp 40 is on and would erase charged streak 45' if it were not off. The light of the lamp 40 is blocked by the shutter 36 so that it falls across the slot 51 of the wall 52.
(as shown in FIG. 2). Shutter 36 is operated by a solenoid 38. As a result, the light from the lamp 40 is blocked by the shutter 36 and does not reach the photoconductor 26, thus creating a charged streak 37. Of course, the erase lamp 24' is patch 30.
The remaining lines 37 are erased, leaving . In this way, patches can occur instead of striations.
Slot 51 must be located close to photoconductor surface 26.

As shown in FIG. 5, placing the test area 30 within the image area 28 is advantageous when a large number of copies are being made over a long period of time, since the density test is periodically performed after, for example, 20 copies have been processed. When doing so, this test requires skipping some copy operations. If the copying process is short, the density test is executed in the cycle after copying the original. On the other hand, Figure 7 shows
Photoconductor 26 to demonstrate a technique that eliminates the need to skip certain copying operations even when making multiple copies over an extended period of time.
FIG. If your copy machine makes copies of two different sizes, for example 216mm x 279mm and 216mm.
If a x356 mm copy can be made, the extra 76 mm in the image area 28 when making a small copy can be used for density testing without skipping copies. FIG. 7 shows the timing required for the erase lamp, the original lamp, and the shutter 36 of FIG. 2, with ◯ indicating an on state and an x indicating an off state. If segmented
If an LED device is used as an erase lamp, and if a charged line is formed in place of the patch 30, the generation of the test area can be achieved by turning off the document lamp at the end of scanning a 279 mm document, as shown in FIG. This is accomplished by momentarily shutting off the erase lamp. Of course, the shutter is not used in this case.

c. Control circuit 111 (see FIG. 6) When the appropriate time of sequential operation of the copier is reached to generate the reference voltage, the logic control of the copier issues a signal that triggers the measurement of the reference sample. This is done by energizing LED 33 in the following manner. The logic signal is a transistor that connects the reference sample input line to ground.
Trigger a switch (not shown). As a result, the negative input voltage of operational amplifier (OP AMP) 61 drops from approximately 8V to approximately ground potential.
This switches the negative input of OP AMP 61 from a higher value to a lower value than the positive input, resulting in a low to high OP AMP output reversal on line 62. The output is then fed back to the positive input to lock the OP AMP 61 at a high output condition that prevents oscillation. The output voltage on line 62 is applied to transistor Q2, turning it on and thus disconnecting light emitting diode (LED) 33 and transistor Q from the 24V supply.
Close the circuit through 2 to ground. As a result, the light is transmitted to LED3 at the exact time of the machine cycle.
3 to the photocell 34, the light beam is emitted from the non-toned photoconductor to the photocell 34.
reflected to.

To generate a sample voltage for the toner-deposited area, a logic signal is issued at the appropriate time in the machine cycle to turn on a transistor switch (not shown) to generate the toner-deposited area in FIG. Connect the sample input signal to ground potential. This drops the negative input to OP AMP 63 from about 8V to ground potential and connects line 64.
Increase the output to. The signal on line 64 turns on transistor Q1 and
conducts the light emitting diode to ground through the
It can be seen that the resistance connected to transistor Q1 is much lower than the resistance connected to transistor Q2. As a result, transistor Q1
The current level through LED3 is much higher than the current level through transistor Q2, so that when the toned sample is exposed to light, LED3
3 to generate a very strong light. The reason for this is
This is because an untoned photoconductor reflects a higher level of light than a toned photoconductor. The intensity of the light that is reflected and excites the photocell must be maintained at approximately the same intensity level whether examining untoned or toned samples. The purpose of this is to ensure a high signal level when verifying either a bright reference sample or a darker sample coated with toner in order to improve the noise margin, as well as to ensure a photocell based on the different light reception levels. The aim is to avoid nonlinearity that occurs in the excitation phenomenon. This is an important feature in devices that are designed without much consideration for variations in component sensitivity.

Referring to the circuit of photocell 34, OP
It can be seen that AMP65 is connected as a transconductance amplifier. When the photocell 34 is off, only a small dark current flows through the OP AMP.
65 between the output and the negative input. However, when the photocell is energized, the current flow is increased considerably and resistor R16
and causes a large voltage drop across R17,
A voltage level of approximately 1V or 2V is generated on line 66. Zener diode 67 limits the voltage level developed on line 66 to 8.5V. This limits the voltage level to a range of 8.5V from the unexcited value of the photocell. Assuming the energized voltage level of the photocell is 2V on line 66, a change from 0V to 2V is transferred through capacitor 68 to an integrator circuit consisting of OP AMP 69, capacitor 70, field effect transistor (FET) Q5, and associated resistors. . Under normal conditions, 16V is applied to the input of OP AMP 69, resulting in a 16V output on line 71. When a light source excites the photocell and produces a voltage, say 2V, on line 66, a voltage change of 2V occurs across capacitor 68 and across capacitor 70.
, and the voltage on line 71 decreases from 16V to 14V. If the light is applied to a non-toned (reference) sample,
The output of OP AMP61 is during the sample period for this toner-free area.
Diode 72 to turn on FET Q6
to bias. Thus, 14V on line 71 is
It passes through FET Q6 and is applied to capacitor 73. The voltage is stored until such time as a toned sample is taken by photocell 34.

When the toned sample is exposed to light, a voltage of 2 volts is again generated on line 66, provided that the toned sample has approximately the correct concentration. This means that regardless of whether light is applied to the reference sample or toner-coated sample, the current flowing through the photocell 34 will be the same because the current flowing through the LED 33 is set to a different current level as described above. It is from. Thus, once again a 2V voltage change occurs across capacitor 68, resulting in a 2V voltage drop across capacitor 70, reducing the voltage on line 71 from 16V to 14V. During the input period from the toned sample area, the FET
Q7 is turned on and FET Q6 remains off. Thus, the 14V or reference voltage on capacitor 73 is applied to the positive inputs of OP AMPs 74 and 75, while the sample input of the toned area on line 72 is connected directly to the negative input of OP AMP 74. And OP AMP7
5 through a voltage divider circuit. For example, if resistance values R21 and R22 are both equal, the potential at the negative input of OP AMP 75 will be the midpoint between the 14V and 16V inputs on line 71, or 15V.

In the OP AMP 74, a 14V reference signal is applied to the positive input while a 14V sample signal of the toned area is applied to the negative input. Since there is no difference in this case, the output of OP AMP 74 indicates that the toner concentration condition is correct and the low toner signal remains off. Similarly, in the OP AMP75, the non-toned sample input is 14V and the toned sample input is 15V.
, and thus the signal indicating an extreme drop in toner concentration is off.

However, assume that the patch to which the toner has been deposited has become significantly diluted in toner density. The result is an extreme increase in the reflection of light from the patch, a high excitation occurs in the photocell 34, and a potential on line 66, say 4V. In this example, a 4V variation occurs across capacitor 68, so the voltage on line 71
Drops from 16V to 12V. 12V is OP here
Appears directly on the negative input of AMP 74 and is compared to the 14V on the positive input, producing a high output and therefore turning on the "low toner" signal. The OP AMP 74 is designed to change output when a 30 mV difference occurs, and the toner low output signal is activated.
Referring to OP AMP 75, the toner deposition sample signal 12V on line 71 is divided down to 16V and produces 14V at the negative input of OP AMP 75 if resistors R21 and R22 are equal. Since both inputs are 14V, the toner extreme drop signal remains off.

Assume that a 6V variation appears on line 66, and therefore the toner-deposited sample is sufficiently toned to excite the photocell by raising the voltage on line 66 from 0V to 6V. the
A 6V variation reduces the voltage on line 71 from 16V to 10V. When 10V is divided by 16V (again R21
and R22), a voltage of 13V is applied to the negative input of OP AMP75.
When this 13V signal is compared to the 14V reference voltage, the toner extreme drop output signal is turned on.

It is desirable to provide a check signal to determine whether the test circuit is ready for operation during normal operation of the copier, ie, when there are no interruptions for test cycles. This is done by a circuit including transistor Q8. When transistor Q8 turns on, the negative input to OP AMP75 is grounded and therefore OP AMP
Increase the output of 75. As a result, the toner extreme drop signal is turned on. At the same time, OP
The voltage level at AMP 74 keeps the toner low output signal off. This creates an abnormal condition where the low toner signal is off and the extremely low toner signal is on. This condition is caused by the operation of transistor Q8, so during copier operation any change in this condition signals the copier logic that some fault has occurred in the test circuit. Transistor Q8 is turned on by the high output from OP AMP76. A high output from OP AMP 76 appears whenever the output of OP AMP 77 is high (ignoring the RC delay time). OP AMP 77 goes high when its negative input is lower than its positive input. Since the regular operating line 66 of the copier is 0V, OP AMP
It can be seen that the voltage at the negative input of 77 is lower than the positive side under normal conditions. However, if an untoned sample or a toned sample is taken, the voltage on line 66 will increase and therefore OP AMP 77
turns off the high output from OP AMP76, and therefore opens the circuit of transistor Q8.

Other quality tests possible with this circuit are:
To indicate when a measurement is performed on a sample without toner when the sample is actually covered with a large amount of toner as if it were a toner-covered sample. In this case, from LED 33 to photocell 34
Only a small amount of light reaches the. This causes photocell 34 to be excited much less than expected, so that the voltage on line 66 does not change appreciably, so that even though the non-toned sample is illuminated,
Transistor Q8 does not turn off because line 66 does not change by more than its steady state value. Therefore, the output of OP AMP 77 remains high and transistor Q8 remains on. In this case, the logic circuit detects that the toner extreme low output signal from OP AMP 75 remains on when it should have turned off to perform the test sequence. This signals the logic circuitry that there is an undesirable toner deposit on the photoconductor surface and that a corrective step is required. Thus, the circuit containing transistor Q8 also checks for unwanted toner build-up on the photoconductor surface and indicates the presence of a problem within the test circuit.

In testing for toner concentration, if a low toner signal is generated, the toner replenisher 35 (see FIG. 3) is operated to drop an amount of toner into the developer device 23. If a low toner signal and an extremely low toner signal are generated, further various actions occur depending on the copier design. For example, the first action would likely be to check for a "cartridge empty" signal from the toner replenisher 35. If the replenisher is empty, call the copier operator. However, if the replenisher stores an adequate amount of toner, the next action would be to shut down the copier. Instead of this,
The toner density check may be repeated after several copy processes until the toner extreme drop signal disappears. At any point, if the extremely low signal remains generated, the copier will be shut down.

As mentioned above, if a small number of copies are made, the test cycle is performed after making these copies. Skipping certain copying operations and performing test cycles in their place may be done when large numbers of copies are being copied over an extended period of time. Providing special control circuitry to interrupt copier operation at appropriate times to perform special test cycles will depend on the functionality required for the particular copier. Such circuit designs are well known in the prior art and do not form part of the present invention. Similarly, control systems for receiving low toner signals and extremely low toner signals for operating replenishers are well known in the prior art.

Although the present invention has been described in the context of a particular embodiment, a two-cycle transfer copier, it can be equally well used in a conventional single-stroke copier.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an electrostatographic copying machine using the present invention, FIG. 2 is a diagram showing the optical system and photoconductor drum of the copying machine of FIG. 1, and FIG. 3 is a passageway of the copying machine. 4 is a diagram showing the reflection intensity sensing element of the toner density control device, and FIG. 5 is a diagram showing the reference area on which toner is not deposited and the developed test area in the reproduced image area of the original. Figure 6 is a circuit diagram for processing reference information and test information, Figure 7 is a test cycle that overlaps with one copy cycle during a long copy process operation. FIG. 2 is a developed view of a photoconductor for explaining the process. 20...Drum, 32...Housing, 21...Charging corona, 33...Light source, 22...Pre-cleaning corona, 34...Photocell, 23...Developing device, 1
DESCRIPTION OF SYMBOLS 11... Control circuit, 24... Erasing lamp, 40... Original lamp, 36... Shutter, 26... Photoconductor, 3
8...Solenoid, 51...Slot.

Claims (1)

[Scope of Claims] 1. A photoconductor, a charged corona for generating a relatively uniform charge on the photoconductor, and forming a latent image corresponding to the image of the original on the charged photoconductor. a developing device having a toner supply device that supplies toner onto the photoconductor to form the latent image; a transfer corona station that transfers the developed latent image to an image bearing member; a plurality of erase lamps arranged to neutralize charge remaining on the photoconductor; and a cleaning station for cleaning and removing residual toner on the photoconductor after transfer; A first surface of the electrical conductor receives an original image of a first dimension.
an area for receiving an original image having a second dimension smaller than the first dimension; and a second area smaller than the first area and contained within the first area. , forming a test area with toner deposited on the first area of the photoconductor surface that is not included in the second area during a copying cycle for copying the original image of the second dimension; and controlling a particular one of the plurality of erase lamps to be turned off for a particular period of time so that the charge imparted on the photoconductor by the charged corona remains in the test area. means for irradiating light onto the test area to which the toner is attached by the toner supply device; and on the test area to which the toner is attached;
A copying machine comprising: detection means for detecting light reflected by the irradiation means and generating a signal representing toner density.