JPS58152273A - Transfer type electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To maintain the image potential of a photoreceptor at a specified value and to increase the speed of copying by expressing the characteristics of the photoreceptor by a specified reference equation, determining the quantity of the light projected by an optical system for projecting an image and correcting the reference equation successively at every copying. CONSTITUTION:A pattern 4 for forming a reference latent image corresponding to the reflection density in the background part of original image is installed on the rear of a top plate 3 on the side where the scanning of glass 2 of an original platen starts, and a temp. detecting element 16 as an element for detecting the characteristics of the photoreceptor 1 is provided near the photoreceptor. The surface potential of the photoreceptor 1 is detected with a detecting element 14. The quantity of the light projected by an optical system 5 for projecting image (the value of the voltage applied on an exposure lamp 6) is determined approximately at the value expressed by a reference equation, and the surface potential and surface temp. from detecting circuits 15, 17 are conducted to a control means 18 for exposure in follow up to the change in the characteristics of the photoreceptor 1 according to a change in temp. or continuous copying, whereby the reference equation is corrected successively.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a transfer type electrophotographic copying machine, and more particularly to a configuration for maintaining the amount of image projection light by an image projection optical system at an optimum value.

BACKGROUND ART In general, in a transfer type electrophotographic copying machine, in order to prevent the occurrence of fog in a copied image and stabilize the image quality, the potential of the electrophotographic photoreceptor after image exposure, specifically, the potential of the electrostatic latent image is controlled. An important problem is to form a reference latent image having a potential equivalent to that of the background portion, and to maintain the potential of the reference latent image at a constant value regardless of usage conditions, environmental conditions, etc.

This is because the potential of the background portion of the electrostatic latent image changes in response to changes in the sensitivity of the photoreceptor.

Therefore, the present inventors took advantage of the fact that there is a substantially constant proportional relationship between the potential of the reference latent image and the exposure lamp voltage, and
A method as shown in FIG. 1 was developed. The type of photoreceptor used in the experiment was a Se/Te alloy photoreceptor.

In FIG. 1, the horizontal axis shows the exposure lamp voltage (LV), the vertical axis shows the potential (IV) of the photosensitive drum surface in the area where the reference latent image is formed, and (VRE) is the final target. It is electric potential. The straight line ^ indicates the characteristics of the photoreceptor under standard usage conditions, environmental conditions, etc. The straight line (A') indicates the characteristics of the photoreceptor during actual use, which vary depending on various usage conditions, environmental conditions, etc.

The final target potential (VRE) is set to a potential that does not cause fogging on the copied image.

Since originals with various contrasts are used for actual copying, it is desirable to prevent fog from occurring in the copied images of the various originals. In this experiment, assuming that the reflection density of the background part of the original image is 0.25 or less, a pattern with a reflection density of 0.25 is used as the reference latent image forming pattern, and the final target potential (VRE) is set at the developing bias. was fixed at 300V, making it 300■. Note that under this condition, the portion of the electrostatic latent image corresponding to the portion of the original image with a reflection density of 0.25 or less, that is, the background portion of the electrostatic latent image, is not developed.

Therefore, under certain conditions of straight line (A), at the beginning of the formation of the reference latent image, a voltage of the value (LVo) is first applied to the exposure lamp, and in response to the detected surface potential ffl (Ivm), (Lvl ) A correction voltage of IVX-IVm is applied, and the same correction is repeated until the detected value of the surface potential reaches the final target potential (VRE), and then the copying process is performed.

However, as shown in Figure 1, (IVX) in the above equation is the tangent on the final target potential (VRE), in addition to the photoreceptor surface potential characteristics under standard conditions with respect to the exposure lamp voltage (tV). , and the value of the surface potential at the point where this tangent intersects with the vertical axis is conveniently set as a constant.

However, in this method, each time the voltage value for the exposure lamp is corrected, the photoreceptor drum is moved from the exposure position to the detection position by the distance (1) (see Figure 4), for a total of 1 correction number X (J
)', the photoreceptor drum must be moved needlessly by a distance of 0.00000000 0000000000000000000000000000000000000000000000000000000000000000000001001.001.002.

By the way, regarding the characteristics of the 5eaTe alloy photoreceptor, the above iMGA) (7) $1, the exact K is (IVX-VRE)
As shown in Figure 2, the value of /LV draws different curves depending on the temperature change of the photoreceptor drum, between when the copying machine is first used (curve B) and after long-term use (curve B'). These changes can be approximated by the quadratic formula (T P C-: surface temperature of the photoreceptor drum) when the temperature is 25°C or higher, and the linear formula when the temperature is below 25°C. It was confirmed through experiments by the present inventors that it can be approximated by .

Furthermore, as shown in Fig. 3, the number of consecutive copies repeated within a short period of time changes with different slopes at the beginning of the repetition (straight line C) and after many repetitions (straight line (, /)). 1
When it is repeated about 0 times, it can be approximated by the linear formula % formula %, and when it is repeated 10 times or more, it can be approximated by the linear formula Kg @
It was confirmed that it can be approximated by logN +Kg.

Purpose Therefore, the present invention has been made by paying attention to the above-mentioned experimental results, and its purpose is to eliminate the slowdown in copying speed by reducing the number of times of correction, and to adjust the image potential of the photoreceptor to environmental conditions. It is an object of the present invention to provide a transfer type electrophotographic copying machine that can quickly maintain a constant value regardless of conditions that affect the characteristics of a photoreceptor such as photoreceptor and usage conditions.

Summary As mentioned above, the optimum image projection light amount varies depending on environmental conditions, etc., but in the present invention, the conditions for obtaining the optimum image projection light amount are expressed using a certain standard formula, and the image projection optical system is The image projection light quantity, that is, the value of ('t, v) shown in FIG. 1 is approximately determined, and the second
As shown in Figures 3 and 3, the standard equation is successively modified in order to accurately approximate the value of (LV) in accordance with changes in the characteristics of the photoreceptor due to temperature changes and continuous copying. I made it.

Specifically, it includes an electrophotographic photoreceptor used to repeatedly form electrostatic latent images, a charging means for uniformly charging the surface of this photoreceptor, and a photoreceptor surface that corresponds to the original image. a reference latent image forming means for forming a reference latent image on the surface of the photoreceptor by the optical system; and a condition detection means for detecting conditions that affect the characteristics of the photoreceptor. a determining means for determining the amount of image projection light by the optical system according to the condition detected by the condition detecting means with a certain correlation specifically expressed by a reference formula; and a reference on the photoreceptor. a means for detecting a latent image surface potential; a means for correcting the amount of image projection light by the optical system so that the surface potential detected by the detection means has a desired value; and a latent image detected by the condition detection means. The transfer type electrophotographic copying machine is characterized by comprising means for successively correcting the reference equation based on usage conditions and the amount of image projection light by the optical system corrected by the correction means.

Embodiment FIG. 4 schematically shows the internal structure of a transfer type electrophotographic copying machine according to the present invention. (1) is a photosensitive drum, which can be rotated in multiple directions counterclockwise in the figure. (2) is a transparent original table glass', and the back side of the upper plate (3) on the original image scanning start side has a reflection density of 0.25, which corresponds to the reflection density of the background part of the original image.
A halftone reference latent image forming pattern (4) is installed.

(5) is an image projection optical system and an exposure lamp (6).

It is composed of reflecting mirrors (7), (8), (9), (10), and a projection lens (11), and when projecting an image, the exposure lamp (6) and the reflecting mirror (7) are connected to the photoreceptor drum (1). Circumferential speed (v
), the reflecting mirrors (8) and (9) can scan leftward in the figure at a speed of (''/2V).

(c) A potential detection element whose detection output is the surface potential detection circuit (1
5). (16) is a temperature detection element installed near the photoreceptor, and its detection output is the surface temperature detection circuit (17
) is entered. Further, an exposure lamp power source (1g') connected to the exposure lamp (6) is connected to an exposure control means (18).
The exposure control means (18) receives outputs from the surface potential detection circuit (15) and the surface temperature detection circuit (17).

Reference numeral (19) denotes a magnetic brush type developing device, in which a fixed developing bias is applied by moving the developer in multiple clockwise directions on a developing sleeve (20) containing a magnet roller (21). Therefore, an electrostatic latent image with a potential of 300 Å or less is not developed.

Also, (22) is a transfer charger, (23) is a copy paper separation charger, (24) is a residual toner cleaner, (
25) is a residual charge eraser lamp.

On the other hand, (26) is a paper feed cassette, and (27) is a paper feed slot.

-La, (28) is a conveyance roller, (29) is a conveyance belt,
(30) is a heat roller type fixing device, (31) is a discharge roller, and (32) is a discharge tray.

Note that the environmental conditions to be detected include temperature, humidity, absolute humidity, and the like. In this example, Se* was used as the photoreceptor.
A Te alloy photoreceptor is used, and since the characteristics of this photoreceptor are highly temperature dependent, the surface temperature of the photoreceptor is detected in this embodiment. Of course, several types of environmental conditions may be detected, but the more objects to be detected, the more complex the standard equations detailed below will be, so it is generally desirable to detect only the most highly dependent conditions. . For example, Cd
In the case of an S resin photoreceptor, humidity detection is desirable.

Next, the principle of determining the reference formula will be explained.

As shown in FIG. 5, (X1e,yt), (X2
* When approximating the correlation between X and y from n sets of data of α and β must be values that minimize the value of S below.

-11 The condition for the minimum value of S is as follows, and α and β that satisfy such conditions can be derived as solutions of the following simultaneous equations.

That is, α and β are derived from the following determinant.

On the other hand, as shown in Fig. 6, (X□, y□), (x2
．． y2)...("If the correlation between X and y is approximated by the formula y-αζ+βχ+γ 01101091.■I based on the least squares method from n sets of data of yl+YJ, then For the same reason, α, β, and r are derived from the following determinant.

Note that approximation of cubic or higher order equations is also possible in the same manner as described above, but in this embodiment, linear equations and quadratic equations are handled.・Subsequently, in this embodiment, the image projection light amount by the image projection optical system (5) [voltage value applied to the exposure lamp (6)]
The process for determining the value will be explained with reference to the flowcharts shown in FIGS.

Briefly, as shown in FIG. 7, after the main switch is turned on, the process proceeds to chart A (FIG. 8), chart B (FIG. 9), and chart C (FIG. 10), and this cycle is repeated m times. This cycle is fixed! (30) This is to make effective use of the time left for initial stabilization during warm-up of heaters, etc., and to modify the standard formula to suit the environmental conditions, and the above 1 m' can be set arbitrarily. .

In addition, immediately before the step in chart A (both after turning on the main switch and turning on the print switch 4, or either one)
A process for controlling charging may be inserted.

Then, each time the print switch is turned on, the flow advances to chart A, chart B' (FIG. 11), and chart C, the reference equation is successively corrected, image exposure is started, and a well-known copying operation is performed.

Note that chart B' may be the same as chart B, but if the photosensitive drum is replaced or the copying machine is stopped for a long period of time, it may be approximated by a pre-stored reference formula. There may be a significant difference between the characteristics of the photoreceptor and the characteristics of the actual photoreceptor, so we purposely used Chart B to ensure durability and avoid slowing down the copying speed due to excessive convergence time to the target value. Being different =
However, since the cycle repeated m times after the main switch is turned on is processed during the warm-up time of the copying machine, there is no problem even if the convergence time is slightly extended. For this reason,
Processing as shown in chart B' is intentionally not performed.

As a specific method for shortening the convergence time, Char)B
As shown in Figure 3), the previous control convergence value is stored separately, and after the print switch is turned on, a weighted average of the stored value and the calculated value of the latest data is calculated. is set as the voltage (LV) to be applied to the next exposure lamp. Note that the contribution coefficient of the factor (γ
1) is selected in the range of 0.1 to 10, and in this embodiment, approximately 1 is appropriate.

In detail, these controls are performed by a microcomputer.
It is designed to be sequence controlled.

As shown in Fig. 8, the random access memory (RAM) of the microcomputer is stored in a standard that has been previously obtained as a result of 0 copying experiments under the condition that the surface temperature (TPC) of the photoreceptor drum is TPC≧25°C. The respective values of the data 3 to h for formula determination and the data i-m for determining the standard formula obtained as a result of 0 copying experiments under the condition of TPC (25° C.) are stored.

In addition, in the above experiment, the temperature (TPC) of the photoreceptor drum was changed, and at that time, the reference latent image surface potential was changed to the final target potential (V
RE), specifically by determining the exposure lamp voltage (LV) suitable for achieving 300V (negative polarity). Note that the constant (IVX) at this time was set to 1180. Further, the charging potential of the photoreceptor drum is 600V (negative polarity). As a result, (TPCl.

LV+) . . . -(TPCn, LVn) n sets of data are obtained.

Specifically, the value of aym is as follows.

a - ETPCL (1,155X109) [=1 b=ΣTPC," (3,411X10)1=1 c =;TPC,"(1,027X10')t
=1 d=ΣTPC, (3,163X] O')L==1 e =n (1,0X103)f-Σφ,
・TPCt (1,759X107) [=1 g-Σφ1・TPO, (5,374X105) [=1 h=Σφ't (1,684X10')t=1 Above, TPC and 25°C However, i-ΣTPC (3,4033X105) [ -1 j-ETPCL (1,767X10) (=1 to = n (1,0X103)l-Σφ,
・TPC, (2,695
), the temperature (TPC) and exposure lamp voltage (LV) data can be obtained after turning on the main switch or every copying cycle by turning on the print switch.

That is, after turning on the main switch, the values of a-m stored in the random access memory (RAM) are read out in step (2), 1 to 5 are calculated in step (2), and the reference formula is calculated in step (3). decide.

In step (2), the photoconductor temperature (TPC) is detected and stored, and in step (2) it is determined whether the photoconductor temperature (TPC) is higher than 25°C. "If YESJ, substitute the value of the photoconductor temperature (TPC) into the 0 equation in step ■, and determine the exposure lamp voltage (LV). If "NO," in step ■
By substituting the value of the photoreceptor temperature (Tpc) into the equation, the exposure lamp voltage (LV) is determined. .

Next, move to chart B in FIG.
1), and in step [phase], a current having the value of ('LV) is applied to the exposure lamp, and slightly prior to this, in step 2, rotational driving of the photosensitive drum is started. Next, in step f@, the photoconductor surface potential (vpc) is detected, and in step 0, it is determined whether 1 vpc-VREI≦ε, that is, the difference between the detected photoconductor surface potential (vpc) and the final target potential (VRE). It is determined whether the difference is within the tolerance (ε).

The photoreceptor surface potential (vpc) in step @ is detected when the exposure lamp (6) voltage (LV) is applied to the exposure lamp, as shown in FIG. Point (a) of drum (1) moves distance (J) 1
The timing is set so that the detection is performed when the surface potential detection element (14) is opposed to the surface potential detection element (14).

If it is determined as "YESJ" in step [phase], image exposure is started and copying operation is performed, and the process moves to chart C in FIG. 9.On the other hand, if it is determined as "NO", in step The applied voltage (LV
) to the value obtained by multiplying this value by the value of IVX-VRE IVX-VPC, and return to the step ■.As long as it is determined to be "NO" in step [phase], step ■~■
Repeat. However, if it is repeated more than the specified number of times,
Exposure lamp burns out, photoconductor drum (etc.). Therefore, if the exposure lamp burns out, the photosensitive drum (etc.
The copy machine is now deactivated.

On the other hand, after the print switch is turned on, as shown in FIG.
M2) and memo it in step O! The next exposure lamp voltage (LV) is determined based on the weighted average value of the previous convergence value stored in J (Ml).

In this case, in step ■, memories (Ml), (M2
) is corrected to the value obtained by multiplying this value by the value of IVX VRE IVX-VPC. Therefore, each time step 0 is passed, the values of memories (Mx) and (Mg) become equal.

Next, new values of 3' to d are calculated by Char)C in FIG. 10, and the reference equation is successively corrected.

That is, the photoreceptor temperature (TPC) is 25° in step [phase].
Determine whether it is higher than C, and if YES, the value of 3 to h is stored in step [phase] (TPC).
, (LV) are substituted into the 0 formula to calculate a' to h',
In step 0, the values 3 to h stored in the random access memory (RAM) are replaced and modified with the values 3' to h', and the process returns to (*4) or (*5) in FIG. Also, “NO
”, then in step [phase], substitute the value of ixm and the stored values of (TPC) and (LV) into the equation 0 to obtain i'
~m' is calculated, and in step [phase], the value of ixm stored in the random access memory (RAM) is calculated as i'~m
'Replace and modify the value of (*4) or (*5) in Figure 7.
Return to

In this chart C, when finding the values 3' to m', the value of arm is multiplied by (1-1/N). However, in this example, N=1000, which is the latest ( TPC,
This is to reduce the contribution rate of the data of LV) to previous data, and to prevent the value of 3 to m from exceeding the storage capacity of the random access memory (RAM) if it is infinitely large.

In the embodiment described above, only the photoreceptor temperature was focused on and controlled as a determining factor of the exposure lamp voltage, but other factors such as the number of continuous copying repetitions, pause time, etc. are also stored as data.
If control is performed that also takes into account changes in the characteristics of the photoreceptor, more accurate and rapid control will be possible.

Therefore, as another example, 1 of the photoreceptor temperature (TPC)
Also, a case will be explained in which the number of consecutive copy repetitions (N) is used as a determining factor.

FIG. 12 shows the process of determining the applied voltage value to the exposure lamp according to FIG. 7, and charts A, B, B
', C are the figures 8, 9, 11, and 1, respectively.
As shown in Fig. 0, C, C, and Ct are the 13th
14.

Basically, the predicted value LV (TPC) obtained by successively modifying the reference formula based on the temperature characteristics of the photoreceptor, and the predicted value LV (N
) and the exposure lamp voltage (LV) applied by the weighted average of
I am trying to decide. Note that the weighted average here means setting the contribution ratio of each factor to the change in photoreceptor characteristics, and multiplying each factor by an appropriate coefficient.

Specifically, in chart A', in step [phase], the value of P~2 stored in the random access memory (RAM) is read out, and in step [phase], it is determined whether the rest time (TR) is O or not. . This rest time (TR) refers to the time between each copy cycle. That is, the step [phase] is for checking whether or not continuous copying is being performed, and the downtime during which no copying operation is performed has also been confirmed as a factor in changing the characteristics of the photoreceptor. If step [phase] is [YESJ], "1" is added to the number of repetitions (N) in step [phase].

Next, in step [phase], it is determined whether the number of repetitions (N) is smaller than 10 or not. [If YESJ, step [
6°K7 is calculated in step [phase], and a reference formula is determined in step [phase].

Also, if “NO”, step [phase] is 8, K.

is calculated, and the reference formula is determined in step [phase]. In step [phase], the exposure lamp voltage LV (
The applied voltage (LV
) to determine. Note that (γ2), which is the contribution coefficient of the factor, is selected in the range of 0.1 to 10, and approximately 1 is appropriate in this embodiment.

On the other hand, chart C' shows the number of repetitions (
Determine whether N) is smaller than 10, and if YES, in step [phase], convert the values of (TPC) and (LV) stored as the value of p −y u into the 0 formula. Substitute P′
~U' is calculated, and the value of p-u stored in the random access memory IJ (RAM) is calculated in step [phase].

~Replace/correct with the value of U'. In addition, [if NOJ, the value of v-z is stored in step [phase] (T
Substitute the values of PC) and (LV) into the formula 0 and calculate V'~Z'.
The value of V 1%-Z stored in
Replace or modify the value.

In addition, in the present invention, the amount of image projection light by the image projection optical system is controlled by regulating the amount of light applied to the electrophotographic photoreceptor during exposure, in addition to controlling the voltage applied to the exposure lamp as shown in the above embodiments. A method such as controlling the width of the slit may also be used.

Effects As is clear from the above explanation, according to the present invention, the characteristics of the photoreceptor are expressed using a certain reference formula to determine the amount of light projected by the image projection optical system, and the characteristics of the photoreceptor during actual use are determined. Since the reference formula is successively corrected for each copy according to changes in the sensitivity of the Since the optimal image projection light intensity of the image projection optical system is determined accurately, it is not necessary to repeat the correction many times for each copy, as in the method shown in Figure 1. Therefore, the copying speed will not be slowed down. Moreover, the above-mentioned reference formula itself not only adapts to usage conditions and environmental conditions, but also varies in characteristics due to the production loft of the photoconductor, variations in the installation position of the image projection optical system, dirt on the optical system, and deterioration of the exposure lamp. Therefore, it is possible to effectively control the image projection light amount suitable for each copying machine.

[Brief explanation of the drawing]

1, 2, and 3 are graphs showing the sensitivity characteristics of the photoreceptor obtained through experiments by the present inventors, and FIG. 4 is a schematic diagram of a transfer type electrophotographic copying machine according to the present invention. Figures 5 and 6 are graphs for explaining the determination of the reference formula, Figures 7 to 1.
FIG. 1 is a flowchart explaining the operation of one embodiment, and FIGS. 12 to 14 are flowcharts explaining the operation of other embodiments. (1)...Photosensitive drum, (4)...Reference latent image forming pattern, (5)...Image projection optical system, (6)...
・Exposure lamp, (14)...Surface potential detection element, (1
5)...Surface potential detection circuit, (16)...Temperature detection element, (17)...Surface temperature detection circuit, (18)...
- Exposure control means, (18')...Exposure lamp power supply. Patent applicant Minolta Camera Co., Ltd. Agent
Patent attorney Seihaku Ao and two others Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 4-, -1A East 1 meeting] Gi 2. -6 w59 figure 10th figure 3 or Kyo 7 small. or"5 Figure 11 Temart δ'6 Book 7"(Sude-1-BorB') Procedural amendment (spontaneous) September 2, 1980 Commissioner of the Japan Patent Office 1 Indication of the case 1988 Patent Application No. 34768 No. 2 Name of the invention Transfer type electrophotographic copying machine 3 Relationship with the case of the person making the amendment Patent applicant address 2-f, Azuchi-cho, Higashi-ku, Osaka City; Yama i station i, S
We will correct the Mill 4 representative drawings Medium Temperature Diagrams 8 and 11 as shown in the attached sheet. Figure 8xl Tomi 2 or π6 Figure 11 χ6

Claims (1)

[Claims] 1. an image projection optical system that projects an image onto an electrophotographic surface used to repeatedly form an electrostatic latent image; a reference latent image forming means that forms a reference latent image on the surface of the photoreceptor by the optical system; condition detection means for detecting conditions that affect body characteristics; and image projection by the optical system according to the conditions detected by the condition detection means with a certain correlation specifically expressed by a reference formula. determining means for determining the amount of light; means for detecting a reference latent image surface potential on the photoreceptor; and controlling the image projection light edge by the optical system so that the surface potential detected by the detecting means becomes a desired value. A transfer device characterized by comprising: means for correcting; and means for successively correcting the reference formula based on the usage conditions detected by the condition detecting means and the amount of image projection light by the optical system corrected by the correcting means. Model electrophotographic copying machine.