JPS6140988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image adjustment correction method for an electrophotographic copying machine.

Conventionally, in this type of image adjustment correction method,
This is done by changing the exposure amount or developing bias potential, and this can be done either by a service person during maintenance or automatically by a built-in device. First, in the case of the former, a sensory test is carried out in which the copied image is visually observed using a reference original for adjustment, but since such a method is sensual, there is a large amount of variation, and it is difficult to identify the root cause of the variation. However, there is also the disadvantage that maintenance intervals must be shortened, and adjustments can only be made by service personnel. In addition, in high-end machines, the exposure amount, latent image potential, and development bias potential are measured with a measuring device and returned to set values, but such means maintain variations in process conditions. Although it has advantages, it has disadvantages in that it can only be adjusted by a service person and that it takes a considerable amount of time.

There is also the latter method described above, in which the electrostatic latent image potential is detected by a potential detector using a reference original, and the exposure amount or bias potential is automatically corrected. It has the disadvantage of high cost because it uses a device. Although the cost can be considerably reduced by using it in conjunction with an auto-bias potential detector, there is a problem in that reliability is considerably low due to the large number of parts.

The present invention has been made in view of these points, and an object of the present invention is to provide an image adjustment correction method for an electrophotographic copying machine that can be adjusted to a constant state with high reliability without requiring any special technology. purpose.

In an electrophotographic copying method in which the quality of a copied image is adjusted by changing the exposure amount or development bias potential, the present invention provides a development bias during development of an electrostatic latent image in response to changes in light amount over time or changes in characteristics over time of a photoreceptor. By detecting the applied current direction or current value and adjusting the exposure amount or developing bias potential so that this current value becomes zero or a constant value, the same copy image quality can be achieved at the same copy image quality adjustment level as the initial one. This feature is characterized in that it is corrected to.

Embodiments of the present invention will be described with reference to FIGS. 1 to 3. First, around the drum-shaped photoreceptor 1, there is a charging section 2, an exposing section 3, a developing section 5 including a developing sleeve 4, a transferring section 6, a static eliminating section 7, and a cleaning section 8.
are arranged sequentially. A light source 11 is provided at the bottom of the contact glass 10 on which the original 9 is placed.
An optical system consisting of a mirror 12, an imaging lens 13, etc. is provided, and a slit 14 for adjusting the amount of exposure is provided immediately in front of the exposure section 3. The wire 15 connected to this slit 14 is wound around an eccentric image adjustment correction dial 16 and then connected to an image adjustment knob 17. It is positioned by engaging with one of the position setting portions 18 that set the three positions. Also,
A bias power source 20 is connected to the developing sleeve 4 via an ammeter 19.

Using the image adjustment condition correction document 1, the initial conditions are set so that the developing bias current is zero at the general document position. If it is used in this state for a period of time, the exposure amount will change over time due to deterioration of the light source 11, dirt on the mirror 12, etc., and changes in the characteristics of the photoreceptor 1 will occur, causing the process conditions to become unbalanced. In this case, the image adjustment correction dial 16 is turned to change the position of the slit 14, thereby changing the exposure amount. That is, in FIG. 3, the opening width of the exposure slit is from the position D _S to D _T
If the position is changed to , the developing bias current becomes zero and can be set to the initial condition.

The principle is that when the photoreceptor 1 is positively charged, the developing bias potential V is as shown in FIG.
_B and the electrostatic latent image potential V _S of the photoreceptor are shown by the dashed line during development. In the state where V _S = V _B , the current becomes zero because the potential is the same, and when V _B > V _S , the developing sleeve 4 A current flows through the photoreceptor 1, and conversely, when V _S >V _B , a current flows from the photoreceptor 1 to the developing sleeve 4. Therefore, the development bias potential V _B which is initially fixed constant in the general document position
(K) Original 9 where the current becomes zero,
That is, assume that the electrostatic latent image potential of the photoreceptor is in a state of V _S (S), and then when similarly measured at a certain time point, the electrostatic latent image potential of the photoreceptor has become V _S (T). Therefore, the current flows from the photoreceptor 1 to the developing sleeve 4 (this state is defined as the direction). Therefore, if the exposure amount is increased by widening the opening width of the slit 14 by turning the image adjustment correction dial, the potential of the electrostatic latent image on the photoreceptor becomes V _S (S).
The development bias current becomes zero and the adjustment is completed. However, in this method, it is impossible to make corrections by developing the original once because the time is too short, so corrections are made by performing development multiple times.

Next, another embodiment of the present invention will be described based on FIGS. 4 and 5. The same parts as in the previous embodiment are designated by the same reference numerals, and the description thereof will be omitted. This embodiment relates to an image adjustment method in which the exposure amount is fixed and the potential level of the developing bias potential is switched by a document type selection button 21 having, for example, three positions.
That is, the document type selection button 21 is connected to the voltage control circuit 22, the voltage generation circuit 23, and the current detection circuit 2.
4, and a discrimination circuit 25 and a switch 26 are connected between the current detection circuit 24 and the voltage control circuit 22.

Therefore, when reference original 1 is used, at the initial start, the electrostatic latent image potential on the photoreceptor is V _S (S) and the developing bias potential is V _B (S), and V _S (S) = V _B
(S), the developing bias current I _B is zero. Then, at a certain point in time, since the exposure amount has decreased, the potential of the electrostatic latent image on the photoreceptor has reached V _S (T). Therefore, since the current line bias current I _B is not zero, the current detection circuit 24
detects this, and based on this signal, the discrimination circuit 25
operates, and the voltage control circuit 22 increases the developing bias potential based on the signal. Then, the developing bias potential becomes V _B (T) and V _S (T) = V _B
(T), the developing bias current becomes zero, and the signal for controlling the voltage from the discrimination circuit 25 is stopped. Since such a state is automatically performed, the correction operation can be sufficiently performed by copying one sheet of the reference original. Of course, when performing this operation, the switch 26 is set to the B side, and during normal copying, it is switched to the A side.

Next, still another embodiment of the present invention will be described based on FIGS. 6 to 8. In this embodiment, the exposure amount changes in three steps, the background latent image potential is calculated and detected in the electrostatic pattern of the original 9, and an additional potential is added to the detected potential to avoid background smearing, and the potential is applied to the developing bias. This relates to an image adjustment method using a so-called auto-bias method in which a potential is applied. First, the developing section 5 is of a wet type, and the developer 27 is driven by a pump 29 from a developer tank 28 in which a developer 27 is stored, and is sent onto a developing plate 30. It is connected to other parts of the developed developing tray 30 through a detection circuit 31, an arithmetic control circuit 32, a switch 33, and a current detection circuit 34, and the A terminal of the switch 33 is also connected to the developing tray 30. . Further, a drive motor 37 for operating the image adjustment correction dial 16 is connected to the current detection circuit 34 via a discrimination circuit 35 and a control circuit 36. Therefore, in the initial stage, the potential of the electrostatic latent image on the photoreceptor is set to the potential V _B applied by auto bias using the reference original 9 that supports V _S (S) at point P in FIG.
has the relationship of V _B =V _S +V _K (additional potential), so the bias current I _B =I _K ≠O. Then, for the same reason as in the above case, the latent image obtained on the reference original 9 at a certain time point is V _S
(T), and the current I _B flows as I _B <I _K .
This state is detected by the surface potential detection circuit 31, and the signal drives the drive motor 37 via the arithmetic control circuit 32, current detection circuit 34, discrimination circuit 35, and control circuit 36 to move the slit 14 and adjust the exposure amount. and stops when the control signal in the determination circuit 35 disappears.

Furthermore, the case shown in FIG. 7 is a case in which the current applied to the bias voltage to the developing plate 30 does not need to be directly measured. The auto bias circuit includes an upper limit bias potential regulation circuit that prevents the bias potential from rising above a certain level in order to prevent the contrast of photographic images from decreasing.
A parallel circuit of a constant voltage element 39 such as a Zener diode or a varistor, a resistor 40, and a light emitting diode 41 is connected in series to the developing plate 30 to which a resistor 40 and a light emitting diode 41 are connected. Therefore, the current flowing through the constant voltage element 39 turns ON and OFF at point P in FIG.
Therefore, the light emitting diode 41 is turned on and off. Therefore, by setting the reference document 9 that provides a photoreceptor electrostatic latent image potential that comes to point P, the same function as in the above case can be obtained.

In each of the above embodiments, the reference original 9 is used. However, it is also possible to adopt a method of setting the detection lamp illuminance so that the amount of exposure that reaches the photoreceptor 1 is constant. . According to such means, the correction operation can be carried out completely automatically by employing any of the methods of the above-described embodiments during the warm-up period after the power is turned on every day.

Since the present invention is configured as described above, even if the process conditions become unbalanced due to changes over time after the initial conditions are set, the current direction or current value applied to the developing bias during development of an electrostatic latent image can be detected. Image adjustment correction can be performed by adjusting the exposure and development bias potential so that this becomes zero or a constant value, and this method is highly reliable, the equipment is inexpensive, and it requires special skills. This has the effect that it is possible to carry out corrections even without having the above.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the present invention, FIG. 2 is a graph showing the relationship between the electrostatic latent image potential on the photoreceptor and the developing bias potential, and FIG. 3 is a graph showing the relationship between the exposure slit opening width and the developing bias current. Graph showing the relationship, FIG. 4 is a side view showing another embodiment of the present invention, FIG. 5 is a graph having the same properties as FIG. 2, and FIG. 6 is a side view showing still another embodiment of the present invention. , Fig. 7 is a circuit diagram with an upper limit bias potential regulation circuit installed, and Fig. 8
The figure is a graph of the same nature as Figure 2.

Claims (1)

[Claims] 1. In an electrophotographic copying method in which the quality of copied images is adjusted by changing the exposure amount or developing bias potential, the applied current of the developing bias when developing an electrostatic latent image is adjusted in response to changes in light amount over time or changes in characteristics over time of the photoreceptor, etc. By detecting the direction or current value and adjusting the exposure amount or developing bias potential so that this current value becomes zero or a constant value, correction is made to the same copy image quality adjustment level as the initial copy image quality. An image adjustment correction method for an electrophotographic copying machine, characterized in that: