JPS60134313A - Ac bias controlling system - Google Patents

Abstract

PURPOSE:To simplify a circuit constitution for controlling an AC bias, by dividing an AC current into positive and negative, detecting its difference, and increasing or decreasing the AC bias so that it becoms equal to a set value. CONSTITUTION:This system controls an AC bias applied to an AC corona discharger 1, and its discharger 1 gives an electrification of positive and negative to the read side of a copying paper by generating alternately a corona discharge of positive and negstive, and it is shielded by a shielding case S except its part. This case S is grounded G through a resistance R1, and also connected to an operational amplifier A through a resistance R2. An integration circuit is formed by connecting a capacitor C1 between the other input terminal of this operational amplifier A and the output terminal, and by this output signal, an output is applied to said discharger 1 through a control part 3 for increasing or decreasing the AC bias of an AC high voltage unit 4. In this way, in case when a positive corona discharge quantity CP is more than a negative CM, it is detected by the integration circuit, and an increase instructing signal of the AC bias is outputted from the control part 3.

Description

Detailed Description of the Invention: Technical Field The present invention relates to an AC bias control system, and more specifically, an AC bias control system that applies an optimal AC bias to corona emitters of electrostatic copying machines, etc. Regarding.

Background and Prior Art> Electrostatic copying machines use a separation charger to peel off the copy paper from the photoconductor after transferring the toner image on the photoconductor onto copy paper, and a charger to separate the copy paper from the photoconductor. It has a static elimination charger, etc. to facilitate the collection of toner, and these chargers apply high voltage alternating current voltage (usually several KV) to perform positive and negative corona discharge. A□C50
A power discharger is used. To explain in more detail, as shown in FIG. 3, there is a photoconductor drum (
11) Around the electrified charge '4'''<' 12
), an exposure member □ (13), a developing device t (14), a transfer charger (is), a separation charger ('ig), and a cleaner (17) are arranged in this order □. Therefore, by applying a DC voltage of several kilovolts to the corona discharger as the charger (12), the photoreceptor drum (
The surface of the exposure member (11) is uniformly charged, and then the exposure member (13
) to irradiate reflected light from a document (not shown) to partially erase the charged state and form an electrostatic image corresponding to the document image. Thereafter, the developing device (14) forms a toner image by adsorbing toner charged to the opposite polarity to the surface of the photoreceptor drum (11), and then feeds the toner while in contact with the photoreceptor drum (11). The back side of the copy paper (P) to be printed is charged with a corona discharger as a transfer charger (15). Here, the DC voltage applied to the corona discharger is set so that the charging by the corona discharger is stronger than the residual potential charged by the charger (12). Thereafter, the copy paper (P) is peeled off from the photosensitive drum (11) by applying an alternating current voltage of several KV to an AC corona fi electric device serving as a separation charger (16). And the cleaner (
17), it is possible to collect the toner remaining on the photosensitive drum (11) and thereafter repeat the above operation again to perform a desired number of copying operations.

Here, in the state 111 (see FIG. 4) where the toner is adsorbed onto the copy paper (P) by the transfer charger (15), the amount of charge on the back side of the copy paper (P) is set to +χ1, and the separation charger (16) If the amount of positive charge irradiated on the back side of copy paper (P) is +χ2, and the negative charge m is -χ3, then
When the AC bias for the separated charge t-(16) is properly set, χ2=χ3, χ2〉〉χ1,
Since χ2+χ118=χ3, the toner is prevented from being attracted to the photoreceptor drum (11) more than necessary, and exhibits good peeling characteristics. However, if the AC bias is not appropriate and, for example, χ2+χ1>χ3, the photosensitive drum (11
) and move toward the cleaner (17), and on the other hand, if χ2+χ1<χ3,
The toner does not adhere well to the copy paper (P), resulting in poor image quality and increased wasted toner.
) has the disadvantage of increasing the burden. Therefore, conventionally, the positive charge amount +
The ratio between χ2 and the amount of negative charge - χ3 is set to a predetermined ratio, but since the rate of occurrence of positive and negative corona discharge by an AC corona discharger is easily influenced by temperature and humidity, Due to environmental changes such as these, the rate of occurrence of positive and negative corona discharges changes significantly, and stable copy paper peeling performance may not be achieved, or even if the peeling performance itself is good, image quality may deteriorate and toner may be wasted. This has disadvantages such as an increase in the burden tJ) on the cleaner (11).

In order to eliminate such inconveniences, a humidity sensor, etc. is used to detect environmental changes and use this detection signal as input to
It has been considered to change the AC bias of the discharger, but in this case, there are problems such as not only the circuit configuration for AC bias control becoming complicated but also a hexavalent one. There is.

In addition, after peeling off the copy paper (P), the photoreceptor drum (
11) Regarding the AC corona discharger as a snow removal charger (not shown) for removing the residual charge of i, the rate of occurrence of positive and negative corona discharges varies depending on environmental changes.
Not only is it not possible to obtain stable static elimination performance, but if a humidity sensor or the like is used to detect environmental changes and change the AC bias, the configuration becomes complicated and expensive.

<Purpose> The present invention was made in view of the above problems, and aims to detect A by directly detecting changes in the rate of occurrence of positive and negative corona discharges.
The purpose of this invention is to provide an AC bias control method that changes the C bias.

The AC bias control method of the present invention to achieve the above objective is to reduce the amount of A flowing into the shield case of a corona discharger, etc.
Divide the C current into positive and negative, detect the difference between the divided positive and negative,
The feature is that the AC bias applied to the corona discharger etc. is increased or decreased so that the detection output becomes equal to the set value.

<Examples> Hereinafter, examples will be described in detail with reference to the accompanying drawings showing examples.

Figure 1 shows A(, josu discharger) as a separate charger.
1) shows an electric circuit for controlling the AC bias applied to the circuit.

The AC corona discharger (1) generates positive and negative corona discharges alternately to give positive and negative charges to the back side of the copy paper (P), and is equipped with a shield case except for the part that directly faces the copy paper (P). (S). Incidentally, since the specific configuration is conventionally known, detailed explanation will be omitted.

The shield case (S) is connected to the ground (G) through a resistor (R1). In addition, the connection point (2) between the shield case (S) and the resistor (R1) is connected to one input terminal of the operational amplifier (A) via the resistor (R2), and the - of the operational amplifier (A>) A 7":y"J (CI') is connected between the input terminal and output terminal of '!5 to form an integrating circuit, and the other input terminal of the operational amplifier (A> is grounded (G ).Furthermore, the output signal of the integrating circuit is input to the A of the AC high voltage unit (4).
A control unit (3) is provided that outputs a signal to increase, decrease, or maintain the C bias, and the output horn signal of the AC high voltage unit (4) is applied to the ΔCC84 discharger (1).
is applied to.

If the above] is achieved, the positive corona discharge and negative corona discharge generated by the AC corona discharger (1),
Current flows through the resistor (R1), and the connection point (2)
A predetermined voltage V is induced. This electric current and voltage V are positive in the case of positive corona discharge, and negative in the case of negative corona discharge, and their respective absolute values increase as the number of corona dischargers increases.

Then, this induced voltage (■) is integrated by an integrating circuit, and the integrated output within a predetermined period is the positive corona radiation (im).
If cp is more than the negative discharger CM, it is positive; if the former is less than the latter, it is negative; if both are equal, it is 1'
becomes zero.

Therefore, this integral output is compared with a preset value, and if the integral output is larger than the set value, a signal instructing to increase the AC bias is output, and the integral output is smaller than the set value. If not, a signal instructing to decrease the AC bias is output, and the integral output is equal to the set value! If not, outputs a signal instructing to maintain the AC bias as it is, and uses this instruction signal as input to control the AC bias.
The AC bias of the C high pressure unit (4) can be increased, decreased or left unchanged.

Therefore, the positive corona discharge amount CP is the negative corona discharge f11
If the amount exceeds CM (see solid line A in Figure 2), the integrating circuit detects this state, outputs an instruction signal to increase the AC bias from the control section (3), and controls the AC high voltage unit (4)♀ Increasing the AC bias will increase the discharge 110M.
It is repeated until the ratio of cP and negative corona discharge fficM reaches a preset ratio (ratio i determined by the set value in the control circuit), and after reaching the preset ratio, , ACC high voltage Konicht/I) AC bias is maintained as it is (see the middle line in the i2 diagram).

On the other hand, when the positive corona discharge ff1cP is smaller than the negative corona discharge amount CM (see the solid line in FIG. 2B), the ratio of both corona discharges 'Jliffi reaches the preset ratio, contrary to the above case. After reducing the AC bias to the point where the AC bias is reduced, that state is maintained (see the broken line in FIG. 2B).

As is clear from the above explanation, due to changes in dryness, turbidity, etc., the ratio between the positive corona discharge m and the negative = IO discharge amount of the AC corona discharger (1) is a preset optimal ratio. The AC bias of the AC high-pressure unit is automatically adjusted to the optimum value if it deviates from the original value, resulting in poor copy quality and wasted toner.□ Stable I! This means that the separation performance of photographic paper (P) can be demonstrated.

It should be noted that this invention is not limited to the above embodiment at all, and can of course be applied not only to an AC corona discharger as a separate charger, but also to an AC corona discharger as a static elimination charger. It is possible to make various other design changes without changing the gist of the invention.

<Effects> As described above, this invention can be applied to shield cases for corona dischargers, etc. The AC current is divided into positive and negative, the difference between the divided positive and negative is detected, and the AC bias applied to the corona discharger etc. is increased or decreased so that the detected output is equal to the set value. It is not necessary to detect a single contact, and an environmental change detection sensor and an accompanying detection data processing device are not required, and the circuit 4M command for AC bias control can be simplified as a whole, which is a unique effect. .

In addition, when applied to a separate charger of an electrostatic compound machine and a static elimination charge sheet, the stable A(C bias control) I'llll performance and static elimination performance can be evaluated.

[Brief explanation of drawings]

Figure 1 shows an example of an electric circuit that implements the AC bias control I l/j formula of this defense, and Figure 2 shows changes in the rate of negative corona discharge due to AC bias. figure,
FIG. 3 is a schematic diagram showing the relationship among the photosensitive drum, various chargers, exposure members, and creep of an electrostatic copying machine, and FIG. 4 is a diagram illustrating the separation of copy paper by a separation chamber. (1)...]] Ronoh h'i electric appliance (3)...control unit, (4)...AC high voltage unit, (S)...shield case. Patent applicant: Mikuchi 1 Kogyo Co., Ltd. Figure 1 Figure 2 A Figure 2 B Figure 3 Figure 4

Claims (1)

[Claims] 1. Divide the AC current flowing into the shield case of the discharge device, etc. into positive and negative parts, □Detect the difference between the divided positive and negative parts, and □Detection output becomes equal to the set value. An AC bias control method characterized by increasing or decreasing the AC bias applied to a corona discharger, etc.