JPH0328711B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge control device for a recording device that maintains a constant voltage applied to an ion flow control member affected by an ion flow from an electrode.

By the way, the term "grounded" in this specification may be actually grounded or may be connected to the housing of the recording device. In the following description, a case will be described in which an electrophotographic copying device is used as a recording device and a scorotron grid is used as an ion flow control member.

A conventional example is shown in FIG. 1 and FIG. 2.

In FIG. 1, by connecting a varistor VD ₁ (or a Zener diode) between the grid 3 and ground, even if the voltage of the high voltage power supply 1 exceeds a predetermined voltage, the ion flow from the charged electrode 2 increases and the grid 3
Even if the voltage V _G applied to the grid 3 increases, the voltage V _G applied to the grid 3 is kept constant. It is true that this method is low cost and highly stable. However, in the case of an electrophotographic copying apparatus, the charging characteristics of the photoreceptor 41 change due to temperature changes, fatigue, etc. Therefore, if the voltage V _G applied to the grid 3 is fixed as shown in FIG. It has the disadvantage of not being able to compensate for changes in characteristics. That is, after the photoreceptor 41 becomes fatigued due to repeated copying, the charged potential of the photoreceptor 41 decreases even if the discharge ion flow remains constant.

The second conventional example to eliminate such drawbacks is
It is a diagram. This is grid 3 with high voltage regulated power supply 1
1, the voltage applied to the grid 3 can be made variable in accordance with changes in the charging characteristics of the photoreceptor 41. However, the disadvantage is that the device itself becomes large. Furthermore, unless the output impedance of the high-voltage stabilized power source 11 is made sufficiently low, the output voltage of the voltage stabilized power source 11 will not be constant due to the flow of current from the grid 3. In other words, a high-voltage stabilized power source with low output impedance is required, and such a high-voltage stabilized power source has the disadvantage of being expensive and unsuitable for manufacturing actual devices.

As mentioned above, a discharge control device for a recording device that eliminates the drawbacks of conventional devices such as not being able to compensate for changes in the charging characteristics of a photoreceptor or being large and expensive has been proposed by the present applicant in the same day. Filed by patent application.

In this invention, a variable impedance element is connected between an ion flow control member and a ground side, and an error amplifier detects the difference between the voltage applied to the ion flow control member and a variable set voltage. The variable impedance element is controlled based on the signal. Such a simple configuration eliminates the conventional disadvantages of not being able to compensate for changes in the charging characteristics of the photoreceptor, or that the device is large and expensive, and makes it possible to control the ion flow control member according to the set voltage. An object of the present invention is to provide a discharge control device for a recording device in which the applied voltage can be freely set and kept constant.

The present invention will be explained with reference to FIGS. 3 to 5. First, the basic principle is shown in Figure 3. This is done by connecting the variable impedance element _VZ between the grid 3 and ground, and controlling the grid 3 by the control circuit 5.
The impedance of the variable impedance element _VZ is changed so that the voltage applied to the variable impedance element VZ becomes constant. According to this basic principle, a high-voltage power supply is not required in terms of circuitry, and the voltage applied to the grid 3 can be set to any value by the control circuit 5.

Next, FIGS. 4 and 5 show an embodiment of the present invention. Note that this is an example applied to a device for negative charging. The voltage V _G applied to the grid is divided and detected by the resistors R ₁ and R ₂ connected between the grid 3 of the Scorotron 2 and the ground, and the difference between this divided voltage and the set voltage V _S is detected by the error amplifier. AMP1, AMP
By amplifying it by 2 and adding it to the base of the transistor Tr connected between grid 3 and ground,
This is to keep the voltage V _G applied to the grid 3 constant. Therefore, by changing the set voltage V _S , the voltage V _G applied to the grid 3 can be changed. Of course, the present invention can also be applied to devices for positive charging. In that case, an NPN type transistor may be used as the transistor Tr, and the polarities of the base protection diode D and the set voltage V _S may be reversed. Here, a scorotron grid is used as an example of the ion flow control member, but it may also be a back plate of a charged electrode or a screen electrode. Further, although a general bipolar transistor is used as the variable impedance element, an FET, a phototransistor on the output side of a photocoupler, CdS, etc. may also be used. Here, the set voltage V _S is made semi-fixed by a variable resistor VR. However, in further development, the potential of the photoconductor can be adjusted by detecting the potential, temperature, fatigue, etc. of the photoconductor, changing the set voltage V _S according to the detected values, and controlling the voltage V _G applied to the grid 3. Of course, it can be stabilized. The present invention is very convenient in making the charging potential variable based on various conditions in this way.

In FIG. 5, a varistor VD ₂ is connected between the grid 3 and the transistor Tr in FIG. 4. With this method, the voltage applied to the varistor VD ₂
Since V _A is constant and the voltage V _G applied to the grid 3 is divided by the varistor VD ₂ and the transistor Tr, the voltage V _T applied to the transistor Tr becomes low. Therefore, the voltage applied to grid 3 V _G
Although the variable range of is narrower than in the case of Fig. 4,
This has no effect at all compared to changes in the charging ability of the photoreceptor. Therefore, there is an advantage that a low-cost transistor Tr with a low collector breakdown voltage can be used. When actually using an OPC photoreceptor, the absolute value is that the voltage applied to the varistor VD ₂ is about 430 [V], and the voltage applied to the transistor Tr is 0 to 100.
It is sufficient to make the voltage variable by about [V].

The present invention relates to an improvement of the discharge control device for a recording device as described above, and is characterized in that the voltage applied to the ion flow control member is used as the power supply to the error amplifier.

An embodiment of the present invention is shown in FIG. 6 and FIG. 7, respectively.

In Figure 6, low power operational amplifiers with low power consumption are used as error amplifiers AMP1 and AMP2, and voltage V _G applied to grid 3 is used as power supplies V ⁺ and V ^- to be supplied to error amplifiers AMP1 and AMP2. It is something to do. Therefore, there is an advantage that no special power supply is required to operate the error amplifiers AMP1 and AMP2. A resistor R ₃ and Zener diodes ZD ₁ and ZD ₂ are connected in series between the grid 3 and the ground, and the contact A of the resistor R ₃ and the Zener diode ZD ₁ is used as an error amplifier.
Connect to the negative power supply terminal V ^- of AMP1 and AMP2.
Further, the contacts B of the Zener diodes ZD ₁ and ZD ₂ are connected to the non-inverting input terminals of the error amplifiers AMP1 and AMP2 to have a midpoint potential. Error amplifier AMP1,
The positive power supply terminal V ⁺ of AMP2 is grounded. In this experiment _{, 12}
[V] was used, so the potential at point A was -24
[V], the potential at point B is -12 [V], -12 [V]
The error amplifiers AMP1 and AMP2 operate based on this. Also, grid 3 and transistor Tr
It is of course possible to lower the withstand voltage of the transistor Tr by connecting a varistor between the transistor Tr and the transistor Tr.

In FIG. 7, the positive power supply V ⁺ of the error amplifiers AMP1 and AMP2 is supplied from outside, and the negative power supply V ^- is supplied using the voltage V _G applied to the grid 3. A resistor R ₄ and a Zener diode ZD ₃ are connected in series between grid 3 and ground, and a resistor R ₄
and contact C of Zener diode ZD ₃ as error amplifier.
Connect to the negative power supply terminal V ^- of AMP1 and AMP2.
Generally speaking, the control section of an electrophotographic copying machine is +5
Since many of them operate with a single positive power supply of [V] or +10 [V], they are suitable when actually incorporated into an electrophotographic copying apparatus. Also in this case, it is of course possible to lower the withstand voltage of the transistor Tr by connecting a varistor between the grid 3 and the transistor Tr.

In the above embodiments, the present invention was applied to an electrophotographic copying apparatus, but it is of course applicable to other recording apparatuses.

As described above, the present invention relates to a discharge control device for a recording device, and uses the voltage applied to the ion flow control member as the power supply to the error amplifier, and does not require a special power supply to operate the error amplifier. The present invention provides a discharge control device for a recording device.

[Brief explanation of drawings]

1 and 2 show a conventional example. An embodiment of a discharge control device to which the present invention is applied is shown in FIGS. 3 to 5. An embodiment of the present invention is shown in FIG. 6 and FIG. 7, respectively. 1... High voltage power supply, 2... Charger (scorotron), 3... Grid, 4... Image holder, 41...
... Photoreceptor, 42 ... Base, 5 ... Control circuit, 11
...High voltage stabilized power supply, VD ₁ , VD ₂ ...Varistor,
V _G ... Voltage applied to the grid (grid voltage),
V _Z ...Variable impedance element, AMP1,
AMP2...error amplifier, Tr...transistor,
D...Base protection diode, VR...Variable resistor, V _S ...Set voltage, _R1 , _R2 , _R3 , _R4 ...Resistance, V _A ...Voltage applied to varistor VD ₂ , V _T ...
Voltage applied to transistor Tr, ZD ₁ , ZD ₂ , ZD ₃
...Zener diode.

Claims (1)

[Claims] 1. An ion flow control member affected by the ion flow from the electrode, a variable impedance element connected between the ion flow control member and the ground side, and a voltage applied to the ion flow control member and a set voltage. and means for detecting a difference between the two and applying a signal of the difference to the variable impedance element, and maintaining a constant voltage applied to the ion flow control member in accordance with the set voltage. A discharge control device,
A recording device characterized in that the voltage applied to the ion flow control member is used as a power source for supplying a signal representing the difference between the voltage applied to the ion flow control member and a set voltage to the variable impedance element. discharge control device. 2. The device according to claim 1, wherein the ion flow control member is a scorotron grid, a charging electrode back plate, or a screen electrode. 3. The device according to claim 1 or 2, wherein a bipolar transistor or FET, or a phototransistor or CDS on the output side of a photocoupler is used as the variable impedance element. 4. The device according to claims 1 to 3, characterized in that a varistor or a Zener diode is connected between the ion flow control member and the variable impedance element. 5. Claims 1 to 4, characterized in that an error amplifier is used as means for applying a signal of the difference between the voltage applied to the ion flow control member and the set voltage to the variable impedance element. The device described.