JPH06222654A - Image forming device - Google Patents

Abstract

PURPOSE:To miniaturize a device and to reduce the cost. CONSTITUTION:A developing roller bias circuit 30 generating a developing roller bias power source (VDV) by using one part(120 of output currents (I1+I2) from the power source device 2P of an electrostatic charger 2 and a toner supply roller bias circuit 40 generating a toner supply roller bias power source (VTS) by using one part of the output currents, are connected to the power source device 2P of the electrostatic charger 2, and bias potential VDV and VTS of specifed potential are impressed on a developing roller and a toner supply roller from the power source device 2P for electrostatic charging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an apparatus having a non-magnetic one-component toner supply roller and a developing roller.

[0002]

2. Description of the Related Art In FIG. 5, reference numeral 1 denotes a photosensitive member which rotates in a predetermined direction and contacts a charging roller forming a charger 2 at a charging location and a developing roller 3 at a developing location. The toner supply roller 4 supplies the non-magnetic single-component toner to the developing roller 3, and 5 is a transfer device.

As shown in FIG. 6, the charging power source device 2P is
A charging potential Vc (for example, -1000) is applied to the charging roller (2).
V) can be applied to charge the peripheral surface of the photoreceptor 1 to the surface potential VS1 (for example, −500V). The developing roller bias power supply device 3P applies a developing roller bias potential VDV (for example, −200V) to the developing roller 3. Further, the toner supply roller bias power supply device 4P
Is the toner supply bias potential VTS (for example, -200
V) can be applied.

In such an image forming apparatus, the exposed surface (electrostatic latent image) of, for example, -50 V is formed by irradiating the peripheral surface of the photoconductor 1 that has passed through the charger 2 with light using a known exposure means. The unexposed portion remains at the surface potential VS1 (-500V). On the other hand, 1 supplied from the toner supply roller 4
The component toner adheres to the peripheral surface of the developing roller 3 at the same potential as the bias potential VDV (-200V).

Therefore, when the toner adhesion amount between the developing roller 3 and the photosensitive member 1 at the developing portion is selected as the characteristic shown in FIG. 7, the set potential difference is +200 V {-[=
Since | VS1 | − | VDV | = | 50 | − | 200 |]}, it is possible to supply toner from the developing roller 3 side to the exposed portion of the photoconductor 1 for development. However, between the unexposed portion and the developing roller 3, -300V = {-[| 5
00 | − | 200 |]} potential difference occurs, so that toner is not attached and cleaning can be performed, so to speak.

When the charging power source device 2P is turned on and driving is started, when the initial peripheral surface portion of the photoconductor 1 located between the charging portion and the developing portion first passes through the developing portion, The initial peripheral surface area is not charged. Therefore, the power source device 1P for the photoconductor bias is supplied until all of the initial peripheral surface portion has passed the development portion for the first time.
Is turned on to apply a photoconductor bias potential of, for example, −100 V so that useless toner is not supplied from the developing roller 3 side.

That is, at a certain time (t1), the charging power supply device 2P and the photoconductor bias power supply device 1P are simultaneously turned on, and the time (T) when all of the initial peripheral surface parts have passed the development part is finished. After the lapse of time, the photoconductor bias power supply device 1
The image forming operation is performed by turning off P and turning on the developing roller bias power supply device 3P and the toner supply roller bias power supply device 4P.

[0008]

By the way, in the above-mentioned conventional structure, each power supply device 1P, 2P, 3P, 4P is provided separately due to a difference in applied voltage, a difference in ON-OFF timing and the like. On the other hand, there is a strong demand for further downsizing and cost reduction. Therefore, if one of the power supply devices can be omitted or combined with another power supply device, it is presumed that the demands can be sufficiently accepted.

It is an object of the present invention to use the developing roller bias power supply device and the toner supply roller bias power supply device also as the charging power supply device so that the overall size and cost of the image can be reduced. To provide a forming apparatus.

[0010]

SUMMARY OF THE INVENTION The present invention provides
When the charging current is, for example, 20 μA, paying attention to the fact that the total of the developing roller bias current and the toner supply roller bias current can be set to, for example, 1 μA or less, and the developing roller bias power supply and the toner supply roller bias power supply are used for charging. It is configured so that it can be generated by utilizing a part of the output current of the power supply device.

That is, the image forming apparatus according to the present invention is
The peripheral surface of the photoconductor that has passed through the charger is irradiated with light to form an exposed portion and an unexposed portion.
In the image forming apparatus formed so as to supply the component toner to the developing roller and to supply the toner from the developing roller side to the exposed portion of the photosensitive member to develop using the potential difference between the photosensitive body side and the developing roller side, To a charging power supply device connected to the charger, a developing roller bias circuit that generates a bias power supply to the developing roller by utilizing a part of the output current of the charging roller, and a toner that generates a bias power supply to the toner supply roller. A supply roller bias circuit is connected, and a bias potential of a predetermined potential is applied from the charging power supply device to each of the developing roller and the toner supply roller.

[0012]

According to the present invention having the above-described structure, since the developing roller bias circuit and the toner supply roller bias circuit are connected to the charging power supply device, the developing roller bias power supply and the toner supply roller are appropriately charged during the charging operation. The bias power supply can be generated from the charging power supply.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) This image forming apparatus has the same basic configuration (1, 2, 3, 4) as that of the conventional example (FIG. 5) as shown in FIG. 2, and the developing roller as shown in FIG. Bias circuit 30
The toner supply roller bias circuit 40 and the toner supply roller bias circuit 40 are connected to the charging power supply device 2P, and the developing roller bias power supply (VD
V) and the toner supply roller bias power source (VST) can be generated by using a part (shunt current I2) of the output current (I1 + I2) of the charging power source device 2P.

Further, the developing roller bias circuit 30 and the toner supply roller bias circuit 40 are connected in series via the Zener diode ZD1 which is a constant voltage element and the switching element (transistor Tr5) shown in FIG. VDV and toner supply roller bias potential VTS are made equal (VDV = VTS ... For example, FIG.
(-200V), the toner supply roller bias potential VTS can be switched to a high value (for example, -300V) during development.

Further, in this embodiment, the constant voltage circuit 10 is provided, and both bias circuits 30 and 40 are connected in parallel with the constant voltage circuit 10 to ensure the breakdown voltage guarantee of the constituent elements of the both bias circuits 30 and 40. There is.

Furthermore, in this embodiment, a voltage setting circuit 31 is additionally provided so that the value of the developing roller bias potential VDV can be variably set, and the amount of toner supplied to the photosensitive member 1 side can be adjusted. That is, the print density can be adjusted.

First, the charging power supply device 2P is capable of applying a charging potential VC (-1000V) to the charger 2 composed of a charging roller, and the charging current I1 (20 μA) and the shunt current I.
2 (for example, 1 μA) can be output, and the controller (not shown) turns ON / OFF at the timing shown in FIG.
To be done. Therefore, the power supply capacity may be slightly increased as compared with the conventional example, and the handling is not changed.

The constant voltage circuit 10 is composed of a Zener diode (constant voltage element) ZD2 and a resistor R13 connected in series, and generates a constant voltage (for example, -400V) lower than the charging potential VC (-1000V). . Therefore,
The breakdown voltage of the transistors Tr2 and Tr3 described later in detail can be reduced by half. Further, since the charging current I1 can be kept constant by providing the constant voltage circuit 10, the developing roller bias and the toner supply roller bias are turned ON / OF.
It is possible to stabilize the load of the charging power supply device 2P regardless of F.

The developing roller bias circuit 30, as shown in FIG. 1, has a reference voltage Vref. , A control voltage generation circuit IC3, and resistors R5 and R6 that generate an inverted input voltage signal of the circuit IC3.
And transistors Tr2 and Tr3 for analog control,
Resistance R4 to R9, and the reference voltage Vref. Corresponding developing roller bias potential VDV can be generated.

More specifically, the control power supply voltage is VDD and the resistor R
The resistance values of R5 and R6 are r5 and r6, and VDV >> Vr
ef. In the case of, (Vref.-VDD) / r5 = (V
DV + Vref. ) / R6, that is, VDV = (Vre
f. −VDD) × (r6 / r5) is established. Also, the resistance value r of each of the resistors R7, R8, R9
7, r8, r9 are the reference voltage Vref. Is set to a standard value, the developing roller bias potential VDV is determined to be −200V.

By the way, the reference voltage Vref. Is generated from the control power supply voltage VDD by resistance division of the resistors R3 and R4. The switching element (transistor Tr1) connected in parallel with the resistor R3 is turned off when the development signal Sd is turned on (OPEN), and turned off (L).
Level), it is turned on. Therefore, when the development signal Sd is turned on at time t2 in FIG. 3, the transistor Tr1 is turned off and the reference voltage Vref. [= V
DD × r3 / (r3 + r4)] is generated, and as a result, the developing roller bias voltage VDV (−200 based on the above equation).
V) can be generated. Further, the developing roller bias potential VDV is set to 5 by using the voltage setting circuit 31 including the 3-state buffer circuit IC1 and the resistors R1 and R2.
You can switch to stages. It is set by setting each output of the circuit IC1 to a combination of H level (VDD), L level (OV), and OPEN.

By switching the developing roller bias potential VDV, the amount of toner supplied from the developing roller 3 to the photosensitive member 1 can be adjusted to adjust the print density. Therefore, instead of the voltage setting circuit 31, each of the resistors R3 and R4 may be a variable resistor type or another variable resistor may be connected between the two resistors R3 and R4. When the transistor Tr1 is ON, Vref. = VDD, the developing bias potential VDV becomes almost zero (0). However, the OFF circuit 35 (the resistors R14, R15, the transistor T) shown by the two-dot chain line in FIG.
By providing r6), the developing roller bias potential VDV can be more surely turned off (0).

Next, the toner supply roller bias circuit 40
Is connected in series with the developing roller bias circuit 30 via the Zener diode ZD1 and the switching element (transistor Tr5), and is arranged on the lower side (constant voltage circuit 10 side). Here, switching element (Tr5)
Turns off when the toner amount increase signal St is turned on (OPEN), and turns on when turned off (L level). That is, when turned on, the toner supply roller bias potential VTS is lower than the developing roller bias potential VDV (for example, -200 V) (-300 V) by the Zener action.
V). On the other hand, if it is kept OFF, both bias potentials VDV and VTS are set to the same potential (-200
V). In any case, the toner supply roller bias potential VTS can automatically follow the developing roller bias potential VDV.

Next, the operation of the first embodiment will be described.
In FIG. 3, at time t1, the charging power supply device 2P and the photoconductor bias power supply device 1P are turned on. Then, as shown in FIG.
The charging potential VC (-1000V) shown in FIG.
The peripheral surface of is charged to -500V. The initial peripheral surface portion, which is pressed between the charging portion and the developing portion at time t1, is charged to the photoconductor bias potential (-100 V).

Therefore, wasteful toner is not consumed even when the developing roller bias potential VDV is not applied when the initial peripheral surface portion passes through the developing portion as the photosensitive member 1 rotates. Subsequent to this, the exposed portion on the peripheral surface of the photoreceptor 1 is set to -50V, and the unexposed portion remains at -500V.

Here, at time t2 when time T1 when all of the initial peripheral surface portion has passed through the developing portion has elapsed, the photoconductor bias power supply device 1P is turned off, and the developing signal Sd in FIG. 1 is turned on (OPEN). To be done. Therefore, the developing roller bias circuit 30 generates the developing roller bias potential VDV (-200V). At this time, since the toner amount increase signal St is OFF (level), both the transistors Tr4 and Tr5 are OFF. Therefore, from the toner supply roller bias circuit 40,
The toner supply roller bias potential VTS (-200V) is generated and output. That is, VDV = VTS.

At time t3 when the exposed portion of -50V reaches the developing portion, the toner amount increase signal St is turned on (OPE
N) and the transistors Tr4 and Tr5 are turned off. Therefore, from the toner supply roller bias circuit 40 connected via the Zener diode ZD1, the toner supply roller bias potential VTS (−30) whose absolute value is larger than the developing roller bias potential VDV (−200V).
0 V) is generated and output. Therefore, the toner supply roller 4
A large amount of toner is supplied from the developing roller 3 to the developing roller 3.

To increase the print density, the voltage setting circuit 31 is used to set the reference voltage Vref. And the developing roller bias potential VDV (for example, −200V + α). In this case, the toner supply roller bias potential V
The TS also automatically follows -200V + α or -300V + α, for example.

According to the first embodiment, however, the developing roller bias power source (VD) is supplied to the power source device 2P of the charger 2 by utilizing a part (I2) of the output current (I1 + I2).
The developing roller bias circuit 30 that generates V) and the toner supply roller bias circuit 40 that generates the toner supply roller bias power supply (VTS) are connected to each other, and the charging power supply device 2
Since the bias potentials VDV and VTS of predetermined potentials are applied from P to the developing roller 3 and the toner supplying roller 4, respectively, the developing roller dedicated to the independent use can be obtained by only slightly increasing the capacity of the charging power source device 2P. The bias power supply device (3P) and the toner supply roller bias power supply device (4P) can be swept away. Therefore, downsizing of the entire apparatus and cost reduction can be achieved, and handling is easy.

Further, since the developing roller bias circuit 30 and the toner supply roller bias circuit 40 are connected in series via the Zener diode ZD1 and the switching element (Tr5), the developing roller bias potential VDV and the toner supply roller bias are connected. The electric potential VTS can be operated with the same or different value. That is, the toner supply roller bias potential VTS can be made to automatically follow the developing roller bias potential VDV, and the amount of toner supplied from the toner supply roller 4 to the developing roller 3 can be increased only during development to achieve clear printing. .

Further, since the developing roller bias potential VDV can be switched in five steps by providing the voltage setting circuit 31, it is possible to adjust the set potential difference between the developing roller bias potential VDV and the peripheral surface (exposure portion) of the photosensitive member 1. The print density can be finely adjusted by.

Since the constant voltage circuit 10 is provided and both the bias circuits 30 and 40 are connected in parallel with the constant voltage circuit 10, the developing roller bias potential VDV and the toner supply roller bias potential VTS are turned on and off. Regardless, the load of the charging power supply device 2P can be made constant, and the constituent elements (Tr
2, Tr3) breakdown voltage can be halved.

(Second Embodiment) This second embodiment is shown in FIG. That is, the developing roller bias circuit 30 is
The reference voltage generation circuit IC2 and the constant voltage element (ZD
1) is composed of resistors R51 and R61 connected in series, and a transistor Tr21 and a resistor R81 whose bases are connected between the resistors R51 and R61.
The voltage V1 generated by the value of the current flowing therethrough is used.

That is, the resistance value of the resistors R51 and R61 is r
In the case of 51, r61 and VDV >> V1, VDV =
It is formed that (r61 / r51) × (V1−Vref.) Holds.

The voltage setting circuit 31 includes resistors R31,
A single-stage set type composed of R41, and a constant voltage circuit 10
Is provided with a current limiting resistor R131.

Thus, also in the second embodiment, the developing roller bias potential VDV and the toner supply roller bias potential VTS can be generated and output from the charging power source device 2P.

[0037]

According to the present invention, a developing roller bias circuit for generating a developing roller bias power source and a toner supply roller for generating a toner supply roller bias power source by utilizing a part of the output current of the power source device of the charger. A bias circuit is connected to apply a bias potential of a predetermined potential to each of the developing roller and the toner supply roller from the charging power supply device, so that the charging power supply device can be independently increased by slightly increasing the capacity. The dedicated developing roller bias power supply device and toner supply roller bias power supply device can be swept away. Therefore, downsizing of the entire apparatus and cost reduction can be achieved, and handling is easy.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is likewise a diagram for explaining the overall configuration.

FIG. 3 is likewise a timing chart for explaining the operation.

FIG. 4 is a circuit diagram showing a second embodiment.

FIG. 5 is a diagram for explaining a conventional example.

FIG. 6 is a diagram for explaining a charging action in the present invention and a conventional example.

FIG. 7 is a diagram for explaining toner adhesion characteristics of the present invention and a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 photoconductor 1P photoconductor bias power supply device 2 charger 2P charging power supply device 3 developing roller 4 toner supply roller 5 transfer device 10 constant voltage circuit 30 developing roller bias circuit 31 voltage setting circuit 40 toner supply roller bias circuit VDV developing roller Bias potential (power supply) VTS Toner supply roller bias potential (power supply)

Claims (1)

[Claims] 1. A peripheral surface of a photoconductor that has passed through a charger is irradiated with light to form an exposed portion and an unexposed portion, and a non-magnetic one-component toner is supplied to a developing roller by a toner supply roller, and the photosensitive member side is exposed. In an image forming apparatus formed so as to supply toner from the developing roller side to the exposed portion of the photoconductor to develop by using a set potential difference from the developing roller side, a charging power supply device connected to the charger. , A developing roller bias circuit that generates a bias power supply to the developing roller by utilizing a part of the output current, and a toner supply roller bias circuit that generates a bias power supply to the toner supply roller are connected to each other for charging. An image forming apparatus characterized in that a bias potential of a predetermined potential is applied from a power supply device to each of the developing roller and the toner supply roller.