JPH0954487A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optionally correct developing density even in the case a gap between an image carrier and a developer carrier is largely changed by detecting the output current of a 1st power source circuit for outputting an AC voltage and changing a signal to be inputted to a 2nd power source circuit through a developing bias power source, and outputting a voltage waveform obtained by superposing respective outputs of the 1st and 2nd power source circuits. SOLUTION: The device is provided with the developer carrier 5 for carrying/ transferring the developer and developing an electrostatic latent image in a developing area and the developing bias power source 9 for impressing a vibration bias voltage on the developer carrier 5. The developing bias power source 9 is provided with the 1st power source circuit 11 for outputting the AC voltage, the 2nd power source circuit 12 for changing the output voltage in accordance with the input signal, a detection circuit 16 for detecting the output current of the 1st power source circuit 11, and a control circuit 17 for changing a signal to be inputted to the 2nd power source circuit 12 in accordance with the output of the detection circuit 16. And the voltage waveform obtained by superposing the output of the 1st power source circuit 11 and the output of the 2nd power source circuit 12 is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a developing device for visualizing an electrostatic latent image formed on an image carrier,
In particular, the present invention relates to a developing device that carries and conveys a developer and applies a vibration bias voltage to a developer carrier that visualizes an electrostatic latent image in a developing area.

[0002]

2. Description of the Related Art Conventionally, a magnetic material (developing magnet) has been used as a developing system for copying machines and printers utilizing electrophotography.
A method of applying an oscillating bias voltage in which an AC voltage component such as a sine wave, a rectangular wave, or a triangular wave is superimposed on a DC voltage component is applied to a developer carrier, which is usually a developing sleeve, having a built-in. The DC voltage component mainly contributes to the density of the developed image, and the AC voltage component mainly contributes to the contrast of the developed image.

In this developing system, the distance between the image bearing member and the developer bearing member is periodically changed due to the eccentricity of the image bearing member, the developer bearing member, or the spacer roller that holds the gap therebetween. It may happen. In this case, the electric field strength between the image carrier and the developer carrier changes periodically, resulting in a change in the density of the developed image.

Further, the distance between the image bearing member and the developer bearing member is usually 50 μm to 500 μm, and it is very difficult to suppress variations in the distance between devices. As a result, there are cases in which the density changes between devices.

In order to solve such a problem, the AC component of the voltage to be applied to the developing device is driven by a constant current,
It has been proposed to drive a DC component at a constant voltage. As a result, the AC electric field strength in the space between the image carrier and the developer carrier is made constant, and the development density corresponding to the change in the space is corrected.

[0006]

However, even in the developing method described in the above publication, the density change due to the variation in the gap between the image bearing member and the developer bearing member cannot be completely corrected. . In particular, when the volume average particle diameter of the developer is large, that is, when the mass of the developer particles is large, the correction cannot be completely performed. The reason is that when the mass of the developer particles is large and the gap is wide, the AC voltage cycle approaches the propagation time of the developer particles, so that the concentration becomes thin as the gap is widened.

As described above, the conventional method cannot arbitrarily correct the change in the gap between the image bearing member and the developing bearing member.

Therefore, an object of the present invention is to provide a developing device capable of arbitrarily correcting the developing density even when the gap between the image bearing member and the developing bearing member is largely changed.

[0009]

The above object is achieved by a developing apparatus according to the present invention. In summary, the present invention includes a developer carrier that carries and conveys a developer to visualize an electrostatic latent image in a developing area, and a development bias power source that applies a vibration bias voltage to the developer carrier. In the developing device having the above, the developing bias power source outputs a first alternating voltage.
Power supply circuit, a second power supply circuit capable of changing an output voltage according to an input signal, a detection circuit detecting an output current of the first power supply circuit, and the second power supply circuit according to an output of the detection circuit. And a control circuit that changes a signal input to a power supply circuit, and outputs a voltage waveform obtained by superimposing an output of the first power supply circuit and an output of the second power supply circuit. is there.

According to another aspect of the present invention, a developer carrying member carrying and carrying a developer to visualize an electrostatic latent image in a developing region, and a vibration bias voltage are applied to the developer carrying member. In a developing device having a developing bias power source, the developing bias power source outputs a constant current AC waveform.
Power supply circuit, a second power supply circuit capable of changing an output voltage according to an input signal, a detection circuit for detecting an output voltage of the first power supply circuit, and a second power supply circuit according to an output of the detection circuit. And a control circuit that changes a signal input to a power supply circuit, and outputs a voltage waveform in which the output of the first power supply circuit and the output of the second power supply circuit are superimposed. Provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device according to the present invention will be described in more detail below with reference to the drawings.

First, with reference to FIG. 2, an overall structure of an embodiment of a developing device which can embody the present invention will be described.

In this embodiment, the developing device 2 is arranged so as to face the image carrier 1 which is, for example, a cylindrical electrophotographic photosensitive member. An electrostatic latent image is formed on the image carrier 1 by a known electrostatic latent image forming unit including a charger and an exposing unit.
The latent image formed on the image carrier 1 is visualized by the developing device 2 into a toner image.

The developing device 2 contains, in a container 3, a developer containing no carrier particles, that is, a one-component insulating developer 4. The developer 4 used in this example is
It contains an insulating magnetic material as a main component, and a small amount of silica fine powder is added. The silica fine powder has the effect of suppressing the frictional charge of the toner within a predetermined range.

The developing device 2 has a cylindrical non-magnetic sleeve made of aluminum, stainless steel or the like, which rotates in the direction of the arrow, a developer carrying member 5 which is a so-called "developing sleeve". A magnet 6 is fixedly arranged in the. The developer 4 is carried by the developer carrier 5 and conveyed to the developing area 7. In the developing area 7, the image carrier 1 and the sleeve 5 face each other with a gap of 50 μm to 500 μm. Then, in the developing area 7, the developer is applied to the electrostatic latent image.

The thickness of the developer on the developer carrying member 5 conveyed to the developing area 7 is regulated by the blade 8, and a developer layer 4'having a predetermined thickness is formed on the developer carrying member 5. .
That is, the blade 8 is a magnetic material such as iron, and the sleeve 5
The magnetic pole N _{1 of the} magnet 6 disposed inside is opposed to each other with the sleeve 5 interposed therebetween. Therefore, the magnetic pole N is
Magnetic lines of force from ₁ are concentrated and a strong magnetic curtain is formed between the blade 8 and the sleeve 5. Due to this magnetic curtain, a one-component magnetic developer layer 4 ′ thinner than the gap between the blade 8 and the sleeve 5 is formed on the sleeve 5.

In the gap between the blade 8 and the sleeve 5, the thickness of the developer layer 4'formed is such that the sleeve 5 and the image carrier 1 are formed.
It is set to be thinner than the minimum gap between them. The developing particles in the developer layer 4 ′ are charged, and the developing particles are generated in the developing area 7 generated by the developing bias power source 9.
Fly by the electric field at.

The developing bias power source 9 is a direct current (DC).
An oscillation bias voltage in which an alternating current (AC) voltage is superimposed on the offset voltage is output. As the AC voltage waveform, a rectangular wave or a sine wave having a frequency of 1.8 KHz to 2.2 KHz is usually selected. The peak-to-peak value of this AC voltage is selected to be about 1.0 KV to 2.0 KV. The DC offset voltage is usually set between the dark potential and the bright potential of the image carrier 1. For example, the dark potential is -650
When V and the bright potential are -200V, for example, the DC offset voltage is set to about -400V to -500V. If the developing particles are negatively charged, the developing particles reciprocate between the image carrier 1 and the developing sleeve 5 due to the oscillating electric field, and finally, the bright potential portion is developed and the dark potential portion is not developed. .

In this embodiment, the developing bias power source, that is,
The DC offset voltage in the vibration bias power supply 9 is controlled. Next, the control method will be described.

FIG. 1 shows an embodiment of an internal circuit diagram of the vibration bias power supply 9. The vibration bias power source 9 has a one-chip microcomputer (hereinafter referred to as “CPU”) 20. The CPU 20 has a logical operation unit (ALU), a random access memory (RAM), and a read-only memory (ROM) storing programs stored therein. Further, the CPU 20 has an AD converter and a DA converter built therein. Examples of such a CPU 20 include M38000 series manufactured by Mitsubishi and 78 manufactured by NEC.
A KII series one-chip microcomputer can be used.

The CPU 20 controls a circuit connected to the CPU 20 in accordance with its built-in program memory to adjust the voltage applied to the developing sleeve 5. CPU 20
The oscillators 18 and 19 capable of ON / OFF control are connected to the. The vibration bias power source 9 will be described later in detail.
Is connected to the P1 terminal of the CPU 20, and the oscillator 18 constituting the first power supply circuit of the
8 oscillates as a square wave of 2 KHz. Further, the oscillator 19 constituting the second power supply circuit of the vibration bias power supply 9 is the CPU 2
0 is connected to the P2 terminal, and the oscillator 19 oscillates as a square wave of 20 KHz when P2 is at a low level.

The 2 KHz square wave output from the oscillator 18 is amplified by the power amplifier 13. The power supplied to the power amplifier 13 is V _CC2 (for example, +2 KV). The peak value of the output voltage of the power amplifier 13 is constant, and its value is V _CC2- α, for example, 22V. The square wave output from the power amplifier 13 is an electrolytic capacitor 2
9 and the high voltage transformer 11 are applied in series. The capacitance of the electrolytic capacitor 29 is chosen so that its impedance is close to zero at 2 KHz. At this time, the DC component of the square wave output from the power amplifier 13 is blocked by the electrolytic capacitor 29, and only the AC component of the square wave is input to the transformer 11. When the difference of the input side of the high voltage transformer 11 N _1, the difference in speed of the output side and N _2, in this embodiment, N ₂ / N ₁ is are set to be 70. Therefore, the output side winding of the high voltage transformer is about 22 × 70 = 15
A square wave voltage with a peak-to-peak value of 40V is output. As described above, the oscillator 18, the power amplifier 13,
The first of the vibration bias power supply 9 by the high voltage transformer 11
The power supply circuit is configured.

On the other hand, 20 KH output from the oscillator 19
The square wave of z is amplified by the power amplifier 14. The power supplied to the power amplifier 14 is supplied from the output of the power amplifier 15. The peak value of the output voltage of the power amplifier 14 is determined by the output voltage of the power amplifier 15. The square wave output from the power amplifier 14 is applied in series to the electrolytic capacitor 32 and the high voltage transformer 12. The impedance of the electrolytic capacitor 32 is 20
Selected to be close to zero at KHz. At this time, the DC component (or low frequency component) of the square wave output from the power amplifier 14 is blocked by the electrolytic capacitor 32, and the AC component of the square wave is input to the high voltage transformer 12. When the number of turns on the input side of the high-voltage transformer 12 is n ₁ and the number of turns on the output side is n ₂ , n ₁ / n ₂ is selected to be 50, for example. When the peak value of the output voltage of the power amplifier 14 is V ₁ , a square wave having a peak-to-peak value of -50V ₁ is output to the output of the high voltage transformer 12. At the output end of the high voltage transformer 12, as shown in the figure, a diode 3
6, the capacitor 33 and the resistor 25 are connected to form a half-wave rectifier circuit. As a result, the capacitor 33 and the resistor 25
When the voltage across the V _2, DC voltage V ₂ = -25V ₁ is output to the resistor and the capacitor 33 25.

As can be seen from the above, the oscillator 1
A second power supply circuit of the vibration bias power supply 9 is constituted by 9, the power amplifiers 14 and 15, the high voltage transformer 12, the diode 36, the capacitor 33, the resistor 25, and the like.

The 2 KHz square wave output from the high-voltage transformer 11 of the first power supply circuit having the above-mentioned configuration is the resistance 21.
Is applied to the developing sleeve 5 via. Capacitor 30
Let C _{30 be} the capacitance of, and the resistance values of the resistors 22 and 23 be R ₂₂ and R ₂₃ , respectively.

[0026]

[Equation 1] When the relational expression of is satisfied, the square wave current output from the high voltage transformer 11 does not flow through the resistor 23 but flows through the capacitor 30 and the resistor 22. That is, the high voltage transformer 11
The square wave current of 2 KHz output from the resistor 22 flows through the resistor 22, the capacitor 30, the transformer 11, the resistor 21, and the developing sleeve 5 in this order.

The high-voltage transformer 12 of the second power supply circuit,
The DC voltage V ₂ generated by the diode 36, the capacitor 33, and the resistor 25 is applied to the developing sleeve 5 via the resistor 23, the transformer 11, and the resistor 21. This DC
Since the voltage V ₂ is direct current, it does not flow through the capacitor 30.

If the DC voltage V ₂ has a low frequency f ₂
It is assumed that there is a fluctuation amount of. At this time,

[0029]

[Equation 2] When the relational expression of is satisfied, the DC voltage V ₂ is applied to the developing sleeve 5 without being affected by the capacitor 30 and the resistor 22.

As described above, the developing sleeve 5 has a square wave of 2 KHz generated by the high voltage transformer 11,
The superposed DC voltage (or DC offset voltage having a low frequency fluctuation component) generated in the high voltage transformer 12 is applied. The DC offset voltage component of this superimposed waveform is adjusted by the detection circuit and control circuit having the following configurations.

In this embodiment, the detection circuit is the diode 3
5, operational amplifier 16, diode 37, capacitor 3
1 has a peak hold circuit composed of a resistor 24. That is, it is a circuit that half-wave rectifies the voltage across the resistor 22 and holds the peak value. The peak value holding output appears across the capacitor 31 and the resistor 24. The peak value of the terminal voltage of the resistor 22 flows to the developing sleeve 5 2
Since it is proportional to the square wave current of KHz, a voltage proportional to the peak value of the square wave current of 2 KHz flowing in the developing sleeve 5 is output across the capacitor 31 and the resistor 24, and the voltage is input to the AD conversion port of the CPU 20. To be done. CP
U20 can measure the square wave current of 2 KHz as a result by reading the AD conversion value.
The CPU 20 detects this 2KH detected by the detection circuit.
Based on the square wave current value of z, the above-mentioned DC offset component is changed by the control circuit described below.

That is, the CPU 20 outputs a certain voltage V _ref from the DA conversion port. When the voltage input to the AD conversion port of the CPU 20 is V _AD , V _ref = KV _AD + Vφ (3) (K is a proportional constant, Vφ is a constant value)
0 outputs V _ref . This voltage V _ref is input to the inverting terminal of the operational amplifier 17 that constitutes the control circuit.

Here, the voltage -25V ₁ output across the resistor 25 is divided by the resistors 26 and 27.
When the resistance values of the resistors 26 and 27 are R ₂₆ and R ₂₇ , the potential at which the resistors 26 and 27 are connected is

[0034]

(Equation 3) Becomes

The voltage V _CC1 is a reference voltage connected to the resistor 27.

The potentials connected to the resistors 26 and 27 are input to the non-inverting terminal of the operational amplifier 17. The operational amplifier 17, the resistor 28, and the capacitor 34 form a so-called error amplifier. The operational amplifier 17 amplifies the minute voltage appearing at the non-inverting terminal and the inverting terminal, and inputs the amplified output to the power amplifier 15. Further, the output of the power amplifier 15 is input to the power supply terminal of the power amplifier 14. As a result, the output amplitude of the power amplifier 14 is controlled. Then, the output voltage of the power amplifier 14 is boosted by the transformer 12 and further half-wave rectified. In this way, negative feedback is applied to the operational amplifier 17, and as a result, the potentials of the inverting terminal and the non-inverting terminal of the operational amplifier 17 become equal. The resistor 28 and the capacitor 34 have a role of complementing the negative feedback. Therefore,

[0037]

(Equation 4) The following relationship holds. However,

[0038]

(Equation 5) Thus, the voltage V ₂ applied to the resistor 25 has a proportional relationship with V _ref . From equations (3) and (6),

[0039]

(Equation 6)

As a result, the voltage V applied to the resistor 25 is
₂ is linearly proportional to the AD input value V _AD input to the CPU 20. The voltage V ₂ is applied to the developing sleeve 5 via the resistors 23 and 21, and the input value V _AD of AD conversion flows into the developing sleeve 5. Since it is proportional to the square wave current of 2 KHz, as a result, a DC offset component linearly proportional to the square wave current of 2 KHz flowing in the developing sleeve 5 is applied to the developing sleeve 5. This control produces the following effects.

That is, if the developing sleeve 5 and the image carrier 1
The wider the gap between the and, the equivalent capacitance of the developing sleeve 5 decreases. At this time, the 2 KHz square wave current flowing through the developing sleeve 5 decreases. And V _AD decreases. If the constant of proportionality K is a negative value in equation (7), -2
5V ₁ increases in the negative direction. That is, the developing sleeve 5
The DC offset voltage applied to V increases in the negative direction. On the contrary, when the gap becomes narrow, the DC offset voltage applied to the developing sleeve 5 decreases in the negative direction.

Even if the gap between the developing sleeve 5 and the image carrier 1 is changed by the operation of the detection circuit and the control circuit having such a structure, the DC component of the electric field generated in the gap is suppressed within a predetermined range. To be

The control characteristic of this embodiment is that the thickness of the gap is indirectly obtained by measuring a square wave current of 2 KHz, and the optimum D corresponding to the gap is calculated according to the equation (7).
That is, the C offset voltage can be applied to the developing sleeve 5 to arbitrarily correct the developing density.

Factors that change the gap between the developing sleeve 5 and the image bearing member 1 are variations in the thickness of the spacer roller inserted between the developing sleeve 5 and the image bearing member 1 between the devices, and this spacer. The thickness may be mechanically worn. According to the present invention, the development density can be suppressed within a predetermined value even if the gap varies due to these factors. Further, due to the eccentricity of the developing sleeve 5 or the image carrier 1, the gap is periodically changed when the developing sleeve 5 and the image carrier 1 are rotated. The frequency at which this gap changes is usually about 0.2 Hz to 5 Hz (this value depends on its rotation speed). If the fluctuation of the frequency is as low as this, the DC offset output circuit unit shown in FIG. 1 can respond, and the uneven density due to the eccentricity can be suppressed low.

In the embodiment described above, reference numeral 2
0 has been described as a one-chip microcomputer incorporating an AD converter and a DA converter. However, instead of the one-chip microcomputer 20, as another example, an analog computer that does not include AD conversion and DA conversion, and can be configured to satisfy the expression (7).

When the one-chip microcomputer 20 is used, the equation (7) can also be expressed by a non-linear relational equation, V _ref = K (V _AD ) ... (7 '). If a non-linear relational expression is used, an arbitrary D can be obtained according to the thickness of the gap between the developing sleeve 5 and the image carrier 1.
C offset voltage can be set.

Example 2 In Example 1, the square wave current value of 2 KHz applied to the developing sleeve 5 was measured, and the DC offset voltage was changed in response to the measurement. At this time, the developing sleeve 5 and the image carrier 1
When the gap between changed, the 2 KHz square wave voltage did not change, only the DC offset voltage changed.

In the second embodiment, when the gap between the developing sleeve 5 and the image carrier 1 changes, the peak of the 2 KHz square wave voltage
The toe peak value changes, and the DC offset voltage is finely adjusted. A circuit diagram of the second embodiment is shown in FIG. Output the DC offset in the second embodiment,
The second power supply circuit section having the oscillator 19, the high voltage transformer 12, etc. is the same as that of the first embodiment shown in FIG.

In FIG. 3, a square wave of 2 KHz is produced,
The first power supply circuit section including the oscillator 18, the high voltage transformer 11 and the like is different from that of the first embodiment shown in FIG. Specifically, the operational amplifier 38, the resistor 40, the capacitor 41,
Further, a power amplifier 39 and resistors 42 and 43 are added. Other parts are exactly the same as those in the first embodiment of FIG. 1, and the same parts as those in FIG. 1 are designated by the same numbers in FIG.

Also in the second embodiment, as in the first embodiment, the square wave current of 2 KHz appearing at the output terminal of the high voltage transformer 11 flows through the capacitor 30 and the resistor 22. The peak value of the square wave current flowing through the resistor 22 is the same as that of the first embodiment.
Similarly, the peak hold is performed by the diode 35, the operational amplifier 16, the diode 37, the capacitor 31, and the resistor 24. In the first embodiment, this peak hold voltage is CP
It was input to the AD conversion port of U20. However,
In the second embodiment, this peak hold voltage is input to the inverting terminal of the newly added operational amplifier 38. The operational amplifier 38, the resistor 40, and the capacitor 41 form a so-called error amplifier.

The non-inverting terminal of the operational amplifier 38 has a reference voltage V
_CC3 is connected. The operational amplifier 38 amplifies the minute voltage generated at the inverting terminal and the non-inverting terminal and transmits the output to the power amplifier 39. The output of the power amplifier 39 is input to the power supply terminal of the power amplifier 13. However, the output voltage of the power amplifier 39 determines the peak value of the square wave output of the power amplifier 13 at the frequency determined by the oscillator 18 (here, 2 KHz). The output of the power amplifier 13 is connected to the electrolytic capacitor 29 and the high voltage transformer 11.

By the negative feedback loop as described above, the voltages at the inverting terminal and the non-inverting terminal of the operational amplifier 38 become equal. Therefore, the current value of the 2 KHz square wave flowing through the developing sleeve 5 is constant.

The output of the power amplifier 39 is proportional to the peak-to-peak value of its 2 KHz square wave. The voltage is divided by the resistors 42 and 43, and the divided voltage is input to the AD conversion port of the CPU 20. CPU2
0 can know the peak-to-peak value of a 2 KHz square wave by reading the voltage input to its AD conversion port.

The voltage input to the AD conversion port of the CPU 20 is V _AD, and the output of the DA converter of the CPU 20 is V _{AD.
In the case of ref} , as in the first embodiment, the equation (3), that is, V
CP the value of V _ref so that _ref = KV _AD + Vφ holds.
U20 adjust. Although K and Vφ are fixed values, they are not the same values as in the first embodiment.

At this time, the DC offset voltage represented by the equation (7) is output across the capacitor 33 and the resistor 25 as in the first embodiment. Then, the DC offset voltage according to the equation (7) is superimposed on the square wave voltage of 2 KHz and output to the developing sleeve 5 via the resistors 23 and 21.

By performing the above control,
The developing sleeve 5 has a square wave of a constant current of 2 KHz,
A voltage obtained by superimposing a peak-to-peak voltage value of the square wave and a DC offset voltage that is linearly proportional is output. If the gap between the developing sleeve 5 and the image carrier 1 becomes wider, the equivalent capacitance between them becomes larger. At this time, since the 2 KHz square wave is performing constant current operation,
As a result, the peak-to-peak voltage of the square wave also increases. On the other hand, according to the equation (7), the DC offset voltage also increases in the negative direction. On the contrary, if the gap becomes narrow, 2K
The peak-to-peak voltage of the square wave of Hz becomes smaller, and the DC offset voltage also becomes smaller in the negative direction.

In this way, the electric field generated between the developing sleeve 5 and the image carrier 1 can be suppressed within a predetermined range in both the square wave component of 2 KHz and the DC offset component.

The characteristic of the control of the present embodiment is that the square wave of 2 KHz is made to be a constant current and the peak-to-peak value of the square wave is measured to indirectly develop the developing sleeve 5.
The thickness of the gap between the image carrier 1 and the image carrier 1 is obtained, and the optimum DC offset voltage corresponding to the gap is applied to the developing sleeve 5 according to the equation (7) to arbitrarily correct the developing density.

[0059]

As described above, in the developing device of the present invention, the AC component of the voltage applied between the image bearing member such as the photosensitive drum and the developer bearing member such as the developing sleeve. (For example, a square wave component of 2 KHz) is detected,
Change the voltage of the DC component sequentially according to the detected value,
Alternatively, the current value of the AC component is made constant, the voltage value of the AC component is detected, and the voltage of the DC component is sequentially changed according to the detected value. Even in the case where the gap between and is largely changed, there is an effect that the development density can be arbitrarily corrected.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of a vibration bias power source for a developing device of the present invention.

FIG. 2 is a schematic configuration diagram of an embodiment of a developing device of the present invention.

FIG. 3 is a circuit diagram of a second embodiment of a vibration bias power source of the developing device of the present invention.

[Explanation of symbols]

 1 image carrier 4 developer 5 developer carrier (developing sleeve) 6 magnetic material 7 development area 9 vibration bias power supply 11 high voltage transformer (first power supply circuit) 12 high voltage transformer (second power supply circuit) 16 operational amplifier (detection) Circuit) 17 Operational amplifier (control circuit) 18, 19 Oscillator 20 CPU

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Otaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoshimi Kuramochi 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Kenfumi Takubo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A developing device having a developer carrying member carrying and carrying a developer to visualize an electrostatic latent image in a developing region, and a developing bias power source for applying a vibration bias voltage to the developer carrying member. In the developing bias power supply, the first power supply circuit that outputs an AC voltage and the second power supply circuit that can change the output voltage according to an input signal
A power supply circuit, a detection circuit that detects an output current of the first power supply circuit, and a control circuit that changes a signal input to the second power supply circuit according to an output of the detection circuit. A developing device which outputs a voltage waveform obtained by superimposing an output of a first power supply circuit and an output of the second power supply circuit. 2. A developing device having a developer carrying member for carrying and carrying a developer to visualize an electrostatic latent image in a developing area, and a developing bias power source for applying a vibration bias voltage to the developer carrying member. In the developing bias power supply, a first power supply circuit that outputs an AC waveform of a constant current, a second power supply circuit that can change an output voltage according to an input signal, and an output voltage of the first power supply circuit A detection circuit for detecting, and a control circuit for changing a signal input to the second power supply circuit in accordance with an output of the detection circuit, the output of the first power supply circuit and the second power supply circuit. A developing device which outputs a voltage waveform in which the output and the output are superimposed.