JP2003345119A - Developing device and image forming apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that can reduce errors caused by the load characteristic and temperature characteristic of a bias application means and can accurately detect the quantity of developer in a developer container and to provide an image forming apparatus having the developing device. <P>SOLUTION: The developing device in which a pair of electrodes 403 of an electrode member are disposed so that capacitance between the pair of electrodes 403 varies according to a quantity of toner in a cartridge and a remaining developer quantity detection circuit 502 is set so as to calculates the quantity of toner in the cartridge according to the capacitance, is provided with a feedback circuit 604 which makes adjustment so that the AC bias voltage of a developing bias circuit 401 has a specific value. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for visualizing a latent image bearing member carrying a latent image as a developer image by applying a developer from the developer bearing member to the latent image bearing member and the developing device. The present invention relates to an image forming apparatus including a device.

[0002]

2. Description of the Related Art Conventionally, in a developing device provided in such an image forming apparatus, the amount of toner as a developer in a developer container is detected, and when the amount of toner in the developer container falls below a predetermined amount. 2. Description of the Related Art There is known a developing device configured to promote replenishment of toner in a developer container.

The detection of the remaining toner amount of the developing device will be described with reference to FIG. Note that FIG. 11 is a schematic diagram showing a schematic configuration of such a developing device.

Such a developing device, as shown in FIG.
A developer container (not shown), a developer carrier 51, an electrode pair 43 which is an electrode member composed of an electrode A and an electrode B which are antenna plates, a developing bias circuit 41 which is a bias applying unit, and a measuring unit. And a remaining toner amount detection circuit 52 which is a calculation unit.

The developing bias circuit 41 is adapted to apply an AC bias to the developer carrying member 51 at a prescribed AC bias value.

The toner remaining amount detecting circuit 52 measures a change in electrostatic capacitance between the electrode A and the developer carrying member 501 and between the electrode A and the electrode B, and based on the electrostatic capacitance, the above-mentioned development is performed. It is configured to calculate the amount of toner in the agent container.

That is, in such a developing device, when an AC bias is applied to the developer carrying member 51 by the developing bias circuit 41, the electrode A and the electrode B are connected between the developer carrying member 51 and the electrode A. An AC bias is applied with an AC bias value I ₁ commensurate with the electrostatic capacitance generated during.
Similarly, an AC bias with an AC bias value I ₂ is applied to the impedance element 35 by the developing bias circuit 41, and this AC bias value I ₂ is used as a reference value for toner amount calculation by the toner remaining amount detection circuit 52. To do. Then, the toner remaining amount circuit 52 calculates and detects the toner remaining amount in the developer container based on the AC bias values I ₁ and I ₂ .

[0008]

However, in the above-described conventional developing device, the developing bias circuit does not have a circuit configuration in which load characteristics and temperature characteristics are sufficiently taken into consideration. When a load fluctuation of several pF occurs, an output fluctuation of several tens of volts occurs. In addition, the Vbe of the high voltage transformer drive transistor has a temperature characteristic of several tens of meters.
Even if V fluctuation occurs, output fluctuation of several tens of V will occur.

These output fluctuations lead to an error in the output value of the remaining toner amount detection, which hinders highly accurate remaining toner amount detection.

In view of this, the present invention reduces the error due to the load characteristic and temperature characteristic of the bias applying means, and can accurately detect the amount of the developer in the developer container, and an image forming apparatus including the developing device. The purpose is to provide a device.

[0011]

SUMMARY OF THE INVENTION The main invention of the present application is to provide a developer container for containing a developer and a developer from the developer container which is disposed so as to face a latent image carrier carrying a latent image. A latent image carrier is rotated while being supported on the surface and is supplied to the latent image carrier. The latent image carrier is developed with the developer from the developer carrier. A developing device for visualizing a developer image, the electrode member being an electrode pair arranged extending in the developer container at right angles or parallel to the axis of the developer carrier, and an AC bias voltage applied to the electrode member. A bias applying means for applying a voltage, a measuring means for measuring the electrostatic capacity between the pair of electrodes, and a calculating means for calculating the developer amount in the developer container based on the electrostatic capacity measured by the measuring means. The electrode pair of the electrode member is provided with electrostatic between the electrode pair. The amount is arranged so as to change according to the amount of developer in the developer container, and the calculating unit calculates the amount of developer in the developer container according to the capacitance value measured by the measuring unit. In the developing device set as described above, the developing device is provided with adjusting means for adjusting the AC bias voltage of the bias applying means to a predetermined value.

Another main invention of the present application is an image forming apparatus for recording an image formed by a series of image forming processes on a recording material, which comprises a latent image carrier and the developing device. An image forming apparatus characterized by the above.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described.

FIG. 1 is a schematic sectional view showing a schematic configuration of a printer as an example of an image forming apparatus according to this embodiment.

As shown in FIG. 1, such a printer includes a photosensitive drum 101, which is a latent image carrier, and a photosensitive drum 1.
01, a charging roller 106 for uniformly charging the surface, and a rotary polygon mirror 103 rotated by a scanner motor 104.
The semiconductor laser 102 as a light source that scans and exposes the laser beam 105 onto the photosensitive drum 101 by emitting the laser beam 105 toward the target, and the electrostatic latent image formed on the photosensitive drum 101 serves as a developer. Developing device 107 for developing with toner, and developing device 107
A transfer roller 108 for transferring the toner image developed at 1 to a recording sheet, which is a predetermined recording material, and a fixing roller 10 for fusing the toner image transferred onto the recording sheet with heat.
9 and 9.

Here, the conveyance of the recording paper of such a printer will be described.

In such a printer, when the cassette paper feed roller 110 makes one rotation, the recording paper is fed from the cassette having the function of identifying the size of the recording paper and sent out to the conveying path. The recording sheet fed from the cassette is conveyed by the conveying roller 114.
In the case of paper feeding from a manual paper feed port that does not have the function of identifying the size of the recording paper, the manual paper feed roller 111 feeds the recording paper from the paper feed port to the transport path. Further, in the case of paper feeding from a cassette that is removable and has a function of identifying the size of the recording paper, the optional cassette paper feeding roller 112 feeds the recording paper from the cassette to the conveyance path. Further, in the case of feeding from an envelope feeder that is detachable and is capable of stacking only envelopes, by using the envelope feeder paper feed roller 113,
The recording sheets are fed one by one into the transport path.

Recording paper fed from other than the envelope feeder is fed to the photosensitive drum 101 by the pre-transfer roller 117 after the front end and the rear end are detected by the pre-feed sensor 116. And the top sensor 1
The writing of the image on the photosensitive drum 101 (recording / printing) and the conveyance of the recording sheet are synchronized with the fed recording sheet by the unit 18, and the length of the fed recording sheet in the conveying direction is measured. To be done. By the paper ejection sensor 119,
The presence or absence of recording paper after fixing is detected, and the discharge roller 120
Then, the recording paper after fixing is discharged to the outside of the machine.

The printed recording paper is the flapper 12
The transfer destination (outside discharge or detachable double-sided unit) can be switched by 1. The recording sheet conveyed to the duplex unit is conveyed to the reversal section by the conveyance roller 122, and the front and rear ends are detected by the reversal sensor 123. When the reversing roller 124 sequentially operates in the forward or reverse direction, the recording paper is reversed and the recording paper is conveyed to the re-feed unit, and the detection re-feed sensor 125 detects the presence or absence of the recording paper in the re-feed unit. And re-feed roller 126
The recording sheet in the sheet re-feeding section is again fed to the transport path.

Next, the control system of such a printer will be described.

FIG. 2 is a block diagram showing the circuit configuration of the control system of the printer according to this embodiment.

In such a printer, as shown in FIG. 2, a printer controller 201 develops image code data sent from an external device (not shown) such as a host computer into bit data necessary for printing by the printer. At the same time, it reads the internal information of the printer and displays it.

Further, the printer engine control unit 202 controls the operation of each unit of the printer engine in accordance with an instruction from the printer controller 201, and notifies the printer controller 201 of printer internal information.

The recording paper conveyance control unit 203 is adapted to drive or stop a motor, a roller or the like for conveying the recording paper in accordance with an instruction from the printer engine control unit 202.

The high voltage controller 204 controls the output of each high voltage in each process such as charging, development and transfer in accordance with the instruction from the printer engine controller 202.

The optical system control unit 205 includes the scanner motor 1
Driving / stopping of 04 and lighting of the laser beam are controlled in accordance with instructions from the printer engine control unit 202.

The fixing temperature controller 207 is adapted to adjust the temperature of the fixing device to the temperature designated by the printer engine controller 202.

The optional cassette control unit 208 is attachable to and detachable from the printer main body, and drives or stops the drive system according to an instruction from the printer engine control unit 202, and also determines whether or not the paper is present and the paper size information. It will be notified to 202.

The duplex unit controller 209 is attachable to and detachable from the printer body, and the printer engine controller 2
According to the instruction 02, the operation of reversing and re-feeding the recording paper is performed, and at the same time, the operation state is notified to the printer engine control unit 202.

The envelope feeder control unit 210 is attachable to and detachable from the printer body, and the printer engine control unit 2
The drive system is driven or stopped according to the instruction 02, and the printer engine control unit 202 is notified of the presence or absence of paper.

Next, the developing device 107 according to the present embodiment.
Will be described.

The developing device 107 includes a cartridge 503 which is a developer container, an electrode pair 403 which is an electrode member, and a developing bias circuit 40 which is a bias applying means including an adjusting means.
1 and a remaining toner amount detection circuit 502 having a measuring unit and a calculating unit.

In the developing device 107 of this embodiment, the electrode pair 403 is arranged inside the cartridge 503, and the electrode pair 40 is formed by using the developing bias of the developing bias circuit 401.
3 is applied with an AC bias, and the remaining toner amount detection circuit 502
The electrostatic capacitance transition between the electrode pair 403 is detected by the display device, and the toner LOW is displayed in several stages according to the detection result.
It is characterized by being optimized so as not to be affected by load characteristics.

FIG. 3 is a view showing a connection state between the cartridge 503 and the printer, and FIG. 4 is a view showing the cartridge 50.
3 is a diagram showing an internal configuration, and FIG. 5 is a diagram showing an example of a circuit configuration of the toner remaining amount detection circuit 502 of the present embodiment.

The developing bias circuit 401 is shown in FIGS.
As shown in, the developer carrying member 501 and one electrode of the electrode pair 403 are connected. Further, the developing bias circuit 401
Is connected to the control circuit 407 of the toner remaining amount detection circuit 502 via the impedance element 402. Then, by the measuring means 408, the impedance element 40
The AC current I ₁₁ from 2 is used to set the reference voltage V _ll for detecting the remaining amount of toner in the cartridge 503.

As shown in FIG. 3, an electrode pair 403 is arranged near the developer carrying member 501, and the electrode pair 403 is arranged.
Is connected to the remaining toner amount detection circuit 502 with the toner capacity Ca (C1 + C2). Therefore, the AC current I _12a applied to the toner capacity Ca is the measuring means 40 shown in FIG.
8 is applied to the amplifier circuit 405 to detect the presence or absence of toner V
It is output as _{12a (= V ll -I 12 ×} R 1).

With such a configuration, it is possible to output a detection value according to the amount of toner that has entered between the developer carrier 501 and one electrode of the electrode pair 403 and between the electrode pair 403.

Here, the toner remaining amount detection of this embodiment will be described in detail with reference to the flowchart shown in FIG.

First, the developing bias circuit 401 applies a developing bias to the developer carrying member 501 (S10).
2).

Then, by the measuring means 408, between the developer carrying member 501 and one electrode of the electrode pair 403, the electrode pair 40
The detection voltage V _12a according to the combined capacitance value of 3 is output (S103).

The value of the detected voltage V _12a is input to the calculating circuit 409 which is a calculating means to calculate the remaining toner amount (S1).
04).

In performing the above-mentioned processing, it is necessary that the output of the developing bias does not fluctuate due to the temperature characteristics and load characteristics of the element.

FIG. 7 shows the developing bias circuit.

The voltage amplifier circuit 601 amplifies the clock signal from the CPU. Current amplifier circuit 602
Is connected to the primary side of the high voltage transformer 603 and drives the high voltage transformer 603. The feedback circuit 604 serving as an adjusting unit rectifies the AC voltage applied to the capacitive element 605, compares the rectified value with the reference voltage Vz, and controls the voltage amplification according to the comparison result.

As described above, the output voltage of the developing bias circuit 401 is made constant by the feedback circuit configuration of the feedback circuit 604 and the output is used for the residual toner detection, thereby eliminating the residual toner amount error due to the temperature characteristic and the load characteristic. It is possible to accurately detect the remaining amount of toner.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The description of the same configuration as the first embodiment is omitted.

The present embodiment is characterized in that the variation due to the temperature characteristic of the bias applying means is reduced. In performing the above-mentioned toner remaining amount detection processing, it is necessary that the developing bias output of the bias applying means does not vary due to temperature characteristics.

FIG. 8 is a diagram showing the circuit configuration of the developing bias circuit which is the bias applying means in this embodiment.

In the developing bias circuit of this embodiment, the voltage amplifier circuit 701 amplifies the clock signal from the CPU. The current amplifier circuit 702 is connected to the primary side of the high voltage transformer 703 and drives the high voltage transformer 703.

The developing bias circuit of the present embodiment has a plurality of electric elements including transistors Q101 and Q102 and a resistor 101 as adjusting means.

The transistors Q101 and Q102 used in the current amplification circuit 702 have temperature characteristics, and tend to increase the input voltage of the high voltage transformer 703 (because VBE has a negative temperature characteristic). Therefore, the resistor R used in the voltage amplifier circuit 701 is
Reference numeral 101 denotes a temperature characteristic element (temperature characteristic of metal film resistance +) that tends to lower the input voltage of the high-voltage transformer 703.
To use. By thus performing the combination that cancels the temperature characteristics of the elements, the variation in the temperature characteristics of the developing bias is reduced.

Further, in this embodiment, the REF voltage circuit is used in order to eliminate the fluctuation of the power supply (Vcc). Also in this circuit, it is necessary to consider the temperature characteristics.

FIG. 9 shows an example of the REF voltage circuit.

In FIG. 9, Q201 is an output stage transistor, ZD201 is a Zener diode for generating a reference voltage, and Q202 is a feedback transistor. The temperature characteristic of Q201 is corrected by the feedback circuit. However, the temperature characteristic of the transistor Q202 is not configured to be corrected. Therefore, the REF voltage tends to be lowered.

Therefore, the Zener diode ZD201 has a temperature characteristic element (5 V) which tends to increase the input voltage.
The above element uses the temperature characteristic +). By performing a combination that cancels the temperature characteristics of the elements in this way, R
The temperature characteristic variation of the EF voltage is reduced. That is, the temperature characteristic variation of the developing bias is reduced.

As described above, by making the output voltage constant in the circuit configuration and using the output for the toner remaining amount detection, it is possible to eliminate the toner remaining amount error due to the temperature characteristic and to accurately detect the toner remaining amount. Become.

(Third Embodiment) Next, a third embodiment of the present invention will be described. The description of the same configuration as the first embodiment is omitted.

The present embodiment is characterized in that fluctuations due to load characteristics are reduced. In performing the toner remaining amount detection process, it is necessary that the output of the developing bias does not change due to the load characteristic.

FIG. 10 is a diagram showing the circuit configuration of the developing bias circuit which is the bias applying means in this embodiment.

In the developing bias circuit of this embodiment, as shown in FIG.
The clock signal from U is amplified in voltage. The current amplifier circuit 802 is connected to the primary side of the high voltage transformer 803 and drives the high voltage transformer 803. The capacitive element 805 is connected in parallel with the capacity of the cartridge 503. When such a connection is made, when a load (capacity) variation of α occurs, the change rate is α / (C1
+ C2), and the ratio can be reduced compared to α / C1 when not connected.

By thus keeping the output voltage constant in the circuit configuration and using the output for the toner remaining amount detection, it is possible to eliminate the toner remaining amount detection error due to the load characteristic and to accurately detect the toner remaining amount. Becomes

[0063]

As described above, according to the invention of the present application, it is possible to accurately detect the amount of the developer in the developer container by reducing the error due to the load characteristic and the temperature characteristic of the bias applying means. it can.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

2 is a block diagram showing a configuration of a control system of the image forming apparatus of FIG.

FIG. 3 is a diagram showing a schematic configuration of a developing device in the first embodiment of the present invention.

FIG. 4 is a diagram for explaining an internal configuration of a developer container provided in the developing device of FIG.

FIG. 5 is a diagram showing a circuit configuration of a bias applying means in the first embodiment of the present invention.

FIG. 6 is a flowchart for explaining a developer amount detecting operation of the developing device according to the first embodiment of the present invention.

FIG. 7 is a circuit diagram showing a configuration of bias applying means in the first embodiment of the present invention.

FIG. 8 is a circuit diagram showing a configuration of bias applying means in a second embodiment of the present invention.

FIG. 9 is a circuit diagram showing a configuration of a REF voltage circuit used for bias applying means in the second embodiment of the present invention.

FIG. 10 is a circuit diagram showing a configuration of a bias applying means according to a third embodiment of the present invention.

FIG. 11 is a diagram for explaining detection of a developer amount in a developer container in a conventional developing device.

[Explanation of symbols] 101 Photosensitive drum (latent image carrier) 107 developing device 401 developing bias circuit (bias applying means) 402 Impedance element 403 Electrode pair (electrode member) 409 Calculation circuit (calculation means) 501 developer carrier 604 Feedback circuit (adjusting means) 805 Capacitance element Q101 transistor (electric element) Q202 Transistor (electric element) R101 resistance (electric element)

Claims (6)

[Claims] 1. A latent image carrier which is disposed so as to face a developer container for containing a developer and a latent image carrier for carrying a latent image and which rotates while carrying the developer from the developer container on its surface. A developing device, comprising: a developer carrying member to be supplied to a body, wherein the latent image carrying member visualizes the latent image as a developer image by applying the developer from the developer carrying member, An electrode member, which is an electrode pair extending in the developer container at right angles or parallel to the axis of the developer carrier, a bias applying means for applying an AC bias voltage to the electrode member, and a space between the electrode pair. And a calculating means for calculating the amount of developer in the developer container on the basis of the electrostatic capacity measured by the measuring means. Capacitance changes depending on the amount of developer in the developer container In the developing device, the calculating unit is set to calculate the amount of developer in the developer container according to the capacitance value measured by the measuring unit. A developing device comprising: an adjusting unit that adjusts a voltage to a predetermined value. 2. The developing device according to claim 1, wherein the adjusting unit has a function of monitoring the AC bias voltage from the bias applying unit and performing negative feedback. 3. The developing device according to claim 1, wherein the adjusting unit includes a plurality of electric elements, and each electric element is configured to cancel the temperature characteristics of the other electric elements. 4. The developing device according to claim 1, wherein the adjusting unit includes a capacitive element connected in parallel with the load to the AC bias voltage from the bias applying unit. apparatus. 5. The developing device according to claim 3, wherein the adjusting unit is configured such that the electric elements are arranged within the shortest distance of 5 cm on the same printed circuit board. 6. An image forming apparatus for recording an image formed by a series of image forming processes on a recording material, the latent image carrier and the developing device according to any one of claims 1 to 5. And an image forming apparatus.