JP2004093699A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of highly accurately measuring an amount of remaining toner. <P>SOLUTION: In a capacitance detecting device 707 which detects the capacitance of a capacitor which is created by a development sleeve 704, an antenna electrode 706, and toner staying between them, the capacitance of the capacitor which varies in a range from the state of being full of toner to an amount of remaining toner which causes an image defect is linearly converted into a voltage, and the capacitance of the capacitor which varies in a range from an amount of remaining toner which causes an image defect to the state of being empty of toner is linearly converted into a voltage, thereby calculating the amount of remaining toner by a CPU 708 based on the obtained voltage. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus.
[0002]
[Prior art]
Conventionally, among electrophotographic image forming apparatuses, a type using a process cartridge 101 as shown in FIG. 15 is known. The process cartridge 101 is a cartridge in which a photosensitive drum 105, a charging roller 103, a developing sleeve 104, a cleaner, and a toner container 102 (on which an antenna electrode 106 is disposed) are formed into a cartridge, and the toner in the toner container 102 is consumed. It is exchanged when it is lost. Therefore, for the purpose of notifying the user of the replacement time of the process cartridge, the toner amount in the toner container 102 is measured, and the measured toner amount is notified to the user.
[0003]
In the measurement of the amount of toner in the toner container 102, the dielectric constant of the material constituting the toner is larger than that in the atmosphere, and the larger the amount of toner distributed between the developing sleeve 104 and the antenna electrode 106, the more static the intermediate amount. Utilizing the fact that the capacitance increases, the capacitance between the developing sleeve 104 and the antenna electrode 106 is measured by the capacitance detecting device 107, and the measured value and the stored data are used by the CPU 108. , The amount of toner in the toner container 102 is calculated.
[0004]
The operation of the capacitance detection device 107 will be described in more detail with reference to FIG. When the process cartridge 101 is mounted on the image forming apparatus, the input terminal 212 is connected to the antenna electrode 106 via an electric contact (not shown), the input terminal 201 is connected to the output of the developing bias power supply, and the developing AC Applied.
[0005]
When a developing AC bias is applied to the developing sleeve 104, a current having a current value corresponding to the capacitance between the developing sleeve 104 and the antenna electrode 106 flows to the input terminal 212, and then passes through the diode 213 to the operational amplifier 204. (Which constitutes the integrating circuit 200 together with the resistor 211 and the capacitor 210), and the input terminal 201 connected to the output of the developing bias power supply has a current value corresponding to the capacity of the capacitor 202. A current flows, and is then input to the non-inverting terminal of the operational amplifier 204 via the diode 203.
[0006]
Then, the output level of the operational amplifier 204 becomes a level corresponding to the difference between the electrostatic capacitance between the developing sleeve 104 and the antenna electrode 106 and the capacitance of the capacitor 202, and is output from the output terminal 215, and is output from the CPU 108 ( 15) is input to the analog input terminal. Then, in the CPU 108, the digital data input to the analog input terminal and converted from analog to digital is compared with the stored data, and the amount of toner in the toner container 102 is calculated.
[0007]
FIG. 17 shows the output characteristics of the capacitance detection device 107. When the toner is full in the toner container 102, the capacitance becomes Cf and the detected voltage value becomes Vf. On the other hand, the capacitance value Ce is a capacitance when an image defect occurs in an image during printing due to a shortage of toner in the toner container 102, and the detected voltage value at this time is Ve.
[0008]
Here, the operation range of the detection voltage is set as large as possible according to the analog input voltage range of the CPU 108 to be connected.
[0009]
As a result, variations occur in the image forming apparatus, such as variations in capacitance between the developing sleeve 104 and the antenna electrode 106, errors that occur during analog-to-digital conversion in the CPU 108, and variations in characteristics of the capacitance detection device. The effect of the error can be reduced.
[0010]
Further, the capacitance detecting device 107 also detects the state of attachment / detachment of the process cartridge 101 to / from the image forming apparatus. When the process cartridge 101 is not mounted, the capacitance value between the developing sleeve 104 and the antenna electrode 106 becomes Cn, and the capacitance becomes smaller than when the process cartridge 101 is mounted. , The detection voltage Vn is output. The reason why the capacitance is reduced in this way is that when the process cartridge 101 is not mounted, the antenna electrode 106 in the process cartridge 101 is naturally not connected to the input of the capacitance detection device 107. In this way, by monitoring the level of the capacitance detecting device 107, it is possible to detect the mounting state of the process cartridge without providing any additional detecting means.
[0011]
[Problems to be solved by the invention]
(1) However, as shown in FIG. 17, the output voltage of the capacitance detection device 107 when the remaining amount of toner in the toner container 102 is small, and the output voltage Vn when the process cartridge 101 is not mounted. For example, if the output characteristics of the electrostatic capacitance detecting device 107 vary, the process cartridge 101 is erroneously detected that the process cartridge 101 is not mounted in spite of the small amount of toner. Had to be done.
[0012]
In order to solve such a problem, the difference between the output voltage of the capacitance detection device when the process cartridge 101 is not mounted and the output voltage when the remaining amount of toner is small is set to be large. However, in this case, the difference between the output voltage when the toner amount is small and the output voltage when the toner amount is large becomes small, and the toner amount is erroneously detected. Will happen.
[0013]
(2) In addition, a contact failure may occur at the electrical contact between the antenna electrode 106 and the capacitance detection device 107. In such a case, it is erroneously detected that the process cartridge 101 is not mounted.
[0014]
(3) Further, if the amount of toner in the toner container 102 is insufficient, an image defect occurs. However, the amount of toner causing the image defect cannot be detected with high accuracy.
[0015]
A first object of the present invention is to provide an image forming apparatus which can solve the above-mentioned problems and can measure the remaining amount of toner with higher accuracy.
[0016]
A second object of the present invention is to provide an image forming apparatus which can solve the above-described problems and can detect an abnormal mounting of a process cartridge.
[0017]
A third object of the present invention is to provide an image forming apparatus which can solve the above-described problems and can detect the remaining amount of toner causing an image defect with high accuracy.
[0018]
[Means for Solving the Problems]
According to an aspect of the present invention, there is provided an electrophotographic image forming apparatus using a toner as a developer, wherein the capacitance of a capacitor formed by at least two electrode members is a level at which an image defect occurs due to toner fullness. First converting means for linearly converting a capacitance that varies according to the remaining amount of toner into a voltage, and a toner empty amount based on the capacitance of the capacitor, which is a level at which the image defect occurs. A second conversion unit that linearly converts a capacitance that changes according to a state into a voltage; and an obtaining unit that obtains a toner amount based on the voltage obtained by the conversion by the first and second conversion units. It is characterized by having.
[0019]
2. The positive cycle half wave according to claim 1, wherein the first conversion means includes a positive cycle half wave current detecting means for detecting a positive cycle half wave current of the alternating current from one of the two electrodes. The capacitance of the capacitor can be measured based on the detection result of the current detection unit, and the second conversion unit detects a half-cycle current of a negative cycle of an alternating current from the other of the two electrodes. And a capacitance of the capacitor can be measured based on a detection result by the negative cycle half-wave current detecting means.
[0020]
In claim 1 or 2, one of the two electrode members may be a toner carrier.
[0021]
According to a fourth aspect of the present invention, in an electrophotographic image forming apparatus having a toner container in a detachable cartridge, a capacitance of a capacitor formed by toner staying in the toner container and at least two electrode members. A first conversion unit that linearly converts a capacitance that changes according to a level from a toner full level to a remaining toner level at which an image defect occurs to a voltage, and a capacitance of the capacitor, A second conversion unit that linearly converts the capacitance that changes according to the amount of remaining toner at a level at which an image defect occurs from the empty toner state to a voltage, and a voltage obtained by the conversion by the first conversion unit Acquiring means for acquiring the remaining amount of toner; and detecting means for detecting the mounting state of the cartridge based on the voltage obtained by the conversion by the second converting means. Characterized in that was.
[0022]
5. The positive cycle half wave according to claim 4, wherein the first conversion means includes a positive cycle half wave current detecting means for detecting a positive cycle half wave current of the alternating current from one of the two electrodes. The capacitance of the capacitor can be measured based on the detection result by the current detection means, and the second conversion means detects a half cycle current of a negative cycle of the alternating current from the other of the two electrodes. It has negative cycle half-wave current detection means, and can detect the mounting state of the cartridge based on the detection result by the negative cycle half-wave current detection means.
[0023]
According to a fifth aspect of the present invention, there may be provided an abnormal state detecting means for detecting an abnormal state of an electric contact for connecting the cartridge to the image forming apparatus based on a detection result by the negative cycle half-wave current detecting means.
[0024]
According to a sixth aspect of the present invention, the image forming apparatus may further include a prohibition unit for prohibiting the acquisition unit from acquiring the remaining amount of toner when the abnormal state detection unit detects an abnormal state.
[0025]
In any one of claims 4 to 7, one of the two electrode members may be a toner carrier.
[0026]
According to a ninth aspect of the present invention, in the electrophotographic image forming apparatus using a toner as a developer, the capacitance of a capacitor formed by at least two electrode members is a level at which an image defect occurs due to a full toner. A converting unit that linearly converts the capacitance that changes according to the remaining amount of toner into a voltage, an obtaining unit that obtains the remaining amount of toner based on the voltage obtained by the conversion by the converting unit, Detecting means for detecting the capacitance of the capacitor corresponding to the generated level of the remaining amount of toner.
[0027]
10. The positive cycle half-wave current detecting means according to claim 9, further comprising a positive cycle half-wave current detecting means for detecting a positive cycle half-wave current of the alternating current from one of the two electrodes. The capacitance of the capacitor can be measured based on the detection result by the means, and the detecting means detects a negative cycle half-wave current of the alternating current from the other of the two electrodes. Current detection means can be provided.
[0028]
According to a ninth aspect, a stop unit for stopping image formation when the detection unit detects the remaining amount of toner at a level at which an image defect occurs can be provided.
[0029]
In any one of claims 9 to 11, one of the two electrode members may be a toner carrier.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0031]
<First embodiment>
FIG. 1 shows a first embodiment of the present invention. This is an example of an image forming apparatus, and the structure is shown in FIG.
[0032]
In this image forming apparatus, only one recording sheet set on the recording sheet tray 402 is sent out from the recording sheet tray 402 by driving the pickup roller 403, and the registration roller 405 is moved in the direction of arrow A by the sheet feeding roller 404. Transported to The recording paper is conveyed to the process cartridge 410 at a predetermined timing by driving the registration roller 405, and an unfixed toner image is formed on the recording paper by a series of processes of electrophotography.
[0033]
As shown in FIG. 1, the process cartridge 410 includes a toner container 702 containing toner, a photosensitive drum 705 serving as an image carrier, a charging roller 703 serving as a charging device, and a developing sleeve 704 serving as a toner carrier. It comprises a photosensitive drum cleaning device (not shown) and an antenna electrode 706.
[0034]
After charging the surface photosensitive member on the photosensitive drum 705 by the charging roller 703, image exposure based on an image signal is performed by an image exposure unit. In the image exposure, main scanning is performed via a polygon mirror 411 that rotates a laser beam from a laser light source 412 in a scanner unit 414 and a reflection mirror 413. A latent image is formed by rotation (sub-scanning) of the photosensitive drum 415. Is done. The latent image formed on the photosensitive drum 705 is developed by the developing sleeve 704 to become a toner image. The developing sleeve 704 is connected to a high-voltage power supply, and a developing bias in which an AC voltage is superimposed on a DC voltage is applied.
[0035]
The antenna electrode 706 is made of a metal member, and is arranged inside the toner container 702 so as to face the developing sleeve 704. The toner is distributed between the developing sleeve 704 and the antenna electrode 706. Since the dielectric constant of the toner is larger than that of air, the capacitance between the developing sleeve 704 and the antenna electrode 706 changes and is distributed according to the amount of toner distributed between the developing sleeve 704 and the antenna electrode 706. It increases as the amount of toner increases.
[0036]
FIG. 3 shows a configuration of the developing bias generation circuit in the high voltage power supply 406 of FIG. In FIG. 3, reference numeral 513 denotes a transformer for generating a DC bias, which is driven by switching of the transistor 515, is rectified by the secondary-side capacitor 512 and the diode 510, and generates a DC voltage in a negative cycle. The output voltage is divided by a resistor 511 and a resistor 520 and compared with a reference voltage of a reference voltage source 517 by an operational amplifier 518. The output of operational amplifier 518 is coupled to transistor 509 to limit the voltage applied to transformer 513. With this configuration, the output is controlled to be a DC voltage of -300V.
[0037]
On the other hand, the AC bias is generated by a transformer 501 driven via transistors 520 and 521 by a clock signal DEVCLK output from an engine controller (not shown). The AC bias is a rectangular wave having an amplitude Vd (= 1500 Vpp) and a frequency fd (= 3 kHz).
[0038]
The toner image formed on the photosensitive drum 705 by such a method is transferred onto recording paper by the transfer roller 406, and an unfixed toner image is formed on the recording paper. Subsequently, the recording paper is conveyed to a fixing roller 407 and a pressure roller 408, where the recording paper is heated and pressurized, and the toner on the recording paper is fixed on the recording paper. The recording paper is further conveyed to the outside of the image forming apparatus 414 by the discharge rollers 409, and a series of recording processing is completed. These series of processes are controlled by a controller (not shown).
[0039]
FIG. 4 shows the configuration of the capacitance detection device 707 of FIG. The capacitance detecting device 707 detects the amount of toner in the toner container by detecting the capacitance between the developing sleeve 704 and the antenna electrode 706. In FIG. 4, reference numeral 601 denotes a connection terminal of the antenna electrode 706, which is connected to the antenna electrode 706 of the process cartridge 410. When a developing bias is applied to the developing sleeve 704, an alternating current It having a magnitude proportional to the capacitance value Ct between the developing sleeve 704 and the antenna electrode 706 flows. The alternating current It is rectified by a diode 604 and a diode 606 connected in opposite directions. A half-wave rectified half-wave current It1 flows through the diode 604, and a half-wave current having a reverse polarity to the half-wave current It1 flows through the diode 606. The current It2 flows. FIG. 5 shows waveforms of the developing bias, the AC current It, and the half-wave currents It1 and It2.
[0040]
The half-wave current It1 is input to an integrating circuit 61 (configured by an operational amplifier 614, a resistor 616, and a capacitor 615), and the half-wave current It2 is configured by an integrating circuit 62 (configured by an operational amplifier 609, a resistor 612, and a capacitor 61). Respectively. The average current value It1 (av) of the half-wave current It1 and the average current value It2 (av) of the half-wave current It2 can be approximated by the following equation. Note that the current in the direction input to the integration circuit is positive.
It1 (av) = fd × Vd × Ct (11)
It2 (av) = − fd × Vd × Ct (12)
Here, Vd is the amplitude of the developing AC bias, and fd is the frequency of the developing AC bias.
[0041]
A terminal 602 is connected to the developing sleeve 704 in the process cartridge 410. 603 is a reference capacitor. The capacitance value Cref of the reference capacitor 603 is set according to the capacitance value between the developing sleeve 704 and the antenna electrode 706. In the present embodiment, a 10 pF capacitor corresponding to a capacitance value between the developing sleeve 704 and the antenna electrode 706 in a state where an image defect occurs due to a shortage of toner in the toner container 702 is used.
[0042]
When the developing bias is applied, an alternating current Ir having a magnitude corresponding to the capacitance value of the capacitor 603 flows.
[0043]
The alternating current Ir is rectified by the diode 605 and the diode 607, and a half-wave rectified half-wave current Ir1 flows through the diode 605, and a half-wave current Ir2 having a polarity opposite to that of Ir1 flows through the diode 607. The half-wave current Ir1 is input to the integration circuit 61, and the half-wave current Ir2 is input to the integration circuit 62. Similarly to the AC current It, the average current value Ir1 (av) of the half-wave current Ir1 and the average current value Ir2 (av) of the half-wave current Ir2 can be approximated by the following equation.
Ir1 (av) = − fd × Vd × Cref (21)
Ir2 (av) = fd × Vd × Cref (22)
Next, the operation of the integration circuit will be described. These integrating circuits smooth the current input to the inverting terminal of the operational amplifier and convert it to a DC voltage. Since It1 (av) + Ir1 (av) is input to the integration circuit 61 and It2 (av) + Ir2 (av) is input to the integration circuit 62, the output values Vs1 and Vs2 of the integration circuits 61 and 62 are as follows. It can be expressed by an equation.
Vs1 = Vr−Rs × fd × Vd × (Ct−Cref) (31)
Vs2 = Vr + Rs × fd × Vd × (Ct−Cref) (32)
Here, Vr is the voltage value of the reference voltage source 608 input to the non-inverting terminal of the operational amplifier, and Rs is the resistance value of the resistors 612 and 616. In the present embodiment, Vt is set to 3.0V. As can be seen from the above equations (31) and (32), the output values Vs1 and Vs2 of the integration circuits 61 and 62 change according to the capacitance value Ct between the developing sleeve 704 and the antenna electrode 706. The two output signals are coupled to analog input terminals of a CPU 708 of an engine controller that controls the image forming apparatus 414 as output signals of the capacitance detection device 707. The outputs of the operational amplifiers 609 and 614 are connected to diodes 617 and 618, respectively. The diodes 617 and 618 limit the level of the output signal, and prevent a voltage exceeding the inputtable range from being input to the analog signal of the CPU 708 (FIG. 1). Here, the level of the output signal is limited to 3.2V.
[0044]
6 and 7 are diagrams showing output characteristics of Vs1 and Vs2. The horizontal axis is the capacitance value Ct between the developing sleeve 704 and the antenna electrode 706, Cf is the capacitance value when the toner in the toner container 702 is full, and Ce is the amount of toner in the toner container 702. Is a capacitance value at a level at which an image defect caused by shortage occurs. Cn is a capacitance value corresponding to a case where the process cartridge 410 is not mounted on the image forming apparatus 414. The output signal Vs1 has a characteristic that fluctuates from 0.3 V to 3.0 V when the toner in the toner container 702 is full to empty.
[0045]
On the other hand, the detectable range of the analog terminal of the CPU 708 (FIG. 1) is from 0 V to 3.3 V, and the signal Vs1 changes over almost the entire detectable range of the analog terminal in accordance with the change in the amount of toner in the toner container 702. Characteristics. By analog-to-digital conversion of the output signal Vs1 inside the CPU 708 and comparing it with data previously stored in a storage device (not shown), the remaining amount of toner in the toner container 702 can be detected.
[0046]
On the other hand, the output signal Vs2 has a small change width of the detection value in a region where the amount of toner in the toner container 702 changes, and the detection value changes in a region of the capacity or less when the toner is almost empty. When the process cartridge 410 is not mounted on the image forming apparatus 414, the characteristic is approximately 0V. The output state of the process cartridge 410 can be detected by converting the output signal Vs2 from analog to digital in the CPU 708 and comparing the output signal Vs2 with a preset level.
[0047]
FIG. 8 is a flowchart illustrating an example of a procedure for detecting the amount of toner in the toner container 702. The toner amount is detected using the output value Vs1 of the capacitance detecting device 707. In step S1002, initial values of parameters used in a series of processes are set. The timer value Ta of the timer operation performed by the CPU 708 is set to 0, and the MIN value Vs1 (min) 3.3 of the output value Vs1 of the capacitance detecting device 707 is set.
[0048]
Here, the MIN value of the output device Vs1 of the capacitance detection device 707 will be described. Vs1 (min) is the minimum value of the output value of the capacitance detecting device 707 that periodically fluctuates due to the toner stirring means in the toner container and changes with the capacitance value between the developing sleeve 704 and the antenna electrode 706. Value. The image forming apparatus 414 determines the toner amount from Vs1 (min).
[0049]
Then, in step S1003, the timer A is started to start the counting operation, and in step S1004, the state of the flag TSE indicating whether the toner can be detected is checked. The flag TSE becomes 1 only when the developing AC bias is in the output state and the output signal Vs1 rises. If the flag TSE is 1, the flow advances to step S1005 to read the output signal Vs1. If the flag TSE is 0, it is determined that the output signal is not valid, and the process does not proceed until the flag TSE changes.
[0050]
The output value Vs1 read in step S1006 is compared with Vs1 (min), and if Vs1 is smaller than Vs1 (min), the value of Vs1 (min) is updated. In step S1008, the timer A value is checked. If the processing time has elapsed for 15 seconds or more, the process proceeds to step S1009. If the processing time has not reached 15 seconds, the process proceeds to step S1004 again to continue sampling the output value. After the operation of the timer A is stopped in step S1009, conversion to the toner amount is performed in step S1010. The conversion into the toner amount is performed using a data table stored in advance in a storage device in the engine controller (not shown). This data table is configured as shown in FIG. 9, in which the relationship between the output voltage and the amount of toner is set. For example, when Vs1 (min) is 1.63 V, the toner amount is converted to 33% from the data table.
[0051]
In step S1011, the converted toner amount value is displayed on the operation panel 401 of the image forming apparatus 414, and a series of processing ends.
[0052]
FIG. 10 is a flowchart showing a series of processing procedures when detecting the mounting state of the process cartridge 410. The detection of the mounting state of the process cartridge 410 is performed using the output value Vs2 of the capacitance detection device 707. In step S1102, initialization of a timer value TB used in a series of processing is performed. Next, after driving the developing AC bias in step S1103, a wait of 10 msec is performed by counting by the timer B in steps S1104 and S1105. This time is the time required for the developing AC bias to rise and the time required for the signal of the output value Vs2 of the capacitance detecting device 707 to rise.
[0053]
In step S1106, Vs2 is read, and the level of Vs2 read in step S1107 is compared with a predetermined level to determine the mounting state of the process cartridge 410. If Vs2 is 1 V or less, it is determined that the process cartridge 410 is not mounted. If Vs2 is 1 V or more, it is determined that the process cartridge 410 is mounted. In steps S1108 and S1112, a flag CRGD indicating the mounting state of the process cartridge is set based on the result in step S1107. Subsequently, in step S1109, the developing AC bias is turned off, the timer B is stopped, and a series of processing ends. The image forming apparatus 414 determines the mounting state of the process cartridge 410 in all controls based on the state of the flag CRGD. When the process cartridge 410 is in the mounted state, the print operation is enabled, and when the process cartridge 410 is not mounted, information is displayed on the operation panel 401 to notify the user.
[0054]
As described above, in the present embodiment, the current from the antenna electrode 706 that changes according to the amount of toner is separated into half-wave currents, and the separated currents are detected by the detection circuits having different characteristics, thereby detecting the amount of toner. And the detection of the mounting of the process cartridge was performed using different detection circuits. This makes it possible to detect the process cartridge mounting state with high reliability while maintaining good toner amount detection accuracy.
[0055]
<Second embodiment>
The present embodiment is different from the conventional example in that a poor electrical contact between the process cartridge and the capacitance detecting device can be detected.
[0056]
The image forming apparatus according to the present embodiment has the same configuration as the image forming apparatus according to the first embodiment. The capacitance detection device according to the present embodiment has the same configuration as the capacitance detection device 707 according to the first embodiment, and includes an antenna electrode provided in a toner container and a capacitance detection device. Is not electrically conductive, no current is input from one input terminal of the electrostatic capacitance detection device, but a developing bias is input to the other input terminal, and the electrostatic capacitance detection device The output of the device is, for example, an output value Vs1 of 3.2V and an output value Vs2 of 0.3V.
[0057]
The processing procedure in the present embodiment will be described with reference to FIG. In step S1302, the output value Vs2 of the capacitance detection device is read, and the output value read in step S1303 is compared with 1V (predetermined level). If the read output value Vs2 is 0.3 V and is 1 V or less, it is determined that the antenna electrode 706 and the capacitance detection device 707 are not electrically connected, and the process proceeds to step S1315. Then, the user is notified by displaying on the operation panel that the capacitance detection device is in an abnormal state. Thereafter, this process ends, and the toner amount is not detected.
[0058]
On the other hand, if the output value Vs2 is 1 V or more in step S1303, in steps S1304 to S1313, the amount of toner in the toner container is detected in the same manner as steps S1003 to S1011 in FIG. Display on the panel.
[0059]
As described above, in this embodiment, the current from the antenna electrode 706 that changes according to the amount of toner is separated into half-wave currents, and the separated currents are detected by detection circuits having different characteristics. The amount of toner is detected based on the result of (1), and the abnormality of the contact of the process cartridge 410 is detected based on the result of the other detection circuit. Was stopped.
[0060]
As a result, it is possible to detect the contact abnormality of the process cartridge with high reliability while maintaining good toner amount detection accuracy, and when the abnormality is detected, the toner amount detection process is stopped. It is possible to prevent erroneous detection of the toner amount when a contact failure occurs.
[0061]
<Third embodiment>
The present embodiment differs from the conventional example in that the printing operation can be stopped when the amount of toner in the toner container reaches the amount of toner that causes image defects.
[0062]
The image forming apparatus according to the present embodiment has the same configuration as the image forming apparatus according to the first embodiment except for the capacitance detection device. The capacitance detection device according to the present embodiment differs from the capacitance detection device 707 according to the first embodiment in that the resistance value of the resistor corresponding to the resistor 612 is different from that of the toner container. The difference is that the output signal Vs2 changes abruptly at the capacitance Ce at which an image defect occurs due to a shortage of the toner amount.
[0063]
FIG. 12 shows an example of the characteristic of Vs1 with respect to the capacitance in the present embodiment, and FIG. 13 shows an example of the characteristic of Vs2 with respect to the capacitance in the present embodiment.
[0064]
The processing procedure in the present embodiment will be described with reference to the flowchart in FIG. In step S1502, initial values of parameters used in a series of processes are set. The timer value Ta of the timer operation performed by the CPU 708 is set to 0, and the MIN value Vs1 (min) 3.3 of the output value Vs1 of the capacitance detecting device 707 is set. Then, in step S1503, the timer A is started to start the counting operation, and in step S1504, the state of the flag TSE indicating whether the toner can be detected is checked. In step S1505, the output value Vs2 is read, and subsequently, it is determined whether the value read in step S1506 is 2 V or more.
[0065]
If the output value Vs2 is not equal to or less than 2 V, the process proceeds to step S1507, and the toner amount is detected. On the other hand, if the output value Vs2 is equal to or less than 2V, it is determined that the toner amount is equal to or less than the level at which an image defect occurs, and the timer A is stopped in step S1514. Further, by displaying on the operation panel 401 that the toner in the process cartridge 701 is empty in step S1516, the user is prompted to replace the process cartridge with a new process cartridge.
[0066]
As described above, the current from the antenna electrode that changes according to the amount of toner is separated into half-wave currents, and the separated currents are detected by two detection circuits having different characteristics. The characteristics of the two detection circuits are different. One of the detection circuits is set to a detection characteristic in which the toner amount in the toner container changes from a full state to an empty state, and is used for detecting the toner amount in the toner container. The other detection circuit has a configuration in which the toner amount is set to a characteristic that rapidly changes at a level at which an image defect occurs, and the output level is detected to prevent the image defect from occurring.
[0067]
This makes it possible to detect whether or not the toner in the toner container of the process cartridge is at a level at which an image defect occurs while maintaining good toner amount detection accuracy.
[0068]
【The invention's effect】
As described above, according to the present invention, the configuration as described above allows the remaining amount of toner to be measured with higher accuracy.
[0069]
Further, according to the present invention, since the configuration is as described above, it is possible to detect a mounting abnormality of the process cartridge.
[0070]
Furthermore, according to the present invention, since the above-described configuration is employed, it is possible to detect the remaining amount of toner that causes image failure with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating a structure of an image forming apparatus 414.
FIG. 3 is a circuit diagram showing a configuration of a developing bias generation circuit in the high voltage power supply 406 of FIG. 2;
FIG. 4 is a circuit diagram showing a configuration of the capacitance detection device 707 of FIG.
FIG. 5 is a diagram showing waveforms of a developing bias, an AC current It, and half-wave currents It1 and It2.
FIG. 6 is a diagram illustrating an example of a characteristic of Vs1 with respect to capacitance in the first embodiment.
FIG. 7 is a diagram illustrating an example of a characteristic of Vs2 with respect to capacitance in the first embodiment.
FIG. 8 is a flowchart illustrating an example of a procedure for detecting a toner amount in a toner container 702;
FIG. 9 is a diagram showing a correspondence between an output voltage and a toner amount in a table.
FIG. 10 is a flowchart showing a series of processing procedures when detecting the mounted state of the process cartridge 410.
FIG. 11 is a flowchart illustrating an example of a processing procedure according to the second embodiment.
FIG. 12 is a diagram illustrating an example of a characteristic of Vs1 with respect to a capacitance according to the second embodiment.
FIG. 13 is a diagram illustrating an example of a characteristic of Vs2 with respect to capacitance in the second embodiment.
FIG. 14 is a flowchart illustrating an example of a processing procedure according to the second embodiment.
FIG. 15 is an explanatory diagram for describing detection of a toner amount in a conventional example.
16 is a circuit diagram showing a configuration of the capacitance detection device 107 in FIG.
FIG. 17 is a diagram illustrating an example of a characteristic of an output voltage of the capacitance detection device 107 with respect to a capacitance in a conventional example.
[Explanation of symbols]
406 High voltage power supply
410 process cartridge
702 Toner container
703 charging roller
704 developing sleeve
705 Photosensitive drum
706 antenna electrode
707 Capacitance detection device
708 CPU

Claims (12)

In an electrophotographic image forming apparatus using a toner as a developer,
A first capacitance that linearly converts the capacitance of a capacitor formed by at least two electrode members, which varies according to the amount of toner remaining from a level at which toner is full to a level at which an image defect occurs, to a voltage; Conversion means;
A second conversion unit that linearly converts the capacitance of the capacitor, which varies according to a remaining amount of toner at a level at which the image defect occurs to a toner empty state, into a voltage,
An image forming apparatus comprising: an obtaining unit configured to obtain a toner amount based on a voltage obtained by the conversion by the first and second conversion units. 2. The positive cycle device according to claim 1, wherein the first conversion unit includes a positive cycle half-wave current detection unit configured to detect a positive cycle half-wave current of an alternating current from one of the two electrodes. Measuring the capacitance of the capacitor based on the detection result by the half-wave current detection means,
The second conversion means includes a negative cycle half-wave current detection means for detecting a negative cycle half-wave current of the alternating current from the other of the two electrodes, and the negative cycle half-wave current detection means An image forming apparatus for measuring the capacitance of the capacitor based on the detection result of the image forming apparatus. The image forming apparatus according to claim 1, wherein one of the two electrode members is a toner carrier. In an electrophotographic image forming apparatus having a toner container in a removable cartridge,
A capacitance of a capacitor formed by the toner stagnating in the toner container and at least two electrode members, the capacitance being changed from a full state of the toner to a remaining amount of toner at a level at which an image defect occurs. First conversion means for linearly converting
A second conversion unit that linearly converts the capacitance of the capacitor, which varies according to a remaining amount of toner at a level at which the image defect occurs to a toner empty state, into a voltage,
Acquiring means for acquiring the remaining amount of toner based on the voltage obtained by the conversion by the first converting means;
An image forming apparatus comprising: a detection unit configured to detect a mounting state of the cartridge based on a voltage obtained by the conversion by the second conversion unit. 5. The positive cycle half-wave current detecting means according to claim 4, wherein said first converting means includes a positive cycle half-wave current detecting means for detecting a positive cycle half-wave current of an alternating current from one of said two electrodes. Measuring the capacitance of the capacitor based on the detection result by the half-wave current detection means,
The second conversion means includes a negative cycle half-wave current detection means for detecting a negative cycle half-wave current of the alternating current from the other of the two electrodes, and the negative cycle half-wave current detection means An image forming apparatus for detecting a mounting state of the cartridge based on a detection result of the image forming apparatus. 6. An image forming apparatus according to claim 5, further comprising an abnormal state detecting section for detecting an abnormal state of an electric contact for connecting said cartridge to the image forming apparatus based on a detection result by said negative cycle half-wave current detecting section. apparatus. 7. The image forming apparatus according to claim 6, further comprising a prohibition unit that prohibits the acquisition unit from acquiring the remaining amount of toner when the abnormal state detection unit detects an abnormal state. The image forming apparatus according to claim 4, wherein one of the two electrode members is a toner carrier. In an electrophotographic image forming apparatus using a toner as a developer,
Conversion means for linearly converting the capacitance of a capacitor formed by at least two electrode members, which varies according to the amount of toner remaining from a level of toner fullness to a level at which an image defect occurs, into a voltage. When,
Obtaining means for obtaining the remaining amount of toner based on the voltage obtained by the conversion by the conversion means;
An image forming apparatus comprising: a detection unit configured to detect a capacitance of the capacitor corresponding to a remaining amount of toner at a level at which the image defect occurs. 10. The positive cycle half wave according to claim 9, wherein the conversion means includes a positive cycle half wave current detecting means for detecting a positive cycle half wave current of an alternating current from one of the two electrodes. Measuring the capacitance of the capacitor based on the detection result by the current detection means,
The image forming apparatus according to claim 1, wherein the detecting unit includes a negative cycle half-wave current detecting unit that detects a half cycle current of a negative cycle of the alternating current from the other of the two electrodes. The image forming apparatus according to claim 9, further comprising a stop unit that stops image formation when the detection unit detects a remaining amount of toner at a level that causes an image defect. The image forming apparatus according to claim 9, wherein one of the two electrode members is a toner carrier.

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