JP2001290349A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of setting a developing condition on an AC current applied to a developing sleeve at the time of developing by grasping the change of a gap between the developing sleeve and a photoreceptor drum in a wide range. SOLUTION: A self-exciting oscillation circuit 110 including the developing sleeve 14s and the photoreceptor drum 10 as its circuit elements is actuated before developing, and self-exciting oscillation frequency Fs changed by depending on electrostatic capacity decided according to the size of the gap between the sleeve 14s and the drum 10 is measured. At the time of developing, bias voltage including an AC component is applied to the sleeve 14s by a separate-exciting oscillation circuit 120. The amplitude (AC voltage Vac) of the AC component at such a time is set to a smaller value as the frequency Fs becomes smaller and smaller based on an Fs-Vac function previously stored in a ROM 160.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image by an electrophotographic process, such as a copying machine, a printer, and a facsimile.
The present invention relates to an image forming apparatus employing a so-called jumping development method.

[0002]

2. Description of the Related Art In a jumping developing method, a developing sleeve having a thin toner layer formed on its surface is opposed to a photosensitive drum with a gap larger than the thickness of the toner layer. The development is performed by applying a bias voltage having an AC voltage component therebetween.

[0003] The AC voltage is controlled to a constant voltage by a constant voltage power supply so that good development can be performed. A gap between the developing sleeve and the photosensitive drum is provided coaxially on both ends of the developing sleeve and coaxially with a spacer roller having a diameter twice as large as the gap between the developing sleeve and the photosensitive drum. It is ensured by contacting it.

However, as the use of the developing device progresses, the spacer roller wears, and the gap between the developing sleeve and the photosensitive drum gradually narrows. When the gap changes, the electric field formed between the developing sleeve and the photosensitive drum changes, no matter how the AC voltage is maintained at a constant voltage, and good development cannot be performed. Therefore, conventionally, prior to development, the voltage of the developing sleeve was measured with an optimal current flowing between the developing sleeve and the photosensitive drum using an AC constant current power supply.
A technique has been developed in which the magnitude of the AC voltage component of the bias voltage is determined based on the measured voltage and the constant voltage power supply is controlled (Japanese Patent Laid-Open No. 7-175282).

[0005]

However, when the voltage applied to the developing sleeve is to be detected by the control CPU of the image forming apparatus, it is usually practical to use an A / D converter. When the voltage is measured, the measurement range becomes narrow, and even if the wear of the spacer roller is enough to withstand actual use, the measurement range may be exceeded. in this case,
It is necessary to switch the A / D converter to another one to change the measurement range.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to set development conditions such as the AC voltage during the development by grasping the change in the gap over a wide range without performing a complicated operation such as switching a measurement range. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

[0007]

In order to achieve the above object, an image forming apparatus according to the present invention comprises an image carrier on which an electrostatic latent image is formed, and a developing device having a developing area opposed to the image carrier. An image forming apparatus having a developer carrier for carrying and transporting the developer, and applying a bias voltage including an AC component between the image carrier and the developer carrier to perform development by a jumping method, A self-excited oscillation circuit that oscillates at a frequency dependent on a capacitance formed in a gap between the image carrier and the developer carrier, frequency detection means for detecting an oscillation frequency in the self-excited oscillation circuit, Condition setting means for setting the condition of the bias voltage based on the frequency, and developing the electrostatic latent image according to the set condition.

According to another aspect of the present invention, there is provided an image forming apparatus, comprising: an image carrier on which an electrostatic latent image is formed; and a developer carrying and transporting a developer to a developing area opposed to the image carrier. And an image forming apparatus that performs a jumping-type development by applying a bias voltage including an AC component between the image carrier and the developer carrier. It is equivalently formed by the capacitance formed by the gap between the developer carrier and the reactance of the transformer for inducing and generating the AC component of the bias voltage between the image carrier and the developer carrier. Transient voltage applying means for rapidly changing an applied voltage on the primary side of the transformer with respect to a resonant circuit, and transiently generating an electrical oscillation determined by a time constant unique to the resonant circuit; and a frequency of the transient electrical oscillation. Frequency detecting means for detecting Based on the issued frequency, a condition setting means for setting the condition of the bias voltage, and performs development of the electrostatic latent image by the set condition.

In addition, a separately-excited oscillation circuit comprising a switching element which is turned on / off in synchronization with a clock signal inputted from the outside and a transformer having a primary coil inserted in a power supply circuit of the switching element is provided. A voltage induced in the secondary coil of the transformer by turning on / off the switching element is applied between the developer carrier and the image carrier as an AC component of a bias voltage; Is characterized in that the magnitude of the amplitude of the AC voltage induced on the secondary side of the transformer of the separately excited oscillation circuit is adjusted.

Further, the developer carrying member is detachably attached to the main body of the image forming apparatus, and means for judging whether or not the attached developer carrying member is unused. , With an unused developer carrier mounted,
Storage means for storing the frequency detected by the frequency detection means, wherein the condition setting means compares the frequency detected after the start of use of the developer carrier with the frequency stored in the storage means, The condition of the bias voltage is set based on a result.

Further, a determining means for determining whether or not the frequency detected by the frequency detecting means is within a specified range, and when the determining means determines that the detected frequency is out of the specified range, Prohibiting means for prohibiting the image formation.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to a single-color digital copying machine (hereinafter simply referred to as "copier").
An example in which the present invention is applied will be described. (Embodiment 1) FIG. 1 is a diagram showing an entire configuration of a copying machine according to an embodiment. The copying machine includes an image reader unit 1 for reading a document image and a printer unit 2 for printing the read image on a recording sheet and reproducing it.

The image reader unit 1 is a well-known one that scans a document image placed on a platen glass and converts the image into an electric signal to obtain image data. The image data obtained by the image reader unit 1
The digital signal is subjected to / D conversion and further subjected to necessary processing such as shading correction, density conversion, and edge enhancement, and then output as a laser diode drive signal.

The printer section 2 forms an image on a recording sheet by an electrophotographic method, and includes an exposure scanning section 4, an image processing section 5, a paper feeding section 6, and the like. The exposure scanning unit 4 includes a laser diode 7, a polygon mirror 8,
A scanning lens 9 and the like are provided. The laser diode 7 receives the drive signal from the control unit 3 and emits light modulated laser light. The emitted laser light is reflected and deflected by a mirror surface of a polygon mirror 8 that is driven to rotate at a constant speed, passes through a scanning lens 9, and exposes and scans the surface of the photosensitive drum 10 of the image processing unit 5.

The image processing unit 5 includes the photosensitive drum 1
0, a cleaner 11, a charging charger 12, a developing device 13, and the like are arranged. Photoconductor drum 10
After the residual toner on the surface of the photoconductor is removed by the cleaner 11 before receiving the exposure, the toner is uniformly charged by the charging charger 12, and when exposed in such a uniformly charged state, An electrostatic latent image is formed on the photoconductor on the surface of the photoconductor drum 10.

The electrostatic latent image is developed by the developing device 13 and visualized as a toner image. This toner image is
The transport belt 1 is fed from the sheet feeding unit 6 in synchronization with the image forming operation and stretched by a driving roller 18 and a driven roller 19.
Transfer charger 1 on the recording sheet conveyed in
After being transferred by the fixing device 5 and thermally fixed by the fixing device 14, the sheet is discharged onto the sheet discharge tray 16, whereby the image formation based on the image data of the document is completed.

An operation panel Pn is provided on the upper surface of the copying machine. The operation panel Pn includes a numeric keypad for inputting the number of copies, a start key for instructing the start of copying, a setting key for setting various copy modes, a display unit for displaying a mode set by the setting key, and the like as a message. It is composed of The developing device 13 is detachable from the copier main body via a holder (not shown) fixed to the main body side, and is a non-contact type one-component developing system using insulating magnetic toner, a so-called so-called developing system. The development is performed by a jumping development method.

As shown in FIG. 2, the developing device 13 has a developing sleeve 14s. A thin toner layer is formed on the surface of the developing sleeve 14s. This is a device that applies a bias voltage between the two to develop the toner by electrostatically flying it. The bias voltage is a DC voltage (hereinafter, referred to as an “offset voltage”).
Also say. ) Is superimposed with an AC voltage.

The interval between the developing sleeve 14s and the photosensitive drum 10 is set to a predetermined interval equal to or greater than the thickness of the toner layer (hereinafter, this interval is referred to as "Ds"). A pair of spacer rollers 14k having a diameter larger than that of the developing sleeve 14s is rotatably mounted coaxially on both ends of the developing sleeve 14s.
By pressing the peripheral surface of 4k against the surface of the photosensitive drum 10 by a biasing means (not shown), the Ds is secured.

FIG. 3 is a block diagram relating to the generation of the bias voltage and a control section for determining the voltage. A self-excited oscillation circuit 110, a separately-excited oscillation circuit 120, a variable constant voltage power supply 130, a variable constant voltage power supply 140, a RAM 150, and a ROM 160 are connected to the CPU 100 of the control unit 3. In this figure, for convenience, the self-excited oscillation circuit 110, the developing sleeve 14s, and the photosensitive drum 10 are shown separately and independently, but the developing sleeve 14s and the photosensitive drum 10 are
Each is included in the circuit elements of the self-excited oscillation circuit 110. Further, the self-excited oscillation circuit 110 and the separately-excited oscillation circuit 120 share some circuit elements as described later.

Self-excited oscillation circuit 110 and separately-excited oscillation circuit 1
20 is selectively operated by a self / other switching signal from the CPU 100. The self-excited oscillation circuit 110 is activated when determining the bias voltage at the time of development prior to development, and the separately excited oscillation circuit 120 is activated at the time of development. The self-excited oscillation circuit 110 includes a variable constant-voltage power supply 13.
0 is used as a power supply to generate a high-frequency oscillation voltage, superimposes the high-frequency oscillation voltage on a DC voltage (hereinafter, also referred to as an “offset voltage”) from another variable constant-voltage power supply 130, and applies it to the developing sleeve 14 s I do. At this time, the amplitude of the high-frequency oscillation component (hereinafter, also referred to as “AC voltage”) is determined by an amplitude setting signal from CPU 100 as described later, and the magnitude of the offset voltage is
It is determined by the offset voltage setting signal.

The self-excited oscillation circuit 110 includes the developing sleeve 14s and the photosensitive drum 10 as described above.
0 functions as a capacitor (C) having a capacitance determined by the facing area and the distance (Ds) between them (hereinafter, when the developing sleeve 14s and the photosensitive drum 10 are treated as capacitors on a circuit, "Cds").

The self-excited oscillation circuit 110 oscillates at a frequency dependent on the capacitance. As the use of the developing device 13 progresses and the spacer roller 14k gradually wears, Ds becomes gradually shorter. As Ds decreases, the capacitance of Cds increases, resulting in a lower oscillation frequency. That is, there is a certain correlation between the oscillation frequency and Ds. When Ds becomes short, it is necessary to change the bias voltage accordingly. In the present embodiment, A
The C voltage is changed. That is, the AC voltage is reduced as Ds becomes shorter.

The CPU 100 monitors a voltage waveform from the self-excited oscillation circuit 110 and detects an oscillation frequency (hereinafter, referred to as “self-excited oscillation frequency Fs”) from the waveform. R
The OM 160 stores a function that associates the self-excited oscillation frequency Fs with the AC voltage Vac (hereinafter, referred to as an “Fs-Vac function”). The AC voltage Vac is determined with reference to the function. At the time of development, the AC voltage V
An amplitude setting signal is output to the constant voltage power supply 130 so that ac is applied to the developing sleeve 14s.

When the separately excited oscillation circuit 120 is operated, the CPU 100 outputs the amplitude setting signal to the constant voltage power supply 13.
At the same time, a synchronous signal for setting the separately excited oscillation frequency Fo to the separately excited oscillation circuit 120 is output to the separately excited oscillation circuit 120. The separately excited oscillation circuit 120 oscillates at a frequency corresponding to the synchronization signal, superimposes a DC voltage from the constant voltage power supply 140 on the AC voltage Vac, and applies the DC voltage to the developing sleeve 14s.

The CPU 100 also controls other components of the image processing unit 5 other than the developing device 13, such as the exposure scanning unit 4 and the paper feeding unit 6. Since it is well known, a detailed description thereof will be omitted. FIG. 4 is a diagram showing an example of a circuit for realizing the function shown in the functional block diagram of FIG. 3, in which the self-excited oscillation circuit 110 is surrounded by a two-dot chain line. The separately excited oscillation circuits 120 are respectively constituted by the above-mentioned portions.

A primary coil 21 composed of an A winding and a B winding of the transformer 20, a secondary coil 22 composed of an F winding magnetically coupled to the primary coil 21, and a secondary coil 22
An LC resonance circuit is constituted by Cds connected to one end of the LC resonance circuit. A variable constant voltage power supply 140 is connected to the other end of the secondary coil 22. When the self / other switching signal of the CPU 100 becomes a High signal, the transistor 30 is turned on, and the transistors 25 and 26 are turned on.

When the transistor 25 is turned on, the base of the oscillation transistor 24 and the tertiary coil 23 (C winding) serving as a feedback coil are conducted. The collector of the transistor 24 is connected to one end of the primary coil 21 and
A voltage is applied to the middle point of the next coil 21 by the constant voltage power supply 130. A part of the output voltage of the transistor 24 is positively fed back by a feedback circuit including a primary coil 21 (B winding), a secondary coil, and a tertiary coil (C winding).

Also, by turning on the transistor 26,
The base of the oscillation transistor 27 and the D winding of the tertiary coil are conducted. The D winding generates a voltage 180 ° out of phase with the C winding, and the voltage is positively fed back to the oscillation transistor 27. Thereby, the transistor 2
Reference numerals 5 and 27 serve as a kind of push-pull operation to increase the oscillation output.

The self-excited oscillation circuit 110 oscillates at a self-excited oscillation frequency Fs determined by the capacitance of Cds and the reactance of the primary coil 21 and the secondary coil. At this time, the voltage of the quaternary coil 31 composed of the E winding, which generates a voltage proportional to the C winding, is monitored by the CPU 100. From the monitoring result, the self-excited oscillation frequency Fs is detected as described later. Is done.

At the time of development, the CPU 100 switches the self / other switching signal to the Low signal and turns off the transistors 25 and 26 by turning off the transistor 30, while the CPU 100 sends the synchronization signal P 1 to the transistor 27. And outputs the synchronization signals P1 and 1 to the transistor 24.
The synchronization signal P2 having a phase shift of 80 ° is output. As a result, the transistor 27 and the transistor 24 are turned on alternately, and the push-pull operation is performed as in the case of the self-excited oscillation. At 22,
A high-frequency oscillation voltage is generated.

When the separately excited oscillation circuit 120 is operated, that is, at the time of development, the CPU 100
4s, the amplitude of the AC component of the bias voltage (AC
Voltage) is the self-excited oscillation frequency F
The amplitude setting signal is set so as to have a size corresponding to s. The voltage generated in the quaternary coil 31 is smoothed by a smoothing circuit including a diode 32 and a capacitor 33, and is input to one input terminal of a differential amplifier 34.
A voltage determined by the amplitude setting signal from the CPU 100 is input to the other input terminal of the differential amplifier 34, and a voltage corresponding to the difference between the voltages of both input terminals is input to the constant voltage power supply 130. The constant voltage power supply 130 changes the magnitude of the output voltage according to the level of the voltage input from the differential amplifier 34.

The CPU 100 has a variable constant voltage power supply 140
, An offset voltage setting signal is output, and the variable constant voltage power supply 140 applies a voltage corresponding to the offset voltage setting signal to the secondary coil 22. FIGS. 5 to 8 are flowcharts related to a series of control of the image forming operation by the CPU 100. Note that this flowchart mainly relates to the image forming process, and the image reading operation by the image reader unit 1 is omitted.

FIG. 5 is a flowchart of the main routine. When the switch of the copying machine is turned on (step S).
1 is Yes), the main power is turned on (step S2),
Initialization processing such as setting various variables in the RAM 150 to initial values is performed (step S3), and the fixing device 1
The warm-up of the fixing roller No. 4 is started (step S4), and a self-excited oscillation frequency Fs measurement routine is executed (step S5).

FIG. 6 is a flowchart of a self-excited oscillation frequency Fs measurement routine. First, the main motor is started (step S10), and the photoconductor drum 10, the developing sleeve 14s, and the like are driven to turn on the charging charger 12 (step S11). Next, the self / other switching signal is set to a high signal (step S12), and a bias voltage is applied to the developing sleeve 14s (step S13). here,
Since the photoconductor drum 10 is not exposed, the photoconductor drum 10 is rotated while being uniformly charged. On the other hand, the developing sleeve 14s is rotated in a state where a thin toner layer is formed on the surface facing the photosensitive drum 10.

In the above state, the monitoring (sampling) of the voltage applied to the E winding (FIG. 4) is executed.
First, the counter value n of the voltage sampling counter inside the CPU 100 is reset (step S14),
The voltage sampling timer for measuring the voltage sampling time interval t1 is reset (step S15).

Next, the value of the voltage sampling counter is set to 1
Is incremented (step S16), the voltage value at that time is measured (step S17), and the measurement result is stored in the memory at the address indicated by the counter value n (address n).
(Step S18). The stored voltage value is
Hereinafter, it is referred to as “voltage data”. Subsequently, it is determined whether or not the value n of the voltage sampling counter has exceeded a predetermined sampling number N (N is a positive integer) (step S19). If not (step S19: No), the voltage sampling timer Waits for the time to elapse (time t1 elapses from the timer reset) (Yes in step S20), and returns to step S15.

Thereafter, until the number of voltage data samples reaches N (Yes in step S19), step S15 is performed.
To repeat the processing of step S20. FIG. 9 (a)
FIG. 9B shows a voltage waveform input to the CPU 100.
It is an enlarged view of the part enclosed by the dashed-dotted line of the said waveform. FIG.
As shown in (b), the sampling causes N pieces of voltage data to be stored in the memory at the sampling interval t1 from the voltage data (n = 1) at a certain time. FIG. 9C is a diagram showing a voltage data storage area in the memory and a storage area for tilt data described later. Here, t1 is a time short enough to detect a maximum value and a minimum value in a voltage waveform in a measurement data analysis routine to be described later, and N is determined in consideration of t1. The number is such that at least one peak (maximum value) and one valley (minimum value) of the waveform can be detected.

When the above sampling is completed (Yes in step S19), the self / other switching signal is switched to a low signal (step S22), the voltage application to the developing sleeve 14s is stopped (step S22), and the charging charger 12 is turned off. (Step S23), the main motor is stopped (Step S24), and a measurement data analysis routine is executed (Step S25).

FIG. 7 shows a flowchart of the local data analysis routine. First, the variable n for specifying the storage address of the voltage data in the memory and the variable s for specifying the storage address of the slope data are set to 1 (step S30), and the voltage data Vn at the address n is read from the memory ( Step S
31). Next, it is determined whether or not (n + 1) exceeds N. If not (Yes in step S32),
The voltage data V (n + 1) at the address (n + 1) is read (step S33).

The value obtained by subtracting Vn from V (n + 1) is stored in variable X (step S34). X indicates the degree of change of the voltage data in the section between (n + 1) and n. Then, it is determined whether the value of X is less than 0, 0, or exceeds 0 (steps S34 and S38). Since it is rare for X to be exactly 0, actually, in the above-described determination, it is determined to be 0 when the absolute value of X is equal to or less than a predetermined value such that the degree of the change is considered to be almost 0. .

When X is less than 0, ie, (n + 1)
If the voltage waveform in the section between と and n falls rightward, the slope data is set to “−1” and the slope data is stored at address s of the memory (step S36). When X is 0, that is, in a section between (n + 1) and n,
If the maximum value or the minimum value of the voltage waveform exists, the slope data is set to “0”, and the slope data is stored at address s.

If X exceeds 0, ie, (n
If the voltage waveform in the section between +1) and n rises to the right, the slope data is set to "+1" and the slope data is stored in the memory at address s (step S41). When the processing following any of the above determinations is performed, the variable n and the variable s are each incremented by 1 (step S3).
7, 40, 42), and returns to step S32.

When the inclination data of the last section "(N-1) to N" is obtained (Yes in step S32), step S32 is executed.
Proceeding to 43, a variable s for specifying the storage address of the inclination data in the memory is set to 1. The inclination data at address s is read out (step S44), and it is determined whether or not the inclination data is 0 (step S45). If it is not 0 (No in step S45), the variable s is incremented by 1 (step S46), and the processes in steps S44 and S45 are performed. That is, the above processing is repeated until the address where the inclination data 0 is stored first can be detected. When the address where the inclination data 0 is stored is detected (Yes in step S45), the address (variable s) is determined. Value) to the variable Y
(Step S47).

Subsequently, in steps S48 to S50, the same processing as in steps S46, S44 and S45 is performed to detect the address where the inclination data 0 is stored for the second time. When the address s is detected (step S5)
0, Yes), the process proceeds to step S51, and (s−X) is used as the period data Ps (= s−X), and the period Ts of the voltage waveform is obtained by an arithmetic expression, Ts = 2 × Ps × t1, and the self-excited oscillation frequency is obtained. Fs is obtained by the following equation (step S52).

Fs = 1 / Ts When the self-excited oscillation frequency Fs is determined, the process returns to the main routine. Returning to FIG. 5, it is determined whether or not the temperature of the fixing roller has reached a predetermined fixable temperature (step S6). When the temperature reaches the predetermined temperature (Yes in step S6), printing is possible.

Next, when a print start instruction is given by pressing a start key or the like (Yes in step S7),
A print routine is executed (Step S8). FIG.
2 shows a flowchart of the print routine. First,
The main motor is started (step S60), the charger 12 is turned on (step S61), the recording sheet is started to pass (step S62), and the exposure scan of the photosensitive drum 10 is started (step S63).

The synchronous signals P1 and P2 are output to operate the separately excited oscillation circuit (step S64), and the Fs-V
The AC voltage Vac is determined with reference to the ac function, and an amplitude setting signal is output to the constant voltage power supply 130 so that the AC voltage Vac is applied to the developing sleeve 14s (step S65). Is activated. Subsequently, the transfer charger 15 is turned on (step S66), the exposure scan of the photosensitive drum 10 is completed (step S67), the output of the synchronization signals P1 and P2 is stopped, and the developing device is turned off (step S68).

Then, the transfer charger 15 is turned off (step S69), the feeding of the recording sheet is terminated (step S70), and the charging charger is turned off (step S7).
1) Stop the main motor (step S72),
The image forming process (print routine) ends. (Modification of First Embodiment) In the above example, the self-excited oscillation frequency Fs is obtained by analyzing the voltage data, but the self-excited oscillation frequency Fs may be obtained as follows.

As shown in FIG. 10, the voltage taken out from the E winding (FIG. 4) is inputted from one input terminal of the comparator 35, and is compared with a reference voltage.
Input to U100. FIG. 11A shows the comparator 3
11 shows the waveform of the voltage taken out from the E winding and input to 5, and FIG. 11B shows the output result from the comparator 35 (input waveform to the CPU 100).

The CPU 100 measures the time t2 from a certain rising edge of the input waveform to the kth rising edge, divides t2 by k to obtain a period Ts, and obtains a self-excited oscillation frequency Fs.
s is obtained by the following equation. Fs = 1 / Ts The measurement accuracy can be improved by increasing the number of k. (Second Embodiment) In the first embodiment, the self-excited oscillation circuit and the separately-excited oscillation circuit are configured so as to partially overlap each other. However, in the second embodiment, the self-excited oscillation circuit and the separately excited oscillation circuit are configured separately and independently.

FIG. 12 is a block diagram relating to the generation of a bias voltage and a control portion for determining the voltage in the second embodiment. Also in this case, only the developing sleeve 14s and the photosensitive drum 10 are common circuit elements of the self-excited oscillation circuit 210. To the developing sleeve 14s, a bias voltage is applied in which an AC voltage generated by the AC voltage generator 240 is superimposed on a DC voltage (offset voltage) generated by the DC voltage generator 230. The CPU 200 includes a D / A converter 250
, An amplitude setting signal is output to each of the oscillation circuits 210 and 220, and both oscillation circuits 210 and 220 generate an AC voltage according to the amplitude setting signal. Further, the CPU 100
Outputs a voltage switching signal to the DC voltage generator 230, and the DC voltage generator 230 generates a DC voltage having a magnitude corresponding to the signal.

The AC voltage generator 240 is connected to the switching circuit 26
By 0, it is connected to either the self-excited oscillation circuit 210 or the separately-excited oscillation circuit 220. The switching is performed by a switching signal from the CPU 200, and when determining a bias voltage during development prior to development,
It is connected to a self-excited oscillation circuit 210 and is connected to a separately excited oscillation circuit 220 during development.

When connected to the self-excited oscillation circuit 210, the self-excited oscillation circuit 210 self-oscillates at a frequency corresponding to the capacitance of Cds, and the AC voltage generator 240 generates the AC voltage at that frequency. The voltage is applied to the developing sleeve 14s. CP
U200 monitors the AC voltage generated by AC voltage generator 240 at this time via A / D converter 270, and stores the monitoring result in memory 270 in the same manner as in the first embodiment. After that, the self-excited oscillation frequency Fs is detected.

The Fs-Vac function is stored in the memory 270 as in the first embodiment. At the time of development, the Fs-Vac function is calculated based on the detected self-oscillation frequency Fs.
-The AC voltage Vac is determined with reference to the Vac function.
An amplitude setting signal is output so that the voltage Vac is applied to the developing sleeve 14s. Further, at the time of development, the CPU 200 outputs an oscillation clock to the separately excited oscillation circuit 220 so that the AC voltage has a predetermined frequency, and outputs an amplitude setting signal obtained from the self-excited oscillation frequency Fs.

Thus, at the time of development, the developing sleeve 1
An appropriate bias voltage according to the magnitude of Ds is applied to 4s. The CPU 20 according to the second embodiment
Since the control contents by 0 are the same as those in the first embodiment described with reference to the flowcharts of FIGS. 5 to 8, the description is omitted. (Modification of Second Embodiment) FIG. 13 is a functional block diagram according to the modification, and corresponds to FIG.
This modified example has basically the same configuration as the above example (FIG. 12) except that it has a comparator 310 instead of the A / D converter 270. The common portions are denoted by the same reference numerals, detailed description thereof will be omitted, and different portions will be mainly described.

In the above example, the voltage data was analyzed to determine the self-excited oscillation frequency Fs.
s may be obtained in the same manner as in the modification of the first embodiment. That is, the voltage extracted from the AC voltage generator 240 is input to the comparator 310, and the result of comparing the voltage with the reference voltage is output to the CPU 200. CPU2
00 measures the time t2 from a certain rising edge of the input waveform from the comparator 310 to the k-th rising edge, divides t2 by k to obtain a period Ts, and then calculates the self-oscillation frequency Fs (= 1 / Ts). (Embodiment 3) Embodiments 1 and 2 above
Then, a resonance circuit is formed by using the developing sleeve 14s and the photosensitive drum 10 as capacitors on the circuit, the resonance circuit is self-excited, and an AC voltage during development is set based on the frequency at that time. did.

Therefore, in the first embodiment, the tertiary coil 23 for positive feedback, the tertiary coil 2
And transistors 30 and 26 for turning on / off the transistors 25 and 26 for turning on and off the feedback current flowing from the transistor 3 to the oscillation transistors 24 and 27, and for turning on and off the transistors 25 and 26 when measuring the self-excited oscillation frequency and during development. However, in the third embodiment, the setting of the AC voltage at the time of development can be performed with a simpler circuit configuration.

FIG. 14 is a diagram showing a circuit configuration according to the third embodiment, and corresponds to FIG. 4 of the first embodiment. The circuit according to the third embodiment has basically the same configuration as that of the circuit of the first embodiment (FIG. 4) except that it has a transistor 41 instead of tertiary coil 23, transistors 25 and 26, and transistor 30. . Therefore, common parts are denoted by the same reference numerals, detailed description thereof will be omitted, and different parts will be mainly described. In the third embodiment, the transformer 40 is configured so that an electromotive force proportional to the F winding is generated in the G winding.

Vcc is applied from the power supply line 42 to the emitter of the transistor 41, and a bias resistor 43 is connected between the emitter and the base. A ringing setting signal composed of a High signal or a Low signal is output from the CPU 100 to the base, and the collector is connected to the base of the transistor 24. In the above configuration, the transistor 41 is in a non-conductive state while the ringing setting signal is at the high signal, and is in a conductive state during the low signal. When the transistor 41 is off, the transistor 24 is off, and when the transistor 41 is on, the transistor 24 is on.

Prior to development, the CPU 100 outputs a low signal of the ringing setting signal for a predetermined time, and turns off the transistor 24 when the current monitor signal reaches a specified value. When the transistor 24 is turned off, L including the primary coil 21 (B winding), the secondary coil 22 and Cds
In the C resonance circuit, damped oscillation transiently occurs as shown in FIG. The frequency (period) of the damped oscillation is also C
It varies with the capacitance of ds, that is, Ds. As the use of the developing device 13 progresses and the spacer roller 14k gradually wears, Ds becomes gradually shorter. As Ds becomes shorter, the capacitance of Cds increases, and as a result, FIG.
The state shown in (a) changes to the state shown in FIG. (B), and the frequency of the damped vibration decreases (the period becomes longer; Tg1 <Tg2). That is, the frequency of the damped oscillation and Ds
There is a certain correlation between. As Ds becomes shorter, it is necessary to change the bias voltage (AC voltage) accordingly.

In the third embodiment, prior to the development, the frequency Fg of the damped oscillation is obtained by the same timing and the same method as in the first embodiment. In the ROM 160,
A function that associates the frequency Fg with the AC voltage Vac (hereinafter, referred to as an “Fg-Vac function”) is stored therein.
The CPU 100 calculates Fg from the detected damped oscillation frequency Fg.
-The AC voltage Vac is determined with reference to the Vac function.
An amplitude setting signal is output to the constant voltage power supply 130 so that the voltage Vac is applied to the developing sleeve 14s.

As described above, in the third embodiment,
Providing a ringing generation circuit 410 (FIG. 14) for generating damped oscillation in the LC resonance circuit, and determining an AC voltage during development from the magnitude of the frequency (period) of the damped oscillation generated in the LC resonance circuit; It was done. In the above example, in a state where a constant current is applied to the B winding of the primary coil 21, the current is cut, the LC resonance circuit is vibrated transiently, and the frequency is measured. However, the present invention is not limited to this, and the frequency of the transient vibration that occurs immediately after energization of the B winding may be measured. Alternatively, the current value of the current flowing through the B winding is suddenly changed from the first current value to a current value different in magnitude from the first current value, and the frequency of the transient vibration generated at that time is measured. You may make it. Fourth Embodiment In the third embodiment, the separately-excited oscillation circuit and the ringing generation circuit are partially overlapped (120 and 410 in FIG. 14), but in the fourth embodiment, they are separately and independently. It was decided to configure.

FIG. 16 is a block diagram of a control part for generating a bias voltage and determining the bias voltage according to the fourth embodiment, and corresponds to the block diagram of FIG. 12 of the second embodiment. The fourth embodiment has basically the same configuration as the second embodiment (FIG. 12) except that a ringing generation circuit 410 is provided instead of self-excited oscillation circuit 210. Therefore, common parts are denoted by the same reference numerals, detailed description thereof will be omitted, and different parts will be mainly described. In this case as well, only the developing sleeve 14s and the photosensitive drum 10 are circuit elements of the ringing generation circuit 410. Also, the AC voltage power supply 240
Has a coil (not shown), and the coil and Cds
And constitute an LC resonance circuit.

The AC voltage generation circuit 240
By 0, it is connected to either the ringing generation circuit 410 or the separately excited oscillation circuit 220. The switching is performed by a switching signal from the CPU 200 as in the second embodiment, and is connected to the ringing generation circuit 410 when determining the bias voltage at the time of development prior to development. Connected to the circuit 220.

When connected to the ringing generation circuit 410,
CPU 200 outputs a ringing current setting signal to ringing generation circuit 410 via D / A converter 250, and while ringing current setting signal is being input, ringing generation circuit 410 outputs AC voltage generation circuit 240
A current of a predetermined magnitude is supplied to the coil (not shown). Next, the CPU 200 stops the output of the ringing current setting signal, and stops the energization of the coil by the ringing generation circuit 410.

Then, damped oscillation occurs transiently in the LC resonance circuit. The frequency of this damped oscillation is obtained by monitoring the voltage (ringing voltage monitor). Thereafter, in the same manner as in the third embodiment, the AC voltage Vac is determined based on the determined frequency, and development is performed. Fifth Embodiment In the first to fourth embodiments, the AC voltage is uniquely determined according to the degree of Ds (detection frequency) (Fs-Vac function or Fg-Vac function). However, the optimum value of the subsequent AC voltage may fluctuate depending on the individual differences of the developing devices and the initial mounting state.

The fifth embodiment is designed to cope with such a case. FIG. 17 is a block diagram relating to generation of a bias voltage and a control portion for determining the voltage in the fifth embodiment.
This corresponds to FIG. 12 of the second embodiment. The fifth embodiment is different from the fifth embodiment in that the developing device has a fuse 511 for determining whether the developing device is unused (new) or not. 18. The point that the CPU determines whether or not the product is an unused item, and in the memory, as shown in FIG.
The configuration is basically the same as that of the second embodiment (FIG. 12) except that a C voltage setting table is stored. Therefore, common parts are denoted by the same reference numerals, detailed description thereof will be omitted, and different parts will be mainly described.

The developing device 510 according to the fifth embodiment has a fuse 511 inside, and one end of the fuse 511 is connected to the terminal 511.
The other end is connected to the terminal 511b. With the developing device 510 mounted on the copier body, the terminal 51
1a is connected to a 5V DC power supply, and the terminal 511b is connected to the input port of the CPU 520 and the collector of the transistor 512. The input port and the collector are grounded via a resistor 513, and the emitter of the transistor 512 is also grounded. The base of the transistor 512 is connected to the output port of the CPU 520.

The CPU 520 outputs the 5 V
(Hereinafter, this voltage is referred to as a "new developing device signal"), it is determined that a new developing device is mounted, and a fuse cutting signal is output from the output port. Then, the transistor 512 is turned on, and a current flows through the fuse 511 to blow the fuse 511. Subsequent to the blowing of the fuse 511, the self-excited oscillation frequency is detected, and the cycle data Ps obtained during the detection is stored in the memory 270 as new cycle data.

The memory 270 also stores A shown in FIG.
The C voltage setting table 530 is stored in advance. AC
The voltage setting table 530 includes the above-described new cycle data and cycle data detected thereafter (after the start of use) (hereinafter, referred to as the cycle data).
This is referred to as “use time cycle data”. ) Is a table for determining the AC voltage. 4 is a table showing a range of abnormal values of the in-use cycle data (a range in which “developing device error” is displayed in the table).

The CPU 520 determines the AC voltage based on the in-use cycle data and the new cycle data with reference to the AC voltage setting table 530. When the detected self-excited oscillation frequency (regardless of the new cycle data and the in-use cycle data) is an abnormal value (AC voltage setting table 53).
0), the operation panel P
A message indicating that "the developing device is abnormal" is displayed on the display unit n, and the function of the copier is stopped to prohibit the subsequent image formation.

FIGS. 19 to 22 are flow charts showing a series of control of the image forming operation by the CPU 520. In the flowcharts of FIGS. 19 to 22, the same processes as those in the flowcharts of FIGS. 5 to 8 are denoted by the same step numbers, and detailed description thereof is omitted. In the fifth embodiment, the sampling number N
Is set to 400, and the sampling time interval t1 is set to 1 μs.

FIG. 19 is a flowchart of the main routine, which corresponds to the flowchart of FIG. In the flowchart of FIG. 19, after step S4,
The point that the developing device new article detection routine (Step S80) is inserted, the abnormality determination of the developing device is performed based on the measurement result after the self-excited oscillation frequency measurement routine of Step S5 (Step S81), and Except that a part of the print routine is different, it is basically the same as the flowchart of FIG.

Developing device new article detection routine (step S8)
FIG. 20 shows a flowchart of (0). First, it is determined whether or not the mounted developing device is new based on the presence / absence of the new developing device signal (step S90). If it is determined that it is not new (No in step S90), the process returns to the main routine. On the other hand, if it is determined that the product is new (Yes in step S90), a fuse cutting signal is output (step S91), the fuse 511 is blown, and a self-excited oscillation frequency Fs measurement routine is executed (step S9).
2). Step S92 is the same as step S5 in FIG. 5 (subroutine in FIGS. 6 and 7), and a description thereof will be omitted.

The periodic data Ps obtained in step S92
Is stored in the memory 270 as new cycle data (step S93), and an abnormality of the newly installed developing device is determined (steps S94 and S96). Whether the new cycle data exceeds 150 (Yes in step S94)
s) If less than 100 (Yes in step S96)
Determines that there is an abnormality in the developing device, displays a message to the effect that "there is an abnormality in the developing device" on the display section of the operation panel Pn, stops the function of the copying machine, and performs the subsequent image formation. It is prohibited (steps S95 and S97).

On the other hand, when the new cycle data is 150 or less,
When it is 0 or more (No in both steps S94 and S96), the process returns to the main routine. Returning to FIG. 19, when the developing device new article detection routine (step S80) ends, the process proceeds to step S5, where the cycle data Ps, that is, the in-use cycle data is detected. The in-use cycle data detected at this time is stored in the memory 270. In addition, the in-use cycle data detected for the first time after the installation of a new article usually has the same value as the new cycle data.

Then, with reference to the AC voltage setting table 530, it is determined whether or not the column where the new cycle data and the in-use cycle data intersect is "Developer error" (step S81). (Step S81: Ye
s) It is determined that there is an abnormality in the developing device, and a message to the effect that "there is an abnormality in the developing device" is displayed on the display section of the operation panel Pn, the function of the copying machine is stopped, and subsequent image formation is performed. Is prohibited (step S82).

If "developing device error" has not been reached (No in step S81), the process proceeds to steps S6 and S7, and a print routine (step S83) is executed.
FIG. 21 is a flowchart of the print routine.
The flowchart shown in this figure is basically the same as the flowchart of FIG. 8 except that step S100 is provided instead of step S65 of the flowchart of FIG. That is, in FIG. 8 (Embodiment 1 or Embodiment 2), the AC voltage is determined from the self-excited oscillation frequency by one “Fs-Vac function”. The difference is that the AC voltage is determined with reference to 530.

FIG. 22 shows an example of the A using the table 530.
It is a flowchart of a C voltage setting routine. First, new cycle data and use cycle data are read from the memory 270 (steps S101 and S102), and an AC voltage is determined with reference to the AC voltage setting table 530 (step S103). An amplitude setting signal is output so as to be applied to 14s. The processing after step S66 is the same as that described with reference to FIG.
The description is omitted.

In the above example, the AC voltage is determined directly from the cycle data by referring to the AC voltage setting table 530. However, the present invention is not limited to this. And the AC voltage may be determined. In this case, the corresponding frequency is stored in the AC voltage setting table instead of the cycle data. Alternatively, instead of the AC voltage setting table, the above-described Fs-Vac function may be prepared.

In the first to fifth embodiments, the amplitude (AC voltage) of the AC component of the bias voltage is changed according to the value of Ds. However, the present invention is not limited to this. May be changed. Alternatively, all three element values, or
The values of two of the three elements may be changed.

[0083]

As described above, in the image forming apparatus according to the present invention, in the self-excited oscillation circuit which oscillates at a frequency dependent on the capacitance formed in the gap between the image carrier and the developer carrier. The condition of the bias voltage is set based on the detected oscillation frequency. In other words, the degree of the gap between the image carrier and the developer carrier is specified by the oscillation frequency of the self-excited oscillation circuit, and the condition of the bias voltage according to the gap is set.

The frequency can be detected, for example, by measuring a half cycle of the voltage waveform. Since the measurement is performed by a timer, the measurement range is not limited. That is, according to the present invention, it is possible to detect the frequency (the distance between the image carrier and the developer carrier) over a wide range without switching the measurement range.

Further, in the image forming apparatus according to the present invention, a bias voltage is applied between the electrostatic capacity formed in the gap between the image carrier and the developer carrier and the bias voltage between the image carrier and the developer carrier. A bias voltage is set based on a frequency of a transient electric vibration generated in a resonance circuit equivalently formed by a reactance of a transformer for inducing and generating a component.

Also in this case, since the degree of the distance between the image carrier and the developer carrier is detected by detecting the frequency in the circuit, the same effect as described above can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a copying machine according to an embodiment.

FIG. 2 is a perspective view schematically showing the vicinity of a developing sleeve of a developing device of the copying machine.

FIG. 3 is a block diagram relating to generation of a bias voltage and a control portion for determining the voltage.

FIG. 4 is a diagram showing an example of a circuit for realizing the function shown in the functional block diagram of FIG.

FIG. 5 is a part of a flowchart relating to a series of controls of an image forming operation.

FIG. 6 is a part of a flowchart relating to a series of controls of an image forming operation.

FIG. 7 is a part of a flowchart relating to a series of controls of an image forming operation.

FIG. 8 is a part of a flowchart relating to a series of controls of an image forming operation.

FIG. 9 is a diagram for explaining a method of detecting the cycle of the oscillation voltage from the oscillation voltage waveform.

FIG. 10 is a diagram for explaining another method for detecting the period of the oscillation voltage.

FIG. 11 is a diagram for explaining another method of detecting the period of the oscillation voltage.

FIG. 12 is a block diagram relating to generation of a bias voltage and a control portion for determining the voltage according to the second embodiment.

FIG. 13 is a block diagram relating to generation of a bias voltage and a control part for determining the voltage according to a modification of the second embodiment.

FIG. 14 is a diagram showing a circuit configuration according to a third embodiment.

FIG. 15 is a diagram showing damped oscillation that occurs transiently in the circuit of the third embodiment.

FIG. 16 is a block diagram related to generation of a bias voltage and a control part for determining the voltage according to the fourth embodiment.

FIG. 17 is a block diagram relating to a control portion for generating a bias voltage and determining the bias voltage according to the fifth embodiment.

FIG. 18 is a diagram showing an AC voltage setting table stored in a memory in the fifth embodiment.

FIG. 19 is a part of a flowchart relating to a series of controls of an image forming operation in the fifth embodiment.

FIG. 20 is a part of a flowchart relating to a series of controls of an image forming operation in the fifth embodiment.

FIG. 21 is a part of a flowchart regarding a series of controls of an image forming operation in the fifth embodiment.

FIG. 22 is a part of a flowchart relating to a series of controls of an image forming operation in the fifth embodiment.

[Explanation of symbols]

 2 Printer unit 3 Control unit 5 Image processing unit 10 Photoconductor drum 13 Developing device 14s Developing sleeve 20 Transformer 35 Comparator 40 Transformer 100 CPU 110 Self-excited oscillation circuit 120 Other-excited oscillation circuit 150 RAM 160 ROM 200 CPU 210 Self-excited oscillation circuit 220 Separately excited oscillation circuit 310 Comparator 410 Ringing generation circuit 510 Developing device 511 Fuse 520 CPU 530 AC voltage setting table

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/00 500 G03G 21/00 372 F term (Reference) 2H027 DA04 DE01 DE07 DE09 EA05 EA15 EC06 EC09 EC20 ED01 ED09 EE07 EE08 EK03 ZA01 2H071 BA03 BA13 BA17 BA33 BA36 DA08 DA15 DA32 DA34 2H073 BA03 BA09 BA13 BA22 BA41 BA45 CA02 CA14 2H077 AD06 AD35 BA07 DA01 EA16 9A001 BB06 HH34 KK42

Claims (5)

[Claims] An image carrier on which an electrostatic latent image is formed; and a developer carrier for carrying and transporting a developer to a development area facing the image carrier. An image forming apparatus for applying a bias voltage including an AC component to a body to perform development by a jumping method, wherein the image forming apparatus depends on a capacitance formed in a gap between the image carrier and the developer carrier. A self-excited oscillation circuit that oscillates at a frequency, frequency detection means for detecting an oscillation frequency in the self-excited oscillation circuit, and condition setting means for setting a condition of the bias voltage based on the detected frequency. An image forming apparatus that develops an electrostatic latent image according to set conditions. 2. An image carrier on which an electrostatic latent image is formed, and a developer carrier for carrying and transporting a developer to a development area facing the image carrier, wherein the image carrier and the developer carrier An image forming apparatus that performs a development by a jumping method by applying a bias voltage including an AC component between the image carrier and the image carrier, comprising: a capacitance formed in a gap between the image carrier and the developer carrier; For a resonance circuit equivalently formed by the reactance of a transformer for inducing and generating an AC component of a bias voltage between the carrier and the developer carrier, the primary-side applied voltage of the transformer is rapidly changed. A transient voltage applying means for transiently generating an electric vibration determined by a time constant unique to the resonance circuit; a frequency detecting means for detecting a frequency of the transient electric vibration; based on the detected frequency, Set the bias voltage conditions An image forming apparatus comprising: a condition setting unit configured to develop an electrostatic latent image according to the set conditions. 3. A separately-excited oscillation circuit comprising a switching element which is turned on / off in synchronization with a clock signal inputted from the outside, and a transformer having a primary-side coil inserted in a power supply circuit of the switching element. The on / off of the switching element causes the transformer 2
A voltage induced in the secondary coil is applied between the developer carrier and the image carrier as an AC component of a bias voltage, and the condition setting means includes a transformer 2 of the separately excited oscillation circuit.
3. The image forming apparatus according to claim 1, wherein the magnitude of the amplitude of the AC voltage induced on the secondary side is adjusted. And a determining means for determining whether or not the mounted developer carrying member is unused, said developer carrying member being configured to be detachable from the image forming apparatus main body. Storage means for storing a frequency detected by the frequency detection means in a state where an unused developer carrier is mounted, wherein the condition setting means detects the frequency after the start of use of the developer carrier. The image forming apparatus according to claim 1, wherein a frequency is compared with a frequency stored in the storage unit, and a condition of the bias voltage is set based on a comparison result. 5. A determining means for determining whether or not the frequency detected by the frequency detecting means is within a specified range, and when the determining means determines that the detected frequency is out of the specified range, the image after that is determined. The image forming apparatus according to claim 1, further comprising a prohibition unit that prohibits formation.