JPH08338828A - Image forming device - Google Patents

Abstract

PURPOSE: To enhance the detection accuracy of a thickness of a film of a photosensitive body. CONSTITUTION: A V-T conversion circuit 34 monitors a conversion output to convert it to a timing signal corresponding to a thickness of a film of a photosensitive drum 9 in a timing delayed by a timing delay generation circuit such that a monitor starting timing of a conversion output from an I-V conversion circuit 30 is delayed by a prescribed time period by catching a timing wherein a current waveform flowing in the photosensitive drum 9 does not have a distortion or a dull. A CPU 59 measures a thickness of a film of the photosensitive drum 9 based on the converted timing signal.

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 which contacts a photoconductor to charge or remove electricity, and more particularly to an image forming apparatus which detects the film thickness of the photoconductor to determine the life. .

[0002]

2. Description of the Related Art A photosensitive drum used in an electrophotographic system or the like has a long life due to its film thickness abrasion due to a durable printing operation and needs to be replaced. In the past, the life of the photosensitive drum was estimated from the toner consumption amount, but it was impossible to make an accurate determination such as when a large number of prints with a low printing rate were made. On the other hand, it is known that the film thickness of the photosensitive drum can be directly detected by measuring the current flowing when the photosensitive drum is charged or discharged by using the contact charging method. However, the waveform becomes dull due to the time constant and temperature characteristics of the voltage source that supplies the high voltage to the photosensitive drum, which leads to the deterioration of accuracy.

[0003]

However, in the above-mentioned conventional example, the film thickness can be detected by monitoring the amount of current accumulated in the photosensitive drum in the following (1),
There was a problem of (2).

(1) Due to the electrical characteristics of the voltage source that supplies a high voltage to the photosensitive drum, the waveform of the current value flowing through the photosensitive drum during charging and discharging is blunted and the film thickness detection accuracy is degraded. It is a factor.

(2) Further, the temporal variation due to the rising variation of the current waveform due to the temperature variation leads to the erroneous detection of the photosensitive drum film thickness.

The present invention has been made in order to solve the above problems, and monitors the current waveform from the photoconductor for a portion without blunting or distortion, or against the change in the current waveform due to temperature or the like. It is possible to improve the accuracy of detection of the film thickness of the photoconductor by detecting a portion that does not change, and to provide an image forming apparatus that can detect the film thickness of the photoconductor while suppressing the influence of environmental changes. To aim.

[0007]

A first aspect of the present invention is an image forming apparatus in which a high voltage is applied to a charged body and the charged body is brought into contact with the photosensitive body to charge or discharge the photosensitive body. A detecting means for detecting a current flowing through the photoconductor, a first converting means for converting a current signal detected by the detecting means into a voltage signal, and a monitor start timing of a converted output from the first converting means. Delaying means for delaying for a predetermined time, second converting means for monitoring the converted output at a timing delayed by the delaying means, and converting the converted output into a time signal corresponding to the film thickness of the photoconductor, the second converting means.
Measuring means for measuring the film thickness of the photosensitive member based on the time signal converted by the converting means.

A second aspect of the present invention is an image forming apparatus for applying a high voltage to a charged body and bringing the charged body into contact with the photoconductor to charge or discharge the photoconductor. First detecting means for detecting a current, first converting means for converting a pre-current signal detected by the first detecting means into a voltage signal, and a peak value of converted output from the first converting means And a second detection means for detecting, and an adjustment for variably adjusting a start timing for monitoring the conversion output output from the first conversion means for a predetermined time based on the detection state of the peak value by the second detection means. Means, second conversion means for monitoring the conversion output at a timing variably adjusted by the adjustment means, and converting the converted output into a time signal corresponding to the film thickness of the photoconductor, and the second conversion means. time Those comprising measuring means for measuring the thickness of the SL photosensitive body based on No..

A third aspect of the present invention is to determine the life of the photoconductor based on the film thickness measured by the measuring means.

[0010]

According to the first aspect of the invention, the delay means is provided so as to delay the monitor start timing of the conversion output from the first conversion means by a predetermined time by capturing the timing at which the waveform of the current flowing through the photoconductor is not blunted or distorted. At a delayed timing, the second conversion means monitors the conversion output and converts it into a time signal corresponding to the film thickness of the photoconductor, and based on the converted time signal, the measurement means causes the film of the photoconductor to be formed. It is possible to increase the accuracy of detecting the thickness of the photoconductor by measuring the thickness.

According to the second aspect of the invention, the timing at which the waveform of the current flowing through the photoconductor does not change with respect to changes with time such as temperature is captured and the monitoring start timing of the conversion output from the first conversion means is varied. The adjusting means based on the detection state of the peak value by the second detecting means,
Of the conversion output output from the conversion means for a predetermined time is variably adjusted, and the second conversion means monitors the conversion output at the adjusted timing to correspond to the film thickness of the photoconductor. It is possible to convert the signal into a signal, and the measuring means measures the film thickness of the photoconductor on the basis of the converted time signal, so that the film thickness can be detected without being influenced by the environmental change of the photoconductor.

According to the third aspect of the invention, the life of the photoconductor is judged based on the film thickness measured by the measuring means, and the accuracy is determined according to the film thickness measured with high accuracy or with the influence of environmental fluctuations removed. This makes it possible to determine the life of the photoconductor well.

[0013]

【Example】

[First Embodiment] FIG. 1 is a sectional view showing the schematic arrangement of an image forming apparatus to which the present invention can be applied. The image forming apparatus of this embodiment is a color laser beam printer utilizing an electrophotographic process (color image forming apparatus). Is. Since the color laser beam printer itself and the image process are known, detailed description thereof will be omitted.

In the figure, 1 is a printer main body (printer), 2 is an interface section, and is a section for inputting digital image data read by a scanner (not shown) or the like. The printer 1 prints out an image corresponding to the data input from the interface unit 2 in full color.

The RGB signals sent from the interface section 2 to the signal processing section 3 are magenta (M), cyan (C), yellow (Y), black (B) in the signal processing section 3.
The image signals of k) are converted and sent to the laser driver 4.

The laser driver 4 modulates the semiconductor laser 5 with respect to the image signal and outputs the modulated laser light L corresponding to the image signal. The laser light L is reflected by the polygon mirror 6, f
Scanning is performed on the photosensitive drum 9 serving as an image carrier via the −θ lens 7 and the mirror 8.

The photosensitive drum 9 is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed (process speed).
The primary charging process is performed so that the electric potential is uniform.

The charging roller 10 is pressed against the photosensitive drum 9 with a predetermined pressing force, is output from the high voltage generator 11, and is supplied with a DC voltage and an AC voltage source 22 from a primary DC voltage source 21 shown in FIG. The superposed signal (vibration signal) of the AC voltage is applied to charge the photosensitive drum 9 by the AC charging method. Then, an electrostatic latent image is formed on the charged surface of the photosensitive drum by scanning the laser beam.

Reference numeral 12 denotes a rotary developing device, which is composed of a magenta developing device 13, a cyan developing device 14, a yellow developing device 15 and a black developing device 16, and four developing devices are alternately in contact with the photosensitive drum 9 and the photosensitive drum 9 is provided. The electrostatic latent image formed above is developed with toner.

A transfer drum 17 winds the paper P fed from the paper cassette 18 around the transfer drum 17, and transfers the image developed on the photosensitive drum 9 to the paper P.

The above-mentioned latent image formation, development and transfer processes are repeated for each image signal of magenta, cyan, yellow and black to obtain four color toners of magenta toner image, cyan toner image, yellow toner image and black toner image. The images are sequentially transferred onto the surface of the same sheet of paper P in a superimposed manner to form a full-color image.

Then, the paper P on which the full-color image is formed is separated from the transfer drum 17, sent to a fixing unit 19 by a conveying device, passes through the fixing unit 19, and is discharged. Reference numeral 20 is a film thickness detection unit.

FIG. 2 is a diagram showing an equivalent circuit of the high voltage generator 11 and the photosensitive drum 9 shown in FIG.

The photosensitive drum 9 is equivalently considered to be an aggregate 25 of minute capacitance components. When the total capacity when the photosensitive drum 9 makes one rotation is C, the length L in the longitudinal direction, the rotation speed Vp, and the time for the photosensitive drum 9 to make one rotation are defined as t, which is uniquely determined. When the film thickness is d, it is defined by the following formula (1).

C = (εr · ε0 · L · Vp · t) / d (1) Further, when the average DC bias voltage value of the bias voltage signal applied to the photosensitive drum 9 is Vd, during the time t. The accumulated charge amount Qd is obtained based on the following expression (2), and from this relationship, the relationship between the primary current Idc23 and the film thickness d of the photosensitive drum 9 is given by the following expression (3). Note that ε0 represents the permittivity in air and εr represents the relative permittivity.

Qd = C · Vd = Idc · t (2) ∴Idc = (C · Vd) / t = (εr · ε0 · L · Vp · Vd) / d (3) where (εr・ Each value of ε0 ・ L ・ Vp ・ Vd is an eigenvalue and is replaced by a constant k, and the film thickness d is inversely proportional to the primary current signal (Idc) 23 as shown in the following expression (4). It can be seen that it changes in a functional manner.

Idc = k / d (4) Therefore, it is possible to estimate the film thickness d of the photosensitive drum 9 by monitoring the primary current signal (Idc) 23. It can also be used to determine whether or not a person has replaced the photosensitive drum 9 from the image forming apparatus.

A film thickness detector 20 detects the primary current signal (Idc23) flowing from the photosensitive drum 9 and detects the photosensitive drum 9.
The film thickness of is detected.

FIG. 3 shows the primary current signal (Id) shown in FIG.
3C is a timing chart showing a control sequence of the high voltage generator 11 and the photosensitive drum 9 for outputting 23.

For example, when a negative voltage is applied from the primary DC voltage source 21 and the photosensitive drum 9 is rotated simultaneously with the charging roller 10, a primary current signal 23 as shown in FIG. 3 is obtained.

Similarly, a primary DC voltage source 2 at negative potential
When one output is returned to the ground potential, the primary current signal 23 has a characteristic opposite to that at the time of charging.

FIG. 4 is a block diagram for explaining the construction of the photoconductor film thickness detection circuit of the image forming apparatus showing the first embodiment of the present invention, which corresponds to the construction of the film thickness detection section 20 shown in FIG. . Further, FIG. 5 is a timing chart for explaining the operation of FIG.

In FIG. 4, the primary current signal (Idc) 23 flowing through the photosensitive drum 9 is converted into a voltage signal by the IV conversion circuit 30, and then a gain amplifier 31 and a low pass filter (hereinafter referred to as LPF). It is input to the detection signal extraction circuit 33 through (abbreviated) 32. The detection signal extraction circuit 33 performs comparison detection using an arbitrary threshold value in order to extract only a signal effective for film thickness detection from the primary current signal (Idc) 23 showing the bipolar characteristic.

Reference numeral 34 denotes a VT (time length) conversion circuit, which is a primary DC current signal (Idc) 2 generated by a difference in film thickness d.
The film thickness detection signal 35 corresponding to the change of 3 is uniquely determined as a time function.

The timing delay generation circuit 38 starts the counting operation of the counter 41 in synchronization with the rising edge of the high voltage output control signal 37 output from the control CPU 36 by the counter preset 39. Counter 4
The reference clock of 1 is supplied from the clock generation source 42. The counter 41 outputs the count-up flag 44 until it counts a predetermined time τd.

On the other hand, as the VT conversion stop signal 40, a signal synchronized with the rising edge of the signal from the detection signal extraction circuit 33 is input to the VT conversion control circuit 43. As a result, the VT conversion control circuit 43 causes the VT conversion circuit 34 to stop the output of the count-up flag 44 at the same time as the VT conversion
The T conversion is started, and ends at the same time when the output of the detection signal extraction circuit 33 disappears.

That is, in the VT conversion circuit 34,
Τd from the rising of the primary DC current signal (Idc) 23
The conversion is started from the time delayed by just that, and the conversion is ended at the same time as the fall of the primary DC current signal (Idc) 23.

Correspondence between the present embodiment and each means of the first invention and its operation will be described below with reference to FIG.

The first invention is a charged body (charging roller 10).
In the image forming apparatus for applying a high voltage to the photoconductor (photosensitive drum 9) to charge or neutralize the photoconductor, the detection unit (I- (Provided in the V conversion circuit 30),
First conversion means (IV conversion circuit 30) for converting the current signal detected by the detection means into a voltage signal, and a delay for delaying the monitor start timing of the conversion output from the first conversion means for a predetermined time. Means (timing delay generation circuit 38) and second conversion means (VT conversion) for monitoring the conversion output at a timing delayed by the delay means and converting it into a time signal corresponding to the film thickness of the photoconductor. Circuit 34) and measuring means (C) for measuring the film thickness of the photosensitive member based on the time signal converted by the second converting means.
PU36) and a timing delay generation circuit 38 so as to delay the start timing of monitoring the conversion output from the IV conversion circuit 30 by a predetermined time by capturing the timing at which the current waveform flowing through the photosensitive drum 9 is not blunted or distorted.
Is delayed, the VT conversion circuit 34 monitors the conversion output and converts it into a time signal corresponding to the film thickness of the photosensitive drum 9. Based on the converted time signal, CP
It is possible for U36 to measure the film thickness of the photosensitive drum 9 to improve the film thickness detection accuracy of the photoconductor.

According to the first embodiment, the current-voltage conversion, the gain amplifier, the detection signal extraction circuit, the voltage-time conversion circuit, and the timing delay section are provided, and the current is delayed from the photosensitive drum by a predetermined time. Since the film thickness is detected after that, it is possible to suppress the accuracy deterioration due to the bluntness and distortion of the current waveform.

[Second Embodiment] FIG. 6 is a block diagram for explaining the arrangement of a photoconductor film thickness detection circuit of an image forming apparatus according to the second embodiment of the present invention. The symbol is attached. FIG. 7 is a timing chart for explaining the operation of FIG.

In FIG. 6, the primary current signal (Idc) 23 flowing through the photosensitive drum 9 is converted into a voltage signal by the IV conversion circuit 30, and then the gain up 31, the LPF 3 are performed.
2. Input to the VT converter 34 through the detection signal extraction circuit 33.

Reference numeral 50 denotes a variable delay type timing generation circuit, which monitors the signal output from the detection signal extraction circuit 33 whether or not a peak value is output from the peak hold circuit 51. Then, at the same time as confirming the peak hold signal 52, the counter preset 53 causes the counter 55 to start counting. The counter 55 executes a counting operation by the clock generation source 42. The reset time setting 54 is the conversion time T in the VT conversion circuit 34.
Has a function to set and set arbitrarily.

The counter 55 starts counting by the counter preset 53 and stops at the reset time setting 54. A conversion variable control circuit 56 outputs a conversion variable control signal 57 to the VT conversion circuit 34 in synchronization with the output of the counter 55.

That is, the primary DC current signal (Idc) 2
The VT conversion circuit 34 is controlled so that the VT conversion is started when the peak of No. 3 is confirmed, the conversion is completed for a predetermined time T, and then the conversion is completed.

In FIG. 7, the primary DC current signal Idc
Peak hold output 52- (1), (2)
(1), 52- (2) and conversion variable control signal 57-
(1) and 57- (2) are shown. The waveform of the primary DC current Idc becomes dull due to the influence of the time constant and the temperature characteristic.

On the other hand, by carrying out peak hold, it is set so that the VT conversion is always executed when a peak appears, and the conversion time is controlled to be constant (T).

Correspondence between this embodiment and each means of the second invention and its operation will be described below with reference to FIG.

A second aspect of the invention is a charged body (charging roller 10).
In the image forming apparatus for applying a high voltage to the photoconductor and bringing the charged body into contact with the photoconductor to charge or discharge the photoconductor drum 9, the first detecting the current flowing through the photoconductor drum 9 is performed.
Detection means (provided in the IV conversion circuit 30), first conversion means (IV conversion circuit 30) for converting the current signal detected by the first detection means into a voltage signal, and the first conversion means. Second detecting means (peak hold circuit 51) for detecting the peak value of the converted output from the first converting means;
Adjusting means (conversion variable control circuit 56) for variably adjusting the start timing for monitoring the conversion output output from the first converting means for a predetermined time based on the detection state of the peak value by the detecting means of FIG. The second conversion means (VT conversion circuit 34) for monitoring the conversion output at a timing variably adjusted by the above and converting it into a time signal corresponding to the film thickness of the photoconductor, and the second conversion means. A measuring unit (CPU 59) for measuring the film thickness of the photosensitive member based on the converted time signal is provided, and the timing at which the waveform of the current flowing through the photosensitive drum 9 does not fluctuate with respect to changes with time such as temperature is captured. The conversion variable control circuit 56 is based on the detection state of the peak value by the peak hold circuit 51 so as to change the monitor start timing of the conversion output from the −V conversion circuit 30. I-V conversion start timing for predetermined time monitor the conversion output which is output from the circuit 30 variably adjusted, the adjustment timing in V-T converting circuit 34
Monitors the conversion output and converts it into a time signal corresponding to the film thickness of the photosensitive drum 9, and the CPU 59 measures the film thickness of the photosensitive drum 9 based on the converted time signal, and the photosensitive drum 9 It is possible to detect the film thickness without being affected by the environmental fluctuation of.

According to the second embodiment, in addition to the configuration of the first embodiment, a maximum value detection circuit is further provided, the maximum value of the current flowing out from the photosensitive drum is detected, and an arbitrary value is detected from the time when it is detected. Since the film thickness is detected for a fixed time, it is possible to prevent the influence of changes in temperature characteristics and the like and improve the film thickness detection accuracy.

The CPU 36 and the CPU 59 are the first
The time signal output from the VT conversion circuit 34 is measured at the timing adjusted by the second embodiment to measure the film thickness of the photosensitive drum 9, and the life of the photosensitive drum 9 is accurately determined from the measured film thickness. It can be determined well or without being affected by environmental changes.

Correspondence between the present embodiment and each means of the third invention and its operation will be described below.

A third aspect of the present invention is a measuring means (CPU 36, C
Since the PU 59) determines the life of the photoconductor based on the measured film thickness, it is possible to accurately determine the life of the photoconductor according to the film thickness measured with the influence of environmental changes removed. it can.

[0054]

As described above, the first aspect of the present invention
According to the invention, the delay means is delayed so as to delay the monitor start timing of the conversion output from the first conversion means by a predetermined time by capturing the timing at which the waveform of the current flowing through the photoconductor is not blunted or distorted. At a timing, the second converting means monitors the converted output and converts it into a time signal corresponding to the film thickness of the photoconductor, and the measuring means measures the film thickness of the photoconductor based on the converted time signal. Therefore, the accuracy of detecting the film thickness of the photoconductor can be improved.

According to the second aspect of the present invention, the timing at which the waveform of the current flowing through the photosensitive member does not change with respect to changes with time such as temperature is captured and the monitoring start timing of the conversion output from the first conversion means is varied. As described above, the adjusting means variably adjusts the start timing for monitoring the converted output output from the first converting means for a predetermined time based on the detection state of the peak value by the detecting means, and the second timing is adjusted at the adjusted timing. The conversion means monitors the converted output and converts it into a time signal corresponding to the film thickness of the photoconductor, and the measuring means measures the film thickness of the photoconductor based on the converted time signal. The film thickness can be detected without being affected by the environmental change of the body.

According to the third aspect of the invention, the life of the photoconductor is judged based on the film thickness measured by the measuring means. Therefore, the film thickness can be measured accurately or according to the film thickness measured under the influence of environmental fluctuation. It is possible to accurately determine the life of the photoconductor.

Therefore, the accuracy of detecting the film thickness of the photoconductor can be improved, and the film thickness of the photoconductor can be detected while suppressing the influence of environmental changes.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus to which the present invention can be applied.

FIG. 2 is a diagram showing an equivalent circuit of the high voltage generating unit and the photosensitive drum shown in FIG.

FIG. 3 is a timing chart showing a control sequence of a high voltage generator and a photosensitive drum for outputting the primary current signal shown in FIG.

FIG. 4 is a block diagram illustrating a configuration of a photoconductor film thickness detection circuit of the image forming apparatus according to the first exemplary embodiment of the present invention.

5 is a timing chart illustrating the operation of FIG.

FIG. 6 is a block diagram illustrating a configuration of a photoconductor film thickness detection circuit of an image forming apparatus according to a second exemplary embodiment of the present invention.

FIG. 7 is a timing chart illustrating the operation of FIG.

[Explanation of symbols]

 30 IV conversion circuit 31 Gain amplifier 32 LPF 33 Detection signal extraction circuit 34 VT conversion circuit 36 CPU 38 Timing delay generation circuit

Claims (3)

[Claims] 1. An image forming apparatus for applying a high voltage to a charged body to bring the charged body into contact with a photoconductor to charge or discharge the photoconductor, and a detection unit for detecting a current flowing through the photoconductor. First conversion means for converting the current signal detected by the detection means into a voltage signal, delay means for delaying the monitor start timing of the conversion output from the first conversion means by a predetermined time, and delay by the delay means Second conversion means for monitoring the conversion output at a specified timing and converting the converted output into a time signal corresponding to the film thickness of the photoconductor, and the photoconductor based on the time signal converted by the second conversion means. And an image forming apparatus for measuring the film thickness of the image forming apparatus. 2. An image forming apparatus for applying a high voltage to a charged body to bring the charged body into contact with a photoconductor to charge or discharge the photoconductor, the first detection detecting a current flowing through the photoconductor. Means, first converting means for converting the current signal detected by the first detecting means into a voltage signal, and second detecting means for detecting the peak value of the converted output from the first converting means. Adjusting means for variably adjusting a start timing for monitoring a conversion output output from the first converting means for a predetermined time based on a detection state of the peak value by the second detecting means, and variably adjusting by the adjusting means. Second conversion means for monitoring the conversion output at a specified timing and converting the converted output into a time signal corresponding to the film thickness of the photoconductor, and the photoconductor based on the time signal converted by the second conversion means. of An image forming apparatus comprising: a measuring unit that measures a film thickness. 3. The life of the photoconductor is determined based on the film thickness measured by the measuring means.
Alternatively, the image forming apparatus described in 2.