JPH0850428A - Image forming device - Google Patents

Abstract

PURPOSE:To optimize the exchange period of a photoreceptor. CONSTITUTION:Between a primary current Idc flowing at the time of electrifying a photoreceptor drum 9 with an electrifying roller 10 and the film thickness (d) of the photosensitive layer of the drum 9, Idc=k/d (where, K is a constant) is established. Therefore, the primary current signal Idc 23 is monitored by a film thickness detecting part 20, to infer the film thickness (d) of the drum 9. Thus, a change in the film thickness (d) of the drum 9 caused by endurance, that is, the electric characteristics of the drum 9 can be accurately grasped and the exchange period of the photoreceptor can be optimized.

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 such as a copying machine or a laser beam printer, and more particularly to an image forming apparatus having a mechanism for detecting the life of a photoconductor.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, a photosensitive layer on the surface of a photosensitive member is worn and deteriorated with long-term use, and image quality is deteriorated. Therefore, the photoconductor that has reached the end of its life needs to be replaced. For example, in the case where the photoconductor is a cartridge, the photoconductor can be replaced by a simple replacement work by a user or the like without a serviceman or the like.

Conventionally, the life of a photosensitive member, which is a reference for replacement, is mechanically determined. That is, the attachment / detachment of the photoconductor cartridge at the time of replacement is detected mechanically or by a sensor, and with this time as a reference, the number of actually printed sheets is accumulated by the mechanical counter. Then, when the accumulated number of sheets reaches the preset number of lives of the photoconductor, it is considered that the photoconductor has reached the end of life, and the photoconductor cartridge is replaced.

[0004]

However, according to the above-mentioned prior art, the optimum replacement cannot be performed based on the change of the actual physical (electrical) characteristics of the photoreceptor due to the use, and the replacement is not possible. There was a problem that the time was not suitable.

That is, at the time of exchanging the photoconductor, the life is determined based on the accumulated number of printers of the mechanical counter with reference to the previous exchange of the photoconductor. (1) For example, the frequency of use is high. Even if the photoconductor is erroneously mounted, the determination cannot be made, and the photoconductor is handled like a new photoconductor. (2) Since the difference between single-color printing and multi-color printing is not considered, the usage frequency of the photoconductor does not match the cumulative number of prints. Therefore, it is conceivable that the deterioration of the photoconductor is progressing although the number of prints is small.

In any of the above cases, the image quality deteriorates before the original life of the photoconductor is reached.

Therefore, an object of the present invention is to provide an image forming apparatus in which the life of the photoconductor is judged based on the electrical characteristics of the photoconductor and the replacement time is optimized. is there.

[0008]

The present invention has been made in view of the above circumstances, and the first invention is to provide a photoreceptor and
An image forming apparatus having a charging member arranged in contact with the photosensitive member and a voltage applying unit for applying a voltage to the charging member, wherein the photosensitive member is charged via the charging member. Current detecting means for detecting a current signal that is output when the photosensitive member is charged or discharged, and the film thickness of the photosensitive layer of the photosensitive member corresponds to the current signal. A film thickness detecting means for detecting the film thickness of the photosensitive layer according to an output is provided.

Further, the film thickness detection means may include an I / V conversion means for converting the current signal into a voltage signal and a V / T conversion means for converting the voltage signal into a time signal. .

Further, the film thickness detecting means may include a time length measuring means for measuring a time length based on the time signal.

In addition, the time length measuring means can output an exchange signal when the time length exceeds a reference time length.

Next, the time length measuring means compares the time length based on the photoconductor before the exchange with the time length based on the photoconductor after the exchange to determine the state of the photoconductor before and after the exchange. You may do it.

Next, the V / T conversion means has means for outputting a plurality of time signals according to a plurality of different amplitudes of the current signal when converting the current signal into a voltage signal,
The time length measuring means can measure the time length based on the plurality of time signals.

The time length measuring means may be independently configured.

According to a second aspect of the present invention, in an image forming apparatus, an image generating unit for inputting print data output from a host device and generating image data to be printed out from the print data, and an image generating unit. A print output unit that inputs the generated image data to print out, a power supply unit that supplies power to the image generation unit and the print output unit, an image generation unit, a print output unit, and a power supply unit And a photoconductor detection unit that detects replacement of the photoconductor from the result of detection of the film thickness of the photoconductor, and the photoconductor detection unit is a print output from the system control unit. It is characterized in that the life of the photoconductor is determined when the number of prints reaches a certain number by means of counting the execution commands.

[0016]

According to the first aspect of the present invention, the electrical characteristics of the photosensitive member, that is, the current signal output when the photosensitive member is charged or discharged corresponds to the film thickness of the photosensitive layer of the photosensitive member. The film thickness of the photoconductor can be detected by detecting the current signal based on the characteristics. For example,
By converting the above current signal into a voltage signal and further converting this voltage signal into a time signal and measuring the time length of this time signal, the usage time of this photoconductor can be estimated.

In addition, a plurality of time signals are output according to a plurality of different amplitudes of the current signal, that is, conversion into a time signal is performed with a plurality of threshold values, thereby improving the accuracy of time length measurement. be able to.

Further, by making the means for measuring the time length independent, it becomes possible to develop the circuit integration.

According to the second aspect of the invention, for example, the print execution signal is counted for each of the single-color / multi-color modes to detect the life of the photoconductor, and the counter for the print execution signal is detected by detecting the replacement of the photoconductor by the film thickness detection. By controlling, it is possible to prevent erroneous detection of the counter of the print execution signal when the photoconductor is replaced by a third party.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 shows a schematic configuration of a color laser beam printer using an electrophotographic process as an example of an image forming apparatus according to the present invention. The configuration and operation will be briefly described below.

An interface section 2 to which digital image data read by a scanner (not shown) or the like is input is arranged above the image forming apparatus main body 1. The image forming apparatus prints an image corresponding to the input image data in full color (image formation) as follows.
It is what is output.

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

The laser driver 4 responds to each image signal by
The semiconductor laser 5 is modulated and the modulated laser light L corresponding to the image signal is output. The laser light L is generated by the polygon mirror 6,
Through the f-θ lens 7 and the reflection mirror 8, a drum-shaped photosensitive member (hereinafter referred to as “photosensitive drum”) as an image bearing member.
9 Scan over.

The photosensitive drum 9 is rotationally driven in the direction of arrow R9 at a predetermined peripheral speed (process speed), and is primary charged by a charging roller 10 as a contact charging member prior to scanning with the laser beam L described above. It The charging roller 10 is pressed against the photosensitive drum 9 with a predetermined pressing force, and a superposition signal (vibration signal) of the DC voltage and the AC voltage output from the high voltage generator (voltage applying means) 11 is applied. By the contact charging method of the AC application method, the surface of the photosensitive drum 9 is uniformly primary-charged to have a predetermined polarity and a predetermined potential.

The photosensitive drum 9 whose surface has been charged is
An electrostatic latent image is formed by scanning the laser light L described above.

The electrostatic latent image on the photosensitive drum 9 is the developing device 1
2 is developed. The developing device 12 includes four developing devices, that is, a magenta developing device 13 and a cyan developing device 1.
4, a rotary developing device having a yellow developing device 15 and a black developing device 16. At the time of development, by rotating the whole, a predetermined developing device provided for development is arranged at a development position facing the surface of the photosensitive drum 9, and toner is attached to the electrostatic latent image on the photosensitive drum 9 to develop. To do.

Below the photosensitive drum 9, a transfer drum 17 is provided.
Is arranged. On the transfer drum 17, the transfer material P fed from the paper feed cassette 18 is wound around the surface,
The toner image on the photosensitive drum 9 is transferred onto the transfer material P.

The above-described series of image forming processes of primary charging, latent image formation, development, and transfer are sequentially repeated for each image signal of magenta, cyan, yellow, and black. For the transfer material P,
Toner images of four colors are sequentially transferred so as to be overlapped with each other to form a full-color image.

Then, the transfer material P on which the full-color image is formed is separated from the transfer drum 17 and sent to a fixing unit 19 by a conveying device, where the toner image on the surface is fixed, and then outside the main body 1 of the apparatus. The paper is ejected.

Next, FIG. 2 shows an equivalent circuit of the high voltage generator 11 and the photosensitive drum 9. The photosensitive drum 9 is equivalently considered to be an aggregate 25 of minute capacitance components. Photosensitive drum 9 is 1
When the total capacity when rotating is C, this total capacity C is
The length L of the photosensitive drum 9 in the longitudinal direction, the rotation speed V _P, and the time for the photosensitive drum 9 to make one rotation are uniquely determined as t, and the film thickness of the photosensitive layer of the photosensitive drum 9 is d. It is represented by [1]. Where ε _r is the relative permittivity, ε
₀ is the dielectric constant of vacuum.

C = (ε _r · ε ₀ · L · V _P · t) / d [1] Also, the bias voltage signal 25 applied to the photosensitive drum 9 is
If the average DC bias voltage value of _Vd is V _d , the amount of charge Q _d accumulated during time t is obtained (Equation [2]). From this relationship, the primary current I _dc 23 and the film thickness d of the photosensitive drum 9 are calculated. The relationship with and is given by equation [3].

Q _d = C · V _d = I _dc · t ... [2] ∴I _dc = (C · V _d ) / t = (ε _r · ε ₀ · L · V _P · V _d ) / d ... [3] Here, each value of (ε _r · ε ₀ · L · V _P · V _d ) is an eigenvalue and is replaced by a constant k, and the film thickness d is the primary current signal I.
It can be seen that it changes like an inverse proportional function with respect to _dc 23 (Equation [4]).

I _dc = k / d ... [4] Therefore, the film thickness d of the photosensitive drum 9 can be estimated by monitoring the primary current signal I _dc 23. The third party determines whether or not the photosensitive drum 9 mounted on the image forming apparatus has been replaced. Reference numeral 20 in FIG. 2 denotes a film thickness detecting portion (film thickness detecting means) according to the present invention, which is the photosensitive drum 9
The primary current signal I _dc 23 output from the above is detected, and the film thickness d of the photosensitive drum 9 is detected from the above equation [4].

FIG. 3 is a timing chart showing a control sequence of the high voltage generator 11 and the photosensitive drum 9 for outputting the primary current signal I _dc 23. For example, primary DC
When a negative voltage is applied from the voltage source 21 and the photosensitive drum 9 is rotated simultaneously with the charging roller 10, a primary current signal I _dc 23 as shown in FIG. 3 is obtained. Similarly, when the output of the primary DC voltage source 21 at the negative potential is returned to the ground potential, the primary current signal I _dc 23 has a characteristic opposite to that at the time of charging.

FIG. 4 is a block diagram of the film thickness detecting section 20 according to the present invention, and FIG. 5 shows output waveforms of main blocks. In FIG. 4, the primary current signal I _dc 23 output from the photosensitive drum 9 is converted into a voltage signal by an I / V conversion circuit (I / V conversion means) 30, and then the gain amplifier 3
1. Low-pass filter (hereinafter referred to as "LPF") 32
Is input to the detection signal extraction circuit 33 via. The detection signal extraction circuit 33 uses a primary current signal I _dc 23 that exhibits bipolar characteristics.
In order to extract only the signal effective for detecting the film thickness from, the comparison detection is performed with an arbitrary threshold value. Reference numeral 34 denotes a V / T conversion circuit (V / T conversion means), which includes a triangular wave generation circuit 35 and a comparison circuit 36a.

FIG. 6 is a timing chart for explaining the operation of the V / T conversion circuit 34. The output signal level of the triangular wave generation circuit 35 changes corresponding to the change of the primary current signal I _dc 23 caused by the difference in the film thickness d. The triangular wave generation circuit 35 changes the slope based on the level fluctuation of the primary current signal I _dc 23 to generate the reference threshold value 3.
The film thickness detection signal 38 as a function of time is uniquely determined by comparing in the comparison circuit 36a with an arbitrary fixed comparison threshold value obtained by 6b.
That is, as shown in FIG. 6, the output time of the film thickness detection circuit 38 is τ1, τ2, corresponding to the inclination of the triangular wave output by the triangular wave generation circuit 35 becoming large as S1, S2, S3, and S4, respectively. It becomes longer in order of τ3 and τ4. Needless to say, it is possible to use not only a triangular wave but also a waveform having a certain slope, such as a trapezoidal wave.

As shown in FIG. 4, the above-mentioned film thickness detection signal 38 is input to a central control processing unit for time control (hereinafter referred to as "time measuring CPU") 37 as time measuring means, and its time length. Is measured. The measurement result is updated in the writable storage circuit (hereinafter referred to as “RAM”) 39. Further, the time measurement CPU 37 calculates the difference from the new data after taking into consideration the change with time of the photosensitive drum 9, and the drum cartridge replacement detection signal 40 and the photosensitive drum 9 have a smaller film thickness d than the current one. It is determined whether the object is thick or thick, and the state determination flag 41 is output. <Second Embodiment> FIG. 7 shows a block diagram of a circuit configuration of a second embodiment of the present invention. In the figure, the primary current signal I _dc 23 output from the photosensitive drum 9 is the I / V conversion circuit 3
After being converted into a voltage signal at 0, the gain amplifier 31, L
Multi-stage VT via PF 32 and detection signal extraction circuit 33
Input to the conversion unit 45. In the multi-stage V / T conversion unit 45, the output of the triangular wave generation circuit 35 is input to the comparison 1 circuit 42a, the comparison 2 circuit 43a, ... And the comparison n circuit 44a, which are n comparison circuits. Each comparison circuit has a reference 1 threshold 42b, a reference 2 threshold 43b, and a reference n threshold 44 having different values.
The time information output from each comparison circuit is input to the time measuring CPU 37. The result is RAM39
When a different photosensitive drum 9 is stored in the printer main body 1, the drum cartridge exchange signal 40 is output from the time measuring CPU 37.

FIG. 8 is a graph showing the relationship between the input voltage signal and the output time signal in the multi-stage V / T converter 45. It can be seen that the slope becomes steeper as the input voltage signal level increases. On the other hand, for example, the criteria 1
Letting τ1, τ2, and τn be the output time differences of the detection signal α and the detection signal β when threshold 42b <reference 2 threshold 43b <reference n threshold 44b, respectively, τ1 <τ2 <
The relational expression of τn holds. That is, it can be seen that when the reference value is set high, the difference time increases, and the detection accuracy improves accordingly.

Therefore, the time measuring CPU 37 selects one having a high detection time accuracy based on the n comparison results output from the multi-stage T / V conversion unit 45, and outputs the state determination flag 41 based on the result. To do. <Third Embodiment> FIG. 9 shows a block diagram of a circuit configuration of a third embodiment of the present invention. Output signal 3 of V / T converter 34
The 8a inputs the result measured by the pulse length measuring circuit 50 as m-bit pulse length data 68 to the data comparing circuit 51 and the data logger 52 composed of RAM or FIFO. The data comparison circuit 51 compares the updated pulse length data 68 with the contents of the data logger 52, and outputs the result as a drum cartridge replacement signal 40 and a state determination flag 41.

FIG. 10 is a block diagram showing details of the pulse length measuring circuit 50, and FIG. 11 is a timing chart showing output signals of main blocks. V / T converter 3
The output signal waveform from No. 4 (see FIG. 9) is input to the latch control signal generation circuit 60 and the counter reset signal generation circuit 61. In the latch control signal generation circuit 60,
Latch 6 at the rising edge of the converter 34 output signal waveform
7 in the counter reset signal generating circuit 61, while the counter reset signal generating circuit 61 uses the falling edge of the output signal waveform of the V / T converter 34 to generate the m-bit counter 64.
Reset signal 63 is output. A counter clock generation 65 supplies a clock to the m-bit counter 64 and the latch 67. The count result of the m-bit counter 64 is immediately latched in the latch 67 as m-bit count data 68. <Fourth Embodiment> FIG. 12 shows a block diagram of a circuit configuration of a fourth embodiment according to the present invention. In the figure, a system control circuit 70 controls the operation of the printer body 1. Main CP
A print execution signal 72 is output from U79 and sent to the print counter selection circuit 74. Also, the main CP
The U 79 outputs a print mode signal 73 for selecting each mode such as monochrome / mono color / full color, and switches the print counter selection circuit 74. This is the specified number of full-color conversions (eg 3000
In the case of monochrome and mono-color printing, the double counter 75 counts up for the first time when the print execution signal 72 is issued twice for the purpose of counting the number of sheets. The print lock signal 77 added by the AND circuit 76 is input to the print counter 71 to execute the counting operation. The count result of the print counter 71 is input to the main CPU 79 again via the j-bit count data bus 78, and the backup memory 80
Is accumulated in

By the way, the primary current signal I _dc 23 flowing out from the photosensitive drum 9 is input to the film thickness detecting section 20, and the drum cartridge exchange signal 40 obtained as a result resets the print count. Furthermore, the state determination flag 4
A warning is given if a member having a film thickness d smaller than that of the photosensitive drum 9 that has been mounted by 1 is mounted, and if a member other than that is mounted, the value of the print counter 71 is set to the main value according to the film thickness value. It is changed by the CPU 79.

[0042]

As described above, according to the first aspect of the present invention, the electrical characteristics of the photosensitive member, that is, the current signal output when the photosensitive member is charged or discharged is the film thickness of the photosensitive layer of the photosensitive member. The film thickness of the photoconductor can be detected by detecting the current signal based on the characteristic of "1. For example, the above-mentioned current signal is converted into a voltage signal, this voltage signal is further converted into a time signal, and the time length of this time signal is measured, whereby the usage time of this photoconductor can be estimated. That is, it is possible to optimally set the replacement time of the photoconductor by detecting the true usage time of the photoconductor based on the electric characteristics of the photoconductor itself and comparing it with the life (lifetime).

In addition, a plurality of time signals are output according to a plurality of different amplitudes of the current signal, that is, conversion into a time signal is performed with a plurality of threshold values, so that the time length measurement accuracy is improved. Therefore, it is possible to further optimize the replacement time of the photoconductor.

Further, by making the means for measuring the time length independent, it becomes possible to develop the circuit integration.

According to the second aspect of the present invention, for example, the life of the photoconductor is detected by counting the print execution signals for each of the single color / multicolor mode, and the counter of the print execution signal is detected by the replacement of the photoconductor by the film thickness detection. By controlling, it is possible to prevent erroneous detection of the counter of the print execution signal when the photoconductor is replaced by a third party. That is,
It is possible to detect the life of the photosensitive drum for each number of prints.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a diagram illustrating an equivalent circuit of a high voltage generating unit and a photosensitive drum according to the first exemplary embodiment.

FIG. 3 is a timing chart showing a sequence necessary for outputting a current signal in the first embodiment.

FIG. 4 is a block diagram of a film thickness detection unit according to the first embodiment.

FIG. 5 is an output timing chart of main blocks of the first embodiment.

FIG. 6 is a waveform diagram and a timing chart showing voltage-time (V · T) conversion of the first embodiment.

FIG. 7 is a block diagram of a film thickness detection unit according to a second embodiment.

FIG. 8 is a waveform diagram showing voltage-time (V · T) conversion in the second embodiment.

FIG. 9 is a block diagram of a film thickness detection unit according to a third embodiment.

FIG. 10 is a block diagram showing details of a pulse length measuring circuit according to a third embodiment.

FIG. 11 is an output timing chart of the pulse length measuring circuit according to the third embodiment.

FIG. 12 is a block diagram illustrating a configuration of an image forming apparatus according to a fourth exemplary embodiment.

[Explanation of symbols]

1 Printer Main Body 2 Interface Section 3 Signal Processing Section 4 Laser Driver 5 Semiconductor Laser 6 Polygon Mirror 7 f-θ Lens 8 Reflection Mirror 9 Photosensitive Body (Photosensitive Drum) 10 Charging Member (Charging Roller) 11 Voltage Applying Unit (High Voltage Generating Unit) 12 developing device 17 transfer drum 18 paper feed cassette 19 fixing unit 20 film thickness detection means (film thickness detection unit) 21 primary DC voltage source 22 primary AC voltage source 23 primary current signal I _dc 25 minute capacitance component aggregate 30 I · V Conversion means (I / V conversion circuit) 31 Gain up 32 Low pass filter (LPF) 33 Detection signal extraction circuit 34 V / T conversion means (V / T conversion circuit) 35 Triangular wave generation circuit 36a Comparison circuit 36b Reference threshold value 37 hours Measuring means (time measurement CPU) 38 Film thickness detection signal 40 Drum cartridge replacement detection 41 State determination flag 42a Comparison 1 circuit 42b Reference 1 threshold 43a Comparison 2 circuit 43b Reference 2 threshold 44a Comparison n circuit 44b Reference n threshold 45 Multi-stage V / T conversion means (multi-stage V / T conversion circuit) 50 Pulse length measurement Circuit 51 Data comparison circuit 52 Data logger 60 Latch control signal generation circuit 61 Counter reset signal generation circuit 62 Strobe signal 63 Reset signal 64 m-bit counter 65 Counter lock generation 66 Inverter 67 Latch 68 Pulse length data 70 System control circuit 71 Print counter 72 Print execution signal 73 Print mode signal 74 Printer selection circuit 75 Double counter 76 AND circuit 77 Print clock 78 Count data bus 79 Main central processing unit (main CPU) 80 Backup Memory

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // G03G 15/08 507 K

Claims (7)

[Claims] 1. An image having a photosensitive member, a charging member arranged in contact with the photosensitive member, and a voltage applying unit for applying a voltage to the charging member, and charging the photosensitive member via the charging member. In the forming apparatus, a current detection unit that detects a current signal output when the photoconductor is charged or discharged via the charging member, and a film thickness of a photosensitive layer of the photoconductor corresponds to the current signal. Based on the above, an image forming apparatus comprising: a film thickness detection unit that detects the film thickness of the photosensitive layer according to the output of the current detection unit. 2. The film thickness detection means comprises an I / V conversion means for converting the current signal into a voltage signal, and a VT conversion means for converting the voltage signal into a time signal. The image forming apparatus according to claim 1. 3. The film thickness detecting means has a time length measuring means for measuring a time length based on the time signal, and the time length measuring means is provided when the time length exceeds a reference time length. The image forming apparatus according to claim 2, wherein an exchange signal is output to the image forming apparatus. 4. The time length measuring means compares the time length based on the photoconductor before replacement with the time length based on the photoconductor after replacement to determine the state of the photoconductor before and after the replacement. The image forming apparatus according to claim 3, wherein 5. The V / T conversion means includes means for outputting a plurality of time signals according to a plurality of different amplitudes of the current signal when converting the current signal into a voltage signal, and the time length. The image forming apparatus according to claim 4, wherein the measuring unit measures the time length based on the plurality of time signals. 6. The image forming apparatus according to claim 4, wherein the time length measuring unit is configured independently. 7. An image generation unit for inputting print data output from a host device and generating image data for print output from the print data; and inputting image data generated by the image generation unit. A print output unit that performs print output, a power supply unit that supplies power to the image generation unit and the print output unit, a system control unit that controls the image generation unit, the print output unit, and the power supply unit, A photoconductor detection unit that detects replacement of the photoconductor based on a result of detection of the film thickness of the photoconductor, and the photoconductor detection unit is a unit that counts print execution commands output from the system control unit. An image forming apparatus characterized in that the life of a photoconductor is judged when the number of prints reaches an arbitrary number.