JP2010078569A - Potential measuring device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep a response time of potential measurement constant, even when a vibration amplitude of a tuning fork type vibrator 8e of a potential sensor 8 is deteriorated by a change with elapse of time, an environmental change or the like, in an image forming device. <P>SOLUTION: A prescribed potential difference is provided between a photoreceptor drum 1 and the potential sensor 8, and an AC detection signal from the potential sensor 8 is measured in that state, and a gain for amplifying the AC detection signal is corrected based on a measurement result. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a potential measuring apparatus, and more particularly to an image forming apparatus having surface potential detecting means for detecting the surface potential of an image carrier.

  FIG. 11 shows a schematic configuration diagram of a conventional potential sensor and its control unit.

  In FIG. 11, reference numeral 8 is a potential sensor 8, and reference numeral 107 is a potential sensor control unit.

  The potential sensor 8 is a piezoelectric element 8a, 8b disposed on both arms of the tuning fork vibrator 8e and the tuning fork vibrator 8e (in the case of FIG. 11, the drive for the piezoelectric element 8b to vibrate the tuning fork vibrator 8e). Piezoelectric element 8b, and the piezoelectric element 8a is a detecting piezoelectric element 8a for detecting vibration of the tuning fork vibrator 8e), a measuring electrode 8f, and a detection circuit 8g.

  On the other hand, the potential sensor control unit 107 includes a control unit 107a, a high-voltage power supply 107b, a detection output signal generation unit 107c, a drive circuit 107d, and an amplification circuit 107e. In FIG. 11, reference numeral 1 denotes a photosensitive drum 1.

  The operation of FIG. 11 will be described.

  When a remote signal input from the outside is turned on, the operation of the potential sensor 8 and the potential sensor control unit 107 is started. First, the drive circuit 107d inputs a drive signal to the piezoelectric element 8b. Then, the tuning fork type vibrator 8e starts to vibrate, and its tip part vibrates in the directions of arrows 8c and 8d, respectively. When the tuning fork vibrator 8e starts to vibrate, the piezoelectric element 8a converts the vibration into an electric signal and outputs it as a vibration detection signal. The drive circuit 107d controls the frequency of the drive signal so that the phase difference between the drive signal and the vibration detection signal becomes a predetermined value. As a result, the tuning fork vibrator 8e continues to vibrate in a resonance state. On the other hand, when the tuning fork vibrator 8e vibrates, the electrostatic capacitance between the measurement electrode 8f and the photosensitive drum 1 periodically changes, thereby changing the charge amount of the measurement electrode 8f, and the change in the charge amount. By converting the voltage into voltage by the detection circuit 8g, an AC voltage signal proportional to the potential difference between the photosensitive drum 1 and the measurement electrode 8f can be obtained.

  Each part constituting the potential sensor 8 operates with an output (point H in FIG. 11) of a high-voltage power supply 107b described later as a reference potential.

  In the control unit 107a, the AC detection signal output from the detection circuit 8g is amplified by the amplification circuit 107e and input to the control unit 107a. In the control unit 107a, the amplitude of the amplified AC detection signal is The output of the high-voltage power supply 107b is controlled so that it becomes zero.

Here, when the amplitude of the AC detection signal is zero, the tuning fork vibrator 8e vibrates, and the capacitance between the measurement electrode 8f and the photosensitive drum 1 is periodically changed. This is a state in which the charge amount of the electrode 8f does not change, and this state indicates that the surface potential of the photosensitive drum 1 and the potential of the measurement electrode 8f, that is, the surface potential of the photosensitive drum 1 and the output of the high voltage generator 107b are the same potential. I mean. Thereby, the surface potential of the photosensitive drum 1 can be obtained. (Zero method)
The potential sensor control unit 107 converts the output of the high voltage generation unit 107b at this time by the detection output signal generation unit 107c, for example, in a relationship as shown in FIG.

  In the case of FIG. 12, when the potential at point H in FIG. 11 (measurement result of the photosensitive drum 1) is + 50V, the output of the detection output signal generation unit 107c is 0V, and the potential at point H is −900V. There is a linear relationship between the measurement result and the output of the detection output signal generation unit 107c such that the output of the detection output signal generation unit 107c is sometimes 3.3V.

  Here, FIG. 13 shows the relationship between the surface potential fluctuation of the photosensitive drum 1, which is the measurement target of the potential sensor 8 in FIG. 11, and the waveforms at the points B and C in FIG.

  A waveform 13-1 in FIG. 13 is a variation example of the surface potential of the photosensitive drum 1 to be measured. In this example, the variation is from −100V to −600V. In accordance with the surface potential fluctuation of the photosensitive drum, the output of the potential sensor control unit 107 changes with a certain response time like a waveform 13-2 C point waveform.

  At that time, at the point B of the potential sensor control unit 107, as shown by the waveform 13-3, the potential difference between the potential at the point H (reference potential of the potential sensor) output from the high voltage power source 107b and the surface potential of the photosensitive drum 1. An AC detection signal corresponding to is generated. The frequency of the AC detection signal at point B is the vibration frequency of the tuning fork vibrator 8e, and the amplitude of the AC detection signal is related to the magnitude of the vibration amplitude of the tuning fork vibrator 8e.

  In FIG. 13, the time until the surface potential of the photosensitive drum 1 fluctuates and the amplitude of the AC detection signal at point B becomes zero is the response time as the potential sensor 8, and the response when the potential sensor 8 is in the initial state. The time is the initial response time t1 in FIG.

  This response time is greatly related to the amplitude of the AC detection signal.If the potential sensor 8 deteriorates and its vibration amplitude decreases, the amplitude of the AC detection signal, which was V1 in the initial value of waveform 13-3, As a result, the response time of the potential sensor 8 decreases from t1 to t2.

In response to this change in response time, it is traditionally determined that the lifetime of the potential sensor has been reached, and replacement is facilitated by sound and light, or even if the measurement time for actual potential measurement is extended and the response time is delayed. It is possible to measure the correct potential.
JP-A-5-2987

  However, in recent years, image sensors have high speed, high image quality, and potential measurement between recording paper during image forming operations. It is requested.

  However, if the potential measurement time is extended in accordance with the deterioration status of the tuning fork vibrator 8e as in the conventional potential measurement device, the time required for the image forming operation will be reduced by that amount. There arises a problem that the productivity of the product decreases.

  In order to solve the above problems, the present invention is a potential measuring apparatus and an image forming apparatus characterized by having the following configuration, and detects deterioration of the tuning fork type vibrator 8e, and adjusts to the degree of deterioration. By adjusting the gain of the subsequent circuit, the response time can be kept constant even if the tuning fork vibrator 8e is deteriorated.

The invention described in claim 1
An electric potential measuring device composed of an electric potential sensor for measuring a surface electric potential of an electric potential measurement object, and a control unit for controlling the electric potential sensor,
The control unit can switch between an open loop and a closed loop, and has a gain adjusting means in an amplification unit that amplifies a detection signal from the potential sensor,
A potential measuring device that generates a predetermined potential difference between a potential measurement target and a potential sensor, and adjusts a gain in an amplification unit based on a detection result of a detection signal in a state where a control circuit is in an open loop. It is.

The invention according to claim 2 is the invention according to claim 1,
Having a bias applying means for applying a predetermined bias to the potential measurement object;
A potential characterized by adjusting a gain in an amplifying unit in a state where a predetermined potential difference is generated between the potential measurement target and the potential sensor by applying a predetermined bias to the potential measurement target by the bias applying means. It is a measuring device.

The invention according to claim 3 is the invention according to claim 1,
Connection switching means for connecting the potential measurement object to the reference potential of the control unit, and bias application means for applying a predetermined bias to the potential sensor,
The potential measurement object is connected to the reference potential of the control unit by the connection switching means, and a predetermined potential difference is generated between the potential measurement object and the potential sensor by applying a predetermined bias to the potential sensor by the bias applying means. In this state, the potential measuring device is characterized in that the gain in the amplifying unit is adjusted.

The invention according to claim 4 is the invention according to any one of claims 1 to 3,
This is a potential measuring device characterized by detecting the amplitude of a detection signal and adjusting the gain so that the detected amplitude value becomes a predetermined value.

The invention of claim 5 is the invention of claim 2,
After applying a predetermined bias, the potential of the measuring object is measured by the surface potential measuring means, and the gain in the amplifying unit is adjusted based on the potential measurement result and the detection result of the detection signal. This is a potential measuring device.

The invention of claim 6 is the invention according to any one of claims 1 to 5,
Has a timer to count the operating time of the potential measuring device,
This is a potential measuring device characterized in that the gain is adjusted every time it operates for a predetermined time.

The invention of claim 7 is the invention according to any one of claims 1 to 6,
An electric potential measuring apparatus having a sensor for detecting an environment in the apparatus and performing gain adjustment when temperature or humidity in the apparatus fluctuates by a predetermined value or more.

The invention according to claim 8 is the invention according to any one of claims 1 to 7,
The closed loop is a control that makes the potential of the potential sensor the same as the potential of the measurement object, and the open loop is a control that does not perform a control that makes the potential of the potential sensor the same as the potential of the measurement object. This is a potential measuring device characterized by this.

The invention of claim 9
An image forming apparatus having a surface potential measuring means composed of a potential sensor for measuring the surface potential of a photoreceptor and a control unit for controlling the potential sensor,
The control circuit can switch between an open loop and a closed loop, and has a gain adjusting means in an amplifying unit that amplifies a detection signal from the potential sensor,
An image forming apparatus characterized in that a predetermined potential difference is generated between a potential measurement target and a potential sensor, and a gain in an amplifying unit is adjusted based on a detection result of a detection signal in a state where a control circuit is in an open loop. It is.

The invention of claim 10 is the invention of claim 8,
Having charging means for charging the photoreceptor to a predetermined potential based on the control voltage;
In a state where a predetermined potential difference is generated between the photoconductor and the potential sensor by charging the surface of the photoconductor to a predetermined potential by the charging means,
An image forming apparatus characterized by adjusting a gain in an amplifying unit.

The invention of claim 11 is the invention of claim 8,
A neutralizing means for neutralizing the photoreceptor, and a bias applying means for applying a predetermined bias to the potential sensor;
The neutralization unit removes the photoconductor, and the bias application unit applies a predetermined bias to the potential sensor, thereby adjusting the gain in the amplification unit in a state where a predetermined potential difference is generated between the photoconductor and the potential sensor. This is an image forming apparatus characterized by that.

The invention of claim 12 is the invention according to any one of claims 8 to 10,
This is a potential measuring device characterized by detecting the amplitude of a detection signal and adjusting the gain so that the detected amplitude value becomes a predetermined value.

The invention of claim 13 is the invention of claim 9,
After charging the surface of the photoconductor to a predetermined potential, the surface potential of the photoconductor is measured by the surface potential measuring means, and the gain at the amplifier is adjusted based on the measurement result of the potential and the detection result of the detection signal. This is an image forming apparatus characterized by that. The invention of claim 14 is the invention of claims 8 to 12,
It has a timer that counts the operating time of the surface potential measuring means,
The image forming apparatus is characterized in that a gain adjustment is performed every time the apparatus is operated for a predetermined time.

The invention of claim 14 is the invention according to any one of claims 8 to 12,
An image forming apparatus having a timer for counting the operating time of the surface potential measuring means, and performing the gain adjustment every time the surface potential measuring means is operated for a predetermined time.

The invention of claim 15 is the invention according to any one of claims 8 to 13,
It has a counter that counts the number of images formed,
An image forming apparatus characterized in that gain adjustment is performed for each predetermined number of image forming operations.

The invention of claim 16 is the invention according to any one of claims 8 to 14,
An image forming apparatus having a sensor for detecting an environment in the apparatus and performing gain adjustment when temperature or humidity in the apparatus fluctuates by a predetermined value or more.

The invention of claim 17 is the invention according to any one of claims 1 to 16,
The closed loop is a control that makes the potential of the potential sensor the same as the potential of the measurement object, and the open loop is a control that does not perform a control that makes the potential of the potential sensor the same as the potential of the measurement object. An image forming apparatus characterized by this.

  According to the present invention, when deterioration related to the response time occurs in the potential sensor, the degree of deterioration is detected in the control system, and the gain of the circuit is adjusted in accordance with the result, so that the initial measurement is performed in the potential measurement system. It is possible to maintain the response characteristics, and it is possible to prevent a delay in response time due to deterioration of the potential sensor.

  Also, when the remote ON time of the potential sensor is integrated and reaches a predetermined value, the number of image formations is counted and the predetermined number is reached, or the environmental sensor monitors the temperature and humidity in the device, and the environmental conditions are By determining the adjustment timing based on parameters that affect the deterioration of the potential sensor, such as when it fluctuates by more than a predetermined value, response time delay due to potential sensor deterioration can be prevented while preventing excessive adjustment. I can do it.

  Furthermore, by removing the charge from the photoconductor and adjusting the gain by applying a bias to the potential sensor side, even in an image forming apparatus in which the charger is a corona discharge type, the gain can be corrected to keep the response time constant. It becomes possible.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

  A first embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS.

  1 to 6 and 10, the same or corresponding members as those in FIGS. 11 to 13 of the conventional example described above are denoted by the same reference numerals, and the description thereof will be omitted.

  As an image forming apparatus according to the first embodiment of the present invention, there is a schematic configuration diagram as shown in FIG. This apparatus is an image forming apparatus for an electrophotographic process.

  In the figure, 1a to 1d are photosensitive members, 2a to 2d are primary charging units, 3a to 3d are exposure units, 4a to 4d are developing units, 53a to 53d are primary transfer units, 6a to 6d are cleaners, 51 Is an intermediate transfer belt, 55 is an intermediate transfer belt cleaner, and 56 and 57 are secondary transfer portions. After the photosensitive member is uniformly charged by the primary charging unit, exposure according to the image signal is performed by the exposure unit, whereby an electrostatic latent image is formed on the photosensitive member. Thereafter, the toner image is developed by the developing unit, and the toner images on the four photoconductors are multiplex-transferred to the intermediate transfer belt by the transfer unit, and further transferred to the recording material P by the secondary transfer unit. The transfer residual toner remaining on the photoreceptor is recovered by a cleaner, and the transfer residual toner remaining on the intermediate transfer belt is recovered by an intermediate transfer belt cleaner 55. The toner image transferred to the recording material P is fixed by the fixing unit 7 to obtain a color image.

FIG. 1 shows a configuration example of the periphery of the photosensitive drum of the image forming apparatus according to the first embodiment of the present invention. (Parts unnecessary for explanation are omitted)
In FIG. 1, reference numeral 1 denotes a photosensitive drum 1. Around the photosensitive drum 1, a charging roller 2, an exposure device 3, a potential sensor 8, a developing device 4, a static elimination device 112, and the like are arranged.

  A charging high voltage output (AC voltage + DC voltage) generated by the charging high voltage circuit 109 is supplied to the charging roller 2 to uniformly charge the surface of the photosensitive drum 1 with a predetermined potential.

  The charging high-voltage circuit 109 outputs a predetermined charging high-voltage output (AC voltage + DC voltage) based on the control value from the controller 111.

  Here, FIG. 2 shows an example of the relationship between the charging DC output control value and the charging DC output. In the case of FIG. 2, the charging DC output changes from 0V to -1000V when the control value is between 2V and 10V. For example, when the charging DC output requires -500V, the controller 111 The control value 6V is output from the charging high voltage circuit 109.

  Returning to FIG. 1, the exposure apparatus 3 is composed of a laser scanner and an optical system, and forms an electrostatic latent image on the surface of the photosensitive drum based on an image signal (not shown).

  The potential sensor 8 is a sensor for detecting the surface potential of the photosensitive drum, and is controlled by the potential sensor control unit 107. The potential sensor control unit 107 outputs the detection result to the controller 111. In addition to the detection value that is the detection result of the potential measurement, the communication between the potential sensor control unit 107 and the controller 111 includes a remote signal for starting the potential measurement and a gain adjustment mode signal used for gain adjustment described later. There is.

  The developing device 4 is supplied with the developing high-voltage output (AC voltage + DC voltage) generated by the developing high-voltage circuit 108, and attaches toner to the electrostatic latent image on the photosensitive drum 1 to form a visible image.

  The development high voltage circuit 108 outputs a predetermined development high voltage output (AC voltage + DC voltage) based on the control value from the controller 111.

  The neutralization device 112 is disposed upstream of the charging roller 2 in the rotation direction of the photosensitive drum 1, and neutralizes the charge remaining on the photosensitive drum 1.

  Next, FIG. 3 shows a schematic configuration diagram of the potential sensor 8 and the potential sensor control unit 107.

  In FIG. 3, reference numeral 8 is a potential sensor 8, and reference numeral 107 is a potential sensor control unit.

  The potential sensor 8 is a piezoelectric element 8a, 8b disposed on both arms of the tuning fork type vibrator 8e and the tuning fork type vibrator 8e (in the case of FIG. 3, the driving for the piezoelectric element 8b to vibrate the tuning fork type vibrator 8e). Piezoelectric element 8b, and the piezoelectric element 8a is a detecting piezoelectric element 8a for detecting vibration of the tuning fork vibrator 8e), a measuring electrode 8f, and a detection circuit 8g.

  On the other hand, the potential sensor control unit 107 includes a control unit 107a, a high-voltage power supply 107b, a detection output signal generation unit 107c, a drive circuit 107d, an amplification circuit 107e, and an open loop switching unit 107f. In FIG. 3, reference numeral 1 denotes a photosensitive drum 1.

  The operation of FIG. 3 will be described.

  When the remote signal input from the controller 111 in FIG. 1 is turned on, the operation of the potential sensor 8 and the potential sensor control unit 107 is started. First, the drive circuit 107d inputs a drive signal to the piezoelectric element 8b. Then, the tuning fork type vibrator 8e starts to vibrate, and its tip part vibrates in the directions of arrows 8c and 8d, respectively. When the tuning fork vibrator 8e starts to vibrate, the piezoelectric element 8a converts the vibration into an electric signal and outputs it as a vibration detection signal. The drive circuit 107d controls the frequency of the drive signal so that the phase difference between the drive signal and the vibration detection signal becomes a predetermined value. As a result, the tuning fork vibrator 8e continues to vibrate in a resonance state. On the other hand, when the tuning fork vibrator 8e vibrates, the electrostatic capacitance between the measurement electrode 8f and the photosensitive drum 1 periodically changes, thereby changing the charge amount of the measurement electrode 8f, and the change in the charge amount. By converting the voltage into voltage by the detection circuit 8g, an AC voltage signal proportional to the potential difference between the photosensitive drum 1 and the measurement electrode 8f can be obtained.

  Each part constituting the potential sensor 8 operates with an output (point H in FIG. 3) of a high voltage power source 107b described later as a reference potential.

In the control unit 107a, the AC detection signal output from the detection circuit 8g is amplified by the amplifier circuit 107e and input to the control unit 107a. In the control unit 107a, the amplitude of the amplified AC detection signal is The output of the high-voltage power supply 107b is controlled so that it becomes zero. Here, when the amplitude of the AC detection signal is zero, the tuning fork vibrator 8e vibrates, and the capacitance between the measurement electrode 8f and the photosensitive drum 1 is periodically changed. This is a state in which the charge amount of the electrode 8f does not change, and this state indicates that the surface potential of the photosensitive drum 1 and the potential of the measurement electrode 8f, that is, the surface potential of the photosensitive drum 1 and the output of the high voltage generator 107b are the same potential. I mean. Thereby, the surface potential of the photosensitive drum 1 can be obtained. (Zero method)
The potential sensor control unit 107 converts the output of the high voltage generation unit 107b at this time by the detection output signal generation unit 107c, for example, in a relationship as shown in FIG.

  Next, the operation when the gain adjustment mode signal is input from the controller 111 of FIG. 1 will be described with reference to the flowcharts of FIGS.

  Piezoelectric elements 8a and 8b are bonded to both arms of the tuning fork vibrator 8e of the potential sensor 8. This bonding state is greatly related to the vibration amplitude of the tuning fork vibrator 8e. That is, when the adhesion state changes due to environmental changes, changes with time, etc., the vibration amplitude decreases, and as a result, the potential measurement time as the potential sensor 8 and the potential sensor control unit 107 becomes longer.

  Therefore, when the vibration amplitude of the tuning fork type vibrator 8e decreases, the gain is adjusted by the amplifier circuit 107e. After the initial state and deterioration of the potential sensor 8, a predetermined value is provided between the potential sensor 8 and the photosensitive drum 1. In a state where there is a potential difference, the gain is corrected so that the amplitude at the point B becomes constant even when the amplitude at the point A in FIG. 3 decreases.

First, when the controller 111 determines that gain adjustment is necessary, the gain adjustment mode is turned on. (Fig. 4 S401)
The controller 111 determines that the gain adjustment is necessary in various cases. For example, when the remote ON time of the potential sensor is accumulated and reaches a predetermined value, the number of image formations is counted, Various cases are envisaged, such as when the predetermined number is reached, or although not shown, the temperature and humidity inside the device are monitored by an environmental sensor and the environmental conditions fluctuate by more than a predetermined value.

When the gain adjustment mode is turned on, the photosensitive drum 1 is rotated by a signal from the controller 111 and the charging high voltage 109 outputs a predetermined high voltage output (for example, −500 V). At the same time, in the potential sensor control unit, the open loop switching unit 107f switches the control system to the open loop by a signal from the control unit 107a. (S402)
That is, the control system is set in an open loop with a predetermined potential difference between the potential sensor 8 and the photosensitive drum 1.

Next, in this state, the amplitude of the AC detection signal output from the detection circuit 8g is measured by the amplification circuit unit 107e. At this time, there is a potential difference of 500 V between the potential sensor 8 and the photosensitive drum 1, and the AC signal amplitude at the vibration amplitude of the tuning fork vibrator 8e at that time is measured. (S403)
(Here, if the measured result is equal to or smaller than the predetermined value, it is determined that the potential sensor 8 is out of order, the gain adjustment mode is terminated, and a display prompting the operator to replace the potential sensor 8 or the like may be displayed. .)
Then, the measured amplitude of the AC detection signal is compared with a reference value. (S404)
Based on the comparison result, the correction gain in the amplification circuit unit 107e is determined and the gain is corrected so that the amplitude at the output of the amplification circuit unit 107e becomes a predetermined value. (S405)
When the gain correction is completed, the gain adjustment mode is turned off, the charging high voltage output is stopped, the rotation of the photosensitive drum 1 is stopped, and the control system is switched to the closed loop. (S406)
Then, the adjustment mode ends.

  FIG. 5 shows a state in which there is a predetermined potential difference between the potential sensor 8 and the photosensitive drum 1, and the potential sensor control unit 107 is in an open loop state, and the gain correction is performed in the initial state of the potential sensor 8 and the post-deterioration amplification circuit 107e. 3 shows the waveforms at points A and B in FIG.

  In FIG. 5, 5-1 is the waveform at point A in the initial state, 5-2 is the waveform at point B in the initial state, 5-3 is the waveform at point A after deterioration, and 5-4 is the waveform at point A. It is a waveform of B point in the state which carried out gain correction after degradation.

  When the above-described gain correction mode is executed, when the vibration amplitude of the potential sensor 8 deteriorates as shown in FIG. 5 in a state where there is a predetermined potential difference between the potential sensor 8 and the photosensitive drum 1, FIG. Even if the waveform amplitude at point A in 3 decreases, the initial state can be maintained for the waveform at point B in FIG. 3 by adjusting the gain in the amplifier circuit 107e.

FIG. 6 shows a comparison of response characteristics between the initial state of the potential sensor 8 and the state after gain correction after deterioration. Here, in FIG.
6-1 shows the surface potential fluctuation of the photosensitive drum 1, which is the measurement target of the potential sensor 8, and here is an example in the case of fluctuation from −100 V to −600 V.

  6-2 is a comparison of the waveform (potential sensor 8 response time) at point C in FIG. 3 after the initial state and deterioration of the potential sensor 8.

  6-3 shows the waveform at point B in FIG. 3 in the initial state, and 6-4 shows the waveform at point B in FIG. 3 after deterioration.

When the surface potential of the photosensitive drum 1 is changed, the surface potential fluctuation of the photosensitive drum 1 is a circuit with the same sensitivity at the point B regardless of the initial state or deterioration of the potential sensor 8 according to the result of the gain correction described above. As a result, as shown in 6-2, similar response characteristics can be obtained both at the initial stage and after deterioration. (Response time t1 in the initial state = Response time t2 after deterioration)
The fact that the response of the potential measurement is the same both in the initial stage and after the deterioration means that the reference potential of the potential sensor 8 changes in the same way. The point B shown in 6-3 and 6-4 The waveform (detected waveform after amplification) is similar.

  In the potential measurement after the completion of the above-described gain correction operation, signal amplification is performed with the gain corrected by the amplifier circuit 107e. Therefore, by performing the above gain correction periodically at a predetermined timing, It is possible to always keep fluctuations in response time within a certain range.

  As described above, the potential of the tuning fork vibrator 8e of the potential sensor 8 is corrected according to the deterioration state of the vibration amplitude, and the gain of the detection signal in the control unit is corrected, so that a constant potential measurement is possible even when deterioration occurs. It is possible to maintain the response time.

  A second embodiment of the image forming apparatus according to the present invention will be described with reference to FIG.

  7, the same or corresponding members as those in FIGS. 11 to 13 of the conventional example and FIGS. 1 to 6 and 10 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. And

  The second embodiment differs from the first embodiment in that the surface potential of the photosensitive drum 1 is output when a predetermined charging high voltage is output before gain adjustment in order to perform gain adjustment with higher accuracy. Is measured and the gain is corrected by the measurement result of the surface potential and the signal amplitude.

  A gain correction method according to the second embodiment will be described with reference to the flowchart of FIG.

First, when the controller 111 determines that gain adjustment is necessary, the gain adjustment mode is turned on. (FIG. 7 S701)
The controller 111 determines that the gain adjustment is necessary in various cases. For example, when the remote ON time of the potential sensor is accumulated and reaches a predetermined value, the number of image formations is counted, Various cases are envisaged, such as when the predetermined number is reached, or although not shown, the temperature and humidity inside the device are monitored by an environmental sensor and the environmental conditions fluctuate by more than a predetermined value.

When the gain adjustment mode is turned on, the photosensitive drum 1 is rotated by a signal from the controller 111 and the charging high voltage 109 outputs a predetermined high voltage output (for example, −500 V). (S702)
Next, the surface potential of the photosensitive drum 1 at that time is measured by the potential sensor 8. It should be noted that the potential measurement here takes a sufficiently longer measurement time than the normal potential measurement so that it responds sufficiently even if the potential sensor 8 is deteriorated. (S703)
When the measurement is completed, the potential sensor control unit switches the control system to an open loop. (S704)
That is, the control system is set in an open loop with a predetermined potential difference between the potential sensor 8 and the photosensitive drum 1.

Next, in this state, the amplitude of the AC detection signal output from the detection circuit 8g is measured by the amplification circuit unit 107e. At this time, there is a potential difference of 500 V between the potential sensor 8 and the photosensitive drum 1, and the AC signal amplitude at the vibration amplitude of the tuning fork vibrator 8e at that time is measured. (S705)
(Here, if the measured result is equal to or smaller than the predetermined value, it is determined that the potential sensor 8 is out of order, and the gain adjustment mode is terminated, and a display prompting the operator to replace the potential sensor 8 may be displayed on the operation unit, not shown). .)
Next, based on the surface potential measured in S703, the amplitude of the AC detection signal measured in S705 is compared with a reference value. Here, based on the reference potential relationship between the potential difference between the potential sensor 8 and the photosensitive drum 1 and the AC detection signal prepared in advance, the AC detection to be obtained in the case of the surface potential measured in S703. The ratio of the AC detection signal actually measured in S705 is calculated with respect to the signal amplitude. (S706)
Next, based on the comparison calculation result in S706, the correction gain in the amplification circuit unit 107e is determined and the gain is corrected so that the amplitude at the output of the amplification circuit unit 107e becomes a predetermined value. (S707)
When the gain correction is completed, the gain adjustment mode is turned off, the charging high voltage output is stopped, the rotation of the photosensitive drum 1 is stopped, and the control system is switched to the closed loop. (S708)
Then, the adjustment mode ends.

  In the potential measurement after the completion of the correction operation, signal amplification is performed with the gain corrected by the amplifier circuit 107e. Therefore, by performing the gain correction periodically at a predetermined timing, the tuning fork of the potential sensor 8 is used. Even when the vibration amplitude of the type vibrator 8e is deteriorated, it is possible to always keep the fluctuation of the response time of the potential measurement within a certain range.

  As described above, before the gain correction, the actual surface potential of the photosensitive drum 1 is measured, and the gain correction is performed based on the surface potential measurement result and the amplitude of the AC detection signal in the closed loop. Thus, correction with higher accuracy is possible, and variation in response time can be further reduced.

  A third embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS.

  8 to 9, the same or corresponding members as those in FIGS. 11 to 13 of the conventional example, FIGS. 1 to 6 and 10 of the first embodiment, and FIG. 7 of the second embodiment are included. The same reference numerals are given, and the description thereof is omitted.

  In the first embodiment, in the gain adjustment mode, the open loop switching unit 107f drops the reference potential of the potential sensor 8 to the reference potential (ground) of the control unit 107 and charges the surface of the photosensitive drum 1 to a predetermined potential. As a result, a predetermined potential difference is formed between the potential sensor 8 and the photosensitive drum 1, but in the third embodiment, the surface of the photosensitive drum 1 is neutralized, while a predetermined potential difference is provided on the potential sensor 8 side. A predetermined potential difference is formed between the potential sensor 8 and the photosensitive drum 1 by applying a bias.

  8 differs from the first embodiment in FIG. 3 in that there is no open loop switching unit 107f, a mode switching signal is output from the control unit 107a to the high voltage power source 107b, and a detection output is also provided. The detection output of the signal generation unit 107c is also input to the control unit 107a.

  Although the open loop switching unit 107f as shown in FIG. 3 does not exist, the high voltage power source 107b applies a predetermined bias to the potential sensor 8 side by the mode switching signal from the control unit 107a, so that the operation is open loop. It will be switched.

  The operation when the gain adjustment mode signal is input will be described with reference to the flowcharts of FIGS.

First, when the controller 111 determines that gain adjustment is necessary, the gain adjustment mode is turned on. (FIG. 9 S901)
The controller 111 determines that the gain adjustment is necessary in various cases. For example, when the remote ON time of the potential sensor is accumulated and reaches a predetermined value, the number of image formations is counted, Various cases are envisaged, such as when the predetermined number is reached, or although not shown, the temperature and humidity inside the device are monitored by an environmental sensor and the environmental conditions fluctuate by more than a predetermined value.

When the gain adjustment mode is turned on, the photosensitive drum 1 is rotated by a signal from the controller 111 and the surface potential of the photosensitive drum 1 is neutralized by a neutralization value.
Further, a mode switching signal is output from the control unit 107a of FIG. 8 to the high voltage power source 107b.

  When the mode switching signal is input, the high-voltage power supply 107b operates to output a predetermined high-voltage output (for example, -500V), the output of the high-voltage power supply 107b is detected by the detection output signal generation unit 107c, and the control unit 107a Thus, feedback control for controlling the output voltage of the high-voltage power supply 107b to be constant is performed by the control unit 107a, the high-voltage power supply 107b, and the detection output signal generation unit 107c.

Then, the output of the high voltage power supply 107b generated here is applied to the potential sensor 8 as a bias. That is, by the above operation, a predetermined potential difference is formed between the potential sensor 8 and the photosensitive drum 1 by applying a predetermined bias to the potential sensor 8 side. (S902)
Next, in this state, the amplitude of the AC detection signal output from the detection circuit 8g is measured by the amplification circuit unit 107e. At this time, there is a potential difference of 500 V between the potential sensor 8 and the photosensitive drum 1, and the AC signal amplitude at the vibration amplitude of the tuning fork vibrator 8e at that time is measured. (S903)
(Here, if the measured result is equal to or smaller than the predetermined value, it is determined that the potential sensor 8 is out of order, and the gain adjustment mode is terminated, and a display prompting the operator to replace the potential sensor 8 may be displayed on the operation unit, not shown). .)
Then, the measured amplitude of the AC detection signal is compared with a reference value. (S904)
Based on the comparison result, a correction gain in the amplification circuit unit 107e is determined and the gain is corrected so that the amplitude at the output of the amplification circuit unit 107e becomes a predetermined value. (S905)
When the gain correction is completed, the gain adjustment mode is turned off, the mode switching signal from the control unit 107a is released, the high voltage generation by the high voltage power source 107b is stopped, the rotation of the photosensitive drum 1 is stopped, and the static elimination operation is further performed. Also stop. (S906)
Then, the adjustment mode ends.

  In the potential measurement after the completion of the correction operation, signal amplification is performed with the gain corrected by the amplifier circuit 107e. Therefore, by performing the gain correction periodically at a predetermined timing, the tuning fork of the potential sensor 8 is used. Even when the vibration amplitude of the type vibrator 8e is deteriorated, it is possible to always keep the fluctuation of the response time of the potential measurement within a certain range.

  When the charging means is corona charging, it is difficult to charge the surface of the photosensitive drum 1 to a predetermined potential due to a change in environmental conditions, etc., so that it is applied not to the photosensitive drum 1 but to the potential sensor 8 as described above. Controlling the bias to be constant makes it possible to perform gain correction with higher accuracy, and to further reduce variation in response time.

1 is a diagram illustrating an overview of an image forming apparatus according to a first embodiment of the present invention. The figure which shows the characteristic of the charging DC output in the image forming apparatus of FIG. 1 is a diagram illustrating an outline of a potential sensor and a potential sensor control unit in the image forming apparatus of FIG. Flowchart of gain correction in the potential sensor control unit in the image forming apparatus of FIG. The figure explaining the waveform of each part of the electric potential sensor control part of FIG. The figure explaining the change of the response time of the electric potential sensor in the image forming apparatus of FIG. Flowchart of gain correction of the image forming apparatus according to the second embodiment of the present invention FIG. 6 is a diagram illustrating an outline of a potential sensor and a potential sensor control unit of an image forming apparatus according to a third embodiment of the present invention. Flowchart of gain correction in the potential sensor control unit in the image forming apparatus of FIG. The figure explaining an example of schematic structure figure of an image forming device The figure explaining the outline | summary of the electric potential sensor of the conventional image forming apparatus, and an electric potential sensor control part. The figure which shows the characteristic of the detection output signal generation part of the conventional potential sensor control part The figure explaining the change of the response time of the potential sensor in the conventional image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Exposure apparatus 4 Developer 8 Electric potential sensor 107 Electric potential sensor control part 107a Control part 107b High voltage power supply part 107c Divided voltage output part 107d Driving circuit 107e Amplifying circuit 107f Open loop switching part 108 Development high voltage part 109 Charging high voltage Part 111 controller

Claims (17)

An electric potential measuring device composed of an electric potential sensor for measuring a surface electric potential of an electric potential measurement object and a control unit for controlling the electric potential sensor,
The control unit can switch between an open loop and a closed loop, and has a gain adjusting means in an amplification unit that amplifies a detection signal from the potential sensor,
A predetermined potential difference is generated between the potential measurement object and the potential sensor, and a gain in the amplifying unit is adjusted based on a detection result of the detection signal in a state where the control circuit is in an open loop. A potential measuring device. Bias application means for applying a predetermined bias to the potential measurement object;
By applying a predetermined bias to the potential measurement object by the bias applying means, a gain in the amplifying unit is adjusted in a state where a predetermined potential difference is generated between the potential measurement object and the potential sensor. The potential measuring device according to claim 1, wherein: Connection switching means for connecting the potential measurement object to a reference potential of the control unit, and bias application means for applying a predetermined bias to the potential sensor,
The potential measuring object is connected to the reference potential of the control unit by the connection switching means, and a predetermined bias is applied to the potential sensor by the bias applying means, whereby a predetermined bias is applied between the potential measuring object and the potential sensor. The potential measuring apparatus according to claim 1, wherein the gain in the amplifying unit is adjusted in a state where the potential difference is generated.   4. The potential measuring device according to claim 1, wherein the amplitude of the detection signal is detected, and the gain is adjusted so that the detected amplitude value becomes a predetermined value. .   After applying the predetermined bias, the potential of the measurement object is measured by the surface potential measuring means, and the gain in the amplifying unit is adjusted based on the potential measurement result and the detection result of the detection signal. The potential measuring device according to claim 2, wherein:   6. The potential measuring device according to claim 1, further comprising a timer that counts an operating time of the potential measuring device, and performing the gain adjustment every time the potential measuring device is operated for a predetermined time. 7. The apparatus according to claim 1, further comprising a sensor for detecting an environment in the apparatus, wherein the gain adjustment is performed when a temperature or humidity in the apparatus fluctuates by a predetermined value or more. Potential measuring device.   The closed loop is a control that makes the potential of the potential sensor the same as the potential of the measurement object, and the open loop is a control that makes the potential of the potential sensor the same as the potential of the measurement object. The potential measuring device according to claim 1, wherein the control is performed without performing the control. An image forming apparatus having a surface potential measuring means composed of a potential sensor for measuring the surface potential of a photoreceptor and a control unit for controlling the potential sensor,
The control circuit is switchable between an open loop and a closed loop, and has a gain adjusting means in an amplifying unit that amplifies a detection signal from the potential sensor,
A predetermined potential difference is generated between the potential measurement object and the potential sensor, and a gain in the amplifying unit is adjusted based on a detection result of the detection signal in a state where the control circuit is in an open loop. An image forming apparatus. Charging means for charging the photoreceptor to a predetermined potential based on a control voltage;
The gain of the amplifying unit is adjusted in a state where a predetermined potential difference is generated between the photoconductor and the potential sensor by charging the surface of the photoconductor to a predetermined potential by the charging unit. The image forming apparatus according to claim 8. Neutralizing means for neutralizing the photoconductor, and bias applying means for applying a predetermined bias to the potential sensor;
In the state where a predetermined potential difference is generated between the photosensitive member and the potential sensor by applying a predetermined bias to the potential sensor by the bias applying unit, while discharging the photosensitive member by the neutralizing unit. The image forming apparatus according to claim 8, wherein a gain in the amplifying unit is adjusted.   11. The potential measuring device according to claim 8, wherein the amplitude of the detection signal is detected, and the gain is adjusted so that the detected amplitude value becomes a predetermined value. .   After charging the surface of the photoconductor to a predetermined potential, the surface potential of the photoconductor is measured by the surface potential measuring means, and the amplification section is based on the potential measurement result and the detection result of the detection signal. The image forming apparatus according to claim 9, wherein a gain of the image is adjusted.   13. The image forming apparatus according to claim 8, further comprising a timer that counts an operation time of the surface potential measuring unit, and performing the gain adjustment every time the surface potential measurement unit is operated for a predetermined time.   14. The image forming apparatus according to claim 8, further comprising a counter that counts the number of image forming sheets, wherein the gain adjustment is performed every predetermined number of image forming operations. 15. The apparatus according to claim 8, further comprising a sensor for detecting an environment in the apparatus, wherein the gain adjustment is performed when temperature or humidity in the apparatus fluctuates by a predetermined value or more. Image forming apparatus.   The closed loop is a control that makes the potential of the potential sensor the same as the potential of the measurement object, and the open loop is a control that makes the potential of the potential sensor the same as the potential of the measurement object. The image forming apparatus according to claim 1, wherein the image forming apparatus is a control that does not perform the operation.

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