JP2009156594A - Surface potential measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface potential measuring device for improving response speed. <P>SOLUTION: By utilizing the relationship between a measurement target and the surface potential measuring device, potential is measured by performing an operation from two points, thus reducing response time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface potential measuring apparatus for measuring a surface potential of a measurement target.

  Conventionally, an electrophotographic image forming apparatus using a photoconductor is known, but in order to always obtain a stable high image quality, the charged potential on the surface of the photoconductor is made uniform in any environment. There is a need to. In order to make the charging potential on the surface of the photoreceptor uniform, the potential on the surface of the photoreceptor is measured by a surface potential measuring device, and the output of the device for charging the photoreceptor is controlled based on the measurement result.

The measurement principle of a conventional surface potential measuring device is shown in FIG. A measurement electrode 603 is disposed facing the measurement object 601, and a shielding electrode 602 having an opening is disposed therebetween. When the shield electrode 602 vibrates alternately in the direction of the left arrow in the figure, the area of the measurement object 601 seen from the measurement electrode 603 changes, and the capacitance C (t) generated between the two changes. Constituting an alternating current flowing through the measuring electrode 603 in accordance with a change in the capacitance C (t) I (t) , in the amplifier circuit of the detection resistor R _S, 2-stage-connected transistor (MOS-type or NPN-type) Is detected as V _O by the measurement circuit 604. Using the principle of the alternating current I (t) to obtain a (V _O is to be zero) potential V of the measuring object 601 by controlling the voltage V _M of the shield electrode 602 (x) to be zero . Nowadays, a surface potential measuring apparatus using a tuning fork vibrator that uses the shielding electrode 602 as a tuning fork and stabilizes the driving frequency by resonance of the tuning fork is used.

A configuration of a surface potential measuring apparatus using a conventional tuning fork type vibrator 703 is shown in FIG. The drive unit 701 applies a drive signal to the drive-side piezoelectric element 702a, and controls the drive frequency of the tuning fork vibrator 703 according to the detection signal received from the detection-side piezoelectric element 702b. The timing circuit 704 generates a timing signal at a predetermined timing of the drive signal. When signal application to the drive side piezoelectric element 702a by the drive unit 701 starts, the tuning fork vibrator 703 starts to vibrate, and an AC signal corresponding to the potential difference between the measurement object 705 and the measurement electrode 706 is obtained. In order to extract only a desired frequency component from the AC signal output from the measurement circuit 707, it passes through the bandpass filter 709, but the signal obtained as a result is weak and is amplified through the amplification circuit 710. The signal amplified by the amplifier circuit 710 is clamped to the reference potential 712 by the clamp circuit 711 based on the timing signal generated by the timing circuit 704. FIG. 8 shows the relationship among the drive signal, timing signal, amplifier circuit output, reference potential, and clamp circuit 711 output. In the figure, (a) is the drive signal, (b ₁ ) is the output of the amplifier circuit 710 when the potential of the measuring object 705 is higher than that of the measuring electrode 706, and (b ₂ ) is the measuring object 705 than the measuring electrode 706. This is the output of the amplifier circuit 710 when the potential is lower. The peak timing of the output of the amplifier circuit 710 is synchronized with the rise and fall of the drive signal (a). (c) is a timing signal, which is a signal synchronized with the fall of the drive signal. (d) is the reference potential 712. (e ₁ ) is the output of the clamp circuit 711 when the potential of the measurement object 705 is higher than that of the measurement electrode 706, and the output (b ₁ ) of the amplifier circuit 710 is synchronized with the timing signal and the reference potential 712 (d ). Further, (e ₂ ) is the output of the clamp circuit 711 when the potential of the measurement object 705 is lower than that of the measurement electrode 706, and the output (b ₂ ) of the amplifier circuit 710 is synchronized with the timing signal and the reference potential 712. It is clamped to (d). The integrating circuit 713 integrates the output of the clamp circuit 711 and converts it to DC. That is, when the potential of the measurement object 705 is higher than that of the measurement electrode 706, the output of the integration circuit 713 is larger than the reference potential 712, and the integration circuit 713 is larger as the potential difference between the measurement electrode 706 and the measurement object 705 is larger. The output of increases. Conversely, when the potential of the measuring object 705 is lower than that of the measuring electrode 706, the output of the integrating circuit 713 is lower than the reference potential 712. Further, the larger the potential difference between the measuring electrode 706 and the measuring object 705, the larger the integrating circuit. The output of 713 is small. That is, when the difference between the output of the integration circuit 713 and the reference potential 712 becomes zero, the potential of the measurement electrode 706 = the potential of the measurement target 705. The error amplifier circuit 714 outputs a difference signal between the output of the integrating circuit 713 and the reference potential 712. When the output of the integrating circuit 713 is larger than the reference potential 712, the output of the error amplifying circuit 714 increases. When the output of the integrating circuit 713 is smaller than the reference potential 712, the output of the error amplifying circuit 714 decreases. The variable power supply circuit 715 outputs a voltage corresponding to the output of the error amplification circuit 714, and feedback control is performed so that the output of the integration circuit 713 is always equal to the reference potential 712. As a result, the current flowing through the resistor R _S is zero. Thus, the output of the variable power supply circuit 715 becomes the voltage of the measurement target 705. Furthermore, the voltage dividing circuit 716 divides the output of the variable power supply circuit 715 at a predetermined voltage dividing ratio and outputs it. A potential corresponding to the voltage division ratio of the target potential is output to V _OUT . An example of the response waveform in this case is shown in FIG. (9-a) is the potential of the measurement object, (9-b) is a detected AC signal obtained by amplifying the alternating current flowing due to the capacitance change between the measurement object 705 and the measurement electrode 706 by the amplification circuit 710, (9-c ) Is the output of the variable power supply circuit 715, which is the potential of the surface potential measuring device. By varying the voltage according to the detection signal from the start of measurement and approaching the potential of the measurement object 705, the signal amount of the detection signal decreases. The voltage at the time when the detection signal becomes zero becomes the potential of the measuring object 705, and the response time must wait until the detection signal becomes zero.
JP 2004-61282 A

  In recent years, high-speed image forming apparatuses have been demanded, and along with this, process speed has been increasing. Therefore, a surface potential measuring device that can follow the speed is required.

  The image forming apparatus will be briefly described with reference to FIG. A plurality of photosensitive drums 1001a to 1001d as image carriers are charged by charging units 1002a to 1002d, latent images are formed by exposure devices 1004a to 1004d, and the latent images are visualized by developing units 1006a to 1006d to obtain visible images. An image forming unit, a primary transfer unit that sequentially transfers a visible image from each of the image forming units to the intermediate transfer member, an intermediate transfer member 1010 that forms a multicolor image based on the visible image, and an intermediate transfer member 1010 The image forming apparatus includes a secondary transfer unit 1012 for transferring the multi-color image onto the recording material, and a fixing device 1014 for fixing the multi-color image transferred onto the recording material onto the recording material. As the intermediate transfer member 1010, a belt-like intermediate transfer belt that is stretched around a plurality of rollers and rotates endlessly, or a cylindrical intermediate transfer drum that rotates about a drum shaft is used. In the image forming process, when the intermediate transfer member 1010 comes close to the plurality of image forming units, a visible image formed on the photosensitive drum is disposed at a position facing the image forming unit and the intermediate transfer member. Then, primary transfer is performed on the intermediate transfer body 1010 by the primary transfer devices 1008a to 1008d charged by the high voltage substrates 1009a to 1009d. The visible images primarily transferred from the plurality of photosensitive drums are superimposed on the intermediate transfer member, and conveyed to a position where the intermediate transfer member is transferred to the recording material as the intermediate transfer member rotates. The visible image on the intermediate transfer body 1010 is acclimatized by the post charger 1011 and secondarily transferred to the fed recording material by the secondary transfer device 1012 charged by the high voltage substrate 1013 at the transfer position. A full-color image is obtained by being fixed by the fixing means 1014. Further, when obtaining a monochromatic image, a monochromatic visible image is primarily transferred onto the intermediate transfer member from a specific image forming unit, and then a monochromatic image is obtained through a process similar to that for forming a full color image. A so-called latent image is formed on the photoreceptor by the exposure apparatuses 1004a to 1004d, and the latent image is developed with powdered toner. The toner is accommodated in developing devices 1006a to 1006d arranged in close proximity to the respective photosensitive members, and a latent image on the photosensitive member is developed by applying a high pressure to the developing devices by high-pressure substrates 1007a to 1007d. become. The photoreceptor, the developing device, the intermediate transfer belt, and the like are driven to rotate by a driving source such as a motor controlled by a DC controller 1016. The fixing device 1014 includes a fixing roller that houses a heater therein, and a pressure roller that presses the fixing roller. The heater is temperature-controlled by a DC controller 1016. When a sheet (recording material) as a transfer material is conveyed through this fixing device, the sheet is heated by a heater and pressurized by a pair of rollers, and the toner image on the sheet is melted and fixed on the sheet. The image is formed and discharged.

  Next, the image forming process will be described more specifically with reference to FIG. In FIG. 10, primary charging grids 1101a to 1101d and surface potential measuring devices 1102a to 1102d, which are not shown and described, are shown. “a” to “d” are taken into consideration when there are four stations. Here, the primary charging grids 1101a to 1101d are electrodes that are arranged between the primary charger and the photosensitive drums 1001a to 1001d in parallel with the primary chargers 1002a to 1002d and are adjusted to a predetermined voltage. The primary charging grids 1101a to 1101d adjust the amount of current flowing from the primary charger to the photosensitive drums 1001a to 1001d so that the charge amounts on the surfaces of the photosensitive drums 1001a to 1001d can be controlled. Next, the surface potential measuring devices 1102a to 1102d are downstream of the exposure position (position irradiated with the laser from the exposure devices 1004a to 1004d) along the rotation direction of the photosensitive drums 1001a to 1001d, and the developing device 1006a. Arranged upstream of ~ 1006d. The surface potential measuring devices 1102a to 1102d measure the charged potentials on the surfaces of the photosensitive drums 1001a to 1001d, thereby making it possible to control image density stabilization and image quality. By making such adjustments every predetermined time, the image quality is kept constant, but adjustments are made during image formation, so that there is no impact on productivity (such as two electrostatic latent It is desirable to measure the potential between images).

FIG. 12 shows the charging characteristics of the photosensitive drums 1001a to 1001d. The charging characteristic represents the relationship between the surface potential of the photosensitive drums 1001a to 1001d and the developing bias applied to the developing devices 1004a to 1004d, which determines the image quality. In the figure, the horizontal axis represents the set potential (grid potential) V _g where the primary charging grids 1101a to 1101d are set, and the vertical axis represents the surface potential (potential amount) V of the photosensitive drums 1001a to 1001d. Further, reference numeral V _D is the dark potential in the figure (the charged surface of the photosensitive drum, the surface potential of the photosensitive drum 1001a~1001d when not exposed), the photosensitive drum when V _L is exposure to light potential (maximum 1001a (Surface potential of ˜1001d), V _dc indicates the set potential of the developing bias. V _L has a tendency to increase as the dark portion potential V _D increases, and the rising curve of the bright portion potential V _L represents this characteristic. The setting value of the developing bias is determined by the allowable value of the ground cover amount of the portion where no image is formed. The occurrence of this ground cover is exceptionally present in toners having different charge amounts (for example, in the developing devices 1006a to 1006d). , exceptionally charge high toner), generated by would have sufficient potential to developing the light-area potential V _D. Accordingly, the development bias V _dc is set to a level that slightly attracts the above-described exceptional toner with respect to the dark portion potential V _{D so} that the above-described background fogging by the exceptional toner does not occur. Further, the potential from the developing bias V _dc for preventing this attraction is referred to as fogging potential V _back and is usually set at about 100 to 200V. As described above, the development bias V _dc is determined, and as a result, light and dark gradations (contrast) are expressed by the contrast potential V _cont between the light portion potential V _L and the development bias V _dc described above. It will be.

In order to maintain the image gradation, the values of V _D and V _L are measured by the surface potential measuring devices 1102a to 1102d between the papers. The response time of the surface potential measuring devices 1102a to 1102d depends on the process speed and the distance between the papers. Necessary conditions can be derived. If the process speed is v _PS and the distance between papers is L _blank , the paper spacing time t _blank is roughly

と表せる。例えば、プロセススピード500[mm/s]、紙間距離25[mm]とすれば、紙間時間は50[ms]である。つまり、50[ms]以内で応答せねばならない。つまり、表面電位測定装置1102a〜1102dの応答時間は最低でも50[ms]以下でなくてはならない。この時V_Lは最大露光電位の為、紙の後端直後に電位の変更が可能であるのでほぼ50[ms]と言えるが、V_Dにおいては帯電電位である為に後端余白後にV_Dになるまでの応答時間があるので、その応答時間を7.5[ms]とすれば両端を考えると表面電位測定装置の応答時間としては35[ms]が必要となる。また、本発明において応答というのは電位が完全に安定した時間を指し、半導体などの応答時間のように出力の10%-90%で規定した時間ではない。

It can be expressed. For example, if the process speed is 500 [mm / s] and the distance between papers is 25 [mm], the time between papers is 50 [ms]. In other words, it must respond within 50 [ms]. That is, the response time of the surface potential measuring devices 1102a to 1102d must be at least 50 [ms] or less. In this case V _L because the maximum exposure potential, but it can be said that almost 50 [ms] since immediately after the rear end of the paper can be changed in potential, V after trailing edge margin for a charging potential in V _{D D} Therefore, if the response time is 7.5 [ms], considering both ends, the response time of the surface potential measuring device needs to be 35 [ms]. In the present invention, the response means a time when the potential is completely stabilized, and is not a time defined by 10% -90% of the output like the response time of a semiconductor or the like.

  In the conventional surface potential measuring device, the response is determined by the resonance period of the tuning fork vibrator and the gain in the circuit. However, in order to change the tuning fork vibrator, it is necessary to increase the resonance frequency. There are inherent disadvantages that are difficult and become unstable if the gain is increased too much. An object of the present invention is to improve the response speed of a surface potential measuring device that measures the potential of the surface of the photoreceptor while suppressing these disadvantages.

  In order to solve the above-mentioned problem, the surface potential measuring device according to claim 1, a measuring electrode disposed opposite to a measuring surface to be a potential measuring object, a measuring means for measuring a signal appearing on the measuring electrode, Measured by a capacitance fluctuation means for generating a mechanical vibration by a drive signal to change the capacitance between the measurement surface and the measurement electrode, a drive signal generation means for generating a drive signal for driving the capacitance fluctuation means, and the measurement means A measurement signal amount detection means for detecting the signal amount of the generated signal, a synchronization signal generation means for generating a synchronization signal from the drive signal generation means, a first power supply device capable of outputting a constant value, and the first A second power supply device capable of outputting a constant value different from that of the one power supply device, a switching means capable of switching between the first power supply and the second power supply, and a signal amount detection means for calculating the measurement target. Determine potential Characterized in that it is constituted by an arithmetic unit.

  The surface potential measuring device according to claim 2 is the surface potential measuring device according to claim 1, wherein the first power supply device, the second power supply device, and the switching means are one variable power supply device. It is characterized by.

  The surface potential measuring device according to claim 3 is the surface potential measuring device according to claim 1 or 2, wherein the measurement signal amount detection means performs a plurality of detections, and the calculation result calculated by the calculation device. It is characterized in that control is performed so that the average of the potential of the object to be measured is used.

  According to a fourth aspect of the present invention, in the surface potential measuring device according to the third aspect of the present invention, control is performed to exclude outliers from the values calculated by the plurality of detections.

  A surface potential measuring device with improved response speed can be provided.

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

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The 1st Example of this invention is shown.

  FIG. 1 is a block diagram of the first embodiment of the present invention, and FIG. 2 is an operation flow thereof.

  The tuning fork vibrator drive unit 101 applies a drive signal to the drive piezoelectric element 102a, and controls the drive frequency of the tuning fork vibrator 103 according to the detection signal received from the detection piezoelectric element 102b. The timing circuit 104 generates a timing signal at a predetermined timing of the drive signal. When signal application to the driving piezoelectric element 102a by the tuning fork vibrator drive unit 101 starts, the tuning fork vibrator 103 starts to vibrate, and an AC signal corresponding to the potential difference between the measurement target 105 and the measurement electrode 106 is generated. can get. At this time, power is supplied to the measurement electrode 106 by the power source A 115 or the power source B 116, and the power source A 115 and the power source B 116 output constant values, and thus have a known potential. The measurement circuit 107 is supplied with a voltage by the float voltage generation unit 108, and passes through the band-pass filter 109 to extract only a desired frequency component from the AC signal output from the measurement circuit 107. Is weak, and is amplified through the amplifier circuit 110. The signal amplified by the amplifier circuit 110 is clamped to the reference voltage by the clamp circuit 111 in synchronization with the timing signal generated by the timing circuit 104, is digitally sampled 112 by A / D conversion, and is input to the arithmetic unit 113. The Here, the clamp of the clamp circuit operates in the same manner as the conventional example shown in FIG. When the calculation unit 113 receives the value, the difference value between the value and the reference is stored internally as a signal value of the AC signal, and the selection unit 114 is different from the power source currently supplying power to the measurement electrode 106. Switch the power supply on the side (power supply B116 if current is power supply A115, power supply A115 if current is power supply B116), wait until the potential of measuring electrode 106 is completely stabilized, Then, the potential of the measuring object 105 is calculated from the two values.

  The operation flow of the above configuration will be briefly described with reference to FIG. When the measurement start signal is received, the measurement is started, the timing signal obtained by the tuning fork drive (S201) is detected (S202), and at the same time, the tuning fork is shifted to the first known potential (S203), and the measurement object 105 and the measurement electrode are detected. The AC signal flowing due to the capacitance change between 106 is detected (S204), the polarity and signal amount of the AC signal are detected (S205), and stored in the memory of the calculation unit 113 (S206). Next, the tuning fork is shifted to the second known potential (S207), and the AC signal flowing due to the capacitance change between the measuring object 105 and the measuring electrode 106 is detected (S208), and the polarity and signal amount of the AC signal are detected. Then, it is stored in the memory of the calculation unit 113 (S210). Using the value in S206 and the value in S210, the potential of the measuring object 105 is obtained by calculation (S211). In addition, the calculation unit 113 sets a wait time until the transition is completed in S207.

FIG. 13 shows a schematic diagram of the present invention. Since the amplitude of the AC signal from the measurement circuit 107 changes over time due to the distance between the measurement electrode 106 and the measurement target 105, the deterioration of the tuning fork vibrator 103, the environmental change, and the like, the amplitude is defined as a variable α. A value obtained by amplifying an AC signal and analyzing its polarity and signal amount is V _SIG , and if the current output is V _O , the relationship between the potential to be measured and V _X can be expressed by the following equation.

演算部が交流信号の増幅ピーク値をタイミング信号に同期して2点分取り込むとし、その値をそれぞれV_SIG1及びV_SIG2とし、その時点での可変電源の出力値をそれぞれV_O1及びV_O2とすると、上記の式より、

Assume that the arithmetic unit captures the amplification peak value of the AC signal for two points in synchronization with the timing signal, the values are V _SIG1 and V _SIG2 , respectively, and the output values of the variable power supply at that time are V _O1 and V _O2 , respectively. Then, from the above formula,

となり、αは次式で計算が可能である。

And α can be calculated by the following equation.

V_Xの値は計算したαを用いて

V _X value is calculated using α

と表す事が可能となる。この演算がS211における演算の方法であり、検出の交流信号の検知にかかる時間(交流信号二波分)と電源回路切替の時間(電位差が在る方が良いが、電位差が少なくとも検出精度が良ければ演算可能であり、例えば100Vならば交流信号一波分で十分である)で検出が可能となる。

Can be expressed. This calculation is the calculation method in S211. The time required for detection of the AC signal for detection (two AC signals) and the time for switching the power supply circuit (It is better that there is a potential difference, but the potential difference has at least good detection accuracy. For example, if it is 100V, one wave of AC signal is sufficient) and detection is possible.

  2 shows a second embodiment of the present invention.

  The configuration diagram in the second embodiment of the present invention is the same as that in FIG. 1, FIG. 3 shows the operation flow in the second embodiment of the present invention, FIG. 4 shows the data acquisition format in the second embodiment, and FIG. The calculation flow in a 2nd Example is shown.

  Since the description of the configuration diagram is the same as that of the first embodiment, a description thereof will be omitted.

  The operation flow will be briefly described with reference to FIG. When the measurement start signal is received, the measurement is started, the timing signal obtained by tuning fork drive (S201) is detected (S202), and at the same time, the tuning fork is changed to the first known potential (S203), and any time from the timing signal is detected. The AC signal flowing due to the capacitance change between the measurement object 105 and the measurement electrode 106 at intervals is detected (S204), the polarity and signal amount of the AC signal are detected (S205), and a plurality of values are stored in the memory of the calculation unit 113. Each is stored (S301). Next, the tuning fork is shifted to the second known potential (S207), and the AC signal flowing due to the capacitance change between the measurement object 105 and the measurement electrode 106 is detected at an arbitrary time interval from the timing signal (S208). The signal polarity and signal amount are detected (S209), and a plurality of values are stored in the memory of the calculation unit 113 (S302). Using the value in S206 and the value in S210, the potential of the measuring object 105 is obtained by calculation (S211). In addition, the calculation unit 113 sets a wait time until the transition is completed in S207.

A method for obtaining the output potential from the detection at the arbitrary time interval will be described with reference to FIG. It is assumed that detection is performed n times from the timing signal. When the frequency of the time detection and F _D, sampling period T _S if issuing a value of at least one wave component is following equation holds.

また、電源A 115が供給源である場合のタイミング信号からn×T_S時間経過した時点での検出値をV_SIGAnとし、電源B 116が供給源である場合のタイミング信号からn×T_S時間経過した時点での検出値をV_SIGBnとして、これらの値からそれぞれ前記した式に基いて計算して各V_Xn値を得る。しかし、これらのV_Xnの中には検出時のノイズ等により値が大きく外れているものがある可能性がある為、それらを除外するよう制御を行う。除外する数をm個とすると、まずV_Xn値の合計から平均値を出し、それに最も値が離れているものを1個除外する。これでV_Xn値の数はn-1個となり、これをm回繰り返す事でm個の除外が出来、結果として残るn-m個のV_Xn値の平均を算出し、その結果を最終的なV_X値とする。

Also, the detected value at the time when n × T _S time has elapsed from the timing signal when the power source A 115 is the supply source is V _SIGAn, and n × T _S time from the timing signal when the power source B 116 is the supply source The detected value at the time when it has passed is set to V _SIGBn , and each V _Xn value is obtained by calculating from these values based on the above-described formulas. However, since there is a possibility that some of these V _Xn values are greatly deviated due to noise at the time of detection, control is performed so as to exclude them. If the number to be excluded is m, the average value is first calculated from the sum of the V _Xn values, and the one that is farthest from it is excluded. The number of V _Xn values is now n-1, and this can be repeated m times to eliminate m, and the average of the resulting nm V _Xn values is calculated and the result is the final V _X value.

The operation flow will be briefly described with reference to FIG. Based on the values stored in S301 and S302 in the operation flow described above, an operation is performed from the expression in the first embodiment (S501), and a plurality of operation results V _Xn values are stored in the memory (S502). At this point, the size of the preset number of exclusions is determined (S503), and if it is large, the average is calculated (S506), and the value is output as a V _X value to finish the calculation. From the preset number of exclusions If it is smaller, the average value of the stored V _Xn values is calculated (S504), data having a large difference is excluded (S505), and the process returns to S503. If the number of remaining data is used as a variable and the data exclusion is written as zero, the average calculation is always the sum of all data in the memory storing the V _Xn value divided by the number of remaining data. Easy to calculate.

It is a block diagram in the 1st Embodiment of this invention. 3 is an operation flowchart according to the first embodiment of the present invention. It is an operation | movement flowchart in 2nd Example of this invention. It is a figure which shows the data acquisition format in 2nd Example of this invention. It is a calculation flowchart in the 2nd example of the present invention. It is a figure which shows the principle of a measurement. It is a block diagram of a prior art example. It is a figure which shows the relationship of an output. It is a figure which shows the response waveform in a prior art example. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus. FIG. 2 is a diagram schematically illustrating a schematic configuration of an image forming unit (image forming unit) of the image forming apparatus. It is a figure explaining the relationship between the grid potential of a primary charger and the surface potential of a photosensitive drum. It is a figure which shows the outline | summary of this invention.

Explanation of symbols

101 Drive unit of tuning fork vibrator
102a Drive piezoelectric element
102b Piezoelectric element for detection
103 tuning fork type vibrator
104 Timing circuit
105 Measurement target
106 Measuring electrode
107 Test circuit
108 Float voltage generator
109 Analog bandpass filter
110 Analog amplifier circuit
111 Clamp circuit
112 Digital sampling (A / D converter)
113 Calculation unit
114 Selector
115 Power supply that outputs the first output
116 Power supply that outputs the second output
601 Measurement target
602 Shielding electrode
603 Measuring electrode
604 measurement circuit
701 Tuning fork vibrator drive unit
702a Drive piezoelectric element
702b Piezoelectric element for detection
703 tuning fork type vibrator
704 Timing circuit
705 Measurement target
706 Measuring electrode
707 Test circuit
709 band pass filter
710 amplifier circuit
711 Clamp circuit
712 Reference potential
713 Integration circuit
714 Error amplification circuit
715 Variable power circuit
716 voltage divider
1001 Photosensitive drum
1002 Primary charger
1101 Primary charging grid
1102 Surface potential measuring device

Claims (4)

A measurement electrode disposed opposite to a measurement surface to be a potential measurement object;
Measuring means for measuring a signal appearing on the measuring electrode;
Capacity changing means for generating mechanical vibration by a drive signal and changing the capacity between the measurement surface and the measurement electrode;
Drive signal generating means for generating a drive signal for driving the capacity varying means;
A measurement signal amount detection means for detecting the signal amount of the signal measured by the measurement means;
Synchronization signal generating means for generating a signal for synchronization from the drive signal generating means;
A first power supply capable of outputting a constant value;
A second power supply capable of outputting a constant value different from the first power supply;
Switching means capable of switching between the first power source and the second power source;
A surface potential measuring device comprising: an arithmetic device that calculates the potential of the measurement object by calculation from the signal amount detection means. The surface potential measuring device according to claim 1,
The surface potential measuring device, wherein the first power supply device, the second power supply device, and the switching means are one variable power supply device. In the surface potential measuring device according to claim 1 or 2,
A surface potential measuring apparatus, wherein a plurality of detections are performed by the measurement signal amount detection means, and an average of calculation results calculated by the calculation apparatus is controlled to be a potential of a measurement target. In the surface potential measuring device according to claim 3,
A surface potential measuring device that performs control to exclude outlying values among the values calculated by the plurality of detections.

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