JP2007051885A - Potential measurement device and potential measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a potential measurement device and potential measurement method, capable of correcting the error components of detection signal for potential measurement of a measuring object surface. <P>SOLUTION: The potential measurement device comprises a capacitance-varying means 103 for varying the capacitance between the surface of a measuring object 101 and a detection electrode 102; the detection means 104 for detecting the charge amount, statically introduced to the detection electrode 102; and a shielding means 105 for selectively making the shielding state of the detection electrode 102 generated from the electric lines of force generated from the surface of the measuring object 101 to the detection electrode 102, for making the incident electric lines of force to the detection electrode 102 fixed for longer than a certain interval, and not shielding state of the detection electrode 102 from the electric lines of force generated from the surface of the measurement object 101 to the detection electrode 102. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a potential measuring device, an image forming apparatus using the same, a potential measuring method, and the like.

In an electrophotographic image forming apparatus using a photoreceptor, when forming a high-quality image, it is necessary to control the image forming apparatus while measuring the potential of the photoreceptor with a potential measuring device. As a potential measuring device, a detection electrode is brought close to a charged photoconductor (measurement object), a capacitance between the photoconductor and the detection electrode is mechanically changed, and a minute electrode guided to the detection electrode by electrostatic induction. There is an example of measuring the charge.

FIG. 11 shows a conceptual configuration diagram of the potential measuring device. In FIG. 11, reference numeral 601 denotes a measurement object, 602 denotes a detection electrode, and 603 denotes charge detection means. The surface potential of the measurement object 601 is VD, the capacitance changed by the capacitance change means is C1, and the signal output from the charge detection means 603 Is represented by VOUT. Here, in order to change the capacitance C1 mechanically, a method of periodically changing the lines of electric force incident on the detection electrode 602 from the measurement object 601 or a method of moving the detection electrode 602 periodically. There is something that adopts.

As an example of the former, by inserting a fork-shaped shutter between the measurement object (photosensitive member) and the detection electrode and periodically moving the shutter in a direction parallel to the surface of the measurement object, the measurement object is placed on the detection electrode. The structure which interrupts | blocks the electric force line which arrives periodically is mentioned. Thereby, the area of the effective detection electrode seen from the measurement surface can be changed, and the electrostatic capacitance between a measuring object and a detection electrode can be changed (refer patent document 1).

There is also a configuration in which a metal shield material having an opening is disposed at a position facing the measurement object, and a detection electrode is provided at the tip of a fork-shaped vibration element. Then, by moving the position of the detection electrode in parallel under the opening, the number of lines of electric force reaching the detection electrode is changed, and the capacitance is changed (see Patent Document 2).

As an example of the latter, the sensing electrode is arranged at the tip of a cantilever-like vibrator, and the cantilever is vibrated, thereby periodically changing the distance between the measurement target and the sensing electrode, thereby increasing the capacitance. There is a configuration to change (see Patent Document 3).
U.S. Pat.No. 4,720,682 U.S. Pat.No. 3,852,667 U.S. Pat.No. 4,763,078

The amount of charge electrostatically induced in the detection electrode is taken out as a detection signal by the detection means for detecting the amount of charge. However, this detection signal includes mechanical vibrations and noise components due to drive signals for generating vibrations. This can be an error component in the relationship between the potential difference between the surface to be measured and the detection electrode and the detection signal. As a result, the detection resolution of the potential measuring device decreases.

Therefore, an object of the present invention is to correct a detection signal error component generated by a change in state such as mechanical vibration of a means for changing a capacitance between a measurement object and a detection electrode or a drive signal. Is to provide.

In view of the above problems, the potential measuring device of the present invention includes a detection electrode,
Capacitance changing means for changing the capacitance between the measurement object and the detection electrode;
Detection means for detecting the amount of charge electrostatically induced in the detection electrode;
Shielding means for shielding the detection electrode from electric lines of force that can occur between the measurement object and the detection electrode;
Have
The shielding means has a means for switching between a shielding state and a non-shielding state so as to obtain a signal from the detection means in a shielding state where the detection electrode is shielded and to obtain a signal from the detection means in a non-shielding state where the sensing electrode is not shielded. It is characterized by that.
In the above configuration, the charge that is electrostatically induced in the detection electrode may be generated by the capacitance changing means when the shielding means is not shielded. In some cases, the influence of the lines of electric force from the measurement target on the detection electrode is generated at the time of shielding. Further, at the time of shielding, the shielding state needs to be maintained for at least a certain period so that the charge amount electrostatically induced in the detection electrode can be detected in a state where the capacitance changing means is driven.

The potential measuring device further includes a correcting unit, and the correcting unit includes a unit for storing a detection signal detected by the detecting unit at the time of the shielding by the shielding unit, and a detecting unit at the time of the non-shielding by the shielding unit. The detection signal to be detected may be provided with means for performing a subtraction process based on the stored detection signal and outputting the result.

Further, in view of the above problems, a potential measuring device of the present invention includes the above-described potential measuring device and an image forming unit, and the surface of the detection electrode of the potential measuring device is opposed to a photoconductor to be subjected to potential measurement of the image forming unit. And the image forming means controls image formation using the signal detection result of the potential measuring device.

In addition, in view of the above problems, the potential measurement method of the present invention includes the measurement object and the detection in a state where the detection electrode is shielded by a shielding means from electric lines of force that may be generated between the measurement object and the detection electrode. Driving a capacitance changing means for changing capacitance between the electrodes and detecting the amount of charge electrostatically induced in the detection electrodes;
Driving the capacitance changing means in a state where the detection electrode is not shielded from electric lines of force generated between a measurement object and the detection electrode, and detecting a charge amount electrostatically induced in the detection electrode;
And measuring the potential of the measurement object based on the detection value detected in each step.

In view of the above problems, the potential measurement method of the present invention detects a potential difference between the surface to be measured and the detection electrode based on the result of measurement using the above-described potential measurement method, and the absolute value of this potential difference is The potential of the detection electrode is changed so as to approach the minimum value (typically 0), and the potential of the detection electrode reached as a result is obtained as the potential of the surface to be measured.

According to the present invention, it is possible to realize a state in which the number of the electric force lines incident on the detection electrode is made constant (fixed) by eliminating the influence of the electric force lines from the measurement target on the detection electrode by the shielding means. Therefore, the error component of the detection signal can be corrected using this. Therefore, it is possible to provide a relatively high precision potential measuring device and potential measuring method. Making the number of electric lines of force constant (fixed) in the present invention includes making the number of lines of electric force zero.

Hereinafter, embodiments of the present invention will be described. One embodiment of the present invention provides a potential measuring device capable of correcting an error component of a detection signal generated by mechanical vibration or a drive signal. At that time, the lines of electric force incident on the detection electrodes are switched to detect the detection signal for measurement and the detection signal for correction.

Specifically, the procedure for correcting the detection signal will be described along one embodiment of the potential measuring apparatus of the present invention. First, a shielding means for shielding the lines of electric force from the surface of the measurement object is inserted between the measurement object (here, the measurement object surface) and the detection electrode, and the electric force lines incident on the detection electrode from the shielding means are controlled. To generate. (That is, the influence of the electric force lines from the measurement object on the detection electrode is eliminated by the shielding means, and the number of electric force lines incident on the detection electrode from the shielding means is made constant (fixed)). At this time, the capacitance changing means is set in the driving state, and the detection signal S1 at this time is measured. Here, in the present invention, “the amount of electric lines of force incident on the detection electrode is made constant (fixed) for a certain period or longer” indicates the following state. That is, by shielding a part or all of the lines of electric force incident on the detection electrode from the measurement object by the shielding means for a certain period or more, the amount of electric lines of force incident on the detection electrode is substantially the same for the certain period. It is a state to maintain the quantity. Next, the shielding means is removed from between the surface to be measured and the detection electrode, the capacitance changing means is driven, electric lines of force are made incident on the detection electrode from the surface to be measured, and the detection signal S2 at this time is measured. Finally, the detection signal S3 is corrected by correcting the detection signal S2 based on the detection signal S1, and is set as the potential of the measurement surface. Thus, based on the signal obtained in the shielding state and the signal obtained in the non-shielding state, the potential of the measurement surface can be measured more accurately.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
1, FIG. 5-a, and FIG. 5-b are schematic diagrams for explaining the configuration and operation of the potential measuring apparatus according to the first embodiment. In FIGS. 1 and 5-a, reference numeral 101 denotes a surface to be measured, 102 is a sensing electrode, 103 is a capacitance changing means, 104 is a detecting means, 105 is a shielding means, and 106 is a correcting means. Reference numeral 201 denotes an electric force line generated from the surface 101 to be measured toward the detection electrode 102, 202 denotes an electric force line incident on the shielding unit 105 from the measurement target surface 101, and 203 denotes the detection electrode 102 from the shielding unit 105. Incident electric field lines. The surface 101 to be measured is a surface having a predetermined potential. For example, it is a part of a charged photoreceptor.

The capacity changing means 103 changes the number of electric lines of force incident on the detection electrode 102 using a mechanical periodic vibrator, and periodically changes the capacity between the surface 101 to be measured and the detection electrode 102. is there. As this capacity changing means 103, one utilizing a resonance phenomenon is generally used. For driving the vibrator, an actuator such as piezoelectric, electrostatic or electromagnetic can be used.

Schematic diagrams for explaining the capacity changing means 103 that can be used in the present embodiment are shown in FIGS. 2-a, 2-b, and 2-c. 2A, the vibrator 301 is periodically vibrated in the direction of arrow C (horizontal with respect to the surface of the detection electrode 102) between the surface 101 to be measured and the detection electrode 102. Thereby, the electric lines of force 201 are periodically interrupted, and the coupling capacity therebetween is changed. When there are a plurality of vibrators as shown in FIG. 2A, the pair of vibrators 301 are vibrated so as to open and close by simultaneously vibrating inward and outward respectively.

In the capacity changing means of FIG. 2B, the detection electrode 102 is disposed on the vibrator 302, and the vibrator 302 is periodically vibrated in the direction of arrow D (perpendicular to the surface of the detection electrode 102). Yes. Thereby, the number of electric lines of force 201 incident on the detection electrode 102 from the surface 101 to be measured is changed, and the coupling capacitance therebetween is changed. In FIG. 2-c, a plurality of detection electrodes 102 are arranged, and a vibrator 303 having an opening 304 corresponding to the detection electrodes 102 is periodically arranged in the direction of arrow E (horizontal with respect to the surface of the detection electrodes 102). Vibrate. Thus, the coupling capacitance between the surface 101 to be measured and the detection electrode 102 is changed.

The capacitance changing means 103 of the present invention is not limited to the configuration shown in FIG. 2, and any device can be used as long as it periodically changes the capacitance between the surface 101 to be measured and the detection electrode 102. it can.

In the above configuration, when the capacitance between the measurement target surface 101 and the detection electrode 102 is changed by the capacitance changing means 103, a charge corresponding to the potential difference between the measurement target surface 101 and the detection electrode 102 is induced on the detection electrode 102. The detection means 104 takes out this electric charge induced | guided | derived to the detection electrode 102 as a detection signal.

An example of the detection unit 104 will be described with reference to the schematic diagrams of FIGS. The detection unit 104 in FIG. 3A has a configuration in which a minute current flowing through the high resistance RIN is converted into a voltage at both ends of the high resistance RIN by the induced charge, and a detection signal is output (VOUT) from the source follower circuit of the FET. Here, VCC is a power supply voltage, and R1 and R2 are resistors. The detection unit 104 in FIG. 3B has a configuration that performs a current-voltage change using a negative feedback mechanism of the operational amplifier OP-AMP and outputs a detection signal VOUT. Here, Rf is a feedback resistor, and Cf is a phase compensation capacitor. The detecting means 104 detects a signal based on the ground potential. In the present invention, the ground potential of the detection means 104 is referred to as a reference potential.

FIG. 4 is a conceptual diagram illustrating the detection signal of this embodiment. As can be seen from this conceptual diagram, the detection signal VOUT can be extracted from the detection means 104 as a signal corresponding to the potential difference ΔVd between the surface 101 to be measured and the detection electrode 102. As can be seen from FIG. 4A, assuming that the detection electrode 102 is fixed to the ground potential, when the potential VD of the surface 101 to be measured changes to an integral multiple of α (V), the amplitude of the detection signal VOUT also changes to that. Increase proportionally.

However, a noise component (Vn) having no correlation with the potential difference ΔVd exists in the detection signal. This occurs due to mechanical vibration of the capacitance changing means 103 or the signal applied to the vibrator. FIG. 4B shows the output of the detection signal VOUT at the potential VD = 0 V of the surface 101 to be measured, which is related to the noise component (Vn). In this way, noise that is the same as or an integral multiple of the vibration frequency of the detection signal VOUT is observed. The phase of the noise is not limited to that shown in FIG.

During actual measurement, a detection signal obtained by adding the signal of FIG. 4B to the signal of FIG. 4A is obtained as VOUT. Hereinafter, VOUT at this time (the potential VD = 0 V of the surface 101 to be measured) is referred to as a noise component Vn. Therefore, the noise component Vn becomes an error factor of the detection signal corresponding to the potential difference ΔVd.

In FIG. 4C, the horizontal axis represents the potential VD of the measurement target surface 101, the vertical axis represents the amplitude of the detection signal VOUT, and the relationship between the two is shown. In FIG. 4C, the straight line does not pass through the origin and has an offset. Therefore, this offset becomes an error, and this is an important factor that determines the detection resolution of the potential measuring device. The intercept with the vertical axis in FIG. 4C is the noise component Vn.

In the present invention, the amount of correction of the detection signal error is detected by measuring the mechanical vibration or the like and the noise component Vn of the drive signal, thereby improving the resolution of the potential measuring device.

This noise component Vn can be measured as a detection signal from the detection means 104 when the potential difference ΔVd between the surface 101 to be measured and the detection electrode 102 is zero. However, in the potential measuring device, it is difficult to fix the surface 101 to be measured such as the surface of the photosensitive member to an arbitrary potential.

5A and 5B are diagrams illustrating a method for measuring the noise component Vn according to the present embodiment. In this embodiment, when the noise Vn is measured for correction, the shielding means 105 is inserted between the surface 101 to be measured and the detection electrode 102 (see FIG. 5-a). The shielding means 105 is fixed at a predetermined potential (for example, the ground potential of the potential measuring device). Therefore, the shielding unit 105 shields the electric force lines 202 generated from the surface 101 to be measured, and makes it difficult to enter the detection electrode 102. That is, the capacitance between the surface 101 to be measured and the detection electrode 102 is a minute value. Even if a mechanical vibration is generated in the capacitance changing unit 103, a detection signal corresponding to the potential difference ΔVd between the surface 101 to be measured and the detection electrode 102 is not output. Reference numeral 204 denotes an electric force line generated from the shielding means toward the capacity changing means.

On the other hand, by changing the potential difference ΔVc between the fixed potential of the shielding means 105 and the detection electrode 102, the number of electric lines of force 203 incident on the detection electrode 102 from the shielding means 105 can be controlled. Here, when the potential difference ΔVc is 0 V, the number of lines of electric force that enter the detection electrode 102 from the shielding unit 105 is 0, and no detection signal corresponding to the potential difference ΔVc is output. Therefore, only the noise Vn is output from the detection signal. However, the potential difference ΔVc may be set to a predetermined value other than 0 V (see the second embodiment described later), and the detection signal corresponding to the potential difference ΔVd described below can be measured more accurately. Thus, it may be set appropriately according to the design of the apparatus.

As described above, when the potential measuring apparatus of this embodiment is used, the shielding means 105 fixed to the same potential as the detection electrode 102 is connected between the surface 101 to be measured and the detection electrode 102 by a switching drive means (not shown). insert. In this state, the noise Vn for correcting the detection signal can be measured from the detection signal.

Further, as shown in FIG. 5B, the shielding unit 105 is configured to be movable in the direction of the arrow B by a switching drive unit (not shown). Therefore, at the time of measuring a photosensitive drum or the like (the potential difference ΔVd between the measurement target surface 101 and the detection electrode 102), the following measurement can be performed. That is, the detection signal corresponding to the potential difference ΔVd can be measured by extracting the shielding means 105 between the surface 101 to be measured and the detection electrode 102 (see FIG. 5B).

In the configuration as described above, the correction means 106 has means for storing a signal when a correction detection signal (noise Vn) is input. Further, when the detection signal for detection (detection signal corresponding to the potential difference ΔVd) is input, the correction means 106 subtracts the correction detection signal stored from the detection signal, and the signal resulting from the subtraction Means for outputting. The subtraction may be subtracted as it is or may be subtracted by multiplying by a predetermined coefficient, and may be set according to the design of the apparatus as appropriate.

By such a method, the noise Vn included in the detection signal can be removed by performing correction based on the information of the noise Vn measured when the shielding unit 105 is inserted. As a result, only the detection signal corresponding more accurately to the potential difference ΔVd can be obtained separately from the noise.

FIG. 6 is a diagram illustrating a flow of the above-described measurement method of the potential measurement device according to the present embodiment. First, in step 401, the shielding means 105 is moved to a position where the lines of electric force input to the detection electrode 102 from the surface 101 to be measured are shielded. Next, at step 402, the signal output from the detection means 104 in a state where the capacitance changing means 103 is driven is measured as a correction signal. In step 403, the correction signal is stored in the correction means 106. Next, in step 404, the shielding means 105 is moved to a position where the lines of electric force input from the surface 101 to be measured to the detection electrode 102 are not shielded. Thereafter, in step 405, in a state where the capacity changing means 103 is driven, the correction means 106 subtracts the correction signal from the detection signal for detection output from the detection means 104, and outputs this as a measurement value. Here, if it is determined in step 406 that it is not necessary to remeasure the correction signal, and if it is determined in step 407 that the measurement may be ended, the process ends here. If it is determined in step 406 that the correction signal needs to be remeasured (for example, if the drive signal for driving the capacitance changing means 103 has changed, remeasurement is necessary), the process returns to step 401. Then start again with the remeasurement of the correction signal. If it is determined in step 407 that the measurement is not finished (for example, if the measurement value is uncertain, remeasurement is necessary), the process returns to step 405 and the measurement value is output again. .

As described above, by using this embodiment, it is possible to correct an error component of a detection signal generated by mechanical vibration or a drive signal. Therefore, according to the present embodiment, a highly accurate potential measuring device can be provided.

Note that the detection unit 104 may not output the same frequency as the vibration frequency. For example, as shown in FIG. 3C, the synchronous detection circuit 104 ′ may be included, and a low-pass filter may be provided after VOUT. Here, SYNC is a vibration synchronization signal, FET is an FET element, and R4, R5, R6, and R7 are resistors. As a result, the time constant at which the detection signal after passing through the low-pass filter changes becomes longer and the error of the detection signal becomes smaller, and the correction detection signal and the detection signal can be subtracted more accurately.

Note that the potential measuring apparatus according to the present embodiment does not necessarily include the correcting unit 106, and the correcting unit 106 may be included in an external control device or the like.

(Second Embodiment)
The second embodiment of the present invention relates to an embodiment characterized by the control method of the potential measuring device. Others are the same as those in the first embodiment.

In the first embodiment, the potential measuring device that measures the potential difference ΔVd between the measurement target surface and the detection electrode as a detection signal by changing the capacitance between the measurement target surface and the detection electrode has been described. . In this apparatus, by increasing or decreasing the potential of the detection electrode so that the detection signal becomes the smallest, it is possible to adopt a method in which the potential of the surface to be measured and the potential of the detection electrode are substantially matched. In this method, since the potential of the surface 101 to be measured can be measured by feeding back the two potentials to coincide with each other, the change in the output of the detection signal due to the distance between the surface 101 to be measured and the detection electrode 102 can be measured. Can be suppressed. For this reason, even when the arrangement accuracy of the surface to be measured and the potential measuring device is low, it has a feature that highly accurate potential measurement can be performed.

Here, as a method of changing the potential of the detection electrode, in the case of the detection means of FIG. 3A, the detection means 104 is driven by a floating power supply (VCC), and the detection electrode is changed by changing the GND level of the floating power supply. A method of changing the potential of 102 can be adopted. In the case of the detection means 104 in FIG. 3B, a method of changing the potential of the detection electrode 102 by applying a voltage to the non-inverting input terminal (+ terminal of OP-AMP) can be employed.

FIG. 7 shows a flow chart of the control method of the potential measuring apparatus according to the second embodiment. First, in step 411, the shielding means 105 is moved to a position where the lines of electric force input from the surface 101 to be measured to the detection electrode 102 are shielded. Next, the signal output from the detection unit 104 in a state where the capacitance changing unit 103 is driven is measured as a correction signal, and the correction signal is stored in the correction unit 106. Next, in step 412, the shielding means 105 is moved to a position where the lines of electric force input from the surface 101 to be measured to the detection electrode 102 are not shielded. Thereafter, in a state in which the capacity changing unit 103 is driven, the correction unit 106 subtracts the correction signal from the detection signal output from the detection unit 104. And this is output as a measured value. These steps are the same as the control method described in the first embodiment.

Here, in step 413, it is determined whether or not this measurement value is 0. If it is 0, the potential of the detection electrode 102 is read as the potential of the surface 101 to be measured in step 414. If it is determined in step 415 that the measurement can be terminated, the process ends.

If the measured value is not 0 in step 413, it is determined in step 416 whether this is positive. If it is positive, the potential of the detection electrode 102 is increased in step 417. In step 419, it is determined whether the correction signal needs to be measured again. If it is determined that it is not necessary to perform remeasurement, the process returns to step 412 to repeat the following steps. If it is determined in step 419 that the correction signal needs to be remeasured, the process returns to step 411 and the correction signal is remeasured and stored again. On the other hand, when it is determined in step 416 that the measured value is negative, the potential of the detection electrode 102 is lowered in step 418. In step 419, the procedure proceeds to the same procedure as described above. If it is determined in step 415 that the measurement is not terminated, the process also proceeds to step 419.

By this control method, the difference between the potential of the surface 101 to be measured and the potential of the detection electrode 102 can be made smaller, and more accurate measurement can be realized. Therefore, it is possible to provide a highly accurate potential measuring device with a small error due to the arrangement distance.

(Third embodiment)
The third embodiment of the present invention relates to a form having the characteristic of the shielding means, and specifically shows a form having the shaping means as a component. Others are the same as those in the first embodiment or the second embodiment. Here, the shaping means of the present invention controls the electric lines of force so as to suppress the disturbance of the electric lines of force that are incident on the detection electrode from the surface to be measured, and to be incident substantially perpendicular to the surface of the detection electrode. Means to do.

FIG. 8A, FIG. 8-B, and FIG. 8-C are schematic diagrams illustrating the potential measuring device according to the present embodiment. 8A is a schematic diagram for explaining the configuration, and FIGS. 8B and 8C are schematic diagrams of cross sections of the potential measuring device.

In the present embodiment, the shaping means 305 having the opening 306 is for shaping the electric lines of force 201 incident on the detection electrode 102 from the surface 101 to be measured. The shaping unit 305 is a conductor having an opening 306 having the same size as the detection electrode 102, and the shaping unit itself is fixed to a predetermined potential (generally, the same potential as the detection electrode 102). In the absence of this shaping means, the electric force lines in the vicinity of the detection electrode 102 are disturbed (an example of the electric force lines shaped in FIG. 8A is shown. However, the distribution of the electric force lines is not limited to this. .) By the shaping unit 305, many electric lines of force are shaped so as to be incident almost perpendicular to the surface of the detection electrode 102. As a result, since the number of lines of electric force incident on the detection electrode 102 can be increased, the detected signal becomes large.

In the present embodiment, the entire shaping unit 305 is movable in the F direction in FIGS. 8-a, 8-b, and 8-c, and also has a function of a shielding unit. When the shaping unit 305 is positioned as shown in FIG. 8B, the shaping unit 305 functions to shape the electric force lines 201 incident on the detection electrode 102. On the other hand, when the shaping unit 305 is moved to the position of FIG. 8C, the electric lines of force 201 to be incident on the detection electrode 102 are shielded by the shaping unit 305. At this time, the shaping means 305 functions as a shielding means. As described above, the shaping unit and the shielding unit are the same, and the function of the shaping unit and the shielding unit is changed according to circumstances.

As a means for moving the shaping means 305, an actuator such as piezoelectric, electromagnetic or electrostatic can be used.

According to the present embodiment, the configuration of the shaping means 305 is movable, so that it also functions as a shielding means. Therefore, the elements constituting the potential measuring device can be reduced, the configuration can be simplified, and the size can be reduced. In addition, a highly accurate potential measuring device can be provided.

In this embodiment, the potential at which the shaping unit 305 is fixed is set to be substantially the same as that of the detection electrode 102 (this can simplify the configuration), but this potential may be movable.

(Fourth embodiment)
The fourth embodiment relates to a form having a feature in capacity changing means. Others are the same as those in the first embodiment or the second embodiment.

The capacity changing means of the potential measuring device of the present embodiment has a configuration in which a shaping means is added to the capacity changing means of FIG. FIG. 9 shows a potential measuring apparatus according to the present embodiment, FIG. 9A is a schematic diagram for explaining the configuration, and FIGS. 9B and 9C are schematic diagrams of cross sections of the potential measuring apparatus. Show.

In this embodiment, a plurality of detection electrodes 102 are arranged in a line, and there is capacitance changing means 303 having an opening 304 having the same size as the detection electrodes 102, and shaping means 305 having the same shape as the capacitance changing means 303. Is arranged. Here, the detection electrode 102 and the shaping means 305 are fixed at predetermined positions (see FIGS. 9B and 9C). Further, it is assumed that the detection electrode 102, the shaping unit 305, and the capacitance changing unit 303 are fixed at the same potential.

A process of detecting the correction signal will be described with reference to FIG. Here, it is assumed that the actuator of the vibrator 303 of the capacity changing means uses a resonance phenomenon. An alternating current (AC) signal having a frequency shifted from the frequency at which resonance occurs is applied to the vibrator 303 so as to be superimposed on the direct current (DC) signal. At this time, since the resonance frequency is not applied to the vibrator 303, the vibrator 303 does not enter a resonance state. That is, in this state, the vibrator 303 can be regarded as not substantially vibrating, but a driving signal (AC signal) equivalent to that at the time of driving is input to the vibrator 303. This means that drive noise equivalent to that during driving occurs.

On the other hand, in this state, the vibrator 303 is moved statically (for example, in the direction of the arrow G) by the direct current (DC) signal and comes to the position of FIG. At this time, the electric force lines 201 incident on the detection electrode 102 are completely shielded by the vibrator 303. Further, the number of lines of electric force incident on the detection electrode 102 is almost zero. That is, the capacitance changing unit (vibrator 303) functions as a shielding unit with respect to the detection electrode 102. Therefore, the number of lines of electric force incident on the detection electrode 102 can be reduced to 0, and the detection signal VOUT can be accurately measured as the noise component Vn of the drive signal.

Here, since a signal of a direct current (DC) component is applied to the vibrator 303, there is a possibility that direct current noise also occurs in the detection signal VOUT. However, the noise of this direct current (DC) component can be easily removed by performing the process of extracting only the alternating current component in the subsequent process (not shown) of the detection means 104.

Next, a process for detecting a detection signal will be described with reference to FIG. At this time, only an alternating current (AC) signal is applied to the capacity changing means 303. The vibrator 303 is mechanically vibrated (in the direction of arrow E) at a certain period as shown in FIG. Thereby, the number of lines of electric force incident on the detection electrode 102 changes periodically, and a detection signal can be obtained from the detection electrode 102.

According to the present embodiment, the correction signal and the detection signal can be obtained with a single actuator, so that the device configuration can be easily reduced and downsized. As a result, a more compact and highly accurate potential measuring device can be provided.

(Fifth embodiment)
The fifth embodiment relates to an image forming apparatus using the potential measuring device of the present invention. The potential measuring device used here is the same as any one of the first to fourth embodiments.

FIG. 10 is a schematic diagram illustrating the image forming apparatus according to the present embodiment. FIG. 10 is a diagram showing the arrangement of the photosensitive drum 501 on a plane perpendicular to the rotation axis H. FIG. In FIG. 10, reference numeral 501 denotes a photosensitive drum, 502 denotes paper, 503 denotes a cleaner, 504 denotes charging means, 505 denotes exposure means, 506 denotes a potential measuring device according to the present invention, and 507 denotes developing means. The image forming unit includes a photosensitive drum 501 as a photoconductor, a charging unit 504, an exposure unit 505, and the like.

The photosensitive drum 501 rotates about the axis H in the direction I. The photosensitive drum 501 is charged by the charging unit 504 and exposed by the exposure unit 505 to form a charged pattern. The potential measuring device 506 measures the potential of the charging pattern on the photosensitive drum 501. Then, the developing unit 507 develops the toner by adsorbing toner or the like only on the charged pattern portion (or only on the charged pattern portion), and the image is transferred onto the paper 502 scanned in the direction J. Thereafter, the photosensitive drum 501 is cleaned by the cleaner unit 503.

In the above configuration, the charging unit 504, the exposure unit 505, and the like are controlled using the measurement result of the potential measuring device 506 to adjust the image. In the above-described image forming apparatus, the degree of eccentricity of the photosensitive drum 501, the difference in the charging level of the charging unit 504, the surface state of the individual photosensitive drum 501, changes with time, and the like exist. Therefore, the charged potential of the charging pattern formed on the photosensitive drum 501 varies depending on the individual image forming apparatus and time. This difference in potential causes a difference in image density on the paper 502 when the image forming apparatus forms an image. As described above, the difference in the charge amount on the photosensitive drum 501 greatly affects the image quality of the image forming apparatus.

The potential measuring device described in any of the first to fourth embodiments can be used for the image forming apparatus as described above. Since the potential measuring device of the present invention can correct an error component of a detection signal generated by mechanical vibration or a drive signal, it can perform highly accurate potential measurement. Therefore, high-quality images can be maintained by controlling the charging unit 504, the exposure unit 505, and the like based on the potential measurement result. Here, the control of the charging unit 504, the exposure unit 505, and the like can be performed by changing the charging voltage of the charging unit 504, or changing the light amount and the light emission time of the exposure unit 505.

As described above, according to this embodiment, an image forming apparatus with high image quality can be provided.

The schematic diagram explaining the structure of the electric potential measurement apparatus which concerns on the 1st Embodiment of this invention. The typical perspective view explaining the example of the capacity | capacitance change means which can be used by this invention. The typical perspective view explaining the example of the capacity | capacitance change means which can be used by this invention. The typical perspective view explaining the example of the capacity | capacitance change means which can be used by this invention. The schematic diagram explaining the example of the detection means which can be used by this invention. The schematic diagram explaining the example of the detection means which can be used by this invention. The schematic diagram explaining the example of the detection means which can be used by this invention. The conceptual graph figure explaining the detection signal of 1st Embodiment. The schematic diagram explaining the method to measure the noise component Vn of 1st Embodiment. The schematic diagram explaining the method to measure the detection signal of 1st Embodiment. The figure showing the flow of the measuring method of the electric potential measuring device which concerns on 1st Embodiment. The figure showing the flow of the measuring method of the electric potential measuring device which concerns on the 2nd Embodiment of this invention. The typical perspective view explaining the electric potential measuring device concerning a 3rd embodiment. The schematic diagram explaining the method to measure the detection signal of 3rd Embodiment. The schematic diagram explaining the method of measuring the noise component Vn of 3rd Embodiment. The typical perspective view explaining the electric potential measuring device concerning a 4th embodiment. The schematic diagram explaining the method of measuring the noise component Vn of 4th Embodiment. The schematic diagram explaining the method to measure the detection signal of 3rd Embodiment. FIG. 9 is a schematic diagram illustrating an image forming apparatus according to a fifth embodiment of the present invention. 1 is a configuration diagram of a general non-contact type potential measuring device.

Explanation of symbols

101, 501, 601 Surface to be measured (photosensitive drum, object to be measured)
102, 602 Detection electrodes 103, 301, 302, 303 Capacitance changing means (vibrator, shielding means)
104, 603 detection means (charge detection means)
105 Shielding means 106 Correction means 305 Shaping means (shielding means)
501, 504, 505 Image forming means 504 Charging means 505 Exposure means 506 Potential measuring device

Claims (8)

A potential measuring device that measures the potential of a measurement object,
A sensing electrode;
Capacitance changing means for changing the capacitance between the measurement object and the detection electrode;
Detection means for detecting the amount of charge electrostatically induced in the detection electrode;
Shielding means for shielding the detection electrode from electric lines of force that can occur between the measurement object and the detection electrode;
Have
The shielding means switches between a shielding state and a non-shielding state so as to obtain a signal from the detection means in a shielding state where the detection electrode is shielded and to obtain a signal from the detection means in a non-shielding state where the sensing electrode is not shielded. A potential measuring device comprising means. Furthermore, it has a correction means,
The correction means stores the detection signal detected by the detection means in the shielding state by the shielding means and the detection signal detected by the detection means in the non-shielding state by the shielding means. 2. The potential measuring device according to claim 1, further comprising means for performing a subtraction process based on the signal and outputting the result. The potential measuring device according to claim 1, further comprising shaping means for shaping electric lines of force reaching the detection electrode from the measurement object. The potential measuring apparatus according to claim 3, wherein the shaping unit is configured to also serve as the shielding unit. The potential measuring apparatus according to claim 1, wherein the capacitance changing unit is configured to also serve as the shielding unit. An electric potential measuring device according to claim 1 and an image forming means, wherein the surface of the detection electrode of the electric potential measuring device is arranged to face a photoconductor to be subjected to electric potential measurement of the image forming means. An image forming apparatus, wherein the forming unit controls image formation using a signal detection result of the potential measuring device. A method for measuring a potential of a measurement object, wherein the measurement object and the detection electrode are in a state in which the detection electrode is shielded by shielding means from electric lines of force that may be generated between the measurement object and the detection electrode. Driving a capacitance changing means for changing the capacitance between and detecting the amount of charge electrostatically induced in the detection electrode;
Driving the capacitance changing means in a state where the detection electrode is not shielded from lines of electric force generated between the measurement object and the detection electrode, and detecting a charge amount electrostatically induced in the detection electrode;
And a step of measuring the potential of the measurement object based on the detection value detected in each step. A potential difference between the surface to be measured and the detection electrode is detected based on the measurement result using the potential measurement method according to claim 7, and the potential of the detection electrode is set so that the absolute value of the potential difference approaches a minimum value. A potential measuring method characterized in that the potential of the sensing electrode reached as a result of the change is obtained as the potential of the surface to be measured.

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