JP4950574B2 - Potential measuring apparatus and potential measuring method - Google Patents

Description

The present invention relates to a capacitance measuring device and 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. 10 shows a conceptual configuration diagram of the potential measuring apparatus. In FIG. 10, reference numeral 501 denotes a measurement object, 502 denotes a detection electrode, and 503 denotes charge detection means. The surface potential of the measurement object 501 is VD, the capacitance changed by the capacitance change means is C1, and the signal output from the charge detection means 503 Is represented by VOUT. Here, in order to change the capacitance C1 mechanically, a method of periodically changing the electric lines of force incident on the detection electrode 502 from the measurement object 501 or a method of moving the detection electrode 502 periodically. There is something that adopts.

In the former, a fork-shaped shutter is inserted between the measurement target (photosensitive member) and the detection electrode, and the shutter is periodically moved in a direction parallel to the surface of the measurement target, so that the electricity reaching the detection electrode from the measurement target is obtained. The structure which interrupts | blocks a force line periodically is disclosed. Then, the potential is detected by changing the capacitance between the measurement object and the detection electrode by changing the effective area of the detection electrode viewed from the measurement surface (see Patent Document 1).

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

In the latter configuration, the sensing electrode is placed at the tip of a cantilevered vibrator, and the cantilever is vibrated to periodically change the distance between the measurement target and the sensing electrode, thereby changing the capacitance. (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

In the potential measuring device or the capacitance measuring device, it is necessary to detect the vibration state in order to stably vibrate the fork-shaped shutter and the vibration element for changing the capacitance. However, in order to detect the state of vibration, it is necessary to separately provide a vibration detection sensor, and the number of components tends to increase.

Therefore, an object of the present invention is to provide a technique for enabling detection of a vibration state without using a vibration detection sensor.

In view of the above problems, the potential measuring device or the capacitance measuring device of the present invention includes a capacitance changing unit that changes the capacitance between the surface to be measured and the detection electrode by mechanical vibration, and a detection electrode by the capacitance changing unit. Charge detection means for detecting the amount of charge electrostatically induced in the device, and vibration generation / detection means for selectively performing vibration generation for exciting the mechanical vibration and detection of the state of the mechanical vibration. It is characterized by that. In view of the above problems, the potential measurement method of the present invention detects the amount of charge that is electrostatically induced in the detection electrode by changing the capacitance between the surface to be measured and the detection electrode by mechanical vibration. A potential measurement method for measuring a potential of a surface to be measured based on a detection result, detecting a state of the mechanical vibration and controlling an excitation mode of the mechanical vibration based on the detection result In addition, the period for exciting the mechanical vibration and the period for detecting the state of the mechanical vibration are set so as not to overlap.

More specifically, the potential measuring device, the capacitance measuring device or these methods according to the present invention apply a period for applying a driving signal for exciting or generating vibration to the vibration generating / detecting means, and applying the driving signal. In addition, there are two periods of a period in which a signal generated by vibration is detected by the vibration generation / detection means. As a result, vibration can be generated and detected by using the vibration generating / detecting means of the single component means.

Further, in view of the above problems, the capacitance determination method of the present invention can reduce the amount of charge electrostatically induced in the detection electrode by changing the capacitance between the surface to be measured and the detection electrode by mechanical vibration. A capacitance measuring method for detecting and measuring a capacitance between a surface to be measured and the detection electrode based on the detection result, and detecting the mechanical vibration state and detecting the result The excitation mode of the mechanical vibration is controlled based on the above, and the period for exciting the mechanical vibration and the period for detecting the state of the mechanical vibration are set so as not to overlap each other. Note that the capacitance measuring device or method of the present invention means that the capacitance of the measurement target surface, the change in the distance between the measurement target surface and the electrode, and the dielectric between the measurement target surface and the electrode are changed by changing the capacitance. It measures the change in rate.

In view of the above problems, an image forming apparatus according to the present invention includes the above-described potential measuring device and an image forming unit, and a surface of the detection electrode of the potential measuring device faces a surface of the image forming unit that is a potential measurement target. The image forming means controls image formation using the signal detection result of the potential measuring device.

According to the potential measuring device, the capacitance measuring device or these methods of the present invention, the vibration generation and the vibration state can be detected by a single means of vibration generation / detection means, so that the comparison can be made without increasing the number of components. Stable vibration can be realized. Therefore, a stable output can be obtained, and a relatively high-performance potential measuring device, capacitance measuring device or these methods can be provided.

Hereinafter, embodiments of the present invention will be described. In the embodiment of the present invention, the amount of charge that is electrostatically induced in the detection electrode is detected by the capacitance changing means that changes the capacitance between the surface to be measured and the detection electrode by mechanical vibration. Further, vibration generating / detecting means for selectively performing the function of exciting the mechanical vibration and the function of detecting the state of the mechanical vibration is provided.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings by exemplifying a potential measuring device.
(First embodiment)
FIG. 1 shows a configuration diagram of the potential measuring apparatus according to the first embodiment. In FIG. 1, 101 is a detection electrode, 102 is a vibrator, and 103 is a means that forms the main part of vibration generation / detection means for exciting the vibration of the vibrator 102 and detecting its vibration state. (This is hereinafter referred to as vibration generation / detection means) 104 is a wiring switching means forming part of the vibration generation / detection means, 105 is a drive signal applying means, 106 is a vibration detection signal amplifying means, and 107 is a drive It is a signal generation means. Reference numeral 108 denotes charge detection means for detecting the amount of charge electrostatically induced in the detection electrode 101.

The vibrator 102 that is a capacity changing unit has a chopper function that periodically shields electric lines of force that reach the detection electrode 101 from a photosensitive drum (not shown) that is a measurement target. In order to generate vibration of the vibrator 102, the vibrator is provided with vibration generation / detection means 103.

FIG. 2, which is a schematic perspective view, shows an example of a vibrator of the potential measuring device according to the present embodiment. In FIG. 2, 201 is a piezoelectric element, 202 is a fixed end of the vibrator 102, 203 is a surface to be measured (surface to be measured), and 204 is a line of electric force generated from the surface to be measured 203 to the detection electrode 101. is there.

FIG. 3 is a diagram illustrating signals of the potential measuring device according to the present embodiment. In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the signal magnitude. FIG. 3A shows an applied signal 110 applied by the drive signal applying means 105. (Although an analog signal is shown here, it may be a digital drive signal such as a pulse signal.) In FIG. 3B, the piezoelectric element 301 is generated by the vibration 112 of the vibrator 102. A vibration detection signal 113 (when the applied signal 110 is not applied and only the vibration of the vibrator 102 is generated) is shown. FIG. 3C shows a signal at the contact A of the wiring switching unit 104. The wiring switching unit 104 is controlled based on a drive signal 115 from the drive signal generation unit 107 described later.

In the example of FIG. 2 of the present embodiment, the piezoelectric element 201 is used for the vibration generating / detecting means 103. The piezoelectric element 201 generates distortion by applying a voltage, and generates vibration 111 by applying an alternating voltage (application signal 110) (see FIG. 3A). The vibrator 102 is fixed to a holding jig at a fixed end 202, and has a structure in which both vibrators 102 generate vibration when the piezoelectric element 201 vibrates (111). The vibrator 102 performs periodic reciprocating vibration in the direction of arrow C. Due to the vibration of the vibrator 102, the electric force lines 204 are periodically shielded, and charges are periodically induced to the detection electrode 101 (inductive charge signal 116).

In the present embodiment, the wiring switching unit 104 is constituted by an analog switch, for example. Of course, a mechanical switch or the like may be used. The contact A of the wiring switching means 104 is selectively connected alternately to the drive signal applying means 105 side and the vibration detection signal amplifying means 106 side at a predetermined fixed period. In this embodiment, this switching operation is repeated for each cycle of the drive signal 115. Not limited to this, if the period during which the vibration generation / detection means performs the vibration generation function and the period during which the detection function is performed are each an integral multiple of the cycle of the drive signal, each function can be suitably performed. it can.

During the period in which the wiring switching unit 104 is connected to the drive signal generation unit 105, the drive signal application unit 105 applies the drive application signal 110 to the vibration generation / detection unit 103. Further, during the period in which the wiring switching unit 104 is connected to the vibration detection signal amplification unit 106, a detection signal 113 corresponding to the vibration 112 of the vibrator 102 is output from the vibration generation / detection unit 103. This uses the characteristic that the piezoelectric element 201 generates a voltage 113 corresponding to the distortion of the piezoelectric element generated by the vibration (112) of the vibrator 102 (see FIG. 3B). The detection signal 113 is converted into a detection amplification signal 114 by the detection means 106 (including the amplification means).

In the drive signal generation means 107, the drive signal 115 is generated based on the information of the amplified signal 114 so that the vibrator 102 operates stably. Specifically, the vibration amplitude of the vibrator 102 is maximized, or the vibration phase of the vibrator 102 with respect to the drive signal 115 becomes a desired phase (typically, a phase shift of 90 degrees). The drive signal 115 is changed. Here, the generated drive signal 115 is transmitted to the drive signal applying unit 105.

By applying a drive signal having a specific vibration frequency of the vibrator 102, a large vibration can be obtained with a small input energy. This is called resonance, and not only can vibration be performed with high efficiency, but also stable vibration can be obtained. In resonance, the sensitivity to the drive signal 115 at a specific frequency (almost unique vibration frequency) is high, and it is difficult to react to the drive signal 115 at other frequencies. In the resonance state, the time constant with which the vibration changes with respect to the frequency of the drive signal 115 is long. Therefore, even if driving and detection are intermittently repeated as in the present embodiment, stable resonance driving can be performed at the frequency of the driving signal 115, and at the same time, the state of vibration can be suitably detected (FIG. 3). (See (c)).

When the operation of the vibrator 102 is stabilized, charges are stably induced in the detection electrode 101 (stable generation of the induced charge signal 116). The charge signal 116 due to the charge induced in the detection electrode 101 is converted into a charge detection signal 117 by the charge detection means 108. Since this charge detection signal 117 can also be obtained stably, the detection accuracy of the potential measuring device is improved.

In the potential measuring apparatus according to the present embodiment described above, the drive signal application period for generating mechanical vibration and the detection period for detecting the state of mechanical vibration have different periods. Only the vibration generation / detection means can apply the drive signal and detect the drive state. Therefore, the vibrator 102 can always be kept in a stable vibration state with a relatively simple configuration. Thus, stable charge induction can be performed on the detection electrode 101, and the charge detection signal is stabilized, so that a highly accurate potential measurement device can be realized.

(Second Embodiment)
The potential measuring device according to the second embodiment has a configuration in which the configuration of the vibration generating / detecting means 103 is different from that of the first embodiment. Others are the same as those in the first embodiment.

In this embodiment, an electromagnetic actuator is used for the vibration generating / detecting means 103. FIG. 4 is a schematic diagram for explaining vibration generation / detection means of the potential measuring apparatus according to the present embodiment. In FIG. 4, 211 is a vibrator, 212 is a support frame, 213 is a torsion spring, 214 is a detection electrode pad, 215 is a wiring, 216 is a magnet, 217 is a coil wiring, 218 is a coil pad, and 219 is a coil substrate. The vibrator 211 is held by a torsion spring 213, and the torsion spring 213 is fixed to the support frame 212. On the surface of the vibrator 211, the torsion spring 213, and the support frame 212, the detection electrode 101, the wiring 215, and the detection electrode pad 214 are disposed. A coil wiring 217 and a coil electrode pad 218 are disposed on the back surface of the vibrator 211, the torsion spring 213, and the support frame 212. A magnet 216 is arranged around the support frame 212 as shown in FIG.

By applying the AC drive signal 115 to the coil 217, mechanical vibration is generated in the vibrator 211 from the relationship between the direction of the magnetic field of the magnet 216 and the direction of the current flowing in the coil 217 (Fleming's left-hand rule). . The vibrator 211 performs torsional vibration in the direction of arrow D about the torsion spring 213 as an axis. Further, during a period in which the drive signal 115 is not applied, an electromotive force is generated in the coil 217 due to the relationship between the vibration direction of the vibrator 211 and the direction of the magnetic field of the magnet 216. By detecting this, the state of vibration of the vibrator 211 can be detected.

By using such an electromagnetic actuator for the vibration generating / detecting means, a large vibration can be obtained efficiently. Therefore, a stable and larger charge detection signal can be obtained with a small configuration. Thus, according to the potential measuring device according to the present embodiment, a more accurate potential measuring device can be realized with a small configuration.

4A is a configuration in which the coil 217 is disposed on the vibrator 211. However, as shown in FIG. 4B, a magnet 216 is disposed on the back surface of the vibration 211 element, and a coil substrate is separately provided. The coil wiring 217 and the coil pad 218 may be arranged on the 219. According to this configuration, the area for arranging the magnet around the vibrator 211 can be reduced, so that a more compact and highly accurate potential measuring device can be provided. In the present embodiment, it has been described that the vibrator 102 is torsionally vibrated, but the mechanical vibration in the present embodiment is not limited to this.

(Third embodiment)
The potential measuring apparatus according to the third embodiment is different from that of the first embodiment in the manner of setting the drive period and the detection period by the wiring switching means 104. Others are the same as those in the first embodiment or the second embodiment.

FIG. 5A is a diagram for explaining switching of the changeover switch of the potential measuring apparatus according to the present embodiment. In FIG. 5A, the horizontal axis represents time, and the vertical axis represents the signal magnitude.

In FIG. 5A, the detection period is longer than the drive period (specifically, 1: 3). With this configuration, the period during which the state of vibration can be detected becomes longer. Therefore, even when the vibration state detection signal is small, the vibration state can be detected more accurately.

In FIG. 5B, the detection period is shorter than the drive period (specifically, 3: 1). With this configuration, the time for applying the drive signal to the vibration generating / detecting means is increased, so that the drive signal applied during the drive period can be reduced. For this reason, even when a large drive signal is required, the load on the drive signal applying unit is reduced, so that a stable drive signal can be applied. Therefore, stable vibration can be obtained even when the drive signal is large.

In FIGS. 5-2 (a) and (b), the drive period and the detection period do not coincide with one cycle of the drive signal of the vibrator. However, the sum of the detection period and the drive period coincides with a multiple of one cycle of the drive vibration of the vibrator. Here, it coincides with one cycle of the drive vibration.

In FIG. 5A, a detection period is provided so that the peak portion of the detection signal can be detected. As a result, the drive period can be set so that the maximum value of vibration can always be monitored and energy can be efficiently applied to the vibrator. On the other hand, in FIG. 5B, a detection period is provided so that the zero cross point of the detection signal can be detected. As a result, it is possible to constantly monitor the phase timing of the vibration and set the drive period so that energy can be efficiently applied to the vibrator.

By using these configurations, it is possible to set the drive period as long as possible while detecting the state of vibration and under certain restrictions, so that the drive can be performed efficiently and further stable vibration of the vibrator can be obtained. be able to.

According to the potential measuring device according to the present embodiment, a more stable vibration can be obtained by setting the drive period and the detection period to a desired ratio. Therefore, a more accurate potential measuring device can be provided.

(Fourth embodiment)
In the potential measurement device according to the fourth embodiment, the charge detection means 108 for detecting the induced charge of the detection electrode 101 is different from the above embodiment. Others are the same as those of the first embodiment or the third embodiment.

6A and 6B are diagrams for explaining some examples of the charge detection unit 108 of the potential measuring apparatus according to the present embodiment. 6A and 6B, reference numeral 301 denotes an analog switch, 302 denotes a band pass filter, and 303 denotes synchronous detection means. 7A and 7B are diagrams for explaining signals in the charge detection unit 108 of the potential measuring device according to the present embodiment. 7A and 7B, the horizontal axis represents time, and the vertical axis represents the signal magnitude. In the description of this embodiment, the same drive period and detection period as those in FIG. 3 are used. However, the drive period and the detection period of the present embodiment are not limited to this.

In the example of FIG. 6A, the charge detection unit 108 includes an analog switch 301. The contact B is grounded to GND during the drive period, and is connected to the detection electrode 101 during the detection period. In general, in the potential measurement device, a signal (noise) other than the charge induced from the photosensitive drum (potential measurement target) to the detection electrode 101 is generated by the drive application signal 110. This causes a decrease in detection resolution when performing highly accurate potential measurement. By using the charge detection means 108 as shown in FIG. 6A, the induction charge is not detected during the drive period in which the drive signal 110 is applied. (In other words, the period during which the signal is output from the charge detection means is included in the period during which the vibration generation / detection means performs the detection function.) Therefore, noise due to the drive signal 110 is detected from the charge detection signal 117. Absent. FIG. 7A shows the charge detection signal 117 at that time. Thereby, the potential measurement which is not influenced by the noise of the drive signal 110 can be performed.

The example in FIG. 6B is a configuration in which a bandpass filter 302 is added to FIG. The center frequency of the bandpass filter 302 is set near the drive frequency of the vibrator 102. Thereby, the fragmentary charge detection signal 117 as shown in FIG. 7-1 (a) can be converted into a continuous signal as shown in FIG. 7-1 (b). This facilitates processing of the charge detection signal 117 at the subsequent stage. Further, since a frequency component far from the vibration frequency can be removed, noise at other frequencies is hardly detected in the charge detection signal 117.

In the example of FIG. 6B, the charge detection unit 108 includes a synchronous detection unit 303 in addition to the configuration of FIG. 6A. Synchronous detection is performed by a synchronous signal (DUTY ratio 50%) synchronized with the driving cycle of the vibrator 102 as shown in FIG. Thereby, as shown in FIG. 7B, the charge detection signal 117 only near the drive frequency component of the vibrator 102 can be easily extracted.

In addition, it is more preferable that the driving period and the detection period are multiples of the driving period of the vibrator 102. In this case, even when the phase of the charge detection means 108 is shifted, an error does not occur in the detected signal value, so that a more accurate value can be detected.

As another embodiment, the charge detection unit 108 includes an analog switch 301 as in FIG. 6A. Here, the operation of the analog switch 301 is different from that described above. The analog switch 301 grounds the contact B to GND during the driving period. Further, during the detection period, when the synchronization signal is HIGH, it is connected to the detection electrode 110, and when the synchronization signal is LOW, it is connected to GND. Specifically, the charge detection signal 117 is as shown in FIG. With this configuration, it is possible to simultaneously perform switching between the driving period and the detection period and highly accurate synchronous detection with a simple configuration.

The potential measurement apparatus according to the present embodiment can detect the induced charge of the detection electrode 110 by using the charge detection unit 108 as described above, reducing the influence of noise due to the drive signal. Therefore, according to the present embodiment, it is possible to realize a highly accurate potential measurement device that is less affected by the drive signal.

(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. 8 is a schematic diagram illustrating the image forming apparatus according to the present embodiment. FIG. 8 is a view showing the arrangement of the photosensitive drum 401 on a plane perpendicular to the rotation axis E. FIG. In FIG. 8, 401 is a photosensitive drum, 402 is paper, 403 is a cleaner, 404 is charging means, 405 is exposure means, 406 is a potential measuring device according to the present invention, and 407 is development means. The image forming unit includes a photosensitive drum 401, a charging unit 404, an exposure unit 405, and the like.

The photosensitive drum 401 rotates about the axis E in the direction F. The photosensitive drum 401 is charged by the charging unit 404 and exposed by the exposure unit 405 to form a charged pattern. The potential measuring device 406 measures the potential of the charging pattern on the photosensitive drum 401. Then, the developing unit 407 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 402 scanned in the direction G. Thereafter, the photosensitive drum 401 is cleaned by the cleaner unit 403.

In the above configuration, the measurement result of the potential measurement device 406 is used to control the charging unit 404, the exposure unit 405, and the like, thereby adjusting the image. In the image forming apparatus described above, there are the degree of eccentricity of the photosensitive drum 401, the difference in the charging level of the charging unit 404, the surface state of the individual photosensitive drum 401, and the change with time. Therefore, the charged potential of the charging pattern formed on the photosensitive drum 401 varies depending on the individual image forming apparatus and time. This difference in potential causes a difference in image density on the paper 402 when the image forming apparatus forms an image. As described above, the difference in the charge amount on the photosensitive drum 401 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 measurement apparatus of the present invention can perform highly accurate potential measurement with a relatively simple configuration, the control of the charging unit 404, the exposure unit 405, and the like is performed based on the result of the potential measurement. You can maintain high-quality images. Here, the control of the charging unit 404 and the exposure unit 405 can be performed by changing the charging voltage of the charging unit 404 or changing the light amount and the light emission time of the exposure unit 405.

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

(Sixth embodiment)
FIG. 9 shows a configuration diagram of a potential measuring apparatus according to the sixth embodiment. FIG. 9 is different from FIG. 9 in that the detection amplification signal 601 from the vibration detection signal amplification unit 106 is input to the charge detection unit 108. Other configurations are the same as those in FIG.

In the present embodiment, the charge detection unit 108 calculates the induced charge signal 116 and the detection amplification signal 601 to obtain the charge detection signal 117. Specifically, the charge detection signal 117 is obtained by performing arithmetic processing for dividing the induced charge signal 116 by the detection amplification signal 601 indicating the magnitude of the vibration of the vibrator 102. By this processing, the charge detection signal 117 can be obtained with high accuracy even when the vibration of the vibrator 102 changes.

For example, when the vibration of the vibrator 102 changes due to a change in the resonance frequency due to heat, etc., the vibration is induced in proportion to the vibration magnitude of the vibrator 102 even if there is no change in the potential of the measurement target surface (not shown). The charge signal 116 changes. As a result, a value different from the actual potential of the measurement target surface is detected. Even in such a case, with the above configuration, the charge detection signal 117 can be corrected to an accurate value.

That is, by using this embodiment, it is possible to perform more accurate potential measurement. Further, even if the vibrator 102 is not controlled with high accuracy so as to have a strictly constant amplitude, high-precision potential measurement can be performed. Thereby, even when the control accuracy of the amplitude of the vibrator 102 by the drive signal generation unit 107 is low, or even when the controllability of the vibrator 102 is low, highly accurate potential measurement can be performed. Therefore, highly accurate potential measurement can be performed with a simpler configuration.

In addition, with the configuration in which the detection amplification signal 114 is eliminated, the drive signal output from the drive signal generation means 107 can be fixed to a constant waveform, and highly accurate potential measurement can be performed. Therefore, the drive signal generation means 107 can be realized with a very simple configuration.

In the present specification, the potential measuring device using the principle of the present invention has been described, but the present invention is not limited to this. It can also be used for a capacitance measuring device having a similar configuration. For example, in a configuration in which the measurement target surface 203 (401, 501) is held at a predetermined potential, the apparatus detects a change in capacitance between the measurement target surface 203 and the detection electrode 101 (502). Can be used. Accordingly, a change in the distance between the measurement target surface and the electrode, a change in the dielectric constant between the measurement target surface and the electrode, and the like can be measured based on the detected change in capacitance.

It is a block diagram which shows the structure of the electric potential measuring apparatus which concerns on the 1st Embodiment of this invention. It is a model perspective view which shows the structure of the vibration generation and detection means of the electric potential measurement apparatus which concerns on 1st Embodiment. It is a graph which shows each signal of the electric potential measurement apparatus which concerns on 1st Embodiment. It is a model perspective view which shows the structure of the vibration generation and detection means of the electric potential measurement apparatus which concerns on the 2nd Embodiment of this invention. It is a graph which shows each signal of the electric potential measurement apparatus which concerns on the 3rd Embodiment of this invention. It is a graph which shows each signal of the electric potential measurement apparatus which concerns on the 3rd Embodiment of this invention. It is a schematic diagram which shows the structure of the electric charge detection means of the electric potential measurement apparatus which concerns on the 4th Embodiment of this invention. It is a schematic diagram which shows the structure of the electric charge detection means of the electric potential measurement apparatus which concerns on the 4th Embodiment of this invention. It is a graph which shows each signal of the charge detection means of the electric potential measurement apparatus which concerns on 4th Embodiment. It is a graph which shows each signal of the charge detection means of the electric potential measurement apparatus which concerns on 4th Embodiment. FIG. 10 is a block diagram showing an image forming apparatus according to a fifth embodiment using the potential measuring device of the present invention in an arrangement relationship on a plane perpendicular to a rotation axis of a photosensitive drum. It is a block diagram which shows the structure of the electric potential measurement apparatus which concerns on the 6th Embodiment of this invention. It is a schematic diagram of a general non-contact type potential measuring device.

Explanation of symbols

101, 502 Sense electrodes 102, 211 Capacitance changing means (vibrator)
103, 104, 201, 216, 217 Vibration generation / detection means (piezoelectric element, magnet, coil wiring, analog switch)
104 Analog switch 106 for vibration generation / detection means Vibration detection signal amplification means 108, 503 Charge detection means (amplification means)
203, 401, 501 Surface to be measured (photosensitive drum, surface to be measured)
216, 217 Electromagnetic actuator (magnet, coil wiring)
301 Analog switch of charge detection means 302 Band pass filter 303 Synchronous detection means 401, 404, 405 Image forming means 404 Charging means 405 Exposure means 406 Potential measuring device 601 Detection amplification signal

Claims (9)

A charge detector for detecting the capacitance change means for changing the capacitance between the surface and the detection electrode to be measured by the mechanical vibration, the amount of charge electrostatically induced to the sensing electrode by the capacitance change means, said have a vibration generating and detecting means for selectively performing the detection of the mechanical vibration of the vibration generator for exciting the mechanical vibration state,
A potential measuring apparatus , wherein a detection period during which the vibration generating / detecting means performs a detection function is set so as to detect a peak portion of a detection signal representing the mechanical vibration state . The potential measuring apparatus according to claim 1, wherein the vibration generating / detecting unit includes a piezoelectric element. The potential measuring apparatus according to claim 1, wherein the vibration generating / detecting unit includes an electromagnetic actuator. The sum of the vibration generation period and the detection period of the vibration generation / detection means is a time that is an integral multiple of the period of the mechanical vibration, respectively. The potential measuring apparatus described. 5. The potential measuring device according to claim 1, wherein a period in which a signal is output from the charge detection unit is included in a detection period in which the vibration generation / detection unit performs a detection function. The potential measuring apparatus according to claim 1, wherein the charge detection unit includes a bandpass filter centered around a frequency of the mechanical vibration. 6. The potential measuring apparatus according to claim 1, wherein the charge detecting means includes synchronous detection means based on the mechanical vibration period. Comprising a potential measuring device and image forming means according to any one of claims 1 to 7, the surface of the sensing electrode of the potential measuring device is disposed to face the subject to face the potential measurement of the image forming means an image forming apparatus characterized by controlling the image formation using the image forming means the signal detection result of the potential measuring apparatus. Detecting the amount of electric charge electrostatically induced to the sensing electrode by varying a static capacitance between the mechanical surface of the measurement object by the vibration detecting electrode, the potential of the surface of the measuring object based on the detection result A potential measurement method for measuring, wherein the state of mechanical vibration is detected, and the excitation mode of the mechanical vibration is controlled based on the detection result, and the period of exciting the mechanical vibration and the The detection period for detecting the mechanical vibration state is set so as not to overlap, and the detection period is set so that the peak portion of the detection signal representing the mechanical vibration state can be detected. Potential measurement method.

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