JP2006337161A - Rotation vibration device and potential measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation vibration device setting approximately equally rotation angles of all parts of a vibration member excluding a part of a rotating shaft by setting sufficiently small the rigidity in the rotation vibration direction around the rotating shaft of at least a part of a part in contact with the rotating shaft, and a potential measuring device using the device. <P>SOLUTION: This rotation vibration device is equipped with the vibration member 5 having a linearly-shaped end, and the vibration member 5 is arranged swingably by rotating around the rotating shaft including the linearly-shaped end. The rigidity in the rotation vibration direction around the rotating shaft of at least the part 6, 7 of the part in contact with the rotating shaft is set smaller than other parts of the vibration member 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a rotary vibration device including a vibration member that can rotate and vibrate around a rotation axis including its linear end, a potential measurement device including the rotary vibration device, and the like.

2. Description of the Related Art Conventionally, for example, in an image forming apparatus that has a photosensitive drum and forms an image by electrophotography, the potential distribution on the surface of the photosensitive drum is appropriately (typically) in any environment in order to obtain a stable image quality. It is necessary to charge the surface of the photosensitive drum so as to be uniform. Therefore, the potential on the surface of the photosensitive drum is measured using a potential measuring device, and feedback control is performed using the result to keep the potential on the surface of the photosensitive drum uniform.

One of the functions that are often required for the potential measuring apparatus used for such a purpose is a function of measuring the surface potential of the measurement target (object to be measured) in a non-contact manner. This is because when the potential measuring device comes into contact with the surface of the photosensitive drum, the potential distribution on the surface of the photosensitive drum is not uniform, which causes a disorder in the formed image.

The principle of such a potential measuring apparatus will be described below. Due to the electric field generated between the surface of the measurement object and the detection electrode built in the potential measuring device, an electric charge of an electric quantity Q proportional to the surface potential V of the measurement object is induced in the detection electrode. The relationship between Q and V is Q = CV (1)
It is expressed by the formula. Here, C is a capacitance between the detection electrode and the surface of the measurement object. From the equation (1), it is possible to obtain the surface potential of the measurement object by measuring the electric quantity Q induced in the detection electrode.

However, it is difficult to directly measure the amount of electricity Q induced in the detection electrode at high speed and accurately. Therefore, as a practical method, by periodically changing the magnitude of the capacitance C between the detection electrode and the surface to be measured, and measuring the alternating current generated at the detection electrode as a potential detection signal current, Conventionally, a method for obtaining the surface potential of a measurement object is often used.

It will be shown below that the surface potential of the measurement object can be obtained by the above method. Assuming that the capacitance C is a function of time t, the potential detection signal current i generated at the detection electrode is a time differential value of the amount of electricity induced at the detection electrode.
i (t) = dQ / dt = d (CV) / dt (2)
It is expressed by the formula. Here, when the change rate of the surface potential V of the measurement target is sufficiently slow with respect to the change rate of the capacitance C, V can be regarded as being constant in the minute time dt. Therefore, equation (2) is
i (t) = dQ (t) / dt = V · dC (t) / dt (3)
It is expressed by the formula.

From the equation (3), the magnitude of the potential detection signal current i generated at the detection electrode is a linear function of the surface potential V of the measurement target. Therefore, the surface potential of the measurement target is measured by measuring the amplitude of the alternating current signal. It is possible to obtain Further, according to the equation (3), if the change rate of the capacitance C is the same, the magnitude of the potential detection signal current i with respect to the surface potential of the measurement object, that is, the sensitivity of the potential measurement device is the amount of change in the capacitance. You can see that they are proportional.

As one method for periodically changing the capacitance C between the detection electrode and the measurement target surface, the capacitance C is periodically changed by changing the distance between the detection electrode and the measurement target surface. The method of letting it be mentioned. The capacitance C between the detection electrode and the surface of the measurement object is approximately C = A · S / x (4)
It is expressed by the following formula. Here, A is a proportional constant related to the dielectric constant of the substance, S is the area of the detection electrode, and x is the distance between the detection electrode and the surface of the measurement object. From equation (4), it can be seen that when the distance x changes periodically, the capacitance C also changes periodically.

As a means for periodically changing the distance between the detection electrode and the surface of the measurement object, the detection electrode is arranged at the tip of the vibration body, and the vibration body is vibrated in a direction perpendicular to the surface of the measurement object. Is mentioned.

As an example of a vibrating body often used for the above means, there is a cantilever in which one end of a diaphragm 3 made of an elastic body shown in FIG. 6 is fixed to a support member 2 (see Patent Document 1). Moreover, a tuning fork (see the conventional example described in Patent Document 2) in which the U-shaped bottom portion of the diaphragm 4 made of an elastic body bent into a U-shape shown in FIG. The detection electrode 1 is disposed at the tip of the vibrating body 3 or the vibrating body 4, and the vibrating plate 3 or the vibrating body 4 is vibrated in a direction perpendicular to the surface of the measuring object 12. A current signal having an amplitude proportional to the potential is obtained.
U.S. Pat. 4763078 JP-A 62-90564

FIG. 6B shows a vibration mode of a cantilever conventionally used as a vibrating body of a potential measuring device that modulates the distance, and FIG. 7B shows a vibration mode of a tuning fork. In any of the vibrating bodies, the rotation angle of the portion near the fixed end of the diaphragm is very small compared to the rotation angle of the tip portion, and the vibration amplitude of the portion close to the fixed end is much smaller than the vibration amplitude of the tip portion. Small. This hinders high sensitivity of the potential measuring device.

The reason is as follows. From equation (4), the area S of the detection electrode may be increased in order to increase the sensitivity of the potential measuring device without changing the vibration frequency and vibration amplitude of the diaphragm. However, even if the detection electrode is arranged over the entire surface of the diaphragm facing the measurement target, the vibration amplitude is very small in the portion near the fixed end of the detection electrode, so that it hardly contributes to an increase in sensitivity of the potential measuring device.

In view of the above problems, the rotational vibration device of the present invention includes a vibration member having a linear end, and the vibration member is arranged to be able to vibrate by rotating around a rotation axis including the linear end. The rigidity in the rotational vibration direction around the rotation shaft of at least a part of the portion corresponding to the shaft is set to be smaller than that of other portions of the vibration member.

Further, in view of the above problems, the potential measuring device of the present invention includes a driving means for rotating and vibrating the rotary vibration device and the vibration member, and the detection electrode is provided on a surface where the vibration member faces the measurement target. It is characterized by providing.

In view of the above problems, an image forming apparatus of the present invention includes the above-described potential measuring device, a signal processing device that processes an output signal obtained from the potential measuring device, and an image forming unit, and includes a detection electrode of the potential measuring device. The image forming means controls the image formation using the signal detection result of the signal processing device.

In the rotational vibration device of the present invention, the rigidity in the rotational vibration direction around the rotation shaft of at least a part of the portion corresponding to the rotation shaft is set sufficiently smaller than the other portions of the vibration member. The rotational angles of all the parts of the vibration member except the same can be made substantially equal, and the displacement of the part close to the rotational axis can be made larger than before. Therefore, when this rotary vibration device is used in a potential measurement device, when the detection electrode is arranged over the entire area or many areas of the surface of the vibration member facing the measurement target, the sensitivity of the portion near the rotation axis of the detection electrode increases. Therefore, the potential measurement device can be further enhanced in sensitivity and accuracy.

Hereinafter, an embodiment of the present invention will be described while explaining the principle of operation and effect of the present invention.

In one embodiment of the potential measuring device including the rotary vibration device of the present invention, the above-described vibration body is used by supporting one end of the linear shape of the vibration plate 5 with torsion springs 6 and 7 as shown in FIG. Solve the problem. The state of vibration of the vibrating body in the present embodiment is as shown in FIG. 1B. The rotation angles of almost all parts of the diaphragm 5 are substantially equal, and the displacement of the part close to the rotation axis is larger than the conventional one. I understand that.

In this embodiment, a flat rectangular diaphragm 5 which is a vibrating member having a linear end is provided, and the linear end and torsion springs 6 and 7 having a certain length (for example, having a rectangular cross-sectional shape). The diaphragm 5 is arranged to be able to vibrate by rotating around a rotation axis including Then, at least a part (here, torsion springs 6, 7) of the portion corresponding to the rotation shaft is set to have a smaller rigidity (difficult to deform) around the rotation shaft than the other portions of the diaphragm 5. Has been. On the other hand, the other part of the diaphragm 5 has such a rigidity that it can vibrate by rotating around the rotation axis while maintaining substantially the same shape. In other words, at least a part of the portion corresponding to the rotation shaft (torsion springs 6, 7) in the rotational vibration direction around the rotation shaft and the rigidity of the other portion of the vibration plate 5 are the rotational vibrations of the vibration plate 5. Each size is set so that can be realized. Such setting is executed by selecting the material and form (thickness, etc.) of each part of the diaphragm and torsion spring. The diaphragm 5 and the torsion springs 6 and 7 can be integrally formed of silicon or the like.

The detection electrode 1 is disposed on the surface of the diaphragm 5 that faces the measurement object 12, and the current signal generated by the detection electrode 1 is disposed on the signal line disposed on the torsion spring 7 and the support plate 9. The signal is input to signal processing means (not shown in FIG. 1) via the pad and signal line. The signal processing means converts the current signal generated at the detection electrode 1 into a measurement signal by impedance conversion, detection, amplification, and rectification.

The potential measuring device including the rotary vibration device of FIG. 1 has torsion springs 6 and 7 having one end fixed to the diaphragm 5 and the other end fixed to the support members 8 and 9. The linear shaft ends and the torsion springs 6 and 7 are arranged so as to be positioned on the same straight line to constitute the rotating shaft. A pair of torsion springs 6 and 7 are arranged across the linear end of the diaphragm 5. The diaphragm 5 includes the detection electrode 1 on a sufficiently wide area facing the measurement object 12, and the diaphragm 5 is rotated and vibrated by a magnetic force, an electrostatic force, a driving force by a piezoelectric element, and the like.

In the present embodiment, the rigidity in the rotational vibration direction around at least a part of the rotational axis of the portion corresponding to the rotational shaft is set to be sufficiently smaller than the other portions of the diaphragm 5. The rotation angles of all the parts of the plate 5 are substantially equal, and the displacement of the part close to the rotation axis can be made larger than before. Therefore, the contribution to the sensitivity increase in the portion near the rotation axis of the detection electrode 1 arranged in the whole area or many areas of the surface of the diaphragm 5 facing the measurement object becomes larger than before, and the potential measuring device is further increased. It becomes possible to achieve higher sensitivity and higher accuracy.

As another example of the above setting method, the form shown in FIG. 4 is also possible. The thickness of the end of the linear shape of the diaphragm 5 is reduced by a U-shaped groove 5a that extends linearly, and the diaphragm 5 has a spacer 10 on the side opposite to the side where the detection electrode 1 is disposed. Via the base 11. Thus, by reducing the thickness of the linear end portion of the vibration member, the rigidity in the rotational vibration direction around the linear end portion serving as the elastic support portion is made smaller than that of the other portions of the vibration member. It is possible to set and vibrate the vibrating member in a cantilever manner. A magnetic body 13 is disposed on the surface of the diaphragm 5 facing the direction opposite to the measurement target 12. An electromagnetic coil 14 is disposed on the base 11 below the diaphragm 5 and is driven by a drive signal source.

In the above-described embodiment, one torsion spring in which one end is fixed to the vibration member and the other end is fixed to the support member is disposed so as to be positioned on the same straight line as the linear end of the vibration member. Just be fine. Moreover, in the said embodiment and modification, the shape of a vibration member, the cross-sectional shape and length of a torsion spring, material, etc. are not restricted to what was mentioned above, It can design variously according to the case.

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

Example 1
FIG. 2A shows the structure of the potential measuring device according to the first embodiment of the present invention. Two torsion springs 6 and 7 are arranged on an extension line of one end of the diaphragm 5, and one end of the torsion springs 6 and 7 is fixed to the diaphragm 5. The other ends of the torsion springs 6 and 7 are fixed to the support plates 8 and 9, and the vibration plate 5 can vibrate only in the rotation direction with the torsion springs 6 and 7 as the central axis. The support plates 8 and 9 are fixed to the base 11 via spacers 10. A magnetic body 13 is disposed on the surface of the diaphragm 5 facing the direction opposite to the measurement target 12. An electromagnetic coil 14 is disposed on the base 11 below the diaphragm 5 and is driven by the drive signal source 15 (see FIG. 2B).

The detection electrode 1 is disposed on the surface of the vibration plate 5 facing the measurement target 12, and a current signal generated at the detection electrode 1 is applied to the signal line 18 disposed on the torsion spring 7 and the support plate 9. The signal is input to the signal processing means 22 through the arranged pad 16 and signal line 19. The signal processing means 22 converts the current signal generated at the detection electrode 1 into a measurement signal by impedance conversion, detection, amplification, and rectification.

The above structure is housed in the shield case 24 (see FIG. 2B). The shield case 24 is made of a conductive material, and a window 25 for inducing an electric field stretched by the measurement object 12 is formed in a portion of the shield case 24 that is above the detection electrode 1.

2 (b) to 2 (d) show the operating principle of the potential measuring device in this embodiment. In the initial state (the state shown in FIG. 2B), no drive current is output from the drive signal source 15, and the diaphragm 5 is parallel to the base 11. In a state where a drive current is output from the drive signal source 15, an attractive force in the direction of the electromagnetic coil 14 is applied to the magnetic body 13 (magnetized in accordance with this magnetic field) fixed to the diaphragm 5 by the magnetic field stretched by the electromagnetic coil 14. As shown in FIG. 2C, the diaphragm 5 rotates downward about the torsion springs 6 and 7 as the center axis. When the drive current is set to 0 in this state, the magnetic field stretched by the electromagnetic coil 14 disappears and the attractive force acting on the magnetic body 13 disappears, and the diaphragm 5 is deformed by the elastic force of the torsion springs 6 and 7 as shown in FIG. As shown above, it rotates upward beyond the initial state.

By outputting a periodic drive current from the drive signal source 15, the diaphragm 5 vibrates in the rotation direction with the torsion springs 6 and 7 as the central axis, and the state of FIG. 2C and the state of FIG. Take alternate states. As a result, the distance between the detection electrode 1 and the surface of the measurement object 12 changes periodically, and a current signal having an amplitude proportional to the surface potential of the measurement object 12 is obtained from the detection electrode 1. The obtained current signal is subjected to impedance conversion, detection, amplification, and rectification using the signal processing means 22 to obtain a measurement signal of the surface potential of the measurement object 12.

As a waveform of the drive signal, any periodic signal having a signal amplitude necessary for driving the diaphragm 5 can be applied, and a sine wave, a triangular wave, a rectangular wave, a pulse wave, or the like can be applied. Further, by using a magnetized magnetic material as the magnetic material 13 and using a sine wave or a rectangular wave with no bias as a driving signal, it is possible to alternately apply an attractive force and a repulsive force to the diaphragm 5. Thereby, since the vibration amplitude of the diaphragm 5 increases, the measurement accuracy of the potential measuring device can be further improved.

As a driving method of the diaphragm 5 in the present embodiment, it is possible to use a driving method that causes the diaphragm 5 to resonate and vibrate by matching the frequency of the drive signal with the resonance frequency of the diaphragm. In particular, when the waveform of the drive signal is a pulse wave, the diaphragm 5 can be resonated at the frequency fc by adjusting to 1 / n (n is a natural number) of the resonance frequency fc of the diaphragm 5. Further, when a resonance driving method is used, the diaphragm 5 can be resonantly vibrated using a vibration element such as a piezoelectric element as a driving means. As an example, FIG. 2E shows a potential measuring device in which the piezoelectric element 26 is disposed between the support plate 8 and the base 11 and the diaphragm 5 is resonated via the support plate 8 and the torsion spring 6.

In the present embodiment, an example in which an electromagnetic coil or a piezoelectric element is used as the driving means has been described, but it is obvious that a driving method using electrostatic force can be applied. In the present embodiment, of course, the same effect can be obtained even if the positions of the magnetic body 13 and the electromagnetic coil 14 are interchanged.

By using a structure in which torsion springs 6 and 7 are fixed to one end of the diaphragm 5 as a vibrating body, it is closer to the rotational axis of the detection electrode 1 than a potential measuring device using a conventional cantilever or tuning fork as a vibrating body. It is possible to increase the contribution to the sensitivity increase of the part. Therefore, it is possible to improve the measurement accuracy of the surface potential of the measurement object as compared with the conventional potential measurement device. Further, since the size of the diaphragm 5 can be reduced, the apparatus can be reduced in size.

(Example 2)
As a second embodiment of the present invention, there are two diaphragms according to the first embodiment, and each diaphragm is vibrated with the same amplitude and opposite phase by one electromagnetic coil. A measuring apparatus will be described.

The structure of the potential measuring device in this example is shown in FIG. Two sets of vibration plates and torsion springs similar to those in the first embodiment are arranged in parallel to each other (vibration plates 29 and 30, torsion springs 31, 32, 33, and 34), and the ends of each torsion spring support the vibration plate and It is fixed to the board. The support plates 8 and 9 are fixed to the base 11 via spacers 10. As a method of arranging the diaphragms 29 and 30, the following method is also possible in addition to the method of arranging the diaphragms so that the tips of the diaphragms face each other as shown in FIG. That is, as shown in FIG. 3 (a-2), the end of the diaphragm is arranged in the same direction, or the end fixed to the torsion spring of the diaphragm is fixed as shown in FIG. 3 (a-3). It is also possible to use a method of arranging them so as to face each other.

Permanent magnets 35 and 36 are fixed to the surface of the vibration plates 29 and 30 opposite to the surface facing the object to be measured (see FIG. 3B-1). The magnetization directions of the permanent magnets 35 and 36 may be magnetized so that the polarities of the ends of the permanent magnets close to the electromagnetic coil 14 are opposite to each other. Therefore, in addition to being magnetized in the direction parallel to the diaphragm and perpendicular to the torsion spring as shown in FIG. 3B, it may be magnetized in the direction perpendicular to the diaphragm as shown in FIG. 3B-2. On the base 11, the electromagnetic coil 14 is disposed in a portion corresponding to the lower side of the vibration plates 29 and 30, and is driven by the drive signal source 15.

Detection electrodes 27 and 28 are arranged on the surfaces of the diaphragms 29 and 30 facing the measurement object 12. Current signals generated by the detection electrodes 27 and 28 are transmitted via signal lines 18 and 20 disposed on the torsion springs 32 and 34, pads 16 and 17 disposed on the support member 9, and signal lines 19 and 21. Input to the differential operation means 23. The differential operation means 23 converts the current signal generated at the detection electrodes 27 and 28 into a voltage signal proportional to the difference between them. The signal processing means 22 converts the voltage signal output from the differential operation means 23 into a measurement signal by detecting, amplifying and rectifying.

The above structure is housed in the shield case 24. The shield case 24 is made of a conductive material, and a window 25 for inducing an electric field stretched by the measurement object 12 is formed in a portion corresponding to the upper side of the detection electrodes 27 and 28.

The operation principle of the potential measuring apparatus in this embodiment is shown in FIGS. When a drive current of magnitude I is output from the drive signal source 15 so that the surfaces of the electromagnetic coil 14 facing the diaphragms 29 and 30 are N poles, repulsive force is applied to the diaphragm 29 and attractive force is applied to the diaphragm 30. Join. Therefore, as a result, as shown in FIG. 3C, the diaphragm 29 rotates upward by the same angle around the torsion springs 31 and 32, and the diaphragm 30 rotates downward by the same angle around the torsion springs 33 and 34, respectively. . Conversely, when a drive current having a magnitude I is output so that the surfaces of the electromagnetic coil 14 facing the diaphragms 29 and 30 are S poles, the diaphragms 29 and 30 are opposite to the previous ones as shown in FIG. Rotate the same angle in the direction. Therefore, by outputting a drive current having the same positive and negative amplitude, such as a sine wave without bias, from the drive signal source 15 to the electromagnetic coil 14, the diaphragms 29 and 30 have the same amplitude and opposite phases. It can be vibrated. At this time, from the detection electrodes 27 and 28, current signals having the same amplitude and opposite phases are obtained in proportion to the surface potential of the measurement object 12. Measurement of the surface potential of the measurement object 12 is performed by converting these current signals into voltage signals proportional to these differences using the differential operation means 23, and further detecting, amplifying and rectifying using the signal processing means 22. A signal is obtained.

Similarly to the first embodiment, in this embodiment, it is possible to use a driving method in which the vibration plates 29 and 30 are resonantly oscillated by adjusting the frequency of the drive signal to the resonance frequency of the vibration plate. In this driving method, it is also possible to use a signal having an amplitude only in one of positive and negative, such as a pulse wave, as the waveform of the driving signal.

In addition to the effects in the first embodiment, the following effects can be obtained by the structure and the driving method as in the present embodiment. That is, two diaphragms are vibrated in the same amplitude and in opposite phases without increasing the number of driving means (electromagnetic coils in the present embodiment), and a measurement signal having a high signal-to-noise ratio using differential arithmetic means. Can be obtained. Therefore, it is possible to further improve the measurement accuracy of the surface potential of the measurement object as compared with the conventional potential measurement device.

A plurality of vibration members, electromagnetic coils, and magnetic bodies having the same configuration may be provided, the vibration members may be driven in the same phase, and current signals from the respective detection electrodes may be added and processed. This also improves the sensitivity of the potential measuring device. Since the configuration of each set can be reduced in size, such a configuration is also possible.

(Example 3)
As a third embodiment of the present invention, a configuration example of an image forming apparatus using the potential measuring device of the present invention will be described.

An image forming apparatus of this embodiment is shown in FIG. Around the photosensitive drum 129, a potential measuring device 123 of the present invention, a charger 124 that can be controlled by the charger controller 125, an exposure device 126, and a toner supplier 127 are installed. A latent image is obtained by charging the surface of the photosensitive drum 129 with the charger 124 and exposing the surface of the photosensitive drum 129 with the exposure device 126. By attaching toner to the latent image by the toner supplier 127, a toner image in which the latent image is developed is obtained. This toner image is transferred to the printing object 130 sandwiched between the feed roller 128 and the photosensitive drum 129, and the toner on the printing object 130 is fixed. Image formation is achieved through these steps. The charger controller 125 constitutes a signal processing device, and the charger 124, the exposure device 126, the photosensitive drum 129, and the like constitute image forming means.

In this configuration, the charged state of the photosensitive drum 129 is measured by the potential measuring device 123 of the present invention, and the measurement signal of the surface potential of the photosensitive drum 129 is output to the charger controller 125. Based on this measurement signal, the charger controller 125 feedback-controls the charging voltage of the charger 124 so that the surface potential of the photosensitive drum 129 after charging becomes a desired value (of the potential measuring device 123 of the present invention). The measurement signal can be fed back to the exposure device 126 to control it). Thereby, stable charging of the photosensitive drum 129 is realized, and stable image formation is realized.

The principal part of the electric potential measurement apparatus in one Embodiment of this invention is shown, (a) Structural drawing (top view and sectional drawing in broken line CC '), (b) Sectional drawing which shows the mode of a vibration of a vibration member. 1A is a perspective view showing a structure, FIG. 2B is a sectional view taken along a broken line DD ′ showing an initial state, and FIG. 1C is a broken line showing a state in which a drive current is output. Cross-sectional view at DD ′, (d) Cross-sectional view at broken line DD ′ showing a state after the drive current is reduced to 0 from the state of (c), (e) Modification using piezoelectric element as drive means FIG. FIG. 2 shows a second embodiment of the present invention, (a-1) a perspective view showing a structure, (a-2) a perspective view showing a structure of another example 1, (a-3) a perspective view showing a structure of another example 2. (B-1) Cross-sectional view taken along broken line EE 'in (b-1) (a-1), (b-2) Cross-sectional view taken along broken line EE' in (a-1), (c) Electromagnetic coil Sectional drawing which shows a mode when an electric current is flowing so that the surface facing the diaphragm may be an N pole. (D) An electric current flows so that the surface facing the diaphragm of the electromagnetic coil is an S pole. Sectional drawing which shows a mode when there is. Sectional drawing which shows the example which a vibration member rotationally vibrates in a cantilever type. Schematic which shows the 3rd Example which is an image forming apparatus using the electric potential measuring apparatus of this invention. The principal part of the prior art example of the electric potential measuring device which has arranged the detection electrode on the cantilever is shown, (a) Structural view (cross-sectional view along the top view and broken line AA ′), (b) Cross-sectional view showing how the cantilever vibrates . The main part of the conventional example of the electric potential measuring device which has arrange | positioned the detection electrode to a tuning fork is shown, (a) Structural drawing (top view and sectional drawing in broken line BB '), (b) Sectional drawing which shows the mode of the vibration of a tuning fork .

Explanation of symbols

1, 27, 28 ... detection electrodes 5, 29, 30 ... vibrating members (vibrating plates)
5a, 6, 7, 31, 32, 33, 34 ... Parts corresponding to the rotation axis (U-shaped groove, torsion spring)
12 ... Measuring object 13, 14, 26, 35, 36 ... Driving means (magnetic material, electromagnetic coil, piezoelectric element, permanent magnet)
123: Potential measuring device of the present invention

Claims (8)

A vibration member having a linear shape end, wherein the vibration member is arranged to be able to vibrate by rotating around a rotation axis including the linear shape end, and at least a part of the portion corresponding to the rotation axis around the rotation axis The rotational vibration device is characterized in that the rigidity in the rotational vibration direction is set to be smaller than that of other portions of the vibration member. 2. The rotary vibration device according to claim 1, wherein the other part of the vibration member has rigidity so as to be able to rotate and vibrate around the rotation shaft while maintaining substantially the same shape. . 3. The rotary vibration device according to claim 1, further comprising a torsion spring having one end fixed to the vibration member and the other end fixed to the support member, and the linear end of the vibration member and the torsion A rotary vibration device, wherein the rotary shaft is configured by being arranged so that a spring is positioned on the same straight line. 4. The rotational vibration device according to claim 3, wherein a pair of the torsion springs are arranged across a linear end of the vibration member. 3. The rotational vibration device according to claim 1, wherein the thickness of the end portion of the linear shape of the vibration member is reduced so that the rigidity in the rotational vibration direction around the rotation shaft is the other portion of the vibration member. A rotational vibration device characterized by being set smaller. 6. The rotary vibration device according to claim 1 and driving means for rotating and vibrating the vibration member, wherein the vibration member includes a detection electrode on a surface facing a measurement object. A potential measuring device. The potential measuring apparatus according to claim 6, wherein the driving unit includes a permanent magnet and an electromagnetic coil, a plurality of the vibration members are provided, one permanent magnet is disposed on each of the vibration members, and the permanent magnet is disposed on the permanent magnet. An electric potential measuring apparatus that vibrates each of vibration members with substantially the same amplitude and in opposite phases by one electromagnetic coil fixedly arranged on the opposite side. 8. The potential measuring device according to claim 6 or 7, a signal processing device for processing an output signal obtained from the potential measuring device, and an image forming means, wherein a portion of the potential measuring device having a detection electrode is a potential of the image forming means. An image forming apparatus, wherein the image forming apparatus is arranged to face a surface to be measured, and the image forming unit controls image formation using a signal detection result of the signal processing apparatus.

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