JP4654884B2 - Multi-degree-of-freedom ultrasonic motor - Google Patents

Description

  The present invention relates to a multi-degree-of-freedom ultrasonic motor, and more particularly to a motor that rotates a spherical rotor around a plurality of axes.

In recent years, an ultrasonic motor for rotating a rotor using ultrasonic vibration has been proposed and put into practical use. This ultrasonic motor generates a traveling wave on the surface of a stator using a piezoelectric element and moves the rotor through a frictional force between the two by bringing the rotor into pressure contact with the stator.
For example, in Patent Document 1, the rotor is pressed against the stator by preloading the rotor with a spring through a bearing, and a driving voltage is applied to a plurality of piezoelectric element plates that are superposed on each other in this state. Discloses a multi-degree-of-freedom ultrasonic motor that rotates a rotor by generating ultrasonic vibration.

JP 2004-312809 A

However, since the bearing is brought into contact with the rotor in order to apply the preload, there is a problem that the torque is reduced due to friction loss.
The present invention has been made to solve such problems, and an object thereof is to provide a multi-degree-of-freedom ultrasonic motor capable of realizing a high torque.

  A multi-degree-of-freedom ultrasonic motor according to the present invention includes a stator, a substantially spherical rotor that is contacted and supported by the stator, stator vibration means that rotates the stator by vibrating the stator, and a preload that faces the surface of the rotor. And a preload member vibrating means for generating a preload that vibrates the preload member at least when the rotor is rotated and preloads the rotor against the stator by the radiation pressure from the preload member.

  As the preload member, a ring member having a curved shape corresponding to the surface of the rotor, or a plurality of curved members each having a curved shape corresponding to the surface of the rotor can be used.

The preload member can be arranged away from the stator, and a piezoelectric element plate can be attached to the preload member as the preload member vibrating means. In this case, the preload member is formed at a node position formed when the preload member vibrates with the piezoelectric element plate. It is preferable to support the member.
Further, the preload member can be formed integrally with the stator, and the stator vibration means can also serve as the preload member vibration means.

The preload member may be configured to be separated from the surface of the rotor when vibrated by the preload member vibrating means, and to hold the rotor in contact with the surface of the rotor when not vibrated.
Further, by controlling the amplitude of the preload member vibrated by the preload member vibrating means, the magnitude of the preload for preloading the rotor with respect to the stator can be changed.
The stator vibration means has three pairs of piezoelectric element plates that generate vibrations in three different directions, and generates a combined vibration in which at least two of the three directions of vibration are combined with their phases shifted from each other. Thus, an elliptical motion can be formed at the contact portion of the stator with the rotor.
Here, in the present invention, the preload refers to a pressure that presses the rotor toward the stator.

  According to the present invention, a multi-degree-of-freedom ultrasonic motor capable of realizing high torque can be obtained.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
1 and 2 show a multi-degree-of-freedom ultrasonic motor according to Embodiment 1 of the present invention. A cylindrical vibrator 3 serving as a stator vibration means is sandwiched between the base block 1 and the stator 2, and the base block 1 and the stator 2 are connected to each other via a connecting bolt 4 passed through the vibrator 3. The multi-degree-of-freedom ultrasonic motor as a whole has a substantially cylindrical outer shape. Here, for convenience of explanation, the central axis of the cylindrical outer shape from the base block 1 to the stator 2 is defined as the Z axis, and the X axis is perpendicular to the Z axis and the Z axis and the X axis are Assume that the Y-axis extends vertically.
The vibrator 3 includes first to third piezoelectric element portions 31 to 33 that are located on the XY plane and overlap each other, and these piezoelectric element portions 31 to 33 are insulating sheets 34. Are arranged in a state of being insulated from the stator 2 and the base block 1 through .about.37.

  A concave portion 5 is formed on the stator 2 on the side opposite to the surface in contact with the vibrator 3, and a spherical rotor 6 is accommodated in the concave portion 5. The recess 5 includes a small-diameter portion 7 having an inner diameter smaller than the diameter of the rotor 6 and a large-diameter portion 8 having an inner diameter larger than the diameter of the rotor 6, and the boundary portion between the small-diameter portion 7 and the large-diameter portion 8 is XY. An annular step 9 located on the plane is formed. The rotor 6 is rotatably supported by contacting the step 9 in the recess 5. Further, the stator 2 has an annular ring member 10 formed so as to protrude substantially in the Z-axis direction from the opening peripheral edge of the recess 5. The ring member 10 is disposed so as to surround the rotor 6 in the circumferential direction, that is, along the circumferential direction of the cross section in the XY plane direction of the rotor, and a part of the rotor 6 is exposed from the tip portion 10 a of the ring member 10. Further, the inner surface of the ring member 10 is opposed to the surface of the rotor 6.

  As shown in FIG. 3, the ring member 10 is formed so that the diameter gradually decreases from the proximal end portion 10 b located at the opening peripheral edge of the recess 5 toward the distal end portion 10 a, that is, toward the Z-axis direction. In addition, as shown in FIG. 4, the cross-section of the ring member 10 has an arc shape that is curved corresponding to the shape of the surface of the rotor 6, that is, the spherical shape.

  For example, the base block 1 and the stator 2 are formed of geralumin, and the entire multi-degree-of-freedom ultrasonic motor forms a substantially cylindrical body having a diameter of about 40 mm and a height of about 100 mm. As the rotor 6, a steel ball having a diameter of 25.8 mm is used. The ring member 10 of the stator 2 has an inner diameter of 25.4 mm, a thickness of 1.5 mm, an inner surface having an arc of curvature of 12.7 mm and an angle of 23 degrees. Stand up to draw.

  As shown in FIG. 5, the first piezoelectric element portion 31 of the vibrator 3 includes an electrode plate 31a, a piezoelectric element plate 31b, an electrode plate 31c, a piezoelectric element plate 31d, and an electrode plate 31e each having a disc shape. It has a superposed structure. Similarly, the second piezoelectric element portion 32 has a structure in which an electrode plate 32a, a piezoelectric element plate 32b, an electrode plate 32c, a piezoelectric element plate 32d, and an electrode plate 32e each having a disk shape are sequentially stacked. 3 has a structure in which an electrode plate 33a, a piezoelectric element plate 33b, an electrode plate 33c, a piezoelectric element plate 33d, and an electrode plate 33e each having a disk shape are sequentially stacked.

As shown in FIG. 6, the pair of piezoelectric element plates 31b and 31d of the first piezoelectric element portion 31 have portions that are divided into two in the Y-axis direction and have opposite polarities, and each has a Z-axis direction (thickness direction The piezoelectric element plate 31b and the piezoelectric element plate 31d are disposed so as to be reversed with respect to each other.
The pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32 are polarized so as to be expanded or contracted in the Z-axis direction (thickness direction) as a whole without being divided into two. The element plate 32b and the piezoelectric element plate 32d are arranged inside out.
In the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33, the portions divided into two in the X-axis direction have opposite polarities, and are opposite to expansion and contraction in the Z-axis direction (thickness direction), respectively. The piezoelectric element plate 33b and the piezoelectric element plate 33d are disposed so as to be reversed with respect to each other.

  As shown in FIG. 1, the electrode plates 31 a and 31 e disposed on both surface portions of the first piezoelectric element portion 31 and the electrode plate 32 a disposed on both surface portions of the second piezoelectric element portion 32. The electrode plate 32e and the electrode plate 33a and the electrode plate 33e disposed on both surface portions of the third piezoelectric element portion 33 are electrically grounded. In addition, the first terminal 31 t from the electrode plate 31 c disposed between the pair of piezoelectric element plates 31 b and 31 d of the first piezoelectric element portion 31 is connected to the pair of piezoelectric element plates 32 b of the second piezoelectric element portion 32. And the second terminal 32t from the electrode plate 32c disposed between the second and third electrode elements 32c and 32d to the third terminal from the electrode plate 33c disposed between the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33. Terminals 33t are respectively drawn out.

Next, the operation of the multi-degree-of-freedom ultrasonic motor according to the first embodiment will be described.
First, when an AC voltage having a frequency close to the natural frequency of the stator 2 is applied from the first terminal 31t to the vibrator 3, the pair of piezoelectric element plates 31b and 31d of the first piezoelectric element portion 31 is divided into two. The portion thus expanded alternately expands and contracts in the Z-axis direction, and generates flexural vibration in the Y-axis direction in the stator 2. Further, when an AC voltage having a frequency close to the natural frequency of the stator 2 is applied from the second terminal 32t, the pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32 repeatedly expands and contracts in the Z-axis direction. The stator 2 generates longitudinal vibration in the Z-axis direction. Further, when an AC voltage having a frequency close to the natural frequency of the stator 2 is applied from the third terminal 33t, the two divided portions of the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33 are in the Z-axis direction. Then, expansion and contraction are alternately repeated, and flexural vibration in the X-axis direction is generated in the stator 2.

Therefore, when an AC voltage having a phase shifted by 90 degrees is applied from both the first terminal 31t and the second terminal 32t, the flexural vibration in the Y-axis direction and the longitudinal vibration in the Z-axis direction are combined to form the rotor 6. Elliptical vibration in the YZ plane is generated in the step 9 of the stator 2 that comes into contact with the rotor 6, and the rotor 6 rotates about the X axis via frictional force.
Similarly, when an AC voltage having a phase shifted by 90 degrees is applied from both the second terminal 32t and the third terminal 33t, the flexural vibration in the X-axis direction and the vertical vibration in the Z-axis direction are combined to form a rotor. The elliptical vibration in the XZ plane is generated at the step 9 of the stator 2 that comes into contact with the rotor 6, and the rotor 6 rotates about the Y axis through the frictional force.
Further, when an AC voltage having a phase shifted by 90 degrees is applied from both the first terminal 31t and the third terminal 33t, the X axis deflection vibration and the Y axis deflection vibration are combined to form the rotor 6. An elliptical vibration in the XY plane is generated in the step 9 of the stator 2 that comes into contact with the rotor 6, and the rotor 6 rotates about the Z-axis via a frictional force.

As described above, the AC voltage obtained by selecting two terminals among the first terminal 31t, the second terminal 32t, and the third terminal 33t of the vibrator 3 and shifting the phase by 90 degrees from both of these two terminals. Is applied to the stator 2, and as shown by broken line arrows in FIG. 7, the in-plane elliptical vibration corresponding to the two selected terminals is formed on the step 9 of the stator 2 in contact with the rotor 6. Occurs.
Here, since the stator 2 has the ring member 10 formed integrally, the ring member 10 is also in a non-contact state with the rotor 6 as shown by a solid arrow in FIG. Will vibrate. Accordingly, the rotor 6 is pressed against the step 9 of the stator 2 by the radiation pressure of the sound wave radiated from the ring member 10. As a result, the frictional force between the rotor 6 and the step 9 is increased, and the rotational force is effectively transmitted to the rotor 6.

As described above, since the preload can be applied to the rotor 6 in a non-contact state by the ring member 10, there is no friction loss between the ring member 10 and the surface of the rotor 6. A highly efficient multi-degree-of-freedom ultrasonic motor can be realized.
Further, the ring member 10 and the rotor 6 do not come into contact with each other to generate noise or the like.

Moreover, since the ring member 10 is provided integrally with the stator 2 and vibrates the ring member 10 using the vibration of the stator 2 by the vibrator 3, a multi-degree-of-freedom ultrasonic motor having a simple configuration can be obtained.
Further, only by selecting two of the three terminals 31t, 32t, and 33t of the vibrator 3 and applying a voltage, the stator 2 vibrates and an elliptical motion for rotating the rotor 6 occurs in the step 9. Preload is applied to the rotor 6 in a non-contact state by the ring member 10, and the rotor 6 can be rotated with multiple degrees of freedom.

  In addition, preload can be applied to the rotor 6 in a non-contact manner using air, electrostatic force, or electromagnetic force. However, in the case of air, the configuration may be complicated because it is necessary to provide a suction device or the like. In the case of electrostatic force or electromagnetic force, the use of electrostatic force or electromagnetic force may be unfavorable because it may affect surrounding equipment. On the other hand, this multi-degree-of-freedom ultrasonic motor has a simple configuration and can be used in an environment where the use of electrostatic force or electromagnetic force is not preferable.

  Further, if the amplitude of the ring member 10 is controlled by driving the vibrator 3, the magnitude of the radiation pressure radiated from the ring member 10 is changed to change the applied pressure of the rotor 6 with respect to the step 9, thereby changing the multiple pressure. It is possible to perform torque control, position control, rotation speed control, and the like of the ultrasonic motor with a degree of freedom.

  Therefore, by attaching an arm, an imaging device, etc. (not shown) to the surface portion of the rotor 6 exposed through the tip 10a of the ring member 10, it is possible to realize a multi-degree-of-freedom actuator, a camera for a wide field of view, and the like. it can.

Embodiment 2. FIG.
Referring to FIG. 8, a multi-degree-of-freedom ultrasonic motor according to Embodiment 2 of the present invention is shown. In the second embodiment, the annular ring member 10 in the first embodiment is divided into four curved members 11 along the circumferential direction thereof. That is, the stator 2 includes four curved members 11 that are integrally formed, and these four curved members 11 are arranged at intervals from each other along the circumferential direction of the rotor 6. Each curved member 11 has a curved shape along the surface of the rotor 6, and the inner surface of each curved member 11 is opposed to the surface of the rotor 6.

  With such a configuration, the four bending members 11 are divided from each other and are independent from each other, so that they easily vibrate. Therefore, pre-loading can be effectively applied to the rotor 6 by causing each bending member 11 to vibrate in a non-contact state with the rotor 6 by driving the vibrator 3.

The bending member 11 can be in a non-contact state with respect to the rotor 6 both when it vibrates and when it does not vibrate, but as shown in FIG. 9, when the vibrator 3 is stopped and does not vibrate, It can also be set as the structure where the front-end | tip part 11a contacts the surface of the rotor 6. FIG. In this way, the tip end portion 11a of the bending member 11 can be brought into contact with the surface of the rotor 6 that is not rotating when the vibrator 3 is stopped, and the rotor 6 can be held. Even in this case, the bending member 11 needs to be separated from the surface of the rotor 6 during vibration. The bending member 11 that is in contact with the rotor 6 when the vibration is stopped may also be lifted from the rotor 6 by the radiation pressure of the sound wave emitted from the bending member 11 during vibration.
Moreover, it is not limited to the four bending members 11, You may divide | segment into three or less or five or more bending members.

Embodiment 3 FIG.
Referring to FIG. 10, a multi-degree-of-freedom ultrasonic motor according to Embodiment 3 of the present invention is shown. In the third embodiment, the ring member 13 is arranged apart from the stator 12 instead of the ring member 10 provided integrally with the stator 12 in the first embodiment. In other words, the ring member 13 and the stator 12 are formed as members independent of each other and are spaced from each other in the Z-axis direction. The ring member 13 has a shape that gradually decreases in diameter as it goes in the Z-axis direction, like the ring member 10 of the first embodiment, and is arranged in a state where the inner surface thereof is close to and opposed to the surface of the rotor 6. As shown by the broken lines in FIG. Four vibrators 15 for vibrating the ring member 13 are attached to the outer surface of the ring member 13. In the vibration mode when the ring member 13 is vibrated by the vibrator 15, it is preferable that the ring member 13 is supported by the support member 14 or attached to the vibrator 15 at a portion that becomes a node.

  As shown in FIG. 12, each vibrator 15 has a structure in which an electrode plate 15a, a piezoelectric element plate 15b, and an electrode plate 15c are sequentially stacked. The piezoelectric element plate 15b of each vibrator 15 is polarized so as to perform deformation behavior of expansion or contraction in the thickness direction thereof, and by applying an independent AC voltage between the electrode plates 15a and 15c, 15 can be driven and controlled. Insulating sheets 16 and 17 are arranged on both surfaces of the vibrator 15, respectively, and the vibrator 15 is arranged in a state of being insulated from the ring member 13 through one insulating sheet 17.

  The stator 12 is connected to each other by the connecting bolt 4 in a state where the vibrator 3 is sandwiched between the stator 12 and the base block 1 in the same manner as the stator 2 in the first embodiment, and is in contact with the vibrator 3 of the stator 12. A concave portion 18 having an inner diameter smaller than the diameter of the rotor 6 is formed on the side opposite to the surface. An annular corner 19 located on the XY plane is formed on the periphery of the opening end of the recess 18, and the rotor 6 is in contact with the corner 19 and is rotatably held.

  Even in such a configuration, two terminals are selected from the first terminal 31t, the second terminal 32t, and the third terminal 33t of the vibrator 3, and the phase is shifted by 90 degrees from both of these two terminals. When each of the AC voltages is applied, vibration is generated in the stator 12, and in-plane elliptical vibration corresponding to the two selected terminals is generated in the corner portion 19 of the stator 12 that is in contact with the rotor 6.

  At this time, when the vibrator 15 is driven and controlled, longitudinal vibration in the thickness direction of the vibrator 15, that is, the direction orthogonal to the surface of the rotor 6 is generated in the ring member 13, and the ring member 13 is not in contact with the rotor 6. Vibrate. Thereby, the rotor 6 is pressed against the corner portion 19 of the stator 12 by the radiation pressure of the sound wave radiated from the ring member 13. Therefore, similarly to the above-described first embodiment, it is possible to realize a high-torque and high-efficiency multi-degree-of-freedom ultrasonic motor and to prevent noise and the like due to contact between the ring member 13 and the rotor 6.

In addition, in the third embodiment, the ring member 13 is driven by the vibrator 15 and the stator 12 is driven by the vibrator 3 so that the ring member 13 can be vibrated independently of the stator 12. By controlling the amplitude of the ring member 13 by driving the child 15, torque control, position control, rotation speed control, etc. of the multi-degree-of-freedom ultrasonic motor can be easily performed.
Further, the ring member 13 can be supported by the support member 14 at the node position formed when the ring member 13 is vibrated by the vibrator 15, and in this way, the influence on the vibration of the ring member 13 is minimized. It is possible to support the ring member 13 while suppressing the pressure to a low level.
Furthermore, the support member 14 can be elastically held with respect to the stator 12 or the base block 1 using a spring or the like (not shown).

  The ring member 13 may be divided into a plurality of bending members along the circumferential direction thereof, as in the second embodiment, and in this case, the plurality of bending members are respectively supported at node positions during vibration. While being supported by the member 14, it can be configured such that one vibrator 15 is attached to each bending member. With such a configuration, since the plurality of bending members are divided from each other and independent from each other, the bending members are easily vibrated, and the rotor 6 can be preloaded effectively.

Although the ring member is disposed in the circumferential direction of the rotor, the ring member is not limited to the circumferential direction as long as the pre-pressure can be generated by the radiation pressure.
Further, the ring member 13 is elastically held so as to be in contact with the rotor 6 when the rotor 6 is stopped, as in the above-described modification of the second embodiment. The ring member 13 itself may be lifted from the rotor 6 by the radiation pressure of the radiated sound wave.

In the above embodiment, the phase of the alternating voltage applied by selecting two of the first terminal 31t, the second 32t, and the third 33t of the vibrator 3 is shifted by 90 degrees. You may change not only 90 degree | times. Moreover, you may change the voltage value of the alternating voltage to apply. The elliptical vibration generated in the stators 2 and 12 can be controlled by variously controlling the AC voltage.
Further, in the above embodiment, the contact between the stators 2 and 12 and the rotor 6 is a corner such as the step 9 or the corner 19, but is not limited to this configuration. If the elliptical motion can be transmitted, the contact may be made on a flat surface, the contact may be made on a curved surface, or may not be annular.

In the above embodiment, the vibrator 3 uses vibrators that generate longitudinal vibrations in the Z direction and flexural vibrations in the X and Y directions as vibrations in three different directions. It is not necessary. In addition, the vibrator that generates vibrations in the three directions uses the first piezoelectric element portion 31, the second piezoelectric element portion 32, and the third piezoelectric element portion 33 and piezoelectric elements corresponding to the respective directions. In order to generate vibration, vibrations from a plurality of piezoelectric element units may be combined, or one piezoelectric element unit is polarized into three or more to generate vibrations in two or more directions in one piezoelectric element unit. You may let them.
In the above embodiment, two of the three directions are selected to generate vibration. However, an AC voltage is applied to all the piezoelectric elements corresponding to the three directions, and the phase and amplitude of vibration in each direction are adjusted. A synthetic vibration may be generated by controlling.

It is sectional drawing which shows the multi-degree-of-freedom ultrasonic motor which concerns on Embodiment 1 of this invention. 1 is a plan view showing a multi-degree-of-freedom ultrasonic motor according to Embodiment 1. FIG. 3 is a perspective view showing a shape of a ring member in Embodiment 1. FIG. FIG. 3 is a partial cross-sectional view showing a ring member in the first embodiment. 3 is a partial cross-sectional view showing a configuration of a vibrator used in Embodiment 1. FIG. 3 is a perspective view showing polarization directions of three pairs of piezoelectric element plates of the vibrator used in Embodiment 1. FIG. 2 is a partial enlarged cross-sectional view of the multi-degree-of-freedom ultrasonic motor according to Embodiment 1. FIG. 6 is a plan view showing a multi-degree-of-freedom ultrasonic motor according to Embodiment 2. FIG. FIG. 10 is a partial enlarged cross-sectional view of a multi-degree-of-freedom ultrasonic motor according to a modification of the second embodiment. 5 is a cross-sectional view showing a multi-degree-of-freedom ultrasonic motor according to Embodiment 3. FIG. 6 is a plan view showing a multi-degree-of-freedom ultrasonic motor according to Embodiment 3. FIG. 6 is a partial cross-sectional view illustrating a configuration of a vibrator used in Embodiment 3. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Base block, 2,12 Stator, 3,15 Vibrator, 4 Connection bolt, 5,18 Concave part, 6 Rotor, 7 Small diameter part, 8 Large diameter part, 9 Step, 10, 13 Ring member, 10a, 11a Tip part 10b Base end part, 11 Bending member, 14 Support member, 15a, 15c, 31a, 31c, 31e, 32a, 32c, 32e, 33a, 33c, 33e Electrode plate, 15b, 31b, 31d, 32b, 32d, 33b, 33d Piezoelectric element plate, 16, 17, 34, 35, 36, 37 Insulating sheet, 19 corners, 31 1st piezoelectric element part, 31t 1st terminal, 32 2nd piezoelectric element part, 32t 2nd terminal, 33 3rd piezoelectric element part, 33t 3rd terminal.

Claims (9)

A stator,
A substantially spherical rotor that is contact-supported by the stator;
Stator vibration means for rotating the rotor by vibrating the stator;
A preload member facing the surface of the rotor;
Preload member vibrating means for generating a preload that vibrates the preload member and preloads the rotor against the stator by a radiation pressure from the preload member when rotating the rotor. Multi-degree-of-freedom ultrasonic motor.   The multi-degree-of-freedom ultrasonic motor according to claim 1, wherein the preload member is a ring member having a curved shape corresponding to a surface of the rotor.   The multi-degree-of-freedom ultrasonic motor according to claim 1, wherein the preload member includes a plurality of curved members each having a curved shape corresponding to a surface of the rotor.   The multi-degree-of-freedom ultrasonic motor according to any one of claims 1 to 3, wherein the preload member is disposed apart from the stator, and the preload member vibrating means includes a piezoelectric element plate attached to the preload member. .   The multi-degree-of-freedom ultrasonic motor according to claim 4, wherein the preload member is supported at a node position formed when vibrating by the piezoelectric element plate.   The multi-degree-of-freedom ultrasonic motor according to any one of claims 1 to 3, wherein the preload member is formed integrally with the stator, and the stator vibration means also serves as the preload member vibration means.   7. The preload member is in a state of being separated from the surface of the rotor when vibrated by the preload member vibrating means, and contacts the surface of the rotor and holds the rotor when not vibrated. The multi-degree-of-freedom ultrasonic motor according to item.   The magnitude | size of the preload which preloads the said rotor with respect to the said stator is changed by controlling the amplitude of the said preload member vibrated by the said preload member vibration means. Multi-degree-of-freedom ultrasonic motor.   The stator vibration means has three pairs of piezoelectric element plates that generate vibrations in three different directions, and generates a combined vibration in which at least two of the three directions of vibration are combined with their phases shifted from each other. The multi-degree-of-freedom ultrasonic motor according to claim 1, wherein an elliptical motion is formed in a contact portion of the stator with the rotor.

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