JP4485238B2 - Ultrasonic motor and electronic device with ultrasonic motor - Google Patents

Description

  The present invention relates to an ultrasonic motor constituted by a rectangular laminated piezoelectric element in which internal electrodes are arranged so that an excitation force can be efficiently used, and an electronic apparatus including the ultrasonic motor.

  In recent years, various types of ultrasonic driving devices using a stretching vibration and a bending vibration of a rectangular piezoelectric diaphragm have been developed. Such an ultrasonic driving device combines two different vibration modes, transmits an elliptical motion generated at a specific position of vibration to the moving body, and moves the moving body linearly or rotationally. Such an ultrasonic drive device is expected to be applied to various applications because it has a simple configuration and can be easily reduced in size. As an example, an ultrasonic motor has been developed in which an integrally sintered laminated piezoelectric element is used as a vibration body and the entire vibration body is used as a drive source.

This ultrasonic motor simultaneously generates two different types of vibration (stretching vibration and bending vibration) in a laminated piezoelectric element, and uses an elliptical motion generated at a specific position of the vibration as a drive source. In order to excite these two types of vibration, several types of internal electrodes corresponding to the type of vibration are provided inside the multilayer piezoelectric element. In order to apply a drive signal to this internal electrode, a short-circuit electrode is provided on the side surface of the laminated piezoelectric element, and this is connected to the internal electrode, thereby leading the drive signal from the surface of the laminated piezoelectric element to the internal electrode. (For example, refer to Patent Document 1).
JP 2000-116162 A

  However, in the above-described ultrasonic motor, since different driving signals are supplied for each type of internal electrode, one short-circuited electrode needs to be placed only in one type of internal electrode and not short-circuited with other types of internal electrodes. was there. For this reason, neither type of internal electrode can be provided on the entire surface, and it is necessary to always provide a blank portion at a position where a short-circuit electrode for conducting conduction between other types of internal electrodes is provided. However, since this blank portion does not contribute to the excitation of the piezoelectric element, there is a problem that the vibration generated by the piezoelectric element is reduced by installing the blank portion.

  Therefore, the present invention aims at high efficiency and high output by arranging the internal electrode at a position where the piezoelectric element is efficiently excited, and providing a blank portion in a portion where the contribution to the excitation of the target vibration is small. An object is to provide an ultrasonic motor and an electronic device with an ultrasonic motor.

In order to solve the above-described problems, the ultrasonic motor of the present invention defines the position of the internal electrode that excites the piezoelectric element and the position of the short-circuit electrode that is electrically connected to the internal electrode, so that the position that most affects the excitation force of the piezoelectric element. The piezoelectric element in which the internal electrode is always disposed and the blank portion is provided in the portion where the contribution to the excitation of the target vibration is small is used as the vibrating body.
By using the piezoelectric element having such a structure, it is possible to efficiently excite the piezoelectric element and to increase the efficiency and output of the ultrasonic motor. In addition, by using an ultrasonic motor provided with such a piezoelectric element as a drive source of an electronic device, it is possible to reduce the power consumption and output of the electronic device.

  The internal electrode is always placed at the position that most affects the excitation force, and the vibrator is made efficient by using a laminated piezoelectric element with a blank portion in the part where the contribution to the excitation of the target vibration is small. It is possible to excite, and it is possible to increase the efficiency and output of the ultrasonic motor configured using the laminated piezoelectric element. Moreover, since it is a simple structure, size reduction and manufacture become easy. In addition, by using an ultrasonic motor provided with these vibrators as a drive source for an electronic device, the electronic device can be reduced in size, thickness, and power consumption.

Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the following embodiment.
(Embodiment 1)
FIG. 1 is a diagram illustrating an ultrasonic motor 1000 according to the present invention. 1 is a perspective view of the ultrasonic motor 1000, and FIG. 2 is a diagram for explaining the vibration amplitude of the vibrating body 10 made of a laminated piezoelectric element. FIG. 3 is a diagram illustrating a specific structure, polarization direction, and electrode arrangement of the vibrating body 10, and FIG. 3A is a three-view diagram of the vibrating body 10, and FIGS. d) and (e) show the polarization directions of the piezoelectric elements 11, 12, 13, and 14 constituting the vibrating body 10 and the arrangement of internal electrodes, respectively.

  As shown in FIG. 1, the ultrasonic motor 1000 includes a vibrating body 10 in which a plurality of piezoelectric elements 11, 12, 13, and 14 are stacked and integrally formed, and a support member 40 provided on the vibrating body 10. And a protrusion 30. Further, a moving body 60 whose moving direction is defined by the guide member 50 is provided under the protrusion 30, and the protrusion 30 is added to the moving body 60 by a pressure member (not shown) engaged with the support member 40. The structure is in pressure contact. In FIG. 1, the support method and the pressurization method are illustrated in a simplified manner. However, in the member engaged with the support member 40, the vibration body 10 is restricted from moving in the moving direction of the moving body 60 and is vibrated. If the pressure is applied to the support member 40 so that a contact pressure is generated between the body 10 and the moving body 60, the method is not limited.

  Next, the vibration of the vibrating body 10 will be described. The vibrating body 10 excites stretching vibration and bending vibration. 2A and 2B are views of the vibrating body 10 as viewed from above in the stacking direction of the piezoelectric elements. FIG. 2A shows the shape of bending vibration and FIG. 2B shows the shape of stretching vibration. In the stretching vibration, the central portion of the vibrating body 10 is a vibration node, and in the bending vibration, the central portion of the vibrating body 10 and three places on the left and right are the nodes of vibration. A support member 40 is provided on the side surface of the central portion of the vibrating body 10 that serves as a vibration node for both stretching vibration and bending vibration, and a protrusion 30 is provided at the position of the antinode of bending vibration. By simultaneously exciting the stretching vibration and bending vibration, the protrusion 30 performs an elliptical motion including displacement in the longitudinal direction of the vibrating body 10 and displacement in the width direction orthogonal to the longitudinal direction, and drives the moving body 60. Here, the first-order mode stretching vibration and the second-order bending vibration have been described, but the order of each vibration mode is not limited, and different vibration modes may be used. It is possible to operate.

  Next, the specific structure, polarization direction, and electrode arrangement of the vibrating body 10 will be described. The vibrating body 10 is configured by stacking four types of piezoelectric elements 11, 12, 13, and 14 in the thickness direction. Here, the order of stacking the piezoelectric elements is 14, 12, 13, 11, 13, 11, 13, 12, 13. Note that the order of stacking the piezoelectric elements is that the unit of the piezoelectric element 11 and the piezoelectric element 13 and the group of the piezoelectric element 12 and the piezoelectric element 13 are stacked except for the piezoelectric element 14 being the top. It can be configured by changing the order in which they are performed or changing the number of sets. As an example of the configuration example, even if the piezoelectric elements 14, 12, 13, 11, and 13 are stacked in the order of the piezoelectric elements 14, 12, 13, 11, 13, 12, and 13, the vibrating body 10 Can be configured.

  Here, each piezoelectric element will be described individually. An internal electrode or a top electrode as shown in FIG. 3 is formed on the surface of each piezoelectric element, and no electrode is formed on the back surface. The piezoelectric element 11 is polarized in the thickness direction throughout. As described above, the piezoelectric element 11 is always paired with the piezoelectric element 13, and the piezoelectric element 11 is laminated on the piezoelectric element 13, so that the piezoelectric element 11 is connected to the internal electrode 81 provided on the surface of the piezoelectric element 11. It is provided between the internal electrode 83 provided on the surface of the piezoelectric element 13. Therefore, when a drive signal is applied between the internal electrode 81 and the internal electrode 83, the piezoelectric element 11 excites stretching vibration in the longitudinal direction.

  In addition, the piezoelectric element 12 is formed by connecting the centers of the length and width, and approximately four regions are polarized in the thickness direction. In addition, as indicated by + or − in the figure, there are two types of polarization directions in one piezoelectric element. Similarly to the above-described piezoelectric element 11, the piezoelectric element 12 is always paired with the piezoelectric element 13, and the piezoelectric element 12 is laminated on the piezoelectric element 13, so that the piezoelectric element 12 is provided on the surface of the piezoelectric element 12. It is provided between the internal electrodes 82 a, 82 b, 82 c, 82 d and the internal electrode 83 provided on the surface of the piezoelectric element 13. Therefore, when a drive signal is applied between the internal electrodes 82a, 82b, 82c, 82d and the internal electrode 83, bending vibration is excited in a plane orthogonal to the thickness direction of the piezoelectric element 12.

  The piezoelectric element 14 is provided with upper surface electrodes 841, 842 a, 842 b, 842 c, 842 d, and 843. These are electrically connected to short-circuit electrodes 881, 882 a, 882 b, 882 c, 882 d, and 883 provided on the side surface of the vibrating body 10. Therefore, the upper electrode 841 is the electrode 81 through the short-circuit electrode 881, the upper electrode 842a is the internal electrode 82a through the short-circuit electrode 882a, the upper electrode 842b is the electrode 82b through the short-circuit electrode 882b, and the upper electrode 842c is the electrode 82c through the short-circuit electrode 882c. The upper surface electrode 842d is electrically connected to the electrode 82d through the short circuit electrode 882d, and the upper surface electrode 843 is electrically connected to the electrode 83 through the short circuit electrode 883. Therefore, a drive signal can be supplied to each of the internal electrodes 81, 82a, 82b, 82c, 82d, 84 only by applying a drive signal to the upper surface electrodes 841, 842a, 842b, 842c, 842d, 843. In addition, about formation of a short circuit electrode, after laminating | stacking and integrating a piezoelectric element, it is possible to form by vapor deposition of metal film, sputtering, or application | coating of a conductive adhesive.

  Here, a pair of the internal electrode and the short-circuit electrode to be short-circuited is determined, and therefore, a blank portion where no internal electrode is provided is necessary for each piezoelectric element so as not to short-circuit other than the determined pair. However, since this blank portion does not contribute to excitation of the piezoelectric element, it is better not to install the blank portion and to provide the internal electrode on the entire surface from the viewpoint of obtaining a larger vibration energy as an output. However, in order to drive the ultrasonic motor 1000, it is necessary to apply different drive signals to the internal electrode 81 and the internal electrodes 82a, 82b, 82c, and 82d, and the blank portion must be installed.

  Therefore, the relationship between the arrangement of the internal electrode and the blank portion and the output of the piezoelectric element is shown in FIGS. FIG. 4 shows the arrangement of the internal electrode and the blank portion for exciting the stretching vibration, and FIG. 5 shows the change of the electromechanical coupling coefficient k due to the arrangement of the internal electrode and the blank portion for exciting the bending vibration. It is obtained from the numerical analysis by. 4A and 5A show internal electrodes (shaded areas) for the piezoelectric element, and FIGS. 4B and 5B show the length X of the internal electrodes (described in the figure). The change of k with respect to is shown. Here, an electro-mechanical coupling coefficient k is used as an index indicating the output of the piezoelectric element. This is the dynamic conversion efficiency between applied electrical energy as input and output vibration energy.

  From the result of FIG. 4B, even if the length of the internal electrode for exciting the stretching vibration is slightly shortened, k is almost flat or slightly increased. Further, as a result of FIG. 5B, the inner electrode for exciting the flexural vibration has the outermost node of the flexural vibration (X = 7.3 mm, indicated by A in the figure) when the length of the internal electrode is shortened. After that, the k, which was almost flat, started to decrease. Therefore, in the laminated piezoelectric element of the ultrasonic motor 1000 of the present invention, the marginal portion of the internal electrode is a long longitudinal end portion of two sides, particularly the marginal portion of the internal electrode that excites bending vibration is bent. It was arranged to be provided on the end side in the longitudinal direction from the outermost node of vibration. Thereby, the vibration energy which is an output can be obtained efficiently.

  From the results of FIGS. 4 and 5, when the arrangement of each blank portion is determined, the arrangement of the short-circuit electrodes is limited. And the short circuit electrode will be arrange | positioned in the position which provided the blank part. However, it is necessary to determine each arrangement so as not to cause a short circuit other than the set of the predetermined internal electrode and short circuit electrode. FIG. 3 shows an example of the arrangement of the internal electrodes and blank portions that are not short-circuited except for the desired set.

  The marginal portion 100 of the internal electrodes 81 and 83 is provided on the end surface side in the longitudinal direction from the outermost node of the bending vibration (the node farthest from the center of the piezoelectric element), and the short-circuit electrodes 881 and 883 that are electrically connected to the internal electrodes 81 and 83 are long. It is provided on the side surface on the direction end surface side. Further, the internal electrodes 82a, 82b, 82c, and 82d are provided from the outermost node of the bending vibration to the end surface in the longitudinal direction, and the blank portion 100 is provided on the end surface in the longitudinal direction so that the internal electrodes 81 and 83 are not electrically connected. . The short-circuit electrodes 882a, 882b, 882c, and 882d that are electrically connected to the internal electrodes 82a, 82b, 82c, and 82d, respectively, are disposed on the side surface on the end face side in the width direction of the piezoelectric element and outside the node of the bending vibration. This makes it possible to reduce the influence on excitation without causing a short circuit other than the set of the predetermined internal electrode and short circuit electrode.

FIG. 6 shows an example of the arrangement of internal electrodes and short-circuit electrodes different from the above. Unlike the above, short-circuit electrodes 882a ′, 882b ′, 882c ′, and 882d ′ that are electrically connected to the internal electrodes 82a ′, 82b ′, 82c ′, and 82d ′ that excite bending vibration are provided on the side surface of the end portion in the longitudinal direction of the multilayer piezoelectric element. The arrangement was provided. Even with such a configuration, since the blank portion 100 ′ can be concentrated on the end surface side in the longitudinal direction, the same effect as the arrangement of FIG. 3 can be obtained.
By arranging the blank portion and the short-circuit electrode as described above, the influence on the excitation of the piezoelectric element is reduced, and high efficiency and high output can be realized.

Next, a method for driving the ultrasonic motor 1000 will be described. When a signal having a predetermined frequency is applied between the upper surface electrodes 841 and 843, the piezoelectric element 11 constituting the vibrating body 10 is subjected to stretching vibration, and has a predetermined frequency between the upper surface electrodes 842a, 842b, 842c, 842d and 843. When a signal is applied, bending vibration is generated in the piezoelectric element 12. Therefore, by changing the phase of the drive signal applied between the upper surface electrodes 841 and 843 and the drive signal applied between the upper surface electrodes 842a, 842b, 842c, 842d and 843, the protrusion 30 provided on the vibrating body 10 is changed. The elliptical motion is performed in a plane orthogonal to the thickness direction of the vibrating body 10. Then, due to this elliptical motion, the moving body 60 in pressure contact with the protrusion 30 moves. By reversing the phase difference between the two signals, the direction of the elliptical motion is also reversed, so that the moving body can control the moving direction in two forward and reverse directions.
As described above, since the vibration of the vibrating body 10 can be used without weakening, the ultrasonic motor 1000 with high efficiency and high output can be realized.

(Embodiment 2)
FIG. 7 shows a vibrator 210 of the ultrasonic motor of the present invention. 7A is a three-sided view of the vibrating body 210, and FIG. 7B is a diagram illustrating a specific structure, polarization direction, and electrode arrangement of the piezoelectric elements 211, 212, 213, and 214 constituting the vibrating body 210. It is. Only differences from the first embodiment will be described below.

In the vibrating body 210 shown in FIG. 7, a plurality of piezoelectric elements 211, 212, 213, and 214 are stacked in the thickness direction as in the first embodiment. The difference from the first embodiment is that the piezoelectric element 211 corresponds to the piezoelectric element 11, the piezoelectric element 212 corresponds to the piezoelectric element 12, the piezoelectric element 213 corresponds to the piezoelectric element 13, and the piezoelectric element 214 corresponds to the piezoelectric element 14. Further, a blank portion 120 is provided at the center in the longitudinal direction and at the end in the width direction of all the internal electrodes. Then, a short-circuit electrode 2883 that is short-circuited with the internal electrode 283 and a short-circuit electrode that is short-circuited with the internal electrode 281 (not shown, disposed opposite to the short-circuit electrode 2883) are central portions on the side surfaces orthogonal to the width direction of the vibrator 210. Provided.
By arranging such an internal electrode, a blank portion, and a short-circuit electrode, it is possible to concentrate the blank portion on the end portion in the longitudinal direction that has little influence on the excitation of the vibrating body 210 and to use electric energy with high efficiency. . This is because the central portion in the longitudinal direction of the vibrating body 210 hardly contributes to the excitation of the bending vibration, and the area of the margin is made as small as possible so as not to affect the excitation.

(Embodiment 3)
FIG. 8 shows a vibrating body 310 of the ultrasonic motor of the present invention. FIG. 8A is a perspective view of the vibrating member 310, and FIG. 8B is a diagram illustrating a specific structure, polarization direction, and electrode arrangement of the vibrating member 310. FIG. Only differences from the first embodiment will be described below.

  In the vibrating body 310 illustrated in FIG. 8, a plurality of piezoelectric elements 311, 312, and 313 are stacked in the thickness direction as in the first embodiment. The vibrating element 310 is configured by stacking the piezoelectric elements 311 and 312 alternately with the piezoelectric element 313 at the top. The difference from the first embodiment is that the polarization direction of the piezoelectric element 311 is one direction, and that bending vibration and expansion / contraction vibration can be excited simultaneously only by the piezoelectric elements 311 and 312. Here, among the upper surface electrodes 3841a, 3841b, 3841c, and 3841d that are electrically connected to the internal electrodes 381a, 381b, 381c, and 381d, a drive signal that is applied to the upper surface electrodes 3841a and 3841d and a drive signal that is applied to the upper surface electrodes 3841b and 3841c are provided. Let them be a COS wave and a SIN wave, respectively.

  As a result, the vibrating body 310 can excite stretching vibration and bending vibration at the same time, and can generate an elliptical motion at a specific position of the vibration. When generating an inverted elliptic motion, the phase difference of each drive signal may be provided in reverse. In addition, as shown in the first embodiment, since the blank portion is provided in a place where the influence on the excitation of the vibrating body 310 is small, it is possible to use electric energy with high efficiency.

By the way, as another driving method of the vibrating body 310 of this configuration, a signal may be applied to only two diagonal internal electrodes to simultaneously excite bending vibration and stretching vibration. That is, the moving direction of the moving body can be changed by applying a signal only to the upper surface electrodes 3841a and 3841d or applying a signal only to the upper surface electrodes 3841b and 3841c.
(Embodiment 4)
An example in which an electronic apparatus is configured using the ultrasonic motor of the present invention is shown in FIG.

  FIG. 9 is a block diagram in which the ultrasonic motor 1000 driven by the drive circuit of the present invention is applied to a drive source of an electronic device. A movable mechanism 90 that operates integrally with a moving body 60 that is frictionally driven by a protrusion 30 provided on the vibrating body 10, a drive control device 103 that applies a drive signal to the vibrating body, and a measuring device that measures the amount of movement of the movable mechanism 90. 102. Here, an example of an automatic stage that uses the movable mechanism 90 as a stage and positions it at a predetermined position will be described.

  Here, the measuring apparatus 102 uses, for example, an optical encoder. The drive control device 103 recognizes the current position of the movable mechanism 90 from the measuring device 102 and moves the movable mechanism 90 in the direction of the target position. If the current position and the target position from the measuring device 102 coincide with each other within a predetermined range, the drive signal input is stopped.

  Note that the electronic apparatus in this embodiment can be applied to a printer, a machine tool, or the like in addition to an automatic stage.

  If the movable body of the ultrasonic motor of the present invention is directly provided with a movable stage or the operation of the movable body is transmitted via a transmission mechanism, an automatic stage, a zoom mechanism of a camera, an autofocus mechanism, a paper feeding device, or It can be applied to electronic devices such as watches.

It is a figure which shows the structure of the ultrasonic motor which concerns on this invention. It is explanatory drawing which shows the vibration mode of the vibrating body of the ultrasonic motor which concerns on this invention. It is a figure which shows the structure of the vibrating body of the ultrasonic motor which concerns on this invention. It is a figure which shows the influence on the excitation force by arrangement | positioning of an internal electrode (stretching vibration). It is a figure which shows the influence on the excitation force by arrangement | positioning of an internal electrode (bending vibration). It is a figure which shows the structure of the other vibrating body of the ultrasonic motor which concerns on this invention. It is a figure which shows the structure of the other vibrating body of the ultrasonic motor which concerns on this invention. It is a figure which shows the structure of the other vibrating body of the ultrasonic motor which concerns on this invention. It is a figure which shows the electronic device using the ultrasonic motor which concerns on this invention.

Explanation of symbols

1000 Ultrasonic motor 10, 10 'Vibrating body 11, 11' Piezoelectric element (stretching vibration)
12, 12 'Piezoelectric element (flexural vibration)
13, 14, 13 ', 14' Piezoelectric element 30 Protrusion 40 Support member 50 Guide member 60 Moving body 70 Pressure member 81, 81 'Internal electrode (stretching vibration)
82a, 82b, 82c, 82d Internal electrode (flexural vibration)
82a ', 82b', 82c ', 82d' Internal electrode (flexural vibration)
83, 83 'Internal electrode (ground)
90 Movable mechanism 100, 100 ′, 101, 120, 130 Margin 102 Measurement device 103 Drive control device 210 Vibrating bodies 211, 212, 213, 214 Piezoelectric elements 281, 282a, 282b, 282c, 282d, 283 Internal electrode 310 Vibrating body 311, 312, 313 Piezoelectric element 381 a, 381 b, 381 c, 381 d, 382 Internal electrode 841, 841 ′, 842 a, 842 b, 842 c, 842 d, 842 a ′, 842 b ′, 842 c ′, 842 d ′, 843, 843 ′ Upper surface electrode 881 Short-circuit electrodes 882a, 882b, 882c, 882d, 882c ', 882d' Short-circuit electrodes 883, 883 'Short-circuit electrodes 2841, 2842a, 2842b, 2842c, 2842d, 2843 Top-surface electrodes 2882b, 2882d, 2883 Short-circuit electrodes 3841a, 384 b, 3841c, 3841d, 3842 upper electrode 3881b, 3881d, 3882 short-circuit electrode

Claims (7)

Ri Do a laminated piezoelectric element of rectangular shape, and the longitudinal direction orthogonal and vibrator for generating an orthogonal direction to the secondary bending vibration of the stacking direction of the piezoelectric element as well as the stretching vibration of the primary in the longitudinal direction, and the In an ultrasonic motor provided with a movable body that is in contact with a protrusion provided on a vibrating body and is moved in accordance with the vibration of the vibrating body,
The vibrating body has at least a short-circuit electrode that conducts internal electrodes for exciting bending vibration on the side surface of the vibrating body in the width direction and on the end surface side in the longitudinal direction from the outermost node of the bending vibration. And an ultrasonic motor. Ri Do a laminated piezoelectric element of rectangular shape, and the longitudinal direction orthogonal and vibrator for generating an orthogonal direction to the secondary bending vibration of the stacking direction of the piezoelectric element as well as the stretching vibration of the primary in the longitudinal direction, and the In an ultrasonic motor provided with a movable body that is in contact with a protrusion provided on a vibrating body and is moved in accordance with the vibration of the vibrating body,
The bending vibration is a vibration in a plane orthogonal to the stacking direction of the multilayer piezoelectric element,
The vibrating body has at least a short-circuit electrode on the side surface of the longitudinal end surface of the piezoelectric element for conducting internal electrodes of the piezoelectric element for exciting flexural vibration, and has a blank portion on two surfaces in the stacking direction of the piezoelectric element. An ultrasonic motor characterized by being provided only on a longitudinal end face side of the vibrating body.   A short-circuit electrode that conducts at least internal electrodes for exciting stretching vibration is provided on the side surface of the vibrating body in the width direction and on the end surface in the longitudinal direction from the outermost node of the bending vibration. The ultrasonic motor according to claim 1.   A short-circuit electrode that at least connects the internal electrodes of the piezoelectric element for exciting the stretching vibration is provided on the side surface of the longitudinal end surface of the vibrating body, and the blank portions on the two surfaces in the stacking direction of the piezoelectric element are provided on the vibrating body. The ultrasonic motor according to claim 1, wherein the ultrasonic motor is provided only on an end surface side in the longitudinal direction.   3. The ultrasonic motor according to claim 1, wherein a short-circuit electrode that conducts at least internal electrodes for exciting expansion and contraction vibration is provided at a central portion in a longitudinal direction of the vibrating body.   6. The internal electrode according to claim 1, wherein the internal electrode is provided in a region surrounded by at least an outermost node portion of bending vibration of the vibrating body and an end portion in a width direction of the vibrating body. The described ultrasonic motor.   An electronic apparatus with an ultrasonic motor, wherein the movable mechanism is driven using the ultrasonic motor according to claim 1 as a drive source.

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