JP6649729B2 - Vibration wave motor - Google Patents

Description

  The present invention relates to a vibration wave motor, and more particularly to a linear vibration wave motor having an elastic body in a plate shape.

  2. Description of the Related Art Conventionally, a vibration wave motor characterized by small size, light weight, high-speed drive, and silent drive has been employed in a lens barrel of an image pickup apparatus. Among these, regarding a vibration wave motor for linear driving, Patent Document 1 discloses the following vibration wave motor.

  The vibration wave motor disclosed in Patent Literature 1 includes a vibration plate having a protrusion, a piezoelectric element that vibrates at a high frequency, and a friction member that presses and presses the protrusion of the vibration plate. This vibration wave motor resonates the diaphragm by high frequency vibration of the piezoelectric element. The driving force is obtained by the elliptical movement of the tip of the protrusion caused by this, and the diaphragm relatively moves with respect to the friction member.

JP 2013-223406 A

  However, the vibration wave motor disclosed in Patent Literature 1 has a problem that the driving efficiency is reduced because the protrusion of the diaphragm does not stably contact the friction member. In the vibration wave motor disclosed in Patent Literature 1, two protrusions on the diaphragm are provided side by side in the relative movement direction. In such a configuration, since the projection of the diaphragm cannot stably contact the friction member, when a dimensional tolerance or assembly tolerance of a component or an external force is generated, the diaphragm is centered on a straight line connecting two contact points. An axial inclination occurs. As a result, unevenness in the wear of the projections and unevenness in the pressure applied to the diaphragm are generated, so that the driving efficiency is reduced.

  Accordingly, an object of the present invention is to achieve an improvement in driving efficiency by stably bringing a protrusion into contact with a friction member.

In order to solve the above problems, a vibration wave motor according to the present invention includes a diaphragm having a plate portion, at least three protrusions provided on the plate portion, and a high frequency fixed to the diaphragm. a piezoelectric element which vibrates, can contact a plurality of the protrusions is pressurized, anda friction member to which the oscillating movable plate relative to said diaphragm, said by the high-frequency vibration of the piezoelectric element A second-order natural vibration mode of bending vibration in a relative movement direction in which the diaphragm and the friction member relatively move, and a second-order natural vibration of bending vibration in a direction orthogonal to the relative movement direction and the pressing direction of the vibration plate. mode is excited, the plurality of the protrusions, in a plane perpendicular to the pressing direction, is not provided on the straight line parallel to the street the relative movement direction center of the plate portion, one side sandwiching the straight line And at least one on the other side Serial provided on belly near the second-order natural oscillation mode of the relative moving direction of the bending section near and the perpendicular direction of the second-order natural oscillation mode of the oscillating bending vibration,
The one side projection and the other side projection are provided near different antinodes of the secondary mode of the bending vibration in the orthogonal direction .

  According to the present invention, by stably bringing the protrusion into contact with the friction member, driving is stabilized, and driving efficiency is improved.

It is a figure explaining the composition of the vibration wave motor of an embodiment of the present invention. It is a mimetic diagram explaining deformation of a diaphragm and a piezoelectric element in a natural vibration mode of an embodiment of the present invention. It is a mimetic diagram explaining deformation of a diaphragm and a piezoelectric element in a natural vibration mode of an embodiment of the present invention. 4 is a graph and a table illustrating an AC voltage applied to the piezoelectric element and deformation of the diaphragm and the piezoelectric element according to the embodiment of the present invention. FIG. 5 is a schematic diagram illustrating a state of vibration of a diaphragm when an AC voltage is applied according to the embodiment of the present invention. FIG. 5 is a schematic diagram illustrating a state of vibration of a diaphragm when an AC voltage is applied according to the embodiment of the present invention. FIG. 5 is a perspective view illustrating a state of vibration of the diaphragm according to the embodiment of the present invention. It is a schematic diagram explaining the elliptical motion of the front-end | tip of the protrusion part of embodiment of this invention. It is a figure explaining the size of the board part of an embodiment of the present invention. 5 is a graph illustrating the relationship between the frequency and the amplitude of the elliptical motion according to the embodiment of the present invention. It is a figure explaining a linear drive using a vibration wave motor of an embodiment of the present invention. It is a bottom view explaining the positional relationship of the press point and the protrusion part of embodiment of this invention. 1 is a schematic diagram illustrating a lens driving device using a vibration wave motor according to an embodiment of the present invention. It is a schematic diagram explaining the composition of the vibration wave motor of the conventional example. It is the schematic explaining the linear drive device using the vibration wave motor of the conventional example.

  Hereinafter, an embodiment for carrying out the present invention will be described with reference to the accompanying drawings. In the drawings, the same members are denoted by the same reference numerals.

(Embodiment)
Hereinafter, embodiments of the present invention will be described. In the present specification, the direction in which the diaphragm 1 and the friction member 3 described later relatively move is referred to as an X direction, and the pressing direction in which the diaphragm 1 described below is pressed against the friction member 3 is referred to as a Z direction. In the Z direction, the direction from the later-described diaphragm 1 to the later-described friction member 3 is defined as a + Z direction, and the direction from the later-described friction member 3 to the later-described diaphragm 1 is defined as a −Z direction. Also, a direction orthogonal to the X direction and the Z direction is defined as a Y direction.

  1A and 1B are diagrams for explaining a basic configuration of a vibration wave motor according to an embodiment of the present invention. FIG. 1A is a plan view, FIG. 1B is a front view, and FIG. c) is a side view, and FIG. 1 (d) is a bottom view. In FIG. 1, the diaphragm 1 has a rectangular flat plate portion 1a, and three projections 1b1, 1b2, and 1b3 provided on the plate portion 1a. The projections 1b1, 1b2, and 1b3 may be formed integrally with the plate 1a by drawing, or another member may be fixed to the plate 1a by bonding.

  The protrusions 1b1, 1b2 and 1b3 are composed of a body provided on the plate 1a and spherical sliding portions 1c1, 1c2 and 1c3 for abutting and sliding on a friction member 3 described later. You. The sliding portions 1c1, 1c2, and 1c3 are provided to protrude from the tips of the protrusions 1b1, 1b2, and 1b3, respectively. The sliding portions 1c1, 1c2, and 1c3 are not limited to spherical projections, but may have columnar or truncated cone projections.

  Connecting portions 1d and 1e which move in synchronization with the diaphragm 1 and are directly or indirectly connected to a diaphragm holding member to be described later at the end of the rectangular plate portion 1a of the diaphragm 1. Is provided. The connecting portions 1d and 1e are provided in portions where the displacement of the vibration of the diaphragm 1 and the piezoelectric element 2 is small, and have a sufficiently low rigidity, so that they have a shape that does not hinder the vibration. Therefore, the connecting portions 1 d and 1 e hardly affect the vibration of the diaphragm 1 and the piezoelectric element 2.

  A piezoelectric element 2 that vibrates at a high frequency is fixed to the diaphragm 1. As shown in FIG. 1A, the piezoelectric element 2 moves in a direction in which a diaphragm 1 and a friction member 3 described later move relative to each other (hereinafter, referred to as a “relative moving direction”; an X direction in FIG. 1A). The piezoelectric element 2 is further divided in two in a direction parallel to the plate portion 1a and perpendicular to the direction of relative movement (hereinafter, referred to as an “orthogonal direction”; Y direction in FIG. 1A). Is divided into two. Therefore, the area is divided into four areas 2a1, 2a2, 2b1 and 2b2 in total.

  Of the four regions, regions 2a1 and 2b1 are polarized in the same direction, and regions 2a2 and 2b2 are polarized in the opposite direction to regions 2a1 and 2b1. The piezoelectric element 2 is divided into four regions 2a1, 2a2, 2b1 and 2b2 divided into two in each of the relative movement direction and the orthogonal direction. Therefore, the regions 2a1 and 2b2 and the regions 2a2 and 2b1 located on the diagonal lines are polarized in opposite directions. As shown in FIG. 2A, the regions 2a1 and 2b2 are assigned to the A phase, and the regions 2a2 and 2b1 are assigned to the B phase. The piezoelectric element 2 further includes an unpolarized region 2c. The region 2c is an electrode used as a ground that is conducted from the entire surface electrode of the back surface 2e of the piezoelectric element 2 through the electrode of the region 2d arranged on the side surface.

  As described above, the vibration wave motor 10 is configured by the vibration plate 1 and the piezoelectric element 2. Next, deformation of the vibration plate 1 and the piezoelectric element 2 caused by high-frequency vibration of the piezoelectric element 2 will be described.

  The high frequency vibration generated in the piezoelectric element 2 excites the diaphragm 1 in a specific natural vibration mode. Due to the high-frequency vibration of the piezoelectric element 2, the second natural vibration mode (hereinafter referred to as “mode 1”) of the bending vibration in the orthogonal direction of the vibration plate 1 and the bending vibration in the relative movement direction of the vibration plate 1. Is excited (hereinafter referred to as “mode 2”).

  2 and 3 are schematic diagrams showing deformation of the diaphragm 1 and the piezoelectric element 2 when the mode 1 and the mode 2 of the diaphragm 1 are excited, respectively. For simplicity, the projections 1b1, 1b2 and 1b3 of the diaphragm 1, the sliding parts 1c1, 1c2 and 1c3, the connecting parts 1d and 1e, and the region 2c are omitted. 2 (a) and 3 (a) are plan views, FIGS. 3 (b) and 3 (c) are front views, and FIGS. 2 (b) and 2 (c) are side views. (A), FIG. 1 (b), and FIG. 1 (c). Of the regions of the piezoelectric element 2, the regions 2a1 and 2b1 are defined as a region A, the regions 2a2 and 2b2 as a region B, the regions 2a1 and 2a2 as a region C, and the regions 2b1 and 2b2 as a region D, respectively.

  The shapes of the vibration plate 1 and the piezoelectric element 2 when the mode 1 of the vibration plate 1 is excited will be described with reference to FIGS. 2B and 2C. FIGS. 2B and 2C show a state in which the regions 2a1 and 2b1 of the region A, the regions 2a2 and 2b2 of the region B are deformed in the same direction, and the regions A and B are deformed in the opposite directions. That is, a state in which the mode 1 of the diaphragm 1 is excited is shown. Defining the case of deformation in the + Z direction as a deformation in the + direction is defined as a deformation in the + direction. FIG. , The region B is deformed in the + direction.

  Similarly, the shapes of the diaphragm 1 and the piezoelectric element 2 when the mode 2 of the diaphragm 1 is excited will be described with reference to FIGS. 3B and 3C. FIGS. 3B and 3C show a state in which the regions 2a1 and 2a2 of the region C, the regions 2b1 and 2b2 of the region D are deformed in the same direction, and the regions C and D are deformed in the opposite directions. That is, the state in which the mode 2 of the diaphragm 1 is excited is shown. FIG. 3B illustrates a case where the region C is deformed in the + direction and the region D is deformed in the − direction. FIG. 3C illustrates a case where the region C is deformed in the − direction and the region D is deformed in the + direction.

  FIG. 4 is a graph and a table for explaining the AC voltage applied to the piezoelectric element 2 and the deformation of the diaphragm 1 and the piezoelectric element 2. FIG. 4A is a graph showing a change in the AC voltage applied to the A phase and the B phase of the piezoelectric element 2, and FIG. 4B shows the sign of the voltage applied to each area 2a1, 2a2, 2b1, and 2b2. FIG. 4C is a table showing the deformation directions of the regions 2a1, 2a2, 2b1, and 2b2.

  As described above, the regions 2a1 and 2b1 are polarized in the + direction, the regions 2a2 and 2b2 are polarized in the-direction, and the regions 2a1 and 2b2 are assigned to the A phase, and the regions 2a2 and 2b1 are assigned to the B phase. ing. Here, "polarized in the + direction" means that a deformation of the same sign as the applied voltage occurs, and "polarized in the-direction" means a deformation of the opposite sign to the applied voltage. Is defined as occurring. For example, when polarized in the + direction, it deforms in the + direction when a + voltage is applied, and when polarized in the-direction, it deforms in the-direction when a + voltage is applied. I do.

  As shown in FIG. 4A, the AC voltage in the regions 2a1, 2a2, 2b1, and 2b2 during the time from P1 to P4 when the AC voltage is applied with the phase of the B phase delayed by about + 90 ° with respect to the A phase. The reference numerals are as shown in FIG. Here, the regions 2a1 and 2b1 polarized in the + direction cause the deformation of the same sign as the voltage shown in FIG. 4B, and the regions 2a2 and 2b2 polarized in the-direction are the voltages shown in FIG. The opposite sign transformation occurs. That is, when the voltage shown in FIG. 4B is applied to each of the regions 2a1, 2a2, 2b1, and 2b2 at times P1 to P4, the regions 2a1, 2a2, 2b1, and 2b2 are applied at times P1 ′ to P4 ′. The deformation in the direction shown in FIG. Note that the times P1 'to P4' are times with a predetermined delay from the times P1 to P4, respectively.

  Here, at time P1 ', 2a1 and 2a2 deform in the + direction, and 2b1 and 2b2 deform in the-direction. That is, since the area C shown in FIG. 3A is deformed in the + direction and the area D is deformed in the-direction, the diaphragm 1 and the piezoelectric element 2 are deformed as shown in FIG. 3B. Similarly, a deformation as shown in FIG. 2B occurs at time P2 ', a deformation as shown in FIG. 3C at time P3', and a deformation as shown in FIG. 2C at time P4 '. That is, as shown in FIG. 4A, when an AC voltage is applied to the piezoelectric element 2 with the phase of the B phase delayed by about + 90 ° with respect to the A phase, the shapes of the diaphragm 1 and the piezoelectric element 2 are changed as shown in FIG. (B), FIG. 2 (b), FIG. 3 (c), and FIG. 2 (c).

  Hereinafter, the elliptic motion generated on the protrusions 1b1, 1b2, and 1b3 of the diaphragm 1 due to the high frequency vibration of the piezoelectric element 2 will be described.

  First, positions where the protrusions 1b1, 1b2, and 1b3 of the diaphragm 1 are provided will be described. As shown in FIG. 1D, the protrusions 1b1 and 1b2 are near the antinode of mode 1 (X1 in FIG. 1D) and at the nodes of mode 2 (Y1 and X1 in FIG. 1D). Y3). The protrusion 1b3 is provided near the antinode of Mode 1 (X2 in FIG. 1D) and near the node of Mode 2 (Y2 in FIG. 1D). That is, the three protrusions 1b1, 1b2, and 1b3 are provided near the nodes of the secondary mode of the bending vibration in the relative movement direction and near the antinodes of the secondary mode of the bending vibration in the orthogonal direction.

  FIGS. 5 and 6 are schematic diagrams showing the state of vibration of diaphragm 1 when an AC voltage is applied with the phase of phase B delayed about + 90 ° with respect to phase A, and FIG. 5 shows projections 1b1 and 1b2. FIG. 6 is a schematic diagram for explaining the trajectory of the tip of the protrusion 1b3. In each figure, FIGS. 5 (a) and 5 (b), FIGS. 6 (a) and 6 (b) correspond to FIGS. 1 (c) and 1 (b), respectively, and FIG. The vibration state at times P1 'to P4' with a predetermined delay from the indicated AC voltages P1 to P4 is shown. 5 and 6, the sliding portions 1c1, 1c2 and 1c3, the connecting portions 1d and 1e, and the piezoelectric element 2 are omitted for simplicity, and in FIG. In FIG. 6, the projections 1b1 and 1b2 are not shown.

First, the trajectories of the tips of the protrusions 1b1 and 1b2 will be described with reference to FIG. As described above, when the AC voltage as shown in FIG. 4A is applied, the diaphragm 1 and the piezoelectric element 2 are shown in FIGS. 3B and 3C at times P1 ′ and P3 ′. Such deformation occurs. As a result, the mode 2 is excited, and the X-direction amplitudes at the tips of the protrusions 1b1 and 1b2 are maximized (A ₂ in FIG. 5B). Further, when an AC voltage as shown in FIG. 4A is applied, the diaphragm 1 and the piezoelectric element 2 at the times P2 'and P4' as shown in FIGS. 2B and 2C. Causes deformation. As a result, the mode 1 is excited, and the Z-direction amplitude of the tips of the protrusions 1b1 and 1b2 is maximized (A ₁ in FIG. 5A). Therefore, when an AC voltage is applied with the phase of the phase B delayed by about + 90 ° with respect to the phase A, elliptic motions are generated at the tips of the protrusions 1b1 and 1b2 as indicated by arrows in FIG. .

Similarly, the trajectory of the tip of the protrusion 1b3 will be described with reference to FIG. When an AC voltage as shown in FIG. 4A is applied, mode 2 is excited in the vibration plate 1 and the piezoelectric element 2 at times P1 ′ and P3 ′, and the amplitude in the X direction at the tip of the protrusion 1b3. Is the maximum (A ₂ in FIG. 6B). Further, the diaphragm 1 and the mode 1 to the piezoelectric element 2 is excited at the time P2 'and P4', Z direction amplitude of the tip of the projection portion 1b3 is maximized (A ₁ in FIG. 6 _(a)). Therefore, when an AC voltage is applied with the phase of the phase B delayed by about + 90 ° with respect to the phase A, elliptic motions are generated at the tips of the protrusions 1b3 as indicated by arrows in FIG. 6B.

  As described above, the application of the AC voltage to the A-phase and the B-phase causes elliptic motion at the tips of the protrusions 1b1, 1b2, and 1b3, respectively. The sliding portions 1c1, 1c2, and 1c3 abut against a friction member 3 described below in a state where the sliding portions 1c1, 1c2, and 1c3 are pressurized. For this reason, the diaphragm 1 obtains the propulsive force by the friction between the friction member 3 described later and the sliding portions 1c1, 1c2, and 1c3 caused by the elliptical motion of the projections 1b1, 1b2, and 1b3, and the propulsion force is obtained, as shown in FIGS. (B) can be relatively moved in the X direction.

  When an AC voltage is applied with the phase of the B phase delayed by about + 270 ° with respect to the A phase, an elliptical motion in the direction opposite to that in FIG. 5 occurs. Therefore, the diaphragm 1 obtains the propulsive force by the friction between the friction member 3 described later and the sliding portions 1c1, 1c2, and 1c3 caused by the elliptical movement of the protrusions 1b1, 1b2, and 1b3, and the propulsion force is obtained, as shown in FIG. ) Can be relatively moved in the direction opposite to the X direction.

  As described above, in the vibration wave motor of the present embodiment, the vibration plate 1 can relatively move with respect to the friction member 3 described later by the elliptical motion generated in the protrusions 1b1, 1b2, and 1b3 due to the high frequency vibration.

  The phase of the elliptical motion generated at the tips of the protrusions 1b1, 1b2, and 1b3 will be described. FIG. 7A is a perspective view showing the diaphragm 1 in a state where the AC voltage is not applied, and FIG. 7B is a diagram showing the diaphragm 1 in the state where the AC voltage is applied from time P1 ′ to P4 ′. It is a perspective view which shows a mode of a vibration. In the figure, dotted lines Y1 to Y3 indicate nodes of mode 2, and dashed lines X1 and X2 indicate antinodes of mode 1. Note that the sliding portions 1c1, 1c2 and 1c3, the connecting portions 1d and 1e, and the piezoelectric element 2 are omitted for easy understanding of the description.

  As described above, as indicated by arrows in FIG. 7B, mode 1 is excited in the diaphragm 1 and the piezoelectric element 2 at times P1 ′ and P3 ′, and at time P2 ′ and P4 ′, FIG. The mode 2 is excited in the diaphragm 1 and the piezoelectric element 2 as shown by the arrow in b). The directions of the displacements generated at the tips of the protrusions 1b1, 1b2, and 1b3 at each time will be described. At time P1 ', the protrusions 1b1 and 1b2 cause displacement in the -Z direction, and the protrusion 1b3 causes displacement in the + Z direction. At time P2 ', the projections 1b1 and 1b2 are displaced in the -X direction, and the projection 1b3 is displaced in the + X direction. At time P3 ', the protrusions 1b1 and 1b2 cause displacement in the + Z direction, and the protrusion 1b3 causes displacement in the -Z direction. At time P4 ', the projections 1b1 and 1b2 are displaced in the + X direction, and the projection 1b3 is displaced in the -X direction. As a result, the projection 1b3 always produces a displacement in the opposite direction with respect to the projections 1b1 and 1b2.

  FIG. 8 is a schematic diagram illustrating the elliptical movement of the tips of the protrusions 1b1, 1b2, and 1b3. FIG. 8A shows the protrusions 1b1 and 1b2, and FIG. 8B shows the elliptical movement of the tip of the protrusion 1b3. As described above, the protrusions 1b1, 1b2, and 1b3 are displaced in the Z direction at times P1 ′ and P3 ′, and are displaced in the X direction at times P2 ′ and P4 ′, and the protrusion 1b3 is moved relative to the protrusions 1b1 and 1b2. The displacement always occurs in the opposite direction. Therefore, the projection 1b3 undergoes an elliptical motion 180 degrees out of phase with the projections 1b1 and 1b2. Among the three projections, the phases of the elliptical motion of some of the projections 1b3 and the ellipse of the other projections 1b1 and 1b2 are shifted by 180 degrees.

  The dimensions (length) of the plate portion 1a of the diaphragm 1 in the relative movement direction and the orthogonal direction will be described below. 9A and 9B are diagrams for explaining the dimensions of the plate portion. FIG. 9A shows the dimensions of the plate portion 1a in the configuration of the embodiment of the present invention, and FIG. 9B shows a modification of the embodiment of the present invention. 3 shows the dimensions of the plate portion 101a. It should be noted that the connecting portions 1d and 1e are not shown in the figure for easy understanding.

In the first embodiment, the dimension L _{1X in} the relative movement direction (X direction in FIG. 9) and the dimension L _{1Y in the} orthogonal direction of the plate portion 101a shown in FIG. The dimension L _1X in the relative movement direction (X direction in FIG. 9) is smaller than the dimension L _{1Y in the} orthogonal direction.
L _1X <L _1Y (1)
That is, in the plate portion 1a, the dimension L _1X in the relative movement direction in which the diaphragm 1 and the friction member 3 relatively move is smaller than the dimension L _{1Y in the} direction perpendicular to the relative movement direction and the pressing direction of the diaphragm 1. .

On the other hand, in a modification of the embodiment of the present invention, the dimension L _{101X in} the relative movement direction and the dimension L _{101Y in the} orthogonal direction of the plate portion 101a shown in FIG. The dimension L _101X in the direction is larger than the dimension L _{101Y in the} orthogonal direction.
L _101X ≧ L _101Y (2)

  Here, the relationship between the amplitude and the frequency at the tip of the projection of the diaphragm when each mode is excited in each configuration will be described.

  FIG. 10 is a graph showing the relationship between the frequency f of the AC voltage and the amplitude A of the elliptical motion of the tips of the protrusions 1b1, 1b2, and 1b3. FIGS. 10A and 10C show the relationship between the frequency f and the amplitude A when the diaphragm 1 is in a free state in which the diaphragm 1 is not pressed in each of the embodiment and the modification of the present invention. FIGS. 10B and 10D show the relationship between the frequency f and the amplitude A in a state where the vibration plate 1 is pressed against the friction member 3 in the embodiment and the modified example of the present invention. I have.

Here, the relationship between the frequency f and the amplitude A in the embodiment of the present invention will be described. As shown in FIG. 10A, in the free state in which the diaphragm 1 is not pressed against the friction member 3, the mode 1 generated in the diaphragm 1 generates the amplitude A _1a in the Z direction at the resonance frequency _f1a. . The mode 2 generated in the vibration plate 1 produces the amplitude _{A 2a} in the X-direction at a resonance frequency _{f 2a.} As shown in FIG. 9A, in the embodiment of the present invention, the dimension L _{1Y in} the orthogonal direction is longer than the dimension L _{1X in the} relative movement direction. Since mode 1 and mode 2 are natural vibration modes due to bending of a flat plate, the resonance frequency becomes lower as the dimension in each direction is larger. Therefore, as shown in Expression (3), the resonance frequency f _1a of mode 1 in the orthogonal direction is lower than the resonance frequency f _2a of mode 2 in the relative movement direction.
f _1a <f _2a (3)

On the other hand, in the pressurized state in which the diaphragm 1 is pressed against the friction member 3, the pressing force acts so as to suppress the vibration generated in the diaphragm 1, so that the resonance frequency increases and the amplitude increases. Become smaller. As shown in FIG. 10B, the resonance frequencies _f1a and _f2a are higher than the resonance frequencies _f1a 'and _f2a ', respectively. Further, the amplitude A _1a and the amplitude A _2a are suppressed by the pressing force and become small as the amplitude A _1a ′ and the amplitude A _2a ′, respectively. Here, when the mode 1 is generated on the diaphragm 1, the protrusions 1b1, 1b2, and 1b3 generate the amplitude A _{1a in the} Z direction as described above, and when the mode 2 is generated on the diaphragm 1, as described above. projections 1b1,1b2 and 1b3 produces an amplitude _{a 2a} in the X direction. Since the pressing force when the diaphragm 1 is pressed against the friction member 3 is in the Z direction, when the diaphragm 1 is pressed, the amplitude A _1a in the Z direction is the same as the direction in which the pressing force is generated. The generated mode 1 is more greatly affected by the pressing force than the mode 2. Therefore, when the free state and the pressurized state are compared, the amount of change in the resonance frequency is larger in mode 1 than in mode 2. Therefore, equation (4) is obtained.
f _1a ′ −f _1a > f _2a ′ −f _2a (4)
From equations (3) and (4), the difference between the resonance frequencies f _2a -f _{1a of the} two natural vibration modes in the free state is calculated as shown in equation (5). The difference f _2a ′ −f _1a ′ between the resonance frequencies becomes smaller.
f _2a ′ −f _1a ′ <f _2a −f _1a (5)

Next, the relationship between the frequency f and the amplitude A in a modification of the embodiment of the present invention will be described. As shown in FIG. 9 (b), longer than the dimension _{L 101Y} better dimension _{L 101X} of the relative movement direction in the embodiment of the orthogonal directions of the present invention. Therefore, as shown in Expression (6), the resonance frequency f _2b of mode 2 in the relative movement direction is lower than the resonance frequency f _1b of mode 1 in the orthogonal direction.
f _1b > f _2b (6)

Further, as described above, when the free state and the pressurized state are compared, the amount of change in the mode 1 is larger than that in the mode 2, so that the equation (7) is obtained.
f _1b ′ −f _1b > f _2b ′ −f _2b (7)
From the expressions (6) and (7), the difference f _1b −f _2b between the resonance frequencies of the two natural vibration modes in the free state is compared with the difference f _1b ′ −f between the resonance frequencies of the two natural vibration modes in the pressurized state. _2b 'becomes larger. Therefore, equation (8) is obtained.
f _1b ′ −f _2b ′> f _1b −f _2b (8)

Here, the elliptical motion generated in the protrusions 1b1, 1b2, and 1b3 in the embodiment of the present invention will be considered. There driving frequency _{f ra} projections 1b1,1b2 and 1b3 Z direction amplitude _{A 1ra} by mode 1 to the AC voltage upon application of, the elliptical motion of the X-direction amplitude _{A 2ra} by mode 2 occurs. At this time, since the difference _{f 2a '-f 1a'} of the two resonant frequencies of the natural oscillation mode of the pressurized small, difference in amplitude _{A 2ra} of amplitudes _{A 1ra} and X direction of the Z-direction is reduced. For this reason, the protrusions 1b1, 1b2, and 1b3 generate an elliptical motion close to a circle having substantially the same amplitude in the Z direction and the X direction, and can be driven stably. On the other hand, in a modified example of the embodiment of the present invention, when an AC voltage having a certain driving frequency f _rb is applied, the difference f _1b ′ −f _2b ′ between the resonance frequencies of the two natural vibration modes in the pressurized state. Is larger, the difference between the amplitude A _{1rb in} the Z direction and the amplitude A _2rb in the X direction is larger. As a result, the protrusions 1b1, 1b2, and 1b3 undergo an elliptical motion that is not a circle but a long ellipse in the Z direction, and thus causes problems such as unstable driving and reduced driving efficiency.

As described above, in the embodiment of the present invention, the dimension L _1X in the relative movement direction of the plate portion 1a is smaller than the dimension L _{1Y in the} orthogonal direction. As a result, the protrusions 1b1, 1b2, and 1b3 have an elliptical motion close to a perfect circle, and can be driven more stably than when the dimension L _{1X in} the relative movement direction is equal to or larger than the dimension L _{1Y in the} orthogonal direction. . For this reason, it is preferable that the dimension L _1X in the relative movement direction of the plate portion 1a be smaller than the dimension L _{1Y in the} orthogonal direction.

  Hereinafter, a linear drive device 20 using a vibration wave motor according to an embodiment of the present invention will be described. FIG. 11 is a schematic diagram of a linear drive device 20 using the vibration wave motor of the embodiment. 11A is a front view as viewed from the (+) direction of the X axis, which is a relative movement direction, FIG. 11B is a side view, and FIG. 11A is a view in FIG. 1C and FIG. (b) corresponds to FIG. 1 (b).

  In FIG. 11, the vibration wave motor includes a vibration plate 1 and a piezoelectric element 2. The vibration wave motor further includes a friction member 3, and the protrusions 1b1, 1b2, and 1b3 are pressed against and contact the friction member 3. Thereby, the friction member 3 moves relative to the diaphragm 1 by the high frequency vibration of the piezoelectric element 2. The diaphragm holding member 4 includes a supporting portion 4a that supports the diaphragm 1 at an upper portion, and the supporting portion 4a supports the diaphragm 1 via the connecting portions 1d and 1e. Further, the diaphragm holding member 4 is provided with a shaft supporting portion 4b at a lower portion thereof, which rotatably supports a roller 5 rotatably sliding on the back surface of the friction member 3. For this reason, the diaphragm holding member 4 can move in synchronization with the diaphragm 1.

  The lower end of the pressure spring 6 acts on the diaphragm 1 and the piezoelectric element 2 via the pressure plate 7, and the upper end acts on the diaphragm holding member 4. The sliding portions 1c1, 1c2 and 1c3 are in contact with the friction member 3 while being pressed by the pressing force of the pressing spring 6. As described above, the diaphragm holding member 4 can obtain a propulsive force in the X direction in the drawing and relatively move in the + X direction by the driving force due to the elliptical motion as indicated by the arrow in FIG. 11B. The roller 5 is provided to reduce sliding resistance at the time of driving, and may be a mechanism such as a rolling roller as long as it has a similar function.

FIG. 12 is a diagram for explaining a position where a pressing force is generated by the pressure spring 6 and a position where the protrusions 1b1, 1b2, and 1b3 and the friction member 3 can come into contact with each other, and shows a bottom surface of the plate 1a of the diaphragm 1. FIG. Points C ₁ , C ₂ and C ₃ indicate the centers of the protrusions 1b1, 1b2 and 1b3, respectively, and the protrusions 1b1, 1b2 and 1b3 are in contact with the friction member 3 at the above three points on the XY plane. . Projections 1b1,1b2 and 1b3 abuts the friction member 3 with the diaphragm _C 1 3 a point not located on a straight line on the XY plane orthogonal to the pressing direction of 1, _{C 2} and _{C 3.} Pressing points P is the point indicating the center of the pressure generated in the vibrating plate 1 and the piezoelectric element 2 by the pressure spring 6, located inside the point C _1, C ₂ and the region T of the triangle formed by connecting the C ₃ ing. Therefore, the pressure point P when the diaphragm 1 is pressed against the friction member 3 is from the region T connecting the points C ₁ , C ₂ and C ₃ where the protrusions _{1 b 1} , _{1 b 2} and ₁ b 3 contact the friction member 3. Is also inside.

  Hereinafter, a lens driving device using the vibration wave motor according to the embodiment of the present invention will be described. FIG. 13 is a schematic diagram of a lens driving unit of a lens driving device equipped with a linear driving device 20 using the vibration wave motor 10 according to the embodiment of the present invention. In FIG. 13, FIG. 13A is a front view seen from the X-axis (+) direction, which is the optical axis direction, and FIG. 13B is a side view in which a part of the frame is cut away. In FIG. 13, the linear drive device 20 includes a diaphragm holding member 4, a lens holder 53, and a drive transmission unit 4 c that connects the diaphragm holding member 4 and the lens holder 53. The linear drive device 20 further includes guide shafts 54 and 55 that support the friction member 3, the frame body 51, the lens 52, and the lens holder 53 and guide them in the optical axis direction (X direction in the drawing). In FIG. 13B, components other than the plate portion 1a, the protrusions 1b1, 1b2 and 1b3 of the diaphragm 1 and the friction member 3 constituting the linear drive device 20 are omitted for convenience of explanation.

  The diaphragm 1 moves along the friction member 3 fixed to the frame 51, and the diaphragm holding member 4 moves in synchronization with this. The lens holder 53 is a driven body connected to the diaphragm holding member 4 by the drive transmitting portion 4c, and moves in synchronization with the diaphragm holding member 4. When the diaphragm holding member 4 moves a predetermined distance in the illustrated X direction according to a movement command from a microcomputer (not shown), the lens holder 53 is moved from 53 to 53 ′ as shown in FIG. Can be moved in range. As described above, the lens 52 can be moved in the optical axis direction by using the vibration wave motor 10 according to the embodiment of the present invention.

  Hereinafter, a conventional vibration wave motor will be described. 14A and 14B are schematic views for explaining the configuration of a conventional vibration wave motor 210. FIG. 14A is a front view, FIG. 14B is a side view, and FIG. 14C is a bottom view. 1 (b), FIG. 1 (c), and FIG. 1 (d). In the conventional example, two projections 201b1 and 201b2 are provided on a plate 201a of the diaphragm 201.

  By applying an AC voltage to the piezoelectric element 202, the plate part 201a is excited with a primary natural vibration mode of bending vibration in the orthogonal direction and a secondary natural vibration mode of bending vibration in the relative movement direction, and the two protrusions 201b1 , And 201b2 produce an elliptical motion. FIG. 15 is a schematic view of a linear drive device 220 using a conventional vibration wave motor 210. FIG. 15 (a) corresponds to FIG. 11 (a), and FIG. 15 (b) corresponds to FIG. 11 (b). I have. FIG. 15C shows a state in which the diaphragm 201, the piezoelectric element 202, and the pressing plate 205 are tilted from the state of FIG. The sliding portions 201c1 and 201c2 are in contact with the friction member 203 while being pressed by the pressing force of the pressing spring 206. As described above, the diaphragm holding member 204 can obtain a propulsive force in the X direction in the drawing and be relatively moved in the + X direction by the driving force due to the elliptical movement indicated by the arrow in FIG.

  In the conventional vibration wave motor 210, when an AC voltage is applied to the piezoelectric element 202, the two projections 201b1 and 201b2 have an elliptical motion having the same phase. Therefore, the sliding portions 201c1 and 201c2 repeatedly contact and separate from the friction member 203 at the same time, and a driving force is generated by friction between the sliding portions 201c1 and 201c2 and the friction member 203. Accordingly, no driving force is generated while the sliding portions 201c1 and 201c2 are separated from the friction member 203, and the propulsion force is reduced because the driving force is directly affected by the external force.

  On the other hand, in the vibration wave motor 10 according to the embodiment of the present invention, the projections 1b1 and 1b2 and the projection 1b3 generate an elliptic motion 180 degrees out of phase. Regarding contact and separation with the friction member 3, the sliding parts 1 c 1 and 1 c 2 and the sliding part 1 c 3 are out of phase by 180 degrees, and the sliding parts 1 c 1 and 1 c 2 and the sliding part 1 c 3 alternately friction. It contacts the member 3. Therefore, the time during which all the sliding portions 1c1, 1c2, and 1c3 are separated from the friction member 3 is shortened, and the propulsion force is higher than that of the conventional example because it is less affected by external force.

  In the conventional vibration wave motor 210, two protrusions 201b1 and 201b2 are provided side by side in the relative movement direction. There are two points in contact with the friction member 203 on the surface of the diaphragm 201 orthogonal to the pressing direction. For this reason, when a dimensional tolerance or an assembly tolerance of a component or an external force is generated, the diaphragm is rotated around the X direction around a straight line connecting two points at which the two sliding parts 201c1 and 201c2 and the friction member 203 abut. 201 is inclined with respect to the friction member 203.

  When driving is performed in a state where the vibration plate 201 is inclined and is in contact with the friction member 203, the frictional contact between the sliding portions 201c1 and 201c2 is not symmetrical in the XZ plane, but is generated in a biased direction. As a result, since the friction member 203 is brought into contact with a desired position, that is, a position off the center of the sliding portions 201c1 and 201c2, the driving efficiency is reduced.

  When the diaphragm 201 is tilted, the pressing force generated by the pressure spring 206 deviates from a straight line connecting the protrusions 201b1 and 201b2. As a result, the pressing force of the pressure spring 206 applied to the vibration plate 201 and the piezoelectric element 202 becomes uneven, so that the driving efficiency is reduced.

  As described above, in the conventional vibration wave motor 210, there is a problem that the inclination of the vibration plate 201 occurs and the sliding portions 201 c 1 and 201 c 2 of the vibration plate 201 do not stably contact the friction member 203, so that the driving efficiency is reduced. .

In contrast, and to the embodiments and the point _C 1 is the vibration wave motor 10 in the projections 1b1,1b2 and 1b3 of the modification, _{C 2} and _{C 3} in the friction member 3 of the present invention in contact. In other words, since the diaphragm 1 stably abuts the friction member 3 at _three points C ₁ , C _2, and C ₃ that are not on a straight line in a plane orthogonal to the pressing direction of the diaphragm ₁ , the dimensional tolerance and the assembly tolerance of the parts Or, even when an external force is generated, the diaphragm 1 does not tilt around the X direction and the Y direction.

As described above, in the vibration wave motor 10 according to the embodiment of the present invention and the modified example thereof, since the vibration plate 1 does not tilt with respect to the friction member 3, the sliding portions 1c1, 1c2, and 1c3 of the vibration plate 1 generate friction. A stable contact with the member 3 can be achieved. As a result, the sliding portions 1c1, 1c2 and 1c3 frictionally contact symmetrically in the XZ plane, so that the sliding portions 1c1, 1c2 and 1c3 come into contact with the friction member 3 at a desired position, that is, at the center of the sliding portions 1c1, 1c2 and 1c3. Can be improved. Also, projections 1b1,1b2 and 1b3 is in contact with the friction member 3 in _C 1, _{C 2} and _{C 3} 3 one point, uneven pressure applied by the pressure spring 6 driving efficiency is improved because it does not.

Above-described above, the vibration wave motor 10 of the present invention is in contact with the protrusion 1b1,1b2 and 1b3 has three points _C 1, _{C 2} and _{C 3} in the friction member 3 of the diaphragm 1, a triangle connecting the three points The diaphragm 1 does not tilt with respect to the friction member 3 because the inside of the region is pressurized. As a result, stable driving can be achieved by stably bringing the protrusions 1b1, 1b2, and 1b3 into contact with the friction member 3.

  In the above-described embodiment, an example in which the pressure plate 7 directly contacts the piezoelectric element 2 to apply pressure is shown, but a buffer may be interposed between the pressure plate 7 and the piezoelectric element 2. By interposing a cushioning material between the pressure plate 7 and the piezoelectric element 2, the pressure plate 7 can press the piezoelectric element 2 without attenuating the high frequency vibration generated in the piezoelectric element 2.

Further, in the above embodiment, the configuration in which the vibration plate 1 is pressed against the friction member 3 by the pressure spring 6 as one compression spring has been described. However, the pressure spring 6 may be a plurality of springs, It may be a spring. When the pressing spring 6 is a plurality of springs, the pressing force positions obtained by superimposing the pressing forces of the plurality of springs are the points C ₁ , C _2, and C at which the protrusions _{1 b 1} , _{1 b 2,} and ₁ b 3 abut on the friction member 3. ₃ so as to be inside the region T connecting them.

  Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and its modifications, and various modifications and changes can be made within the scope of the gist. For example, the vibration wave motor may be an ultrasonic motor whose diaphragm vibrates ultrasonically.

  INDUSTRIAL APPLICABILITY The present invention can be used for electronic devices that require a small and light weight and a wide driving speed range, particularly for a lens driving device.

DESCRIPTION OF SYMBOLS 1 Vibration plate 1a Plate part 1b1, 1b2, 1b3 Projection part 1c1, 1c2, 1c3 Sliding part 1d, 1e Connecting part 2 Piezoelectric element 3 Friction member 4 Vibrating plate holding member 5 Roller 6 Pressure spring 7 Pressure plate 51 Frame 52 lens 53 lens holder 54, 55 guide shaft 10 vibration wave motor 20 linear drive device _{C 1,} C 2, _{C 3} points T region

Claims (6)

A diaphragm having a plate portion and at least three protrusions provided on the plate portion;
A piezoelectric element fixed to the diaphragm and vibrating at a high frequency;
A plurality of the protrusions are pressurized and can contact, a friction member relatively moving with the diaphragm,
Has,
The vibration plate has a secondary natural vibration mode of bending vibration in a relative movement direction in which the vibration plate and the friction member relatively move due to the high frequency vibration of the piezoelectric element, and pressurization of the relative movement direction and the vibration plate. A second-order natural mode of bending vibration in the orthogonal direction orthogonal to the direction is excited,
A plurality of said projections, in a plane perpendicular to the pressing direction, is not provided in the plate portion around the through direction of the relative movement in a parallel straight line, and at least on one side and the other side sandwiching the straight line One by one provided near the node of the second-order natural vibration mode of bending vibration in the relative movement direction and near the antinode of the second-order natural vibration mode of bending vibration in the orthogonal direction;
The vibration wave , wherein the protrusion on the one side and the protrusion on the other side are provided in the vicinity of antinodes having different secondary natural vibration modes of the bending vibration in the orthogonal direction. motor. The plate portion, the vibration wave motor according to claim 1, the dimensions of the phase-to-mobile direction, characterized in that the smaller than the dimensions of the Cartesian direction.   2. The vibration wave motor according to claim 1, wherein the phase of the elliptical motion of some of the protrusions is shifted by 180 degrees from the phase of the elliptical motion of the other protrusions.   The position of the pressing force when pressing the vibration plate against the friction member is located inside a region connecting the plurality of points where the protrusion contacts the friction member. The vibration wave motor as described.   The piezoelectric element is divided into two or more divided regions in each of the relative movement direction and the orthogonal direction, and diagonally located regions of the regions are polarized in opposite directions. Item 3. The vibration wave motor according to item 2.   The vibration wave motor according to any one of claims 1 to 5, wherein the vibration wave motor is an ultrasonic motor in which the diaphragm vibrates ultrasonically.

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