JP7346450B2 - Displacement magnification mechanism and actuator - Google Patents

Description

The present invention relates to a displacement magnifying mechanism and an actuator.

2. Description of the Related Art Displacement magnification mechanisms are known that magnify and output small displacements of piezo elements (piezoelectric elements).

Patent Document 1 describes an output section, a piezoelectric element arranged symmetrically with respect to the output section, caps arranged on both sides of the piezoelectric element, and sides that roll into contact with caps other than the caps that roll into contact with the output section. A buckling type actuator is disclosed that includes a block and a frame that rigidly connects the side blocks.

Japanese Patent Application Publication No. 2014-82930

By the way, the positions between the cap on one side of the piezoelectric element and the side block and between the cap on the other side of the piezoelectric element and the output section are maintained by friction between the parts. However, minute slippage occurs due to loads originating inside the actuator due to assembly errors and parts intersection errors, and external loads such as external forces. This minute slippage accumulates as the number of operating cycles increases, and there is a risk that the components may become misaligned. For example, although a gap is provided between a piezoelectric element having caps on both sides and the frame, misalignment of the cap may cause the cap or the piezoelectric element to come into contact with the frame.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a displacement magnification mechanism and an actuator that suppress positional displacement of components.

A displacement magnifying mechanism according to one aspect of the embodiment includes a telescopic element having capacitive properties, a fixed part that rolls into contact with one end of the telescopic element, and a fixed part that rolls into contact with the other end of the telescopic element, and expands and contracts the telescopic element. an output section that is displaced in an output direction different from the expansion/contraction direction of the expansion/contraction element; a positional displacement suppressing structure for suppressing positional displacement, the positional displacement suppressing structure includes a connecting structure that rollably connects the fixing part and the elastic element, and a connecting structure that rollably connects the output part and the elastic element. At least one of the connecting structures is formed in at least one connecting structure, and at least one rolling surface of the fixed part and the output part is in a direction perpendicular to a plane consisting of the output direction of the output part and the stretching direction of the elastic element. The concave curved surface is defined by a convex first circular arc in which the locus of the rolling contact has a first curvature when viewed from above, and a concave second circular arc having a second curvature when viewed in the output direction of the output section. The rolling surface of the elastic element that comes into contact with the concave curved surface has a locus of rolling contact that has a third curvature when viewed in a direction perpendicular to a plane consisting of the output direction of the output section and the elastic direction of the elastic element. The convex curved surface is defined by a third convex arc having a curve, and a fourth convex arc having a fourth curvature when viewed in the output direction of the output section.

According to the present invention, it is possible to provide a displacement magnifying mechanism and an actuator that suppress positional displacement of components.

FIG. 3 is a perspective view of an actuator unit. FIG. 3 is a perspective view of the actuator unit with a portion of the outer shell cut away. FIG. 3 is a partial cross-sectional view of the actuator unit. A sectional view of the displacement magnification mechanism. FIG. 3 is a schematic diagram showing the forces acting on each component of the displacement magnification mechanism. FIG. 3 is a perspective view of a displacement magnification mechanism. FIG. 3 is a front view of the displacement magnification mechanism. FIG. 3 is a plan view of the displacement magnification mechanism. FIG. 3 is a perspective view of a fixing portion of the displacement magnification mechanism according to the first embodiment. FIG. 3 is a perspective view of a cap of the displacement magnifying mechanism according to the first embodiment. FIG. 3 is a plan view of the displacement magnification mechanism according to the first embodiment. FIG. 3 is a schematic diagram illustrating positional displacement due to rotation around the yc axis. FIG. 3 is a schematic diagram illustrating positional displacement due to rotation around the yc axis. FIG. 3 is a schematic diagram illustrating positional displacement due to rotation around the yp axis. FIG. 3 is a schematic diagram illustrating positional displacement due to rotation around the yp axis. FIG. 3 is a schematic diagram illustrating positional displacement due to rotation around the yp axis. 7 is a table illustrating the combination of each radius of curvature and the effect of suppressing deviation in the displacement magnification mechanism according to the first embodiment. FIG. FIG. 7 is a perspective view of a fixing part of a displacement magnification mechanism according to a second embodiment. FIG. 7 is a perspective view of a cap of a displacement magnification mechanism according to a second embodiment. FIG. 7 is a plan view of a displacement magnification mechanism according to a second embodiment. 7 is a table illustrating the combination of each radius of curvature and the effect of suppressing deviation in the displacement magnifying mechanism according to the second embodiment. FIG. 7 is a diagram illustrating the configuration of a displacement magnifying mechanism according to a modification. FIG. 7 is a diagram illustrating the configuration of a displacement magnifying mechanism according to a modification.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In each drawing, the same or corresponding configurations are designated by the same or corresponding symbols, and the description thereof will be omitted.

The actuator unit 1 will be explained using FIGS. 1A to 1D. 1A to 1D are diagrams showing the configuration of the actuator unit 1. FIG. Specifically, FIG. 1A is a perspective view of the actuator unit 1. FIG. 1B is a perspective view of the actuator unit 1 with a portion of the outer shell 15 cut away. FIG. 1C is a partial cross-sectional view of the actuator unit 1 in the yz plane. FIG. 1D is a cross-sectional view of the displacement magnification mechanism 10 in the yz plane.

The actuator unit 1 is a drive unit that constitutes a capacitive actuator. The actuator unit 1 mainly includes a displacement magnification mechanism 10, an output joint 20, a spring preload adjustment mechanism 30, and a piezo preload adjustment mechanism 40.

The displacement magnifying mechanism 10 is a mechanism that magnifies the displacement of an elastic element having capacitive properties by utilizing a buckling phenomenon. In this embodiment, the expandable element having capacitive properties is a piezo element, and is made of, for example, laminated ceramics. However, the elastic element may be a magnetostrictive element, a hydraulic cylinder, a pneumatic cylinder, or the like. The displacement magnification mechanism 10 mainly includes a pair of piezo elements 11, a pair of fixed parts (also referred to as "side blocks") 12, an output part (also referred to as "center block") 13, and a preload adjustment. It has a spring 14 and an outer shell (also referred to as a "frame") 15.

Each of the pair of piezo elements 11 has one end connected to the fixed part 12 via a rolling joint, and the other end connected to the output part 13 via a rolling joint. Caps CP1 and CP2 are joined to both end surfaces of the piezo element 11 in the longitudinal direction. Note that in this embodiment, the caps CP1 and CP2 exist as separate and independent members from the piezo element 11, but they may be formed integrally with the piezo element 11. The rolling joint between the piezo element 11 and the fixed part 12 is a rolling contact between the curved end surface (rolling surface) of the cap CP1 joined to one end of the piezo element 11 and the curved end surface (rolling surface) of the fixed part 12 ( connection via line or point contact). That is, in the connection structure between the piezo element 11 and the fixed part 12, the end curved surface (rolling surface) of the piezo element 11 is coupled to the end curved surface (rolling surface) of the fixed part 12 so that it can roll. Further, the rolling joint between the piezo element 11 and the output section 13 is formed by the curved end surface (rolling surface) of the cap CP2 joined to the other end of the piezo element 11 and the curved end surface (rolling surface) of the fixed section 12. Consists of a connection via rolling contact (line contact or point contact). That is, the connection structure between the piezo element 11 and the output section 13 is such that the end curved surface (rolling surface) of the piezo element 11 is connected to the end curved surface (rolling surface) of the output section 13 such that it can roll. In addition, in FIG. 1D, a circle C1 represents a circle including a locus of a contact point that contacts the end curved surface of the cap CP1 on the end curved surface of the fixing part 12, and a circle C2 represents a circle that includes the locus of the contact point that contacts the end curved surface of the cap CP1 on the end curved surface of the fixing part 12. Alternatively, the circle C3 represents a circle including the locus of the contact position that contacts the curved end surface of the output section 13, and the circle C3 represents a circle that includes the locus of the contact point that contacts the curved end surface of the cap CP2 on the curved end surface of the output section 13. That is, the operation of the rolling joint between the piezo element 11 and the fixed part 12 is defined by the circle C1 and the circle C2. Further, the operation of the rolling joint between the piezo element 11 and the output section 13 is defined by the circle C2 and the circle C3.

Each of the pair of piezo elements 11 expands in the longitudinal direction (z-axis direction) when a voltage is applied, causing a buckling phenomenon, and causes the output section 13 to move in a direction perpendicular to the longitudinal direction with a displacement larger than the elongation displacement. (y-axis direction). That is, the expansion and contraction movement of the piezo element 11 is converted into rotational movement by the rolling joint, and the expansion and contraction displacement is expanded. This results in a linear reciprocating motion in the output section 13. In this way, the displacement magnification mechanism 10 converts the output of each of the pair of piezo elements 11, and biases and displaces the output section 13 in a predetermined output direction that is different from the expansion and contraction direction of the piezo elements 11. . Note that the displacement of the output section 13 will be referred to as "enlarged displacement" below.

The output unit 13 is a functional element that transmits the output of the displacement amplifying mechanism 10 to the outside. In this embodiment, the output section 13 has its +y side end connected to the preload adjustment spring 14 and its -y side end connected to the output joint 20.

The preload adjustment spring (also referred to as "PCS (Preload Compensation Spring)") 14 is an example of a biasing means that biases the output section 13 of the displacement magnifying mechanism 10 with a constant characteristic. In the present embodiment, the preload adjustment spring 14 adjusts the expansion displacement-thrust force characteristic, which is the relationship between the expansion displacement of the output section 13 and the thrust generated by the expansion displacement. Specifically, the preload adjustment spring 14 is composed of a plate spring including a pair of curved parts curved so as to bulge in the -y direction, the center part of which is fixed to the output part 13, and both ends of which are used for adjusting the spring preload. It is connected to a pair of fixed parts 12 via a mechanism 30. The preload adjustment spring 14 generates a force in the y-axis direction that offsets the thrust caused by the enlarged displacement of the output section 13. Hereinafter, the force generated by the preload adjustment spring 14 will be referred to as "offset force." With this configuration, the preload adjustment spring 14 can determine the direction of expansion displacement of the output section 13 and stabilize the behavior of the output section 13.

The spring preload adjustment mechanism 30 is a mechanism that adjusts the offset force produced by the preload adjustment spring 14. In this embodiment, the spring preload adjustment mechanism 30 is composed of a wedge block. By adjusting the positions of both ends of the preload adjustment spring 14 in the y-axis direction, the user can adjust the offset force, which is the force with which the central portion of the preload adjustment spring 14 presses the output section 13 in the -y direction.

The piezo preload adjustment mechanism 40 is a mechanism that applies and adjusts preload to the four rolling joints in the displacement amplification mechanism 10. In this embodiment, the piezo preload adjustment mechanism 40 regarding the piezo element 11 is configured with a cap CP1, a guide GD1, and a shim SH1, as shown in FIG. 1D.

The cap CP1 is a member attached to one end of the piezo element 11 to form a rolling joint between the piezo element 11 and the fixed part 12.

The guide GD1 is a member that guides the cap CP1 to be removably attached to one end of the piezo element 11, and is fixed to the cap CP1. The cap CP1 and the shim SH1 are configured to transmit the thrust generated by the piezo element 11 with high efficiency. Therefore, it is preferably made of a material with high elasticity and strength, such as steel or ceramics. The guide GD1 is configured to ensure alignment of the cap CP1 and the piezo element 11 and to protect the outer surface of the piezo element 11. Therefore, it is preferably made of a material with lower elasticity than the piezo element 11, or has a structure with lower elasticity. Note that the cap CP1 and the guide GD1 may be integrally formed.

The shim SH1 is a member that can be placed between the cap CP1 and one end of the piezo element 11 within the guide GD1, and is used to adjust the distance between the cap CP1 and one end of the piezo element 11. That is, the greater the width of the shim SH1 in the z-axis direction, the greater the preload on the four rolling joints.

Although the piezo preload adjustment mechanism 40 has been described as being disposed at one end of the piezo element 11 (on the fixed part 12 side), it may be disposed on the other end of the piezo element 11 (on the output part 13 side). .

The piezo preload adjustment mechanism 40 adjusts the distance between the left end contact point and the right end contact point to be shorter than the natural length. Therefore, the rolling surfaces of the rolling joint always come into rolling contact while being subjected to a force greater than a predetermined value. Note that the contact point at the left end is the contact point between the end curved surface of the left cap CP1 and the end curved surface of the left fixing part 12, and the right end contact point is the contact point between the end curved surface of the right cap CP1 and the right end curved surface. This is the point of contact with the curved end surface of the fixed part 12. In addition, the natural length of each member arranged in a straight line in the z-axis direction under no load (cap CP1, left piezo element 11, cap CP2, output section 13, cap CP2, right piezo element 11, cap CP1 ) in the z-axis direction.

The outer shell 15 is a functional element that fixes the distance between the pair of fixing parts 12. In this embodiment, the outer shell 15 is a member formed to surround the pair of piezo elements 11, the pair of fixing parts 12, and the output part 13, and when a buckling phenomenon occurs in the displacement magnification mechanism 10, the outer shell 15 This prevents the distance between the fixed parts 12 from increasing.

With the above configuration, the displacement magnifying mechanism 10 has characteristics that can magnify the displacement of the piezo element 11 by 100 times or more, and can transmit 70% or more of the output energy. Further, since it has the characteristics that there is no energy loss due to static thrust maintenance and the expanded displacement is relatively large, the displacement expanding mechanism 10 can be applied to, for example, a brake actuator that requires a clamping operation.

Next, the output characteristics of the displacement magnification mechanism 10 will be explained using FIG. 2. FIG. 2 is a schematic diagram showing the forces acting on each component of the displacement magnification mechanism 10.

The output characteristic of the displacement magnification mechanism 10 is expressed as shown in equation (1), taking into account the actuator characteristics of the piezo element 11 and the motion conversion characteristics by the displacement magnification mechanism 10.

Note that kPCS represents the mechanical compression rigidity of the spring preload adjustment mechanism 30, and kPZT represents the mechanical compression rigidity of the piezo element 11. Moreover, kF represents the mechanical tensile rigidity of the outer shell 15 in the longitudinal direction, and kJ represents the mechanical compressive rigidity of the rolling joint. Further, kS represents the overall mechanical rigidity of the displacement magnifying mechanism 10 in the displacement direction of the piezo element 11, and depends on the mechanical tensile rigidity kF of the outer shell 15 and the mechanical compressive rigidity kJ of the rolling joint. Further, L represents the distance between the rotation center of the rolling joint regarding the fixed part 12 and the rotation center of the rolling joint regarding the output part 13. Further, FV represents a piezo thrust force, FPL represents a piezo preload force by the piezo preload adjustment mechanism 40, and FZ represents a mechanical thrust force generated inside the piezo element 11 depending on the amount of displacement of the piezo element 11. Further, zPZT represents the displacement of the piezo element 11, and zS represents the total displacement of the rolling joint and the outer shell 15 in the displacement direction of the piezo element 11. Further, d is a piezoelectric constant, and VPZT represents a voltage applied to the piezo element 11. Further, α represents the angle between the contact points. The inter-contact angle α is the angle of a line segment connecting the contact point between the piezo element 11 and the fixed part 12 and the contact point between the piezo element 11 and the output part 13 with respect to the reference line. The reference line is a straight line that connects the center of rotation of the rolling joint with respect to the fixed part 12 and the center of rotation of the rolling joint with respect to the output part 13 when the enlarged displacement Y is zero. Note that y0 in FIG. 2 represents a constant amount of displacement (preload) with respect to the preload adjustment spring 14.

The first equation of equation (1) indicates the balance of forces in the direction of the enlarged displacement Y of the output section 13. The second equation shows the motion conversion characteristic by the displacement magnifying mechanism 10. The third equation shows the balance of forces in the direction of displacement of the piezo element 11. Note that z is the center of the arc where the cap CP1 makes rolling contact (line contact or point contact) with the curved end surface of the fixed part 12, and the center of the arc where the cap CP2 makes rolling contact (line contact or point contact) with the curved end surface of the output part 13. ) represents the distance from the center of the arc. Furthermore, in the second equation, the influence of expansion and contraction of the piezo element 11 is approximated by a minute change in the diameter of the cap. This approximation is adopted, for example, when a circle including the outline of the curved end surface of the cap CP1 and a circle including the outline of the curved end surface of the cap CP2 are designed to be concentric circles C2 (see FIG. 1D). It is possible.

Next, the displacement magnification mechanism 10 will be further explained using FIGS. 3A to 3C. 3A to 3C are schematic diagrams showing the configuration of the displacement magnification mechanism 10. Specifically, FIG. 3A is a perspective view of the displacement magnification mechanism 10. FIG. 3B is a front view of the displacement magnification mechanism 10 viewed from a direction perpendicular to the yz plane. FIG. 3C is a plan view of the displacement magnification mechanism 10 viewed from a direction perpendicular to the zx plane. Note that in FIGS. 3A to 3C, the output joint 20, spring preload adjustment mechanism 30, preload adjustment spring 14, etc. are omitted from illustration. Further, in FIG. 3A, the outer shell 15 is shown transparently, and in FIG. 3B, illustration of the outer shell 15 is omitted. In the examples of FIGS. 3A to 3C, the rolling surfaces of the caps CP1 and CP2, the rolling surface of the fixed part 12, and the rolling surface of the output part 13 are illustrated as cylindrical surfaces.

As shown in FIG. 3A, the yc axis indicates the output direction of the output section 13 and is an axis parallel to the y axis passing through the center of the output section 13. The displacement magnification mechanism 10 has a symmetrical structure with respect to a plane passing through the yc axis and parallel to the xy plane. The zp axis is an axis that coincides with the extension direction of the piezo element 11 and passes through the center of the piezo element 11. The yp axis is perpendicular to the zp axis, perpendicular to the x axis and the zx plane, and is an axis passing through the center of the piezo element 11.

As shown in FIG. 3B, Rs indicates the radius of curvature of the rolling surface of the fixed part 12. Rc indicates the radius of curvature of the rolling surface of the output section 13. Rp indicates the radius of curvature of the rolling surface of the cap of the piezo element 11.

Here, as shown in FIG. 3C, when the rolling surfaces of the caps CP1 and CP2, the rolling surface of the fixed part 12, and the rolling surface of the output part 13 are cylindrical surfaces, the piezo element 11 is geometrically Not restricted. In other words, the geometrical not bound by. Therefore, if the piezo element 11 is displaced in the x-axis direction, there is a risk that the piezo element 11 will come into contact with the outer shell 15. When the piezo element 11 comes into contact with the outer shell 15, the performance of the actuator unit 1 is degraded and the life of the actuator unit 1 is shortened due to wear.

Next, the displacement magnifying mechanism 10 according to the first embodiment will be described using FIGS. 4A to 4C. 4A to 4C are diagrams illustrating the configuration of the displacement magnifying mechanism 10 according to the first embodiment. Specifically, FIG. 4A is a perspective view of the fixing part 12 of the displacement amplifying mechanism 10 according to the first embodiment. FIG. 4B is a perspective view of the cap CP1 of the displacement magnification mechanism 10 according to the first embodiment. FIG. 4C is a plan view of the displacement magnification mechanism 10 according to the first embodiment in the zx plane. The displacement magnifying mechanism 10 according to the first embodiment is different from the displacement magnifying mechanism 10 shown in FIGS. 3A to 3C in the shape of the rolling surface of the rolling joint.

Further, the displacement magnification mechanism 10 according to the first embodiment has a positional displacement suppressing structure that suppresses positional displacement of components in the x direction. That is, the positional displacement suppressing structure is arranged in a direction (x-axis direction) perpendicular to a plane (yz plane) consisting of the output direction of the output section 13 (y-axis direction) and the expansion/contraction direction (z-axis direction) of the piezo element 11. On the other hand, displacement of the component (piezo element 11) is suppressed. The positional displacement suppressing structure is configured by the shape of the rolling surface of the fixed portion 12 and the shape of the rolling surface of the cap CP1. Further, the positional displacement suppressing structure is configured by the shape of the rolling surface of the output portion 13 and the shape of the rolling surface of the cap CP2.

As shown in FIG. 4A, the fixed portion 12 has a saddle-shaped rolling surface, in other words, a concavely curved rolling surface. Here, the concave curved surface is a curved surface that forms a concave arc when cut along a plane perpendicular to the locus of the rolling contact. Moreover, Rs indicates the radius of curvature of the rolling circle. The rolling circle of the fixing part 12 is a circle that includes the locus of the contact point that contacts the end curved surface of the cap CP1 on the end curved surface of the fixing part 12, and is a circle on a plane parallel to the yz plane. rs indicates the radius of curvature of the curved surface of the fixed portion 12. In addition, in FIG. 4A, the locus of the center of a circle with a radius of curvature rs is indicated by cs. The locus cs is on the same plane as the circle with the radius of curvature Rs, is concentric with the circle with the radius of curvature Rs, and is a circular arc with the radius Rs+rs. Further, the plane of the circle with the radius of curvature Rs and the plane of the circle with the radius of curvature rs are planes rotated by 90° about the line connecting the centers of the two circles. The rolling surface of the fixed portion 12 is a curved surface formed by sweeping a circular arc with a radius of curvature rs along a rolling circle with a radius of curvature Rs.

As shown in FIG. 4B, the cap CP1 has a rolling surface that is a convex curved surface. Here, the convex curved surface is a curved surface that forms a convex circular arc when cut along a plane perpendicular to the locus of the rolling contact. Moreover, Rp indicates the radius of curvature of the rolling circle. The rolling circle of the cap CP1 is a circle that includes the locus of the contact point of the end curved surface of the cap CP1 that contacts the end curved surface of the fixed part 12, and is a circle on a plane parallel to the yz plane. rp indicates the radius of curvature of the curved surface of the cap CP1. Further, in FIG. 4B, the locus of the center of the circle with the radius of curvature rp is indicated by cp. The locus cp is on the same plane as the circle with the radius of curvature Rp, is concentric with the circle with the radius of curvature Rp, and is a circular arc with the radius Rp−rp. Further, the plane of the circle with the radius of curvature Rp and the plane of the circle with the radius of curvature rp are planes rotated by 90° about the line connecting the centers of the two circles. The rolling surface of the cap CP1 is a curved surface formed by sweeping an arc with a radius of curvature rp along a rolling circle with a radius of curvature Rp.

The rolling surface of the output part 13 has a rolling surface that is a concave curved surface defined by the radius of curvature Rc of the rolling circle and the radius of curvature rc of the curved surface, similarly to the rolling surface of the fixed part 12. Further, the rolling surface of the cap CP2 has a rolling surface that is a convex curved surface defined by the radius of curvature Rp of the rolling circle and the radius of curvature rp of the curved surface, similar to the rolling surface of the cap CP1.

Further, the radius of curvature of a circle passing through the joint contact points in the left and right fixing parts 12 is assumed to be rss. Further, the radius of curvature of a circle passing through the joint contact point in the fixed part 12 and the joint contact point in the output part 13 is assumed to be rsc. Note that when the Rp of the caps CP1 and CP2 at both ends of one piezo element 11 are the same circle, rsc has approximately the same value as Rp.

With such a configuration, the operation of the rolling joint between the cap CP1 of the piezo element 11 and the fixed part 12 is defined by a rolling circle with a radius of curvature Rs and a rolling circle with a radius of curvature Rp. Further, the operation of the rolling joint between the cap CP2 of the piezo element 11 and the output section 13 is defined by a rolling circle with a radius of curvature Rp and a rolling circle with a radius of curvature Rc. Therefore, the displacement magnification mechanism 10 according to the first embodiment can perform a displacement magnification operation similarly to the displacement magnification mechanism 10 shown in FIGS. 3A to 3C in which the end curved surface is a cylindrical surface.

Next, regarding the displacement magnifying mechanism 10 according to the first embodiment, the combination of each radius of curvature and the effect of suppressing deviation will be described.

In the following description, as a precondition, the radius of curvature rs of the curved surface of the fixed part 12 and the radius of curvature rc of the curved surface of the output part 13 will be explained as being equal (rs=rc). Further, the description will be made assuming that the radius of curvature rp of the curved surface of each cap CP1, CP2 is equal. Further, since the rolling joint is geometrically established, rp≦rs is satisfied.

In the displacement magnifying mechanism 10 according to the first embodiment, as shown in FIG. 4C, the end curved surface of the fixing portion 12 is a concave curved surface, and the end curved surface of the cap CP1 of the piezo element 11 is a convex curved surface. Further, the end curved surface of the output section 13 becomes a concave curved surface, and the end curved surface of the cap CP2 of the piezo element 11 becomes a convex curved surface. Thereby, displacement of the piezo element 11 in the x-axis direction can be suppressed.

5A to 5B are schematic diagrams illustrating positional deviation due to rotation around the yc axis. Note that rs1 represents the radius of curvature of the curved surface of the left fixed portion 12. rs2 represents the radius of curvature of the curved surface of the right fixed portion 12. rps1 represents the radius of curvature of the curved surface of the cap CP1 that contacts the left fixed part 12. rps2 represents the radius of curvature of the curved surface of the cap CP1 that contacts the fixing part 12 on the right side.

FIG. 5A shows a case where the radius of curvature rs of the fixed part 12 is greater than or equal to the radius of curvature rss of a circle passing through the joint contact points of the left and right fixed parts 12 (rss≦rs). A circle with a radius of curvature rss is included in the overlap between a circle with a radius of curvature rs1 and a circle with a radius of curvature rs2. Therefore, the circle with the radius of curvature rss can rotate within the overlap between the circle with the radius of curvature rs1 and the circle with the radius of curvature rs2. Therefore, the assembly of the left and right piezo elements 11 and the output section 13 can rotate about the yc axis as the rotation axis.

FIG. 5B shows a case where the radius of curvature rs of the fixed part 12 is less than the radius of curvature rss of a circle passing through the joint contact points of the left and right fixed parts 12 (rs<rss). The circle with the radius of curvature rss protrudes from the overlapping portion of the circle with the radius of curvature rs1 and the circle with the radius of curvature rs2. Therefore, the circle with the radius of curvature rss cannot rotate within the overlap between the circle with the radius of curvature rs1 and the circle with the radius of curvature rs2. Therefore, it is possible to suppress the assembly of the left and right piezo elements 11 and the output section 13 from rotating about the yc axis as the rotation axis.

FIGS. 6A to 6C are schematic diagrams illustrating positional deviation due to rotation around the yp axis. rps represents the radius of curvature of the curved surface of the cap CP1 that contacts the fixed part 12. rpc represents the radius of curvature of the curved surface of the cap CP2 that contacts the output part 13.

In FIG. 6A, the radius of curvature rs of the fixed part 12 is greater than or equal to the radius of curvature rsc of a circle passing through the joint contact point in the fixed part 12 and the joint contact point in the output part 13, and the radius of curvature rp of the cap CP is less than or equal to the radius of curvature rsc. The case (rp≦rsc≦rs) is shown. In this case, a circle with a radius of curvature rsc is included in the overlap between a circle with a radius of curvature rs and a circle with a radius of curvature rc. Therefore, the circle with the radius of curvature rsc can rotate within the overlap between the circle with the radius of curvature rs and the circle with the radius of curvature rc. Furthermore, the piezo element 11 including the caps CP1 and CP2 fits within a circle with a radius of curvature rsc. Therefore, the piezo element 11 can rotate about the yp axis as the rotation axis.

In FIG. 6B, the radius of curvature rs of the fixed part 12 is greater than or equal to the radius of curvature rsc of a circle passing through the joint contact point in the fixed part 12 and the joint contact point in the output part 13, and the radius of curvature rp of the cap CP is greater than or equal to the radius of curvature rsc. The case (rsc≦rp≦rs) is shown. In this case, the piezo element 11 including the caps CP1 and CP2 protrudes beyond the circle with the radius of curvature rsc. However, the "overlapping part between the circle with the radius of curvature rs and the circle with the radius of curvature rc" includes the "overlapping part between the circle with the radius of curvature rpc and the circle with the radius of curvature rps". Therefore, the "overlapping part between the circle with the radius of curvature rpc and the circle with the radius of curvature rps" can rotate within the "overlapping part between the circle with the radius of curvature rs and the circle with the radius of curvature rc". Therefore, the piezo element 11 can rotate about the yp axis as the rotation axis.

FIG. 6C shows a case where the radius of curvature rs of the fixed part 12 is less than the radius of curvature rsc of a circle passing through the joint contact point in the fixed part 12 and the joint contact point in the output part 13 (rp≦rs<rsc). The circle with the radius of curvature rsc protrudes from the overlapping portion of the circle with the radius of curvature rs and the circle with the radius of curvature rc. Therefore, the circle with the radius of curvature rsc cannot rotate within the overlap between the circle with the radius of curvature rs and the circle with the radius of curvature rc. Therefore, it is possible to suppress the piezo element 11 from rotating about the yp axis as the rotation axis.

Next, positional deviation due to rotation around the zp axis will be explained. When the radius of curvature rs of the fixed part 12 is greater than or equal to the radius of curvature rsc of the circle passing through the joint contact point in the fixed part 12 and the joint contact point in the output part 13 (rsc≦rs), the piezo element 11 rotates about the zp axis as the rotation axis. can do. On the other hand, when the radius of curvature rs of the fixed part 12 is less than the radius of curvature rsc of the circle passing through the joint contact point in the fixed part 12 and the joint contact point in the output part 13 (rs<rsc), the piezo element 11 rotates the zp axis as the rotation axis. It is possible to suppress rotation as follows.

FIG. 7 is a table explaining the combination of each radius of curvature and the effect of suppressing deviation in the displacement magnifying mechanism 10 according to the first embodiment. Note that in the table, the cross marks indicate ranges that do not satisfy the geometric condition (rp≦rs). The black triangle is the range in which displacement in the x direction is suppressed. The white triangle mark is the range in which displacement in the x direction is suppressed and rotation around the yc axis is suppressed. The double circles indicate the range in which displacement in the x direction is suppressed, rotation around the yc axis is suppressed, rotation around the yp axis is suppressed, and rotation around the yz axis is suppressed. In this way, by appropriately selecting the radius of curvature rs of the fixed part 12 (the radius of curvature rc of the output part 13) and the radius of curvature rp of the cap CP, it is possible to suppress misalignment of components within the displacement magnifying mechanism 10. . Note that the preload force of the piezo element 11 and the radius of curvature of each curved surface are designed so that the joint contact stress is within an allowable value.

Next, the displacement magnification mechanism 10 according to the second embodiment will be described using FIGS. 8A to 8C. 8A to 8C are diagrams illustrating the configuration of the displacement magnifying mechanism 10 according to the second embodiment. Specifically, FIG. 8A is a perspective view of the fixing part 12 of the displacement amplifying mechanism 10 according to the second embodiment. FIG. 8B is a perspective view of the cap CP1 of the displacement magnifying mechanism 10 according to the second embodiment. FIG. 8C is a plan view of the displacement magnification mechanism 10 according to the second embodiment on the zx plane. The displacement magnification mechanism 10 according to the second embodiment has a rolling joint, compared with the displacement magnification mechanism 10 shown in FIGS. 3A to 3C and the displacement magnification mechanism 10 according to the first embodiment shown in FIGS. 4A to 4C. The shapes of the rolling surfaces are different.

As shown in FIG. 8A, the fixed portion 12 has a rolling surface that is a convex curved surface. Here, Rs indicates the radius of curvature of the rolling circle. The rolling circle of the fixing part 12 is a circle that includes the locus of the contact point that contacts the end curved surface of the cap CP1 on the end curved surface of the fixing part 12, and is a circle on a plane parallel to the yz plane. rs indicates the radius of curvature of the curved surface of the fixed portion 12. Further, in FIG. 8A, the locus of the center of the circle with the radius of curvature rs is indicated by cs. The locus cs is on the same plane as the circle with the radius of curvature Rs, is concentric with the circle with the radius of curvature Rs, and is a circular arc with the radius Rs-rs. Further, the plane of the circle with the radius of curvature Rs and the plane of the circle with the radius of curvature rs are planes rotated by 90° about the line connecting the centers of the two circles. The rolling surface of the fixed portion 12 is a curved surface formed by sweeping a circular arc with a radius of curvature rs along a rolling circle with a radius of curvature Rs.

As shown in FIG. 8B, the cap CP1 has a saddle-shaped rolling surface, in other words, a concavely curved rolling surface. Here, Rp indicates the radius of curvature of the rolling circle. The rolling circle of the cap CP1 is a circle that includes the locus of the contact point of the end curved surface of the cap CP1 that contacts the end curved surface of the fixed part 12, and is a circle on a plane parallel to the yz plane. rp indicates the radius of curvature of the curved surface of the cap CP1. Further, in FIG. 8B, the locus of the center of the circle with the radius of curvature rp is indicated by cp. The locus cp is on the same plane as the circle with the radius of curvature Rp, is concentric with the circle with the radius of curvature Rp, and is a circular arc with the radius Rp+rp. Further, the plane of the circle with the radius of curvature Rp and the plane of the circle with the radius of curvature rp are planes rotated by 90° about the line connecting the centers of the two circles. The rolling surface of the cap CP1 is a curved surface formed by sweeping an arc with a radius of curvature rp along a rolling circle with a radius of curvature Rp.

The rolling surface of the output part 13 has a rolling surface that is a convex curved surface defined by the radius of curvature Rc of the rolling circle and the radius of curvature rc of the curved surface, similarly to the rolling surface of the fixed part 12. Further, the rolling surface of the cap CP2 has a rolling surface that is a concave curved surface defined by the radius of curvature Rp of the rolling circle and the radius of curvature rp of the curved surface, similarly to the rolling surface of the cap CP1.

Further, the radius of curvature of a circle passing through the joint contact points in the left and right fixing parts 12 is assumed to be rss. Further, the radius of curvature of a circle passing through the joint contact point in the fixed part 12 and the joint contact point in the output part 13 is assumed to be rsc. Note that when the Rp of the caps CP1 and CP2 at both ends of one piezo element 11 are the same circle, rsc has approximately the same value as Rp.

With such a configuration, the operation of the rolling joint between the cap CP1 of the piezo element 11 and the fixed part 12 is defined by a rolling circle with a radius of curvature Rs and a rolling circle with a radius of curvature Rp. Further, the operation of the rolling joint between the cap CP2 of the piezo element 11 and the output section 13 is defined by a rolling circle with a radius of curvature Rp and a rolling circle with a radius of curvature Rc. Therefore, the displacement magnification mechanism 10 according to the second embodiment can perform a displacement magnification operation similarly to the displacement magnification mechanism 10 shown in FIGS. 3A to 3C in which the end curved surface is a cylindrical surface.

Next, regarding the displacement magnification mechanism 10 according to the second embodiment, the combination of each radius of curvature and the effect of suppressing deviation will be described.

In the following description, as a precondition, the radius of curvature rs of the curved surface of the fixed part 12 and the radius of curvature rc of the curved surface of the output part 13 will be explained as being equal (rs=rc). Further, the description will be made assuming that the radius of curvature rp of the curved surface of each cap CP1, CP2 is equal. In addition, since the rolling joint is geometrically established, rs≦rp is satisfied.

In the displacement magnifying mechanism 10 according to the second embodiment, as shown in FIG. 8C, the end curved surface of the fixing portion 12 is a convex curved surface, and the end curved surface of the cap CP1 of the piezo element 11 is a concave curved surface. Further, the end curved surface of the output section 13 becomes a convex curved surface, and the end curved surface of the cap CP2 of the piezo element 11 becomes a concave curved surface. Thereby, displacement of the piezo element 11 in the x-axis direction can be suppressed. Further, it is possible to suppress the assembly of the left and right piezo elements 11 and the output section 13 from rotating about the yc axis. Further, it is possible to suppress the piezo element 11 from rotating about the yp axis as the rotation axis.

Next, positional deviation due to rotation around the zp axis will be explained. When the radius of curvature rp of the cap CP1 is greater than or equal to the radius of curvature Rs of the rolling circle of the fixed portion 12 (Rs≦rp), the piezo element 11 can rotate about the xp axis as the rotation axis. On the other hand, when the radius of curvature rp of the cap CP1 is less than the radius of curvature Rs of the rolling circle of the fixed part 12 (rp<Rs), it is possible to suppress the piezo element 11 from rotating about the zp axis.

FIG. 9 is a table explaining the combination of each radius of curvature and the effect of suppressing deviation in the displacement magnification mechanism 10 according to the second embodiment. Note that in the table, the cross marks indicate ranges that do not satisfy the geometric condition (rp≦rs). The circles indicate ranges in which displacement in the x direction is suppressed, rotation around the yc axis is suppressed, and rotation around the yp axis is suppressed. The double circles indicate the range in which displacement in the x direction is suppressed, rotation around the yc axis is suppressed, rotation around the yp axis is suppressed, and rotation around the zp axis is suppressed. In this way, by appropriately selecting the radius of curvature rs of the fixed part 12 (the radius of curvature rc of the output part 13) and the radius of curvature rp of the cap CP, it is possible to suppress misalignment of components within the displacement magnifying mechanism 10. . Note that the preload force of the piezo element 11 and the radius of curvature of each curved surface are designed so that the joint contact stress is within an allowable value.

Although the displacement magnification mechanism according to the present embodiment has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications may be made within the scope of the gist of the present invention as described in the claims. It is possible to transform and change.

In the displacement magnification mechanism 10 according to the first embodiment, the end curved surface of the fixed part 12 and the end curved surface of the output part 13 are concave curved surfaces, and in the displacement magnification mechanism 10 according to the second embodiment, the end curved surface of the fixed part 12 is a concave curved surface. Although the end curved surface of the output section 13 has been described as being a convex curved surface, it is not limited to this. For example, the curved end surfaces of the fixing portion 12 and the cap CP1 may have uneven curved surfaces shown in FIGS. 4A to 4C or FIGS. 8A to 8C, and the curved end surfaces of the output portion 13 and the cap CP2 may have cylindrical surfaces. Further, the curved end surfaces of the output portion 13 and the cap CP2 may have uneven curved surfaces shown in FIGS. 4A to 4C or FIGS. 8A to 8C, and the curved end surfaces of the fixing portion 12 and the cap CP1 may be cylindrical surfaces. Even in this case, by appropriately selecting the radius of curvature of each curved surface, the effect of suppressing deviation can be achieved. Moreover, by forming one side into a cylindrical surface, processing costs can be reduced.

Furthermore, in the displacement magnification mechanism 10 according to the first embodiment and the second embodiment, the radius of curvature rs of the curved surface of the fixed part 12 and the radius of curvature rc of the curved surface of the output part 13 are described as being equal (rs=rc). However, it is not limited to this, and may be different. Further, although the radius of curvature rp of the curved surfaces of the caps CP1 and CP2 has been described as being equal, the radius of curvature rp is not limited to this, and may be different.

Further, although the locus of the rolling contacts in the fixed part 12 and the output part 13 has been described as a convex arc (a circle with a radius of curvature Rs, a circle with a radius of curvature Rc), it is not limited to this. The locus of the rolling contact may be a straight line, a concave arc, or a non-circular curve, and is not limited to this.

An example in which the locus of the rolling contact is a straight line will be explained using FIGS. 10A to 10B. 10A to 10B are diagrams illustrating the configuration of a displacement magnification mechanism 10 according to a modification. FIG. 10A shows an example of a fixed portion 12 in which the locus Ls of the rolling contact is a straight line and forms a saddle-shaped (concave curved) rolling surface. Note that the cap CP1 that comes into contact with the fixed portion 12 is the cap CP1 whose rolling surface is a convex curved surface as shown in FIG. 4B. Further, FIG. 10B shows an example of the fixed portion 12 in which the locus Ls of the rolling contact is a straight line and has a convex curved surface. Note that the cap CP1 that comes into contact with this fixing portion 12 becomes the cap CP1 whose rolling surface has a saddle-shaped shape (concave curved surface) as shown in FIG. 8B. In this way, even if the locus of the rolling contact is a straight line, it is possible to have a configuration that suppresses displacement.

This application claims priority based on Japanese patent application No. 2018-238656 filed on December 20, 2018, and the entire contents of these Japanese patent applications are incorporated by reference into this application.

1 Actuator unit (actuator)
10 Displacement magnification mechanism 11 Piezo element 12 Fixed part 13 Output part 14 Preload adjustment spring 15 Outer shell 20 Output joint 30 Spring preload adjustment mechanism 40 Piezo preload adjustment mechanism CP1, CP2 Cap

Claims (7)

a stretchable element having capacitive properties;
a fixed part that rolls into contact with one end of the elastic element;
an output part that rolls into contact with the other end of the elastic element and is displaced in an output direction different from the expansion and contraction direction of the elastic element according to the expansion and contraction of the elastic element;
a positional displacement suppressing structure that suppresses positional displacement of the elastic element with respect to a direction perpendicular to a plane consisting of the output direction of the output section and the elastic direction of the elastic element ;
The positional displacement suppressing structure is
formed into at least one connection structure of a connection structure that rollably connects the fixing part and the elastic element and a connection structure that rollably connects the output part and the expansion and contraction element,
At least one rolling surface of the fixed part and the output part is
a convex first circular arc in which the locus of the rolling contact has a first curvature when viewed in a direction perpendicular to a plane consisting of the output direction of the output section and the expansion/contraction direction of the expansion/contraction element;
a concave curved surface defined by a second concave arc having a second curvature when viewed in the output direction of the output section;
The rolling surface of the elastic element that comes into contact with the concave curved surface is
a convex third circular arc in which the locus of the rolling contact has a third curvature when viewed in a direction perpendicular to a plane consisting of the output direction of the output section and the expansion/contraction direction of the expansion/contraction element;
a convex curved surface defined by a fourth convex arc having a fourth curvature when viewed in the output direction of the output section;
Displacement magnification mechanism. The fourth curvature of the convex curved surface is equal to or less than the second curvature of the concave curved surface,
The second curvature of the concave curved surface is smaller than the curvature of a circle passing through a contact point between the fixed part and one end of the elastic element and a contact point between the output part and the other end of the elastic element,
The fourth curvature of the convex curved surface is smaller than the curvature of a circle passing through a contact point between the fixed part and one end of the elastic element and a contact point between the output part and the other end of the elastic element.
The displacement magnifying mechanism according to claim 1. The concave curved surface is formed by sweeping the second circular arc along the first circular arc, and the convex curved surface is formed by sweeping the fourth circular arc along the third circular arc.
The displacement magnification mechanism according to claim 1 or claim 2. a stretchable element having capacitive properties;
a fixed part that rolls into contact with one end of the elastic element;
an output part that rolls into contact with the other end of the elastic element and is displaced in an output direction different from the expansion and contraction direction of the elastic element according to the expansion and contraction of the elastic element;
a positional displacement suppressing structure that suppresses positional displacement of the elastic element with respect to a direction perpendicular to a plane consisting of the output direction of the output section and the elastic direction of the elastic element ;
The positional displacement suppressing structure is
formed into at least one connection structure of a connection structure that rollably connects the fixing part and the elastic element and a connection structure that rollably connects the output part and the expansion and contraction element,
At least one rolling surface of the fixed part and the output part is
a convex first circular arc in which the locus of the rolling contact has a first curvature when viewed in a direction perpendicular to a plane consisting of the output direction of the output section and the expansion/contraction direction of the expansion/contraction element;
a convex curved surface defined by a second convex arc having a second curvature when viewed in the output direction of the output section;
The rolling surface of the elastic element that comes into contact with the convex curved surface is
a convex third circular arc in which the locus of the rolling contact has a third curvature when viewed in a direction perpendicular to a plane consisting of the output direction of the output section and the expansion/contraction direction of the expansion/contraction element;
a concave curved surface defined by a fourth concave arc having a fourth curvature when viewed in the output direction of the output section;
Displacement magnification mechanism. The second curvature of the convex curved surface is equal to or less than the fourth curvature of the concave curved surface,
the second curvature of the convex curved surface is smaller than the first curvature;
the fourth curvature of the concave curved surface is smaller than the first curvature;
The displacement magnifying mechanism according to claim 4. The convex curved surface is formed by sweeping the second circular arc along the first circular arc,
The concave curved surface is formed by sweeping the fourth arc along the third arc,
The displacement magnification mechanism according to claim 4 or claim 5. An actuator comprising the displacement magnifying mechanism according to any one of claims 1 to 6 .

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